some brightness questions (1 Viewer)

[...]

hmm

its been around 2 years since i did astrophyiscs, so i've basically forgot everything about it

so i've got a few questions here;

(1)Two stars have the same luminosity but start A is four times further away than star B, what is the ration of the brightness of the stars as measured on the surface of the earth

(2)Two stars have the same size but the temperature of star A is four times the temperature of star B. What is the ration of the luminosities of the two stars


now reading these 2 questions and from reading back the notes during HSC, i don't think i've been given enough information?

any help is appreciated!
thanks!

 

[treelovinhippie]

Doesn't anyone do astrophysics? ... I come in here hoping to find some helpful info and find there's been one thread in the last month

We've just finished the topic and I'm currently trying to finish off summaries of the dot points before the half yearly.

Anyways... having not done summaries as yet, I think you do need more info there + a HR diagram handy.

The difference between brightness is found using this formula: Ia/Ib = 100^((Mb-Ma)/5)) , where Mb = magnitude of dimmer star; Ma = magnitude of brighter star

Or you could possibly use d=1/p , where d=distance(pc); p=parallax(arcsec)