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:

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.

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!

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.

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!

Rain Check

Sorry. I'm frantically trying to finish some homework. I'll have to post the stuff I promised another day.

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.

Get it?

Anyone...?