Astronomy C

[syo_astro]

I don't really like using google docs for scioly stuff unless I really need to share a large doc, and even then my partner and I usually just share it by meeting up with a flashdrive. We generally just copy the rules into a doc, separate DSOs onto another, and fill it up with anything we can find. Also, we separate math into another doc. If you look at the rules alone that is chock full o' vocab. But there are many concepts of math and whatnot like I said. You'd probably also like the oh so many lovely diagrams we get . Any questions on that?

[astro124]

Very useful document however, like others have said before me, Google Doc isn't the most popular.

Also, pertaining to stellar evolution for 2013(unrelated to the Google Doc), in the webinar the national event supervisor mentions to stay in within the lines that are 3rd and 4th from the top in a picture of stellar evolution she puts in the Webinar (picture is linked below). Do the lines that she's talking about, have to do with a classic main sequence high mass star turning into a BSG/RSG or do these lines talk about protostars becoming BSGs/RSGs and then turning into something else.

Picture: http://web.hallym.ac.kr/~physics/course ... ewline.jpg Once again, she said to stay within the lines that are 3rd and 4th from the top.

[syo_astro]

Someone can check me on this. The way I've always interpreted that diagram was it describing the various tracks for stellar evolution. For example, the lowest mass nebulae/protostars turn into brown dwarfs, while the highest mass nebulae/protostars turn into BSGs and then supernovae. Reading those lines across you see it just say that relatively high mass protostars turn into BSGs and then either go Type II SN+BH or R(S?)G to either directly Type II/Neutron star or to that fluctuation to a B(S?)G (depending on mass) onto that end track.
For me, though, I wouldn't fully take everything she says (as in she doesn't say exactly what you need to know on the basis of everything for the whole event in those videos). Mainly just to say, look up the evolution track of Cygnus X-1. You'll be interested to see the row it fits on . But overall, those are nice guides to show you where to start off exploring various tracks, and her videos are a great start off point for anyone. Of course, there are other diagrams utilizing the HR diagram which show the tracks too that you should know. For astronomy, you tend to start off at the simplest diagrams possible to digest and understand better, and then we could say the young one "evolves" into quite the master astro googler/researcher XD.

[astro124]

Okay, so about the Schwarzschild Radius. Isn't it the point where an object becomes or doesn't become a black hole, so for example if an object has a physical radius less than its Schwarzschild then it becomes black hole but if the physical radius is more than its Schwarzschild Radius, then it doesn't become a black hole. So would the equation for this be:

R=2GM/csquared

G is the gravitational constant
M is the mass of the object in question
C squared is the speed of light squared
R is the Schwarzschild Radius of the object in question

I just want clarification to see if this is correct.

Also, can some one explain the gravitational constant.

[JustDroobles]

Okay, so about the Schwarzschild Radius. Isn't it the point where an object becomes or doesn't become a black hole, so for example if an object has a physical radius less than its Schwarzschild then it becomes black hole but if the physical radius is more than its Schwarzschild Radius, then it doesn't become a black hole. So would the equation for this be:

R=2GM/csquared

G is the gravitational constant
M is the mass of the object in question
C squared is the speed of light squared
R is the Schwarzschild Radius of the object in question

I just want clarification to see if this is correct.

Also, can some one explain the gravitational constant.

Yes, that is correct. Another more exact definition is that the Schwarschild radius is the radius at which the escape velocity equals the speed of light for a sphere of a given mass.

The gravitational constant G is the same constant used to relate the gravitational force between two objects in the gravitational force equation F=GmM/r^2
I believe it is just a fundamental constant of the universe, I am not sure whether it has some deeper meaning.

G = 6.67E-11 N*m^2/kg^2

This is not the same as acceleration due to gravity on Earth which is g=9.8 m/s^2.

EDIT: It's also worth noting that the Schwarzchild radius equation is the same as the escape velocity equation with escape velocity equal to c.

escape velocity, v=sqrt(2GM/r)

Also, for extra fun, the escape velocity equation can be derived by setting kinetic energy of an object equal to its gravitational potential energy.

(mv^2)/2=GmM/r

[iridium]

I'm sorry if this sounds like a pretty basic question--I've only in the last couple weeks started really focusing on astronomy. When you're looking at an image of a DSO, is there an easy way to determine what band of the EMR spectrum was used to generate it? I can tell what band was used if I have that image or a similar one with all of my astronomy stuff (and I've been gathering more pictures, so it's getting easier), but if I don't have a similar image I'm pretty clueless.

Also, what does LHa (as in LHa115-N19) stand for? That was the only DSO-related question on the Mentor (OH) invitational test yesterday that I had no idea on.

Thanks

[fourLoko]

I don't think there's a way to tell without having the image.

And for the LHa my guess is Lyman H-alpha because I think the gas is ionized, but I can't find anything from googling

[syo_astro]

Heh, and Alpha and I were just working on putting up a black hole post onto the blog! But aside from that, let's see. It's not necessarily a basic question to ask about IDing the wavelength of the image, but here's the thing. There isn't an exact easy way since certain images will use completely different color or other symbols of wavelength. A general rule I could give would be that bluer parts are usually representative of lower wavelength, while the opposite is true in redder parts. That's because even if blue was X-rays and red was infrared, it would probably be understood to be lower, higher wavelength respectively since that blue is lower wavelength than red. But even then, probably find as many images as you can and stick them into your notes. In my binder, I basically put a whole 2+ pages at the end of every DSO just for images. I know it's way too much, but pictures are pretty . As you said, it gets easier with the more pictures you see...even when they give us black and white images like at my regionals >.<. Also, certain objects you'll KNOW can only be taken in a few wavelengths. Certain emit more gamma rays, X-rays, UV, optical, infrared, and radio. The more you know about the objects, the more you'll learn! Also, you can do what I do and go on apod everyday to see always see new images XD. It's fun!

[iridium]

Ok, thanks

[astronomy4ever]

Does anyone know (or know where I could find) the apparent or absolute magnitudes for IGR J17091, LHa115-N19 or Rho Ophiuchi Cloud complex?