Thursday, April 16, 2009

Determining Cosmic Distances

So I got my first astronomy question! Thanks pitrowski89 for asking!

He asked: How do Astronomers know how far away the farthest galaxy is?

I'll try my best to answer the question.

The truth is they don't have an exact estimate on how far away the galaxies are because of how extremely far away they are. This only becomes more difficult when astronomers start to view galaxies on the edge of the universe. Since our universe is expanding and is so incredibly large any galaxy viewed on the edge of our universe would be almost as old as the universe itself. However, with the use of powerful telescopes and computers capable of performing immense mathematical calculations (for instance general relativity) they have come up with a pretty good idea of how far away the farthest galaxies are. This is mainly through the technique of measuring a galaxy's red shift in the light spectrum, or how fast it is moving away from us.

Closer galaxies are a bit easier to determine the distance to. There are many techniques astronomers have used to measure these distances and most of them give us accurate and proven answers. The most popular way for measuring any cosmic distance is by first finding the distance to nearby stars. Stars are easy to find the distance to because they can tell the size and brightness of a star by its color (an indication of how hot it is). The measurement of a star's brightness is called its magnitude. The brighter the object, the lower its magnitude (the Sun appears to us on Earth as -26.73). Since we are on Earth we can easily measure how bright a star's magnitude appears to us. This is called the apparent magnitude. The problem with this is that a really big, hot star that is far away might appear to have the same magnitude as a relatively normal star that is closer to us. For this reason there is also absolute magnitude, or a measure of how bright a star would be if viewed from one light year away (the Sun is actually -4.83). Like mentioned earlier, the color of the star is then used to determine how bright the star should be. Knowing both how bright a star appears, and how bright it would be if viewed from a standard distance, astronomers can then figure out how far away the star is.

The problem with galaxies is that they are much to big to be given an absolute magnitude. For this reason astronomers need to use different techniques to find out how far away galaxies are. There are tons of methods that have proven to be successful in helping us determine these distances. Here are most of them:

One of the most popular and proven methods for determining the distance to galaxies is actually based on the same principal as the one used for finding stars. There are some kinds of stars that don't have a standard brightness, they fluctuate. These stars are called variable stars. Though there are several different types of variable stars, only one of them, Cepheid variable stars, change brightness on regular intervals. Because Cepheid variable stars are very large stars (5-20 times bigger than the Sun) they are luminous enough to be seen in other galaxies, with the use of a powerful telescope that is. Since all Cepheid variable stars are about the same temperature, the only determinant left in how far away it is based on how big the star is. This is determined by measuring how long the variation in brightness is of the star. The longer the period, the larger the Cepheid variable star. And voila! The distance to the questioned galaxy can be determined.

Unfortunately, the farthest galaxies from us are so faint that we cannot see any individual stars in them. Sometimes we get lucky and a supernova of a star occurs (the brightest event known) which can shed some light on a galaxy's distance. Unfortunately, like I mentioned in the beginning, the galaxy is expanding. Anything we see now is what happened billions of years ago. How far away those galaxies are now is totally left up to theory. The current estimate is about 13 billion light years away or about 80,000,000,000,000,000,000,000 miles! Because this galaxy is so far away, on the edge of the universe per se, it is almost as old as the universe itself. This galaxy would be one of the first things created after the Big Bang.

If you have any questions about anything I have said feel free to ask! I tried to be as simple in explaining the question as possible. If you don't understand something I have said and want clarification I'd be happy to help you. My ability to explain this stuff in a logical fashion could make or break my decision to become an Astronomy teacher. :-D


Monday, April 13, 2009

Beginner Stargazing Tips

Hey there!
Since I will be posting quite a bit about astronomy and stargazing I just wanted to give some advice for all those that are new and interested in this fascinating hobby. Stargazing is such an easy and inexpensive way to spend a night or add a little more excitement to an evening walk.

1.) The first thing you need in order to start stargazing is a place to do it at. The first place you should consider is your backyard, since it is the closest. Though mine is not very good for viewing, the backyard is often the best place to start.
Since I live in a crowded city area (Chicago), there is a lot of light pollution and smog. The best and really the only way to get around this obstacle is to try and get as far away from it as possible. I frequently try to venture about 20 miles away because that's all my gas budget allows, but the further you can get away the better. It's amazing the difference can make in your ability to see the stars and planets just by simply finding the darkest place possible. If you are not capable, or do not have the time to get away from the lights, try going to the darkest place near you. I frequently go to Springrock Park, in Western Springs because it has enough trees and obstacles (trees and such) to block the light for a small improvement in viewing. It's also open til 11pm.

2.) If you do go somewhere else to view the sky make sure you are allowed to be there and know its time schedule. My friends and I have been driven away from stargazing by the cops on numerous occasions and have become a lot more aware of what the limitations are in each place we view at. It can be difficult to find these places, especially here in the suburbs, so if you feel the need to, call your local town hall or other local government office and find out the time schedules for area parks and what not.

3.) Make sure you dress appropriately! Even in the summer time the temperature is much cooler at night. You should always prepare yourself for the possibility that you will get cold. Star-gazing often requires or causes you to sit still for long periods of time, this will cause you to get chilly.

4.) The best viewing tool any astronomer has is their eyes. While binoculars and telescopes are a ton of fun, they are not necessary for viewing most objects. Your eyes allow you to view a much larger field of view and don't require any of the tampering and hassle that telescopes and binoculars do.

5.) Your peripheral vision is a lot better at catching light than the center of your gaze. If you are having difficulty looking at one particular star, cluster, or planet allow your gaze to wander just a little bit off target. You'll be amazed to find that you can see a lot better this way. You can begin to see the different colors of stars and planets as well!

6.) If you want the best viewing experience you need to let your eyes adjust to the darkness. About 20 minutes will do! If you feel you need a flashlight for light, try covering the end of it with red paper or cellophane since red light effects the eyes less than white light.

7.) The best nights to view the sky are nights right after it has rained. Rain washes a lot of pollutants out of the air and and as such makes for much clearer skies.

8.) Though the Moon is a great thing to look at in itself, it is also the worst thing to have when you want to view anything else. Since the moon is so bright, one should try stargazing on nights when the moon isn't around or when it is at a phase where it isn't so bright.

9.) An easy way to at least get a general idea of where things are located in the sky is to know where the North Star (Polaris) is. The easiest way to find this is to be able to find the Big Dipper. If you know where the Big Dipper is you can follow the two stars on the outer edge of the "dipper" part of the Big Dipper. Using an imaginary line drawn through the two stars, you are pointed directly to the North Star, which happens to be the at the tip of the Little Dipper and the brightest star in it. If you need a better idea of this just follow this link.

I hope you enjoy yourselves and what you can see with just these basic tips in mind. If you have any questions about anything I have said or any questions about how you can get into astronomy or stargazing feel free to ask me; I would love to help.


Wednesday, April 8, 2009

Astronomy Post: Ask me anything to help get this blog rolling!

Though anyone who knows me well already knows this, I just feel the need to explain to anyone who doesn't that I am quite passionate about astronomy. Fact: I'm a closet nerd. Since astronomy is a big hobby of mine and a possible candidate for a future career (high school astronomy teacher), I think I am going to start blogging a bit about the topic of astronomy.

I will try to post anything interesting that is going to occur, like meteor showers, eclipses, etc. so that those not as obsessed with astronomy as myself, could perhaps see something interesting.

For starters I'd be happy to talk about or answer any questions that you might have about astronomy or space? I can explain most anything about basic star viewing techniques/telescopes, constellations, black holes, planets, stars, or weird theories that many people could care less about. I have the new starry night software on my laptop and would be happy to use it to answer any questions I cannot answer off of the top of my head. :)


First Post

So this is my first post.........Sweet! I'm currently sitting in the College of DuPage library, sipping on a 24oz cup of 7-11 coffee, reading the Chicago Tribune Online. I keep losing focus and have started to surf the web. Here's what I looked at:

My car is older than me. I've driven or been driven around my entire life in my car. I drive a 1987 Volvo 240 station wagon, a tank, through and through. Sure it's in great shape, not a spot of rust...but it's radio doesn't work unless it's raining or a pig flies by. A friend of mine calls it Vinnie because it sounds like a name an old man would have. And that's what it is an old even creaks and pops when you start it in the morning. Needless to say...I want a new car but I can't afford one...I frequently fantasize about having a new car...nothing ridiculous or outlandish...but a cheap, fuel-efficient car that I could buy, and pay gas on, for cheap.,0,6871221.story

This is an article I am writing a brief report on for my Sociology class. It scares the crap out of me because I ran at least 2 yellow lights on my way to school this morning. Sociologically this new "service" creates jobs, stops law violators, and boosts local revenues from issued tickets. But seriously...I've never got a ticket and I've occasionally made traffic violations when no one was looking, give me a break!