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.

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

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)

Class Summary

Very much of what we have discussed in class can be summed up in the Hertzsprung-Russell (H-R) diagram...

Copyright Addison Wesley

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.)

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.)

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