This one is intended to give a brief background of Astronomy.
I will ask 10 basic questions about Astronomy, then do my best to find the answers to those questions in the title Principles of Astronomy by Stanley P. Wyatt.
1. The first and most basic question one might want to start with is... What exactly IS Astronomy?
Wyatt describes: "The province of astronomy stretches from here, the surface of our home planet, outward to the most remote celestial objects that can be detected by present-day optical and radio telescopes."
Interesting. So basically he describes it as the study of, well, EVERYTHING. Maybe it's not quite that broad, but it does include stars, galaxies, moons, planets, black holes, and most importantly how they are observed.
2. What do Astronomers actually do?
"The business of the astronomer, like that of any scientist, is both observational and interpretive. He has eyes, and he has instruments, that extend his sight in many ways and provide him with enormously more information than can be learned by eyesight alone."
He also goes on to explain that they are not just information "collectors." Astronomers strive to put reason to the discoveries they make. Like any old scientist they are not simply satisfied with just the "what" they want to find out the "how" and "why" and "when." They yearn to learn (yes that rhymed) why things in the outer portions of the universe behave the way they do.
3. What tools do Astronomers use?
Of course astronomers use telescopes, computers, spacecrafts, and cameras. And besides spacecrafts and maybe telescopes I'm sure everyone here knows and understands how to use the other two. But other tools ESSENTIAL to expansion of astronomical knowledge are mathematics, physics, and other sciences. These tools help astronomers calculate how far away certain stars are, how fast the speed of light is, and tons of other things.
4. So what does any of this have to do with us?
"Because [the Earth's] surface is the habitat where we live, dream, and think, the earth is the astronomical body we know most about."
Wyatt is saying that things like time of day and weather are incorporated with astronomy. If we didn't have astronomy we could tell you that it is 78.6 degrees Fahrenheit outside, but we would not be able to tell you why. We understand why there are seasons too... Because of the way Earth orbits the Sun.
5. What are some of Earth's basic characteristics?
Well, first off, Earth is not an exact sphere as some might think. It is an oblate spheroid. because the earth spins so fast, it changes shape a little bit, and flattens at the poles ever so slightly. Earth's terrain also varies by about 12 miles from Mount Everest to the Mariana trench. The Earth is still extremely smooth, though, in comparison to its size. My 11th grade physics teacher actually told me that if you shrunk the earth down to the size of a Billiard's cue ball, it would be MUCH smoother.
6. How does astronomy help with things like voyages to the moon?
Trips to the moon, mars, and other places in the solar system have been made much easier with the study of astronomy. Scientists and Physicists had to calculate how much force one needs to "lift" a shuttle into outer space. They also must calculate at what angle to re-enter earth's atmosphere, and how fast to do so. A lot of these calculations must account for the gravitational pull of the earth. Space missions are much safer today with the findings of astronomers.
7. How can we find out how old a star is?
Wyatt states that the life of every star is finite. Meaning no star will last forever. So how do we know how long these bright balls of extremely hot gases have been around? Without getting TOO much into the math behind all of this, well say that Einstein's formula (E=mc^2) is used to tell us that a star radiating energy is losing mass. And that the rate of loss of mass is proportional to the luminosity of the star. That is the basic understanding of how it is calculated, we may get into the actual math on a later post if I feel like it.
8. How are stars born?
"Each kind of star spends a minor part of its luminous life in gravitational contraction, then at age zero begins the much longer interval of hydrogen-burning, and finally there follows a shorter time of evolution."
In easier terms: there is a dense, hot cloud of gas... somewhere out in the galaxy. This cloud of gas starts to collapse and a hot core begins to form. Thus the birth of a star. A little confusing, I know. We still know only a tiny bit of how stars actually form so this answer can be a little vague at times. Maybe this is something I can study and expand our knowledge of.
9. Okay, we know the basics of how they are formed. Now how do stars die?
A star can explode its entire mass outward at such a speed that all its atoms escape their bonds.
OR
A stars nuclear and gravitational energy are completely used up, and because it can no longer radiate, it becomes a dense black sphere.
Again it is not something we can observe up close, or make realistic experiments for, so it is hard to make some astronomical information clear.
10. Is our galaxy contracting or expanding?
I stumbled upon this question as I was reading through the text. I had never thought anything in the universe we know would contract. I've always been told that it is getting infinitely LARGER. Let's see what Wyatt has to say...
"If the galaxy were growing in size, the average Doppler shift in stellar spectra would be to the red." Conversely, the shift is blue if stars were coming together. "There is at present no clear-cut evidence that the average radial velocity of the stars is other than zero."
He basically says that since we don't see stars shifting away or towards us, the galaxy is neither contracting nor expanding.
For now, at least.
Works Cited
Wyatt, Stanley P. Principles of Astonomy. Boston: Allyn and Bacon, 1964. Print.
