Astronomy C

[Theigh]

Guys, thank you for the information provided, i was actually searching for some answers, but your conversations helped me to understand some of the rules i couldn't. Besides this i have some health issues, and i need to use xanax , but when I'm here I feel so much better!

[orangewhale]

Proper motion in terms of angle is just the angle divided by the time, exactly as you said. To find proper motion in units of distance per time, you'll need to know the distance and use the small angle approximation to determine the length of the angular proper motion (or if it's close enough, the approximation may not be very good and you'll have to use tangent of the angle).

So if I'm given that a star travels 3.45 mas in 44 years at a distance of 167 pcs and I'm trying to get the tangential velocity (this is a problem from the 2017 Golden Gate invitational that I've been stuck on), I would do 3.45/1000/3600 to convert it to degrees, divide that by 44 for the proper motion in degrees/year, and multiply it by 167 to get the tangential velocity? When I do that and convert to km/sec, I get an answer about 100 times less than the given answer of 364 km/sec. Can anyone tell me what I'm doing wrong?

[Unome]

Proper motion in terms of angle is just the angle divided by the time, exactly as you said. To find proper motion in units of distance per time, you'll need to know the distance and use the small angle approximation to determine the length of the angular proper motion (or if it's close enough, the approximation may not be very good and you'll have to use tangent of the angle).

So if I'm given that a star travels 3.45 mas in 44 years at a distance of 167 pcs and I'm trying to get the tangential velocity (this is a problem from the 2017 Golden Gate invitational that I've been stuck on), I would do 3.45/1000/3600 to convert it to degrees, divide that by 44 for the proper motion in degrees/year, and multiply it by 167 to get the tangential velocity? When I do that and convert to km/sec, I get an answer about 100 times less than the given answer of 364 km/sec. Can anyone tell me what I'm doing wrong?

I think you should be converting to radians to get an accurate ratio. Note that the key for that test is incorrect on math in several places.

[Diactaeon]

Hello, this is my first time doing Astronomy this year, and im rather overwhelmed by all the topics
What are the important things to have in a binder for DSO's?

[Unome]

Hello, this is my first time doing Astronomy this year, and im rather overwhelmed by all the topics
What are the important things to have in a binder for DSO's?

The data table from Wikipedia (augmented with info from other sources if needed for that particular DSO), lots of different images with descriptions (including the part of the EM spectrum and the telescope/satellite/etc. that took the image), light curves and spectra (also with descriptions), and text with important info (e.g. how it was formed, what type of object it is, what it may do in the future, pretty much anything). It typically takes me around 1 hour per DSO (I did all of them right after the rules came out), though if you're new to the event it'll probably take a little longer.

[Magikarpmaster629]

Writing a test and I've gotta say the DSO choices are interesting...not what I was expecting. No Cepheids at all (unless I really missed something lol)? And no Eta Carinae, Crab Nebula, or Kepler's SNR. Also NGC 6357 and NGC 7822 seem kinda out of place, not quite sure what to do about them (6357 makes a little sense, really unsure about 7822). The rest seem interesting, especially Geminga and B0355, and SN 1987A.

[syo_astro]

Webinars up! [With a new webinar presenter for Div B:D]

http://chandra.harvard.edu/edu/olympiad.html

[Shaunak]

Hi. I'm new to Astro. I need help. How do you calculate absolute magnitude of a star given its radius and temperature?

Also any tips for the formulas I need to know? Thanks

[jonboyage]

Hi. I'm new to Astro. I need help. How do you calculate absolute magnitude of a star given its radius and temperature?

Also any tips for the formulas I need to know? Thanks

https://scioly.org/wiki/images/c/c6/Formula_Sheet.pdf

This has a lot of the general formulas that you might need to know for this event.

To find the absolute magnitude, you would have to use the equation to find luminosity first and then use or where is absolute magnitude.

Hope this helped!

[syo_astro]

WARNING:
Don't link to that formula sheet on the wiki. There are some errors in it, and nobody has updated it b/c idk who has the original file...

It would probably be better to link to another site as a "primary source" of sorts. Also, darn beat me to it, was going to suggest questions to learn from instead of just giving the formulas . Nonetheless, the questions I would ask when solving a problem like this (hopefully instructive):

1) What can I do with R and T? What useful quantities can I get from them?
(In this case, you can refer to the Stefan-Boltzmann Law, you should always think of the most common formulas first, such as parallax, distance modulus, Stefan-Boltzmann Law, Wien's Law, etc)

2) How does this quantity relate to the question / quantity I need to find?
(In this case, the Luminosity L, you can find from Stefan-Boltzmann Law, which does in fact relate to absolute magnitude. Absolute magnitude is defined from putting a given luminosity value on a new scale, which involves a negative and a log. The 4.83 is also important, and the importance should be looked into!)