Monday, April 1, 2013
And Another Thing!
Copernicus was super awesome and everything, but I just wanted to give a little credit where credit was due to Aristarchus, the man who thought of heliocentricity long before Copernicus.
Friday, March 15, 2013
Magnetism of the Sun
What are sunspots? Did you know that sunspots occur as a part of a cycle? The dark spots are extremely hot, but they appear to be dark, because they are relatively cool (almost 2,000K cooler) compared to the regions of the photosphere surrounding them. The parts of the spots are called the umbra and the penumbra, just like the darker and lighter parts of the shadows cast during eclipses, and sunspots can be larger than the Earth! However, these spots are not shadows. They are brighter than the a full moon appears. The Sun rotates differentially, meaning that part of it rotates faster than the rest, and this sort of rotation seems to wrap its magnetic field up like a cord (according to the Babcock model). Every 11 years, this causes the magnetic poles of the Sun to flip, meaning that its north pole becomes its south pole, and its south pole becomes its north pole. The surface of the sun has a "magnetic carpet" of looped magnetic fields, and as the surface rotates, turbulence whips up the gas and giant loops of ionized gases get flung out, and sunspots are what we observe of these disturbances. This is why sunspots always come in pairs, and they are the north and south "poles" of these loops. Every cycle, there are anywhere from just a few to over 100 sunspots, and the Maunder butterfly diagram which portrays the pattern the sunspots make is aptly named. These magnetic disturbances can be measured using the Zeeman effect, where an atom being passed through a magnetic field is able to absorb multiple wavelengths of photons, each representing the strength of the magnetic field. The magnetic field of a sunspot can be a few thousand times that of Earth's, and the cool temperature is thought to be caused because the fields may slow down the gas, which in turn slows down local convection. The heat is then thought to be deflected around the sunspot since infrared images also detect greater heat surrounding these spots. Interestingly enough, since we were discussing ice ages in class today, there was an extremely low record of sunspot activity in the sixteen and seventeen hundreds which coincided with a "mini ice age" in the northern hemisphere, which may or may not spell causation, but it is still compelling. We still do not understand the Sun's magnetic cycle, and it is something I would like to study. Some other magnetic phenomena of the sun include: prominences, which are giant loops of ionized gas trapped inside a magnetic arch that go through the photosphere, chromosphere, and even the lower corona; solar flares, which are strong enough to affect Earth's magnetic field and even disrupt navigation systems; and coronal holes, which is when magnetic loops break and do not reconnect with the Sun. This solar magnetic activity also causes auroras on Earth. Many other stars have starspots, but they are too far away to see. Through spectroscopic observations, however, we are able to study them and their magnetic cycles. By the way, I got all of this information from Foundations of Astronomy by Michael A. Seeds.
"All cannot live on the piazza, but everyone may enjoy the sun." -Italian proverb
"All cannot live on the piazza, but everyone may enjoy the sun." -Italian proverb
Nuclear Fusion
As we have learned, stars manufacture their energy through nuclear fusion. According to Modern Physics by Serway, Moses, and Moyer, nuclear fusion occurs "[w]hen two light nuclei combine to form a heavier nucleus," and is both a confirmation and consequence of special relativity. It is very thought-provoking that "the total rest mass of the products is less than that of the reactants" in a reaction, but this fact and the amount of energy released during nuclear fusion demonstrate Einstein's mass-energy equivalence. This has to do with the binding energy, and the amount depends on the atomic mass. The peak of the function of binding energy (pictured below) occurs at the mass number of iron, which means we cannot obtain elements "heavier" than iron through fusion.
Our textbook, An Introduction to Modern Astrophysics by Carroll and Ostlie, tells us that the likelihood of fusion depends on the kinetic energy of the collision. The peak from the graph below corresponds to the collision of two protons at the central temperature of the Sun and depends on a very narrow range of temperature of the gas and the charges and masses of the reactants involved. This makes fusion very difficult to achieve here on Earth...
Nevertheless, physicists are trying to find a way to convert water into deuterium and use it as fuel for controlled nuclear fusion. It seems impossible to even be able to originate nuclear fusion, let alone finding a way to control and then harness the staggering amount of energy it would create, and I don't like the fact that we would be using the most precious resource we have, but given our current energy crisis and the pursuit of cleaner, sustainable energy, it seems like at least a hopeful future candidate for a source of alternative fuel. On the plus side, the process isn't radioactive. Oh, and it isn't impossible. Click here to see how a 14-YEAR-OLD MADE A NUCLEAR FUSION REACTOR.
How a nuclear fusion reactor works: (according to howstuffworks.com)
In order to achieve the high temperatures and pressures needed for nuclear fusion, reactors will either use magnetic confinement, which uses electromagnetism to heat and compress hydrogen plasma (which is the process France's International Thermonuclear Experimental Reactor (ITER) will be using) or inertial confinement, which uses lasers or ion beams to do the same thing. In order to get the hydrogen plasma, hydrogen gas streams will be heated by accelerators and then compressed by super magnets. Not many people at school know this, but I was an aviation electrician/mechanic in the Marine Corps, and one of my first licenses was my universal technician's certification to work with air conditioners. I'm telling you this because this nuclear reactor looks everything like an air conditioner to me:
See what I mean? The way that the reactor generates power is just like almost any other power plant, once the heat has been produced, by either process I mentioned before. The heat is used to turn water into steam which turns a generator. The simplicity of this design is beautiful.
I encourage you to research this on your own, and if you do, please comment below which method you favor. I like the magnetic confinement process, personally. The inertial confinement setup is much more complicated, and it takes 192 laser beams to work!
Also, click here to educate yourself about California's Renewable Energy Transmission Initiative (RETI)!
(P.S. happy belated birthday, Albert! 3.14)
Our textbook, An Introduction to Modern Astrophysics by Carroll and Ostlie, tells us that the likelihood of fusion depends on the kinetic energy of the collision. The peak from the graph below corresponds to the collision of two protons at the central temperature of the Sun and depends on a very narrow range of temperature of the gas and the charges and masses of the reactants involved. This makes fusion very difficult to achieve here on Earth...
Nevertheless, physicists are trying to find a way to convert water into deuterium and use it as fuel for controlled nuclear fusion. It seems impossible to even be able to originate nuclear fusion, let alone finding a way to control and then harness the staggering amount of energy it would create, and I don't like the fact that we would be using the most precious resource we have, but given our current energy crisis and the pursuit of cleaner, sustainable energy, it seems like at least a hopeful future candidate for a source of alternative fuel. On the plus side, the process isn't radioactive. Oh, and it isn't impossible. Click here to see how a 14-YEAR-OLD MADE A NUCLEAR FUSION REACTOR.
How a nuclear fusion reactor works: (according to howstuffworks.com)
In order to achieve the high temperatures and pressures needed for nuclear fusion, reactors will either use magnetic confinement, which uses electromagnetism to heat and compress hydrogen plasma (which is the process France's International Thermonuclear Experimental Reactor (ITER) will be using) or inertial confinement, which uses lasers or ion beams to do the same thing. In order to get the hydrogen plasma, hydrogen gas streams will be heated by accelerators and then compressed by super magnets. Not many people at school know this, but I was an aviation electrician/mechanic in the Marine Corps, and one of my first licenses was my universal technician's certification to work with air conditioners. I'm telling you this because this nuclear reactor looks everything like an air conditioner to me:
I encourage you to research this on your own, and if you do, please comment below which method you favor. I like the magnetic confinement process, personally. The inertial confinement setup is much more complicated, and it takes 192 laser beams to work!
Also, click here to educate yourself about California's Renewable Energy Transmission Initiative (RETI)!
(P.S. happy belated birthday, Albert! 3.14)
Class Summary
Very much of what we have discussed in class can be summed up in the Hertzsprung-Russell (H-R) diagram...
Some of the topics we discussed in class do not belong in the H-R diagram, but many do, and I will point them out along the way. We first discussed the celestial sphere, which is an inaccurate model, but useful nonetheless. It changes slowly enough that we can use it as a map and a calendar. (I find this an interesting, albeit rudimentary combination of space and time.) We also learned a bit of history; about other sets of orientations that astronomers use, such as the equatorial coordinates; and phenomena such as precession and the tilt of Earth's axis, which dictate which star is our "North star" and which season we are experiencing, and all of these concepts are fundamental to guide our observations.
However, measurements which appear on the H-R diagram such as the distances to and absolute magnitudes of stars cannot be obtained without celestial mechanics, which was the next chapter we covered. Kepler's laws of planetary motion, proper motion, Newton's laws, and stellar parallax gave us the tools we needed to make our first plots on the H-R diagram. Aristarchus was an astronomer in ancient Greece, and he was able to calculate the distance to the sun using geometry and solar parallax, but once we were able to understand the kinematics of our solar system, Christiaan Huygens and Giovanni Cassini were able to calculate the distance to the sun much more accurately using Venus, Mars, and stellar parallax. Since most stars are so far away, stellar parallax is extremely difficult to detect and was kind of a "missing link" for astronomers. For example, it provided proof that Earth moves and gave us a sort of measuring stick, but although its conceptual implications were vast, it was only marginally helpful to us mathematically. Even so, from the distance and apparent magnitude, the absolute magnitude of stars can be found, and the luminosity and size and mass may also be calculated using a bit of kinematics and studying binary systems as well.
Another breakthrough in being able to take measurements was the invention of quantum mechanics. Understanding blackbody radiation enabled us to add color and temperature to our H-R diagram! Kirchhoff's laws helped us to understand the temperature a little better, and they also helped us to understand the density of gases in and around stars. Stellar spectra gave us information about the composition, surface composition, temperature, and size of the stars, and even their radial velocities! Spectral series, absorption and emission features, the photoelectric effect, and equations from Maxwell, Boltzmann, and Saha gave us even more insight into the stars, and this information is represented on the H-R diagram by stellar classification (OBAFGKMLTY).
Radiative transport helped us to learn more about the energies, differential temperatures, optical depths, random walk paths, and opacities of stars, which actually gave us information about the stars' ionizations, cores, radiative and convective zones, and overall structures. Using these energies along with densities, competing pressures, and sizes of stars and conservation of mass, we were able to understand the composition even more intricately. Understanding how stars generate their power through fusion opened the door to understanding their life cycles, and their impressive temperature dependences are evident on the H-R diagram.
Finally, returning to the Virial theorem which we were introduced to in the first half of the quarter, we were able to explain how and why stars form. Using the initial mass function, the circle of life of stars can be traced on the H-R diagram. All true stars (those which generate their fuel through hydrogen fusion) begin their zero-age on the main sequence. Smaller stars "burn" their fuel at conservative rates, and it burns so uniformly and completely that they never develop a hydrogen shell and never become giants. Since they do lose some mass, they slide down the main sequence a little, and only leave once there is no longer any hydrogen fusion in their cores. Since they are not massive enough to ignite the helium they spent their lifetimes creating, they simply die unremarkable deaths. Medium mass stars and stars with greater mass experience much more eventful lives, and the crazier the shorter. These stars move all over the H-R diagram! Once the hydrogen in their cores is exhausted, the stars condense and may leave the main sequence. At this point, less massive stars experience a helium flash, and more massive stars become more degenerate. Then the triple alpha process takes over, which is the fusion of helium, and the stars move up and to the right on the H-R diagram. If the stars are massive enough, they will begin fusing carbon. The most massive stars will fuse all the way up to iron. Due to the Virial theorem, there will be thermal pulsing as the stars expand and contract, each time throwing off mass and energy. All the while, these stars are migrating around the H-R diagram. This is the general lifecycle for these types of stars, and depending on their masses, they will either become white dwarfs and settle down at the lower left corner of the H-R diagram, neutron stars, or black holes. Companion stars transfer their lost mass to each other and even go through multiple novas!
Using the initial mass function and the H-R diagram, we can get a good idea of the measurements we can't take directly or even indirectly. (Stars tend to be guilty by association.)
Of course, we also learned about telescopes and interferometry, exoplanets, and even global warming. The next step is to take what we've learned and apply it...on the final! (And in life.) Good luck, everyone, and don't forget to do your part to minimize your carbon foot print!
Some of the topics we discussed in class do not belong in the H-R diagram, but many do, and I will point them out along the way. We first discussed the celestial sphere, which is an inaccurate model, but useful nonetheless. It changes slowly enough that we can use it as a map and a calendar. (I find this an interesting, albeit rudimentary combination of space and time.) We also learned a bit of history; about other sets of orientations that astronomers use, such as the equatorial coordinates; and phenomena such as precession and the tilt of Earth's axis, which dictate which star is our "North star" and which season we are experiencing, and all of these concepts are fundamental to guide our observations.
However, measurements which appear on the H-R diagram such as the distances to and absolute magnitudes of stars cannot be obtained without celestial mechanics, which was the next chapter we covered. Kepler's laws of planetary motion, proper motion, Newton's laws, and stellar parallax gave us the tools we needed to make our first plots on the H-R diagram. Aristarchus was an astronomer in ancient Greece, and he was able to calculate the distance to the sun using geometry and solar parallax, but once we were able to understand the kinematics of our solar system, Christiaan Huygens and Giovanni Cassini were able to calculate the distance to the sun much more accurately using Venus, Mars, and stellar parallax. Since most stars are so far away, stellar parallax is extremely difficult to detect and was kind of a "missing link" for astronomers. For example, it provided proof that Earth moves and gave us a sort of measuring stick, but although its conceptual implications were vast, it was only marginally helpful to us mathematically. Even so, from the distance and apparent magnitude, the absolute magnitude of stars can be found, and the luminosity and size and mass may also be calculated using a bit of kinematics and studying binary systems as well.
Another breakthrough in being able to take measurements was the invention of quantum mechanics. Understanding blackbody radiation enabled us to add color and temperature to our H-R diagram! Kirchhoff's laws helped us to understand the temperature a little better, and they also helped us to understand the density of gases in and around stars. Stellar spectra gave us information about the composition, surface composition, temperature, and size of the stars, and even their radial velocities! Spectral series, absorption and emission features, the photoelectric effect, and equations from Maxwell, Boltzmann, and Saha gave us even more insight into the stars, and this information is represented on the H-R diagram by stellar classification (OBAFGKMLTY).
Radiative transport helped us to learn more about the energies, differential temperatures, optical depths, random walk paths, and opacities of stars, which actually gave us information about the stars' ionizations, cores, radiative and convective zones, and overall structures. Using these energies along with densities, competing pressures, and sizes of stars and conservation of mass, we were able to understand the composition even more intricately. Understanding how stars generate their power through fusion opened the door to understanding their life cycles, and their impressive temperature dependences are evident on the H-R diagram.
Finally, returning to the Virial theorem which we were introduced to in the first half of the quarter, we were able to explain how and why stars form. Using the initial mass function, the circle of life of stars can be traced on the H-R diagram. All true stars (those which generate their fuel through hydrogen fusion) begin their zero-age on the main sequence. Smaller stars "burn" their fuel at conservative rates, and it burns so uniformly and completely that they never develop a hydrogen shell and never become giants. Since they do lose some mass, they slide down the main sequence a little, and only leave once there is no longer any hydrogen fusion in their cores. Since they are not massive enough to ignite the helium they spent their lifetimes creating, they simply die unremarkable deaths. Medium mass stars and stars with greater mass experience much more eventful lives, and the crazier the shorter. These stars move all over the H-R diagram! Once the hydrogen in their cores is exhausted, the stars condense and may leave the main sequence. At this point, less massive stars experience a helium flash, and more massive stars become more degenerate. Then the triple alpha process takes over, which is the fusion of helium, and the stars move up and to the right on the H-R diagram. If the stars are massive enough, they will begin fusing carbon. The most massive stars will fuse all the way up to iron. Due to the Virial theorem, there will be thermal pulsing as the stars expand and contract, each time throwing off mass and energy. All the while, these stars are migrating around the H-R diagram. This is the general lifecycle for these types of stars, and depending on their masses, they will either become white dwarfs and settle down at the lower left corner of the H-R diagram, neutron stars, or black holes. Companion stars transfer their lost mass to each other and even go through multiple novas!
Using the initial mass function and the H-R diagram, we can get a good idea of the measurements we can't take directly or even indirectly. (Stars tend to be guilty by association.)
Of course, we also learned about telescopes and interferometry, exoplanets, and even global warming. The next step is to take what we've learned and apply it...on the final! (And in life.) Good luck, everyone, and don't forget to do your part to minimize your carbon foot print!
"We are from another generation of stars before the sun." -Professor Siana
10% of my final grade from Astronomy 1B. :)
(I don't know if I need to cite this, but I used my Astronomy 1A and 1B notes, homework, and test answers for some of this post.)
Thursday, March 14, 2013
The Ending Has Been Written
In case you were wondering about how it's all going to end, here's your "confirmation."
(See Entropy Statistics.)
(See Entropy Statistics.)
Saturday, March 9, 2013
My Sundial and My Compass
When I was in Qatar six or seven years ago, I bought this brass sundial/compass for my grandpa, because he was a Lieutenant Junior Grade in the Navy and drove a pt boat (pictured below) during World War II. He survived the war (mostly because it ended just as he arrived in Manila), but sadly, the reason I have this sundial is because he passed away a couple years ago, and my grandma returned it to me. Then she joined him in heaven only weeks after he passed. I'm very glad that I got to know my grandparents, and that I got to see them both and say goodbye before they left this earth. They were my moral compass when I was growing up, and I hope to pass on what I learned from them to my children and grandchildren. (I have so many pictures of both of my grandparents that I wanted to post, but I thought these two of my grandpa and his pt would be the most relevant for this post.)
selvbiografi
By the way, I wrote a book a few years ago.
I thought I'd post some excerpts from the book after writing about the harmony of our solar system...
The Conductor
He steps onto the floor unnoticed,
Pauses for a moment, then
With humble dignity he takes
His place on the great stage.
The orchestra is silent now,
Though moments gone they were bedlam,
And now so void of movement that
You hear him turn the page.
As though to his fingers attached
Are notes and treble clefs and staffs
The players keep their eyes on them
As every song is played.
Their sheets of music are useless
As he commands the tubas play
Yet picks out delicate notes and
Then sends them up the harpists' way.
Though he has only two hands and
One baton vice their multitude,
Each player knows exactly what
The conductor conveys.
And even in the audience,
And though his back is turned to you,
You feel his passion, though you can
Deny it, as you may.
(As a side note for coincidence's sake, Molchanov cast Jupiter as the role of conductor of this orchestra, and as a Sagittarius, Jupiter is my ruling planet. Also, this poem is found on page 23 of my book, and I was born on the 23rd of November. However, those are only coincidences. I wrote The Conductor for my brother, who shares a birthday with Galilei Galileo, and is therefore an Aquarius and ruled by Uranus.)
Wonder
The purest form of innocence
Explores the world wide-eyed
Bare-bottomed little child carefree
She has nothing to hide
Each new day brings discovery
The sky is limitless
What keeps it from cascading down?
Becomes a noble quest
If the answer cannot be found
A fable takes its place
While drifting clouds do fill her courts
Each presenting his case
Those Who Seek Still Find
I've looked for wisdom everywhere
To the ends of the Earth
Although my toes touched seawater
I continued my search
Tallest mountain overtaken
And oldest tree studied
I held my ear up to the wind
To hear who set it free
I've found something strong that was made
From something delicate
A rose, though fragile, produces
A most powerful scent
The terrible engulfing fire
Is honest though it burns
And many things in life are fair
Gravity works, Earth turns
My hunt led me to Orion
And I whispered to him
How close am I in my pursuit?
Can you see truth's footprints?
He met my query with silence
As I had known he would
A storyteller in the square
Did me a deal more good
"A thief approached a sleeping town
As did the dawning sun
The stranger forfeited the race
And so the morning won..."
"Sometimes," he told me, "we must learn
"Not just how far to go
"But also when we should give up
"It's important to know."
I still seek out wisdom today
But don't travel as far
It is not required of those
With a discerning heart
Solarium
How does the delicate clear glass
Support the universe,
And not the rigid beams of brass
Like seams, when pressured, burst?
A woman now knows the answer
To this simple question
But long ago a child entered
The great Solarium
"Who left you diamonds on the roof?"
She asked constellations
They had no voice, but spoke of truth
Found in Solariums
One day a sparrow hit a wall,
Wanting inside the room
The girl cried as she watched it fall
Death by Solarium
A kiss was sheltered from the wind
But not protected from
Two wounded wet eyes looking in
The bright Solarium
Beyond a secret garden hedge
Down an old statue comes
Not everything can be witnessed
Inside Solariums
Green plants do grow rather nicely
When someone sings to them
A nursery quite becoming
Of a Solarium
How many scholars studied there,
Where curious minds run?
A healthy knowledge fills the air
In the Solarium
And mirrored in the crystal plane
Captive her reflection
Old soul tonight with moon will wane
Goodbye Solarium
Musical Spheres
Fellow classmate and blogger The Mad Physi gave me a beautiful gift this quarter: a book called QUADRIVIUM.
This book is actually a collection of four ancient books, partly written during the time of Pythagorus, and have been studied by Cassiodonus, Philolaus, Timaeus, Archytus, Plato, Aristotle, Eudemus, Euclid, Cicero, Philo the Jew, Nichomachus, St. Clement of Alexandria, St. Origen, Plotinus, Dionysius the Areopagite, Bede, Alcuin, Al-Khwarizmi, Al-Kindi, Eriugena, Gerbert d'Aurillac, the Bretheren of Purity, Fulbert, Ibn Stina (Avicenna), Hugo of St. Victor, Bernardus Silvestris, Bernard of Clairvaux, Hildegard of Bingen, Alanus ab Insulis, Joachim of Fiore, Ibn Arabi, Grosseteste ("the great English scientist"), Roger Bacon, Thomas Aquinas, Dante, and Kepler. (Talk about name dropping.)
In Book IV, harmonics, scales, chord progression and more are discussed in the most fascinating way, with amazing visual representations of harmony through the use of a harmonograph (speaking of which, I am going to build one, and you can, too!) There is a section in this book entitled The Music of the Spheres, and the spheres it discusses are the planets of our solar system. I've heard of a more general concept like this before, more of a symphony of the entire universe, and I would like to share what the book had to say about "planets playing in tune" and some more recent developments on the subject...
As you may know, Kepler studied the motion of the planets. During his study, he wrote Harmoniae Mundi, or "harmony of the world," in which he compared the planets' angular velocities with harmonics. He set about calculating these harmonies based on the association previously given the seven known "planets" (including Earth's moon) with the seven musical notes. Below is a photo from the book showing the comparison between the ancient system and Kepler's interpretation.
The pentagons inscribed within the
(at the time this book was written) known orbits of Mercury and Venus and by Earth and Mars (pictured at right) are used in the book to prove the harmony of the worlds. Book II is all about geometry, and it was highly regarded during the time these books were written and studied; therefore, any explanation using geometry was not only a good argument, but it was actually regarded as being sacred.
The illustration below depicts two models which show how the planets were believed to orbit and sadly reveal a source of discord in the ancient sheet music...
Heavenly Harmony and Earthly Harmonics, a paper from the Quarterly Journal of the Royal Astronomical Society, tells us that the ancient Greeks, including Plato and Aristotle, believed in the "harmony of the spheres," and that the planets played music as they swept through space. Throughout the Middle Ages, this belief persisted, with the romanticized piety of notion that this music was the planets themselves praising God. In 1596, Kepler wrote Mysterium Cosmographicum, within a couple years after Shakespeare wrote about the "harmony of heaven" in The Merchant of Venice. In Mysterium, Kepler used simple geometry to provide a logical explanation for this accepted harmony. I assume this is the same geometry as I showed you earlier with the pentagons. However, although most of his calculations were astonishingly accurate, they were based on the assumptions that there were only six planets, as you saw in the inaccurate illustration of the motion of the planets.
Later work by less famous Molchanov cast Jupiter as the "conductor" of this orchestra, and included the entire solar system. His "commensurability" concept which uses linear equations of the planets' orbits and their frequencies to explain their resonance is much more accurate, and much more rigorous. Here are the linear equations of the frequencies, where m denotes frequency:
.
If you found this interesting, be sure to check out what my fellow classmate wrote about galactic geometry on her blog, The Mad Physi, and read what my other classmate wrote about the physics behind music in his blog, Up and Atom! Also, here is a video of a harmonograph in action!
In Book IV, harmonics, scales, chord progression and more are discussed in the most fascinating way, with amazing visual representations of harmony through the use of a harmonograph (speaking of which, I am going to build one, and you can, too!) There is a section in this book entitled The Music of the Spheres, and the spheres it discusses are the planets of our solar system. I've heard of a more general concept like this before, more of a symphony of the entire universe, and I would like to share what the book had to say about "planets playing in tune" and some more recent developments on the subject...
As you may know, Kepler studied the motion of the planets. During his study, he wrote Harmoniae Mundi, or "harmony of the world," in which he compared the planets' angular velocities with harmonics. He set about calculating these harmonies based on the association previously given the seven known "planets" (including Earth's moon) with the seven musical notes. Below is a photo from the book showing the comparison between the ancient system and Kepler's interpretation.
The pentagons inscribed within the
(at the time this book was written) known orbits of Mercury and Venus and by Earth and Mars (pictured at right) are used in the book to prove the harmony of the worlds. Book II is all about geometry, and it was highly regarded during the time these books were written and studied; therefore, any explanation using geometry was not only a good argument, but it was actually regarded as being sacred.
The illustration below depicts two models which show how the planets were believed to orbit and sadly reveal a source of discord in the ancient sheet music...
Heavenly Harmony and Earthly Harmonics, a paper from the Quarterly Journal of the Royal Astronomical Society, tells us that the ancient Greeks, including Plato and Aristotle, believed in the "harmony of the spheres," and that the planets played music as they swept through space. Throughout the Middle Ages, this belief persisted, with the romanticized piety of notion that this music was the planets themselves praising God. In 1596, Kepler wrote Mysterium Cosmographicum, within a couple years after Shakespeare wrote about the "harmony of heaven" in The Merchant of Venice. In Mysterium, Kepler used simple geometry to provide a logical explanation for this accepted harmony. I assume this is the same geometry as I showed you earlier with the pentagons. However, although most of his calculations were astonishingly accurate, they were based on the assumptions that there were only six planets, as you saw in the inaccurate illustration of the motion of the planets.
Later work by less famous Molchanov cast Jupiter as the "conductor" of this orchestra, and included the entire solar system. His "commensurability" concept which uses linear equations of the planets' orbits and their frequencies to explain their resonance is much more accurate, and much more rigorous. Here are the linear equations of the frequencies, where m denotes frequency:
In every case, he is off in his calculations by less than a percent, and his second equation gets replaced by
.
Also, not only do these equations work, there are also accurate equations for the planets' moons. Computer systems are currently being programmed and tested in order to better understand these resonances. These models have not found fault with the numerology of Molchanov, meaning that there really is a harmony to the solar system. The frequency ratios of arbitrary solar systems in these computer models 2, 9/4 to 7/3, and 5/2 are favored, and these are representative of our solar system.
However, there is also discord predicted in the symphony of all solar systems. Just as in a poorly engineered bridge, improper resonances lead to the destruction of weak celestial instruments: inadequately small masses and or playing out of "key" (with the wrong frequencies), according to the computer models. Smaller masses with unstable orbits will either be "swallowed up or smashed." (I imagine the cacophony of someone banging, disharmoniously, on the low keys of a piano at this moment.) Hopefully, this already happened in our solar system, or it won't affect us while we are living in this beautiful evolution of harmony.
If you found this interesting, be sure to check out what my fellow classmate wrote about galactic geometry on her blog, The Mad Physi, and read what my other classmate wrote about the physics behind music in his blog, Up and Atom! Also, here is a video of a harmonograph in action!
Sunday, March 3, 2013
Fiat Lux
Why can't we see past the sun's photosphere?
We learned in class that optical depth depends on the opacity of a gas, and that opacity is determined by energy, essentially, whether it be from bound-bound transitions of elements in atoms, bound-free or free-free absorption, or from electron scattering. Furthermore, we learned about thermodynamic equilibrium, specifically, local thermodynamic equilibrium (LTE) and the "random walk" that photons take on their journey to freedom. If the path of the average length of one of these little strolls is much shorter than the distance over which the temperature changes significantly, the photons experience LTE, meaning they will be quite comfortable and needn't dress in massless layers or bother bringing a massless coat. In fact, they needn't wear anything at all, for they won't even be seen. They will be traveling under the cloak of opacity. This occurs in the interior of stars where the temperature is so high that photons can get into their birthday suits without worrying about peeping tom's engaging in voyeurism due to the fact that all of the atoms will be ionized, and there will be no wavelengths which permit transparency from a bound-bound transition, for example. (As of now, scientists have not been able to disprove the fact that photons living inside stars have formed nudist colonies, and that they simply don't want to be seen.)
But at the photosphere, these jaybirds exchange their safe LTE, which only depends on single parameter temperature, for a more risqué set of conditions, which includes many more degrees of freedom and greatly increases their chances of being seen. According to Harvard's "Breakdown of Local Thermodynamic Equilibrium" by George W. Collins, II, Maxwell-Boltzmann statistics and the Saha-Boltzmann ionization-excitation are sufficient to describe the distribution of energy levels, and that these levels will be constant under LTE. However, Collins states that in the upper atmosphere of stars, the density is not enough to support LTE, and here we must use different equations to lure our little photon friends from their primitive way of life and get them to realize their full potential in the form of useful light. Okay, so I'm paraphrasing. However, Collins does discuss some of the "phenomena which produce departure from Local Thermodynamic Equilibrium": the principle of detailed balancing, interlocking, and collisional ionization and photoionization.
In detailed balancing, every process, such as absorption and emission, must be balanced, and the jumps in energy levels must also balanced. In the upper atmospheres of stars, the rate of energy emitted per wavelength through atomic collisions is not able to be represented by the Planck function, and since this is not possible under thermal equilibrium, the fact that these collisions are able to occur are evidence of a breakdown in LTE. The example Collins gives is when transition from the first to the third energy level is more favorable than a transition to the second energy level in a hypothetical atom which only has three energy levels, and the fact that the transitions back down to the second and first energy levels will not be balanced.
Interlocking is when two different absorption lines have the same upper energy level. To be honest, I barely understood detailed balancing, and interlocking is even more confusing to me. Basically, the same breakdown of LTE occurs when there is an imbalance of the cyclical processes as there was in detailed balancing, only in addition, strong lines which are formed under non-LTE conditions appear weaker because they share the highest energy level with weaker lines from inside the star. The example given was that red, singly ionized Calcium lines appear abnormally weak due to the photons given off by their interlocked lines. Also, to summarize both detailed balancing and interlocking, when there are more reactions among photons than there are of particles, there will be a breakdown of LTE. It makes sense that this would happen when there are comparatively less ions, since that means there will be less particles zipping about.
In the uppermost atmospheres of stars, there is still ionization occurring, through collisions and photoionization, although at a greatly reduced rate than that inside the star. And this is very interesting, but not all particles depart from LTE at the same temperature! But this makes sense. Remember that local thermodynamic equilibrium depends on the mean free path, and in a gas, different particles have different cross sections and number densities, therefore different mean free paths. Since electrons are the last particles to remain in thermodynamic equilibrium, when comparing collisions and photoionization, only at high temperatures and densities can there be more reactions among particles than among photons, so it only makes sense that at the cooler, less dense outer atmospheres of stars can photoionization dominate over collisional ionization. In conclusion, this is additional evidence of departure from LTE in the upper atmosphere of most stars.
Although scientists haven't been able to prove that photons aren't little nudists, I'm going to be bold and conjecture that they are not. I pretty much just added that bit to see if anyone was actually reading this.
We learned in class that optical depth depends on the opacity of a gas, and that opacity is determined by energy, essentially, whether it be from bound-bound transitions of elements in atoms, bound-free or free-free absorption, or from electron scattering. Furthermore, we learned about thermodynamic equilibrium, specifically, local thermodynamic equilibrium (LTE) and the "random walk" that photons take on their journey to freedom. If the path of the average length of one of these little strolls is much shorter than the distance over which the temperature changes significantly, the photons experience LTE, meaning they will be quite comfortable and needn't dress in massless layers or bother bringing a massless coat. In fact, they needn't wear anything at all, for they won't even be seen. They will be traveling under the cloak of opacity. This occurs in the interior of stars where the temperature is so high that photons can get into their birthday suits without worrying about peeping tom's engaging in voyeurism due to the fact that all of the atoms will be ionized, and there will be no wavelengths which permit transparency from a bound-bound transition, for example. (As of now, scientists have not been able to disprove the fact that photons living inside stars have formed nudist colonies, and that they simply don't want to be seen.)
But at the photosphere, these jaybirds exchange their safe LTE, which only depends on single parameter temperature, for a more risqué set of conditions, which includes many more degrees of freedom and greatly increases their chances of being seen. According to Harvard's "Breakdown of Local Thermodynamic Equilibrium" by George W. Collins, II, Maxwell-Boltzmann statistics and the Saha-Boltzmann ionization-excitation are sufficient to describe the distribution of energy levels, and that these levels will be constant under LTE. However, Collins states that in the upper atmosphere of stars, the density is not enough to support LTE, and here we must use different equations to lure our little photon friends from their primitive way of life and get them to realize their full potential in the form of useful light. Okay, so I'm paraphrasing. However, Collins does discuss some of the "phenomena which produce departure from Local Thermodynamic Equilibrium": the principle of detailed balancing, interlocking, and collisional ionization and photoionization.
In detailed balancing, every process, such as absorption and emission, must be balanced, and the jumps in energy levels must also balanced. In the upper atmospheres of stars, the rate of energy emitted per wavelength through atomic collisions is not able to be represented by the Planck function, and since this is not possible under thermal equilibrium, the fact that these collisions are able to occur are evidence of a breakdown in LTE. The example Collins gives is when transition from the first to the third energy level is more favorable than a transition to the second energy level in a hypothetical atom which only has three energy levels, and the fact that the transitions back down to the second and first energy levels will not be balanced.
Interlocking is when two different absorption lines have the same upper energy level. To be honest, I barely understood detailed balancing, and interlocking is even more confusing to me. Basically, the same breakdown of LTE occurs when there is an imbalance of the cyclical processes as there was in detailed balancing, only in addition, strong lines which are formed under non-LTE conditions appear weaker because they share the highest energy level with weaker lines from inside the star. The example given was that red, singly ionized Calcium lines appear abnormally weak due to the photons given off by their interlocked lines. Also, to summarize both detailed balancing and interlocking, when there are more reactions among photons than there are of particles, there will be a breakdown of LTE. It makes sense that this would happen when there are comparatively less ions, since that means there will be less particles zipping about.
In the uppermost atmospheres of stars, there is still ionization occurring, through collisions and photoionization, although at a greatly reduced rate than that inside the star. And this is very interesting, but not all particles depart from LTE at the same temperature! But this makes sense. Remember that local thermodynamic equilibrium depends on the mean free path, and in a gas, different particles have different cross sections and number densities, therefore different mean free paths. Since electrons are the last particles to remain in thermodynamic equilibrium, when comparing collisions and photoionization, only at high temperatures and densities can there be more reactions among particles than among photons, so it only makes sense that at the cooler, less dense outer atmospheres of stars can photoionization dominate over collisional ionization. In conclusion, this is additional evidence of departure from LTE in the upper atmosphere of most stars.
Although scientists haven't been able to prove that photons aren't little nudists, I'm going to be bold and conjecture that they are not. I pretty much just added that bit to see if anyone was actually reading this.
Sunday, February 24, 2013
Let's Get Weird
This post is more of a personal confession of weirdness than anything else. I do not expect to get any points for it.
There is a condition known as Autonomous Sensory Meridian Response (ASMR), and I won't bore you with the details, but it affects people in different ways, and it is triggered by various different stimuli. You can Google it, if you're interested. There is a rapidly growing ASMR community on YouTube that I am a part of, and tonight one of the ASMRers posted an amazing new video that I would like to share with you. I have been watching these types of videos for about five years now, even before they were calling it ASMR. I don't think I'm actually addicted, but I have been watching them every single night for a little over a year and a half, and I do watch them every single night, even if I go to bed really late. The only time I don't is if I don't have Internet where I am or my phone or Mac is dead, and I don't have a charger or something like that...
Anyway, like I said, this video was pretty good, and it has to do with space travel, so it is kind of relevant, even though it isn't very realistic. If you'd like to leave a comment, I'm interested in what you have to think about space travel in the future.
For the best experience, get into a comfortable position and use headphones when watching. This video has binaural audio, which means that wearing headphones will create a "3-D" effect. I hope you enjoy!
There is a condition known as Autonomous Sensory Meridian Response (ASMR), and I won't bore you with the details, but it affects people in different ways, and it is triggered by various different stimuli. You can Google it, if you're interested. There is a rapidly growing ASMR community on YouTube that I am a part of, and tonight one of the ASMRers posted an amazing new video that I would like to share with you. I have been watching these types of videos for about five years now, even before they were calling it ASMR. I don't think I'm actually addicted, but I have been watching them every single night for a little over a year and a half, and I do watch them every single night, even if I go to bed really late. The only time I don't is if I don't have Internet where I am or my phone or Mac is dead, and I don't have a charger or something like that...
Anyway, like I said, this video was pretty good, and it has to do with space travel, so it is kind of relevant, even though it isn't very realistic. If you'd like to leave a comment, I'm interested in what you have to think about space travel in the future.
For the best experience, get into a comfortable position and use headphones when watching. This video has binaural audio, which means that wearing headphones will create a "3-D" effect. I hope you enjoy!
Tuesday, February 19, 2013
Entropy Statistics
Last summer the Higgs Boson, the particle associated with the corresponding Higgs field, which is responsible for the fact that matter has mass, was found. Now, according to Yahoo!News, livescience.com, and Space.com, the Higgs may also be able to determine whether the universe will end in a "big crunch," a "big rip," a "big freeze," or at all. This debate has been going on for some time now, and one of the biggest problems trying to find the answer is that we do not yet understand dark energy. Fundamentally, we don't know why the universe is expanding, or why this expansion is so rapid. Apparently, from what physicists can understand, the fate of the universe depends upon the mass of the Higgs boson, which teeters on the critical mass which determines how stable the vacuum of empty space-time is. Joseph Lykken, a theoretical physicist at the Fermi National Accelerator Lab had this to say: "You won't actually see it, because it will come at you at the speed of light. So in that sense don't worry." I would like to add that you needn't worry at all, since this tentative event will not occur for billions of years, if it even happens at all. But for the sake of discussion, what do you think will happen?
Monday, February 18, 2013
Tropical Titan Tributaries
So another of my favorite astronomy topics is "planetary" geology, but I'm actually more interested in their "lunar" geology...
You may be wondering how there could be lakes on the moon and how they don't evaporate. The lakes are very shallow, and in some areas may only be ankle deep, so how are they getting recharged? Well, just as Earth has a water cycle of condensation, precipitation, and evaporation (and transpiration, which we can ignore in this analogy, since we don't know if there is life on Titan...yet), Titan has a similar Methane cycle. It also has a thick atmosphere, which may contribute to the lakes and makes the moon difficult to study. However, astronomers do not believe that the Methane cycle provides enough precipitation to supply these extremely large, albeit shallow, lakes, and postulate that "a likely supplier is an underground aquifer," according to Caitlin Griffith, a Cassini team associate. Here is a video from How the Universe Works on the Discovery Channel website explaining how Saturn's satellites may have formed. In the model, a methane comet smashed into one of Saturn's moons, which exploded and recombined into the current planets and rings. This may be the original source of the methane in these lakes.
Titan's lakes make it the only other celestial body besides Earth to have confirmed existence of liquid on its surface. Astronomers are trying to see if the Saturnian moon shares something else in common with terra firma: life. The life forms on Titan might inspire hydrogen and expire methane, similar to exotic anaerobic microbes found on Earth. The conditions on Titan are obviously different from those in which the thermophiles live in Earth's oceans, but this form of respiration is one of the possibilities that astrobiologists are considering.
I hope you found this post interesting, and if you are interested in learning more about Saturn and its moons, I suggest researching the controversial ice volcanoes and how Saturn's rings stay "replenished." Also, if you have any requests for me to blog about, please leave them in the comments section below.
Friday, February 15, 2013
This Just In!
About an hour ago in Russia, a meteor whizzed by, causing explosions, shattering windows, and injuring almost 1,000 people! Supposedly, it has nothing to do with tonight's asteroid. What else will happen today? Read the story here!
Thursday, February 14, 2013
Duck, but Don't Cover!
If you want to have a chance to see the asteroid that will be grazing overhead tomorrow night, this website might help. :P
Happy searching!
Happy searching!
Monday, February 11, 2013
Move Over, Rover
MAVEN, which stands for Mars Atmosphere and Volatile EvolutioN, will be the next mission to Mars and will study the atmosphere, according to ScienceDaily.
(I did not know what the word maven meant, so I looked it up at dictionary.com, which defines maven as a noun that means expert or connoisseur.)
Right now, MAVEN is being tested to ensure that it will be able to withstand the harsh conditions in space and on Mars. If everything goes according to plan, the "connoisseur" will be launching in November. MAVEN is going to be gathering data about the planet's possible past habitability. You can read more about Mave's poor turkeyless-Thanksgiving on the principal investigator's website, lasp.colorado.edu.
Now what the heck does habitability mean, and why would past habitability matter? To me, and I think the prof. would agree with me, "habitability" by the University of Colorado at Boulder's and many others' standards refers to habitability by Earthlings specifically, or at least Earthling-like creatures. If this is so, then would past habitability mean anything? Why does it matter if we find evidence that Earthlings (unlikely) or Earthling-like creatures used to live on Mars? And why research that? Is it so hard to believe that life forms on other planets wouldn't have different needs, and wouldn't that make all planets "habitable" by some life form or other?
Wait. Earth is habitable by Earthlings. But for how long? Maybe MAVEN can help us see into our own future and try to prevent a similar fate from happening to us. If Mave discovers that Mars used to be inhabitable by Earthlings, and if he (yes, I said he) can determine what caused it to become uninhabitable, those would be invaluable findings. And imagine, what if there had been Earthling-like creatures on Mars at one time? What if...?
Feel free to comment below what you think about the MAVEN mission and it's potential results.
(I did not know what the word maven meant, so I looked it up at dictionary.com, which defines maven as a noun that means expert or connoisseur.)
Right now, MAVEN is being tested to ensure that it will be able to withstand the harsh conditions in space and on Mars. If everything goes according to plan, the "connoisseur" will be launching in November. MAVEN is going to be gathering data about the planet's possible past habitability. You can read more about Mave's poor turkeyless-Thanksgiving on the principal investigator's website, lasp.colorado.edu.
Now what the heck does habitability mean, and why would past habitability matter? To me, and I think the prof. would agree with me, "habitability" by the University of Colorado at Boulder's and many others' standards refers to habitability by Earthlings specifically, or at least Earthling-like creatures. If this is so, then would past habitability mean anything? Why does it matter if we find evidence that Earthlings (unlikely) or Earthling-like creatures used to live on Mars? And why research that? Is it so hard to believe that life forms on other planets wouldn't have different needs, and wouldn't that make all planets "habitable" by some life form or other?
Wait. Earth is habitable by Earthlings. But for how long? Maybe MAVEN can help us see into our own future and try to prevent a similar fate from happening to us. If Mave discovers that Mars used to be inhabitable by Earthlings, and if he (yes, I said he) can determine what caused it to become uninhabitable, those would be invaluable findings. And imagine, what if there had been Earthling-like creatures on Mars at one time? What if...?
Feel free to comment below what you think about the MAVEN mission and it's potential results.
Friday, February 8, 2013
Telescopes...and Microscopes?
How did the constellations Telescopium and Microscopium get their names? (Careful. It isn't because you need a telescope to see one and a microscope to see the other...)
Astronomers may not use microscopes to look at the sky, but they have been using telescopes to look at it for centuries. Galileo Galilei didn't invent the telescope, but he was the first person known to point one towards the sky, and telescopes have come a long way since then.
For example, they are even able to "see" things that are "invisible." With the Chandra X-ray Observatory, we are able to detect black holes. The Chandresekhar limit separates stable white dwarfs from unstable ones which either collapse into neutron stars or black holes. Both contain extremely high energy, and since the Chandra telescope is used to observe these stellar remnants, it was named after the man who determined the Chandresekhar limit-Subrahmanyan Chandresekhar. After researching this telescope and Chandresekhar himself a little bit, I came to realize that the observatory was launched only four years after his death. It's sad to know he didn't live to see it.
The website chandra.harvard.edu had many wonderful things to say about Chandresekhar, and it has some pretty cool facts about the observatory, too. My two favorite facts from their website are that the space mission that launched Chandra was the first NASA shuttle mission commanded by a woman, and that Chandra can observe x-rays from particles up to the last second before they "disappear!"
I have a newfound admiration and respect for Chandresekhar after researching for this blog. After reading about his life and personality, he is definitely going on my list of people dead or alive with whom I would like to have dinner. I thought it would be nice to add a quote from him, and I really liked this one that I found: "Indeed, I would feel that an appreciation of the arts in a conscious, disciplined way might help one to do science better." I wonder what he meant by that.
Subrahmanyan Chandresekhar
19 October 1910 - 21 August 1995
There's two dates in time
That they'll carve on your stone
And everyone knows what they mean
What's more important
Is the time that is known
In the little dash there in between
-Garth Brooks
Thursday, January 31, 2013
asteroids and uranus
According to Fox News, next month (on my oldest brother's birthday), an asteroid half the size of a football field (about 50 m wide) is expected to come between Earth and the moon, and even under the orbit of GPS satellites! It is calculated to get within about 17,000 miles of the Earth, and may interfere with satellites and radar. And the article also had this to say:
Check out this link for more details.
In other news,
Telescope sees past clouds of gas and into depths of Uranus.
Amateur astronomers will have a shot at observation, too. The asteroid will get fairly bright as it approaches until it resembles a star of 8 magnitudes. Theoretically, that would make it an easy target for backyard telescopes but the problem is speed, explains Yeomans.I don't know how quickly this thing is going to be moving, but I have lots of practice tracking airplanes with my backyard telescope. Maybe I have a shot of seeing this sucker.
Check out this link for more details.
In other news,
Telescope sees past clouds of gas and into depths of Uranus.
Evan Ackerman reveals in this article that there's more to Uranus than a constant hovering cloud of methane. All it took was observing it with the Keck II telescope in the infrared spectrum to see what's really going on underneath all that smelly gas. I understand that you may have had aggrandized notions of Uranus in the past, but this news probably wrecked'em.
Wednesday, January 23, 2013
Extragalactic Astronomy
I went to Professor Siana's colloquium last week, and I decided to take notes so that I could write a blog about it. Hopefully I don't butcher this too badly...
Before the presentation, the title, Finding the Ultra-Faint Galaxies that Ionized the Universe already had me thinking. I remember learning about the ionization of the universe a few years ago, but I hadn't thought about it since.
The first slide showed the Andromeda Galaxy in the ultraviolet spectrum, and Professor Siana explained that we were able to study Andromeda very well, since it is our closest neighboring galaxy. But how are we able to study farther, older galaxies, especially since really old galaxies are thirty times smaller than they are now? And also, how did we go from being so tiny to the size that we are today? (I guess I'm using the galactic 'we', here...) And on top of all that, he explained that by measuring redshift, we can determine that galaxies also used to make more stars half a universe age ago. The three steps to this process are to first find galaxies at each epoch, then determine their luminosities over all wavelengths, which will yield their star formation rate, and finally add all of the galaxies. Simple, right? Well, not really, but you get the idea.
To categorize galaxies into epochs, their flux densities were plotted versus their observed wavelengths in angstroms. (Galaxies which are observed below a certain wavelength, also known as a "rigbert', spelling phonetically, are able to ionize hydrogen.) In the infrared, we lose data, since the galaxies are already "red" and shifting redder, specifically at the Lyman break, at around one-thousand angstroms. In the graph, redshift is denoted by the letter 'z' and breaks up and defines epochs. To give an idea of the z-scale, the absolute most distant galaxies observed are around ten.
The second step involves luminosity functions which convert luminosity to star formation density. Using these, it has been determined that at ten billion years ago there was a peak in star formation. One of the next slides asked, "How Low Can You Go?" and was referring to detecting faint galaxies and went on to explain their importance. We now know that there was a host of galaxies which provided gamma ray bursts which enriched the intergalactic medium with heavy elements as a function of time, and carbon was plentiful everywhere. When the universe was about a third of a million years old, it was ionized; on its one hundred-million-year birthday, it became neutral; and four hundred million years later, it became ionized again. What's up with that?
Maybe stars ionized it. The research shows that at z=7, everything was ionized. Because of this, were all galaxies free to roam? Sources of ionizing background don't cancel out the sinks. So we use gravitational lensing, which was theorized first and then detected and confirmed in 1919, to find some hiding galaxies indirectly. We got to see some pretty cool famous lensed galaxies on the next slide, such as CB58 from the nineties, the Cosmic Horseshoe, the Cosmic Eye, and even an app called GravLens HD, designed by Eli Rykoff, which could turn any image into a lensed "galaxy," and Professor Siana told us about how he got to do some spectra with Spitzer in 2008 on some aromatic hydrocarbons. Some of the pros of gravitational lensing are magnification and higher spacial resolution, and some of the cons are that we are constrained by the accuracy of the lens model, and that high magnification over large areas complicate mass profiles, like when dealing with galaxy clusters, for example. The last con presents a real problem. The newest deep field photo is of Abell A1689 (z=2), and is being taken of the greatest area with large magnification in a single pointing over 60 orbits of UV imaging using the Hubble telescope, which has produced half of the data so far. There are 30+ galaxies in the optical/near infrared from this imaging. We got to see a four orbit image (z=2) using color selection, by his own grad student Alavi. There's a lot of star formation we've been missing due to dust obscuration, which scatters blue light, and we must correct for how "red" a galaxy "looks," and we need to know the spectral slope. The new information from this deep imaging is giving us this data.
Future work: Professor Siana and will work on Deep Keck Spectroscopy to observe rest wavelengths, gas inflow and outflow, hot gas explodes out of young dward galaxies, circumgalactic medium, ionizing photon escape fraction, ionizing radiation which must escape galaxies Fesc>0.2, photoionization cross sections, and gas opaque at NHI>2E+17cm-2. He's also going to be looking for a massive amount of gas to condense and cool and then get the heck out of the way!
My favorite quote from the presentation is: "The UV escape fraction remains problematic." -X Fan (I guess he's not a fan anymore.)
Anyway, I did not fully understand everything that was presented in the talk, but I feel like I understood it better than I was able to explain it. If anyone else who went to the colloquium wants to add anything, or if there are any corrections to be made, please let me know!
Before the presentation, the title, Finding the Ultra-Faint Galaxies that Ionized the Universe already had me thinking. I remember learning about the ionization of the universe a few years ago, but I hadn't thought about it since.
The first slide showed the Andromeda Galaxy in the ultraviolet spectrum, and Professor Siana explained that we were able to study Andromeda very well, since it is our closest neighboring galaxy. But how are we able to study farther, older galaxies, especially since really old galaxies are thirty times smaller than they are now? And also, how did we go from being so tiny to the size that we are today? (I guess I'm using the galactic 'we', here...) And on top of all that, he explained that by measuring redshift, we can determine that galaxies also used to make more stars half a universe age ago. The three steps to this process are to first find galaxies at each epoch, then determine their luminosities over all wavelengths, which will yield their star formation rate, and finally add all of the galaxies. Simple, right? Well, not really, but you get the idea.
To categorize galaxies into epochs, their flux densities were plotted versus their observed wavelengths in angstroms. (Galaxies which are observed below a certain wavelength, also known as a "rigbert', spelling phonetically, are able to ionize hydrogen.) In the infrared, we lose data, since the galaxies are already "red" and shifting redder, specifically at the Lyman break, at around one-thousand angstroms. In the graph, redshift is denoted by the letter 'z' and breaks up and defines epochs. To give an idea of the z-scale, the absolute most distant galaxies observed are around ten.
The second step involves luminosity functions which convert luminosity to star formation density. Using these, it has been determined that at ten billion years ago there was a peak in star formation. One of the next slides asked, "How Low Can You Go?" and was referring to detecting faint galaxies and went on to explain their importance. We now know that there was a host of galaxies which provided gamma ray bursts which enriched the intergalactic medium with heavy elements as a function of time, and carbon was plentiful everywhere. When the universe was about a third of a million years old, it was ionized; on its one hundred-million-year birthday, it became neutral; and four hundred million years later, it became ionized again. What's up with that?
Maybe stars ionized it. The research shows that at z=7, everything was ionized. Because of this, were all galaxies free to roam? Sources of ionizing background don't cancel out the sinks. So we use gravitational lensing, which was theorized first and then detected and confirmed in 1919, to find some hiding galaxies indirectly. We got to see some pretty cool famous lensed galaxies on the next slide, such as CB58 from the nineties, the Cosmic Horseshoe, the Cosmic Eye, and even an app called GravLens HD, designed by Eli Rykoff, which could turn any image into a lensed "galaxy," and Professor Siana told us about how he got to do some spectra with Spitzer in 2008 on some aromatic hydrocarbons. Some of the pros of gravitational lensing are magnification and higher spacial resolution, and some of the cons are that we are constrained by the accuracy of the lens model, and that high magnification over large areas complicate mass profiles, like when dealing with galaxy clusters, for example. The last con presents a real problem. The newest deep field photo is of Abell A1689 (z=2), and is being taken of the greatest area with large magnification in a single pointing over 60 orbits of UV imaging using the Hubble telescope, which has produced half of the data so far. There are 30+ galaxies in the optical/near infrared from this imaging. We got to see a four orbit image (z=2) using color selection, by his own grad student Alavi. There's a lot of star formation we've been missing due to dust obscuration, which scatters blue light, and we must correct for how "red" a galaxy "looks," and we need to know the spectral slope. The new information from this deep imaging is giving us this data.
Future work: Professor Siana and will work on Deep Keck Spectroscopy to observe rest wavelengths, gas inflow and outflow, hot gas explodes out of young dward galaxies, circumgalactic medium, ionizing photon escape fraction, ionizing radiation which must escape galaxies Fesc>0.2, photoionization cross sections, and gas opaque at NHI>2E+17cm-2. He's also going to be looking for a massive amount of gas to condense and cool and then get the heck out of the way!
My favorite quote from the presentation is: "The UV escape fraction remains problematic." -X Fan (I guess he's not a fan anymore.)
Anyway, I did not fully understand everything that was presented in the talk, but I feel like I understood it better than I was able to explain it. If anyone else who went to the colloquium wants to add anything, or if there are any corrections to be made, please let me know!
Monday, January 14, 2013
What do I think an astronomer does?
I know there are many different kinds of astronomers, and for every kind of astronomer there is a multitude of varying jobs he or she can have. Some astronomers study planets, and some study black holes, while still others study dust. They all observe the universe, although some are interested in "looking at" it through different wavelengths than others. Some are interested in biology and others in geology. I think it's a safe bet to say that they all have to use at least some indirect methods to get their data. Although some astronomers get data from satellite telescopes and rovers, and others even travel to outer space themselves, there are some things that just cannot be observed directly. And this brings me to what astronomers do in general; they work to understand the "final frontier" of space, one of the biggest mysteries known to man, and it takes ingenuity. Some may use this information to search for life outside of Earth, and some seek answers about the beginning of time.
If I become an astronomer, I would like to study "star birth" (I really like that term), the sun's magnetic cycle, or planetary geology. It's very selfish of me, though. I have no reason to want to study these things other than to satisfy my own curiosity. Sometimes I worry that it will be too difficult to get a job as an astronomer, but mostly I just feel guilty that I am not pursuing a career that will contribute to society in a more direct way, especially during hard times for my country. I dream of all the adventures I could have exploring other worlds, but in the back of my mind, I wish there was a more noble cause for astronomy. I truly love astronomy, yet I find it is more difficult to justify studying astronomy than to recount all that is done in it's name.
If I become an astronomer, I would like to study "star birth" (I really like that term), the sun's magnetic cycle, or planetary geology. It's very selfish of me, though. I have no reason to want to study these things other than to satisfy my own curiosity. Sometimes I worry that it will be too difficult to get a job as an astronomer, but mostly I just feel guilty that I am not pursuing a career that will contribute to society in a more direct way, especially during hard times for my country. I dream of all the adventures I could have exploring other worlds, but in the back of my mind, I wish there was a more noble cause for astronomy. I truly love astronomy, yet I find it is more difficult to justify studying astronomy than to recount all that is done in it's name.
Sunday, January 13, 2013
Safely observe solar activity
Some solar activity can be observed using a pinhole projector, and I will explain how to make one in this post. It is important to note that a pinhole projector lacks great resolution, and therefore cannot be used to observe certain phenomena. Again, never look directly at the sun.
Shoe boxes or tubes are typically used when making a pinhole projector. I used a shoebox because it allows easy access while constructing the pinhole. Keep in mind that the further the light travels through the hole to the backdrop, the larger the image will be, but if the box or tube is too long, the image might be too blurry.
On one END of the box or tube, cut out a small square, and tape a slightly larger piece of aluminum foil over the hole, making sure to seal any gaps with opaque tape. Then poke a tiny pinhole through the foil. Near the other end of the box on the SIDE, cut out a viewing hole. (Make sure you do not cut a hole in the other END of the box.) And, of course, put the lid back on if using a shoebox. You can seal the lid as well, if you like.
While using your pinhole projector, be careful not to look at the sun! In order to align your projector, simply face your shadow and point the pinhole side of the box or tube in the general direction of the sun over your shoulder. Use the shadow of the projector to line it up with the sun and then look inside your viewing hole at the image of the sun!
My boyfriend took this picture through the viewing hole of my projector during a solar eclipse last spring.
As you can see, there are two images of the solar eclipse being projected. Why do you think that is?
I have heard that this method can be used to view sunspots, but I don't believe that is possible. During the Venus transit last year, I was not able to view it using my pinhole projector, because the shadow cast by Venus was much too small. However, there is another popular technique that supposedly works. Using solar filters on binoculars, you can project the image of the sun onto a white background, but be careful! Paper and other materials can catch on fire if you do this for too long! Of course, never look directly at the sun. ScienceDaily.com recommends: "To help block out extra sunlight, cut holes in card stock and fit it over the lenses." Spotting Sun Spots
Also, if you have a telescope and a solar filter, you can view sunspots directly or project the image onto white computer paper, and if you really want to be fancy, you can build a sun funnel!
Michael A. Seeds' Foundations of Astronomy tells us that sunspots are evidence of the sun's great magnetic fields. Like Earth, the sun has north and south magnetic poles, and like Earth, the sun's poles switch. However, while Earth's polar flips seem to be sporadic, the sun has an 11-year "magnetic cycle" in which the poles reverse their magnetic direction. There are a few models which try to explain the sunspot cycle, but we still do not know why this magnetic activity occurs. The magnetic activity of the sun is extremely interesting to me. Let me know if you would like to hear more about it.
I have yet to try observing sunspots, but if you have or try it out, let me know what you did and your results!
Shoe boxes or tubes are typically used when making a pinhole projector. I used a shoebox because it allows easy access while constructing the pinhole. Keep in mind that the further the light travels through the hole to the backdrop, the larger the image will be, but if the box or tube is too long, the image might be too blurry.
On one END of the box or tube, cut out a small square, and tape a slightly larger piece of aluminum foil over the hole, making sure to seal any gaps with opaque tape. Then poke a tiny pinhole through the foil. Near the other end of the box on the SIDE, cut out a viewing hole. (Make sure you do not cut a hole in the other END of the box.) And, of course, put the lid back on if using a shoebox. You can seal the lid as well, if you like.
While using your pinhole projector, be careful not to look at the sun! In order to align your projector, simply face your shadow and point the pinhole side of the box or tube in the general direction of the sun over your shoulder. Use the shadow of the projector to line it up with the sun and then look inside your viewing hole at the image of the sun!
My boyfriend took this picture through the viewing hole of my projector during a solar eclipse last spring.
I have heard that this method can be used to view sunspots, but I don't believe that is possible. During the Venus transit last year, I was not able to view it using my pinhole projector, because the shadow cast by Venus was much too small. However, there is another popular technique that supposedly works. Using solar filters on binoculars, you can project the image of the sun onto a white background, but be careful! Paper and other materials can catch on fire if you do this for too long! Of course, never look directly at the sun. ScienceDaily.com recommends: "To help block out extra sunlight, cut holes in card stock and fit it over the lenses." Spotting Sun Spots
Also, if you have a telescope and a solar filter, you can view sunspots directly or project the image onto white computer paper, and if you really want to be fancy, you can build a sun funnel!
Michael A. Seeds' Foundations of Astronomy tells us that sunspots are evidence of the sun's great magnetic fields. Like Earth, the sun has north and south magnetic poles, and like Earth, the sun's poles switch. However, while Earth's polar flips seem to be sporadic, the sun has an 11-year "magnetic cycle" in which the poles reverse their magnetic direction. There are a few models which try to explain the sunspot cycle, but we still do not know why this magnetic activity occurs. The magnetic activity of the sun is extremely interesting to me. Let me know if you would like to hear more about it.
I have yet to try observing sunspots, but if you have or try it out, let me know what you did and your results!
Thursday, January 10, 2013
Rain Check
Sorry. I'm frantically trying to finish some homework. I'll have to post the stuff I promised another day.
Wednesday, January 9, 2013
AU
Michael A. Seeds defines an astronomical unit (AU) in his book Foundations of Astronomy as "the average distance from Earth to the sun; 1.5 x 10^8 km, or 93 x 10^6 miles." If you divide this distance by the speed of light, you find that it takes approximately eight minutes for light to reach us from the sun.
In the background picture of my blog, I am looking at the sun through my telescope during the last Venus transit of our lifetimes. The next one won't be until 11 Dec 2117! (www.transitofvenus.org)
I used a filter, of course. Never look directly at the sun.
Here are some photos from the Venus transit, 06 Jun 2012:
It was very difficult to take a picture of the Venus transit through the telescope, but my boyfriend did it! Can you see that tiny black dot on the sun? That's Venus! The transit of Venus can be used to determine how far away from the sun we are, also known as an AU. (Seeds)
Here are two other safe ways to observe the sun. There are special glasses that are made for looking at the sun, and special instruments that project the sun onto a white surface. The dark dot on this surface is the shadow cast by Venus.
Tomorrow I will show you how to make a pinhole projector to safely observe a solar eclipse and also how to observe sun spots and what they are.
Tuesday, January 8, 2013
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