Thread: A Few Questions...

Hi, I have a few questions for you guys (I'm studying for a test right now on Astronomy).

1) What is the only thing that is different among all types of electromagnetic radiation?

2) What is a spectroscope? What does it do?

3) What elements are in stars?

4) How are stars different?

5) What are the two key factors when determining a stars luminosity?

6) In what stage do most stars spend their lives?

7) What are perihelion and aphelion?

8) What are circumpolar constellations?

Wikipedia. You'll get answers to all your questions there and you can follow the citations for more in-depth insight. Also, Google is your friend (as well as your textbook).

I am saying the above, because we are not really in the business of doing people's homework (which, I think, studying for a test includes) for them, unless the student can show that he has already made an attempt and are stuck or need some clarification on a few points. If this is the case, there are quite a few members that would be more than willing to help. :wink:

It is done in this way, because by far the best way to learn is to figure the answers out by yourself. We will gladly nudge you towards your answers if you had made an attempt to do this.

So: Have you been studying and are stuck on a few specific points not provided by your textbook?

Yep, pretty much. I'm pretty sure that electromagnetic radiation are differed by frequency and wave lengthm but I'm not sure. We don't really use our textbook too much (only for 1 or 2 topics of the many). We have one main powerpoint but a lot of that isn't included. Pretty much we learned everything in a planetarium (for most of our unit we were in there) so a lot of stuff we just needed to know from our heads.

Spectroscopes aren't mentioned, we just discussed them in class.

I know there's gas in stars, but i'm not sure what else.

I'm not sure about how stars are different.

For stars luminosity - I know apparent magnitude and absolute magnitude, is that it?

For the stage stars spend most of their lives in - Main Sequence?

Perihelion and Aphelion - no idea

Circumpolar Constellations -I know it's the little dipper, big dipper, and 3 other main ones, but not sure exactly what they are.

There are about 40 different things on our review sheet, and those are the ones I do not know.

Originally Posted by marcut

Hi, I have a few questions for you guys (I'm studying for a test right now on Astronomy).

4) How are stars different?

5) What are the two key factors when determining a stars luminosity?

6) In what stage do most stars spend their lives?

Of all the questions I had, these are the only ones I need answered now.
Thanks in advance.

If you can afford it, I'd suggest to consult a decent textbook. A good chioce would be:

Karttunen: Fundamental Astronomy

I can give you a few hints though.

4) Think of the basic properties you can measure or simply see. Maybe it helps to compare the planets in our solar system first, and you will already get an idea about the difference of individual stars. Have you heard about the Hertzsprung-Russell-Diagram?

5) This is a bit vague. I suppose this directly refers to a section in your paperworks. It directly follows from the fundamental properties of stars.

6) Again, the Hertzsprung-Russell-Diagram gives you the answer. Just imagine the stages the stars go through.

Originally Posted by Dishmaster

5) This is a bit vague. I suppose this directly refers to a section in your paperworks. It directly follows from the fundamental properties of stars.

Thanks for the advice. Do you think absolute and apparent magnitude would be logical answers?

It all depends on what you can assume to be known. As I mentioned, it is vague. Sure the luminosity directly relates to the absolute magnitude of a star. But it is not a very physical property. The standard definition, mathematically speaking, is



where R is the stellar radius and F is the photon flux. F again - on first order - almost only depends on the surface temperature. Have you heard about the Stefan-Boltzmann law? A physicist would tell you that this is the appropriate answer.