Class Notes (811,170)
Canada (494,539)
Brock University (11,942)
Astronomy (161)
ASTR 1P02 (68)

Wednesday January 30 astro lecture.docx

2 Pages
Unlock Document

Brock University
Bozidar Mitrovic

Wednesday January 30, 2013 Astro Lecture: Black Holes & Einstein’s General Theory of Relativity: Black Holes - if the core of a high mass star has mass above about 3M the degenerate neutrons cannot prevent its gravitational collapse and it collapses into a single point (so-called singularity) - the escape velocity from a body (Earth, Moon, Sun, Star…) is the velocity that an object has to have so that it can escape the gravitational confine of the body - for earth the escape velocity from it is about 11 km/s - it can be shown that V*2esc (escape velocity) = 2GM/R (gravitational constant) - for given mass (M) Vesc increases with decreasing R - singularity, escape velocity > the speed of light, escape velocity is equal to the speed of light, event horizon, escape velocity < speed of light - Schwarzschild Radius Rs is the radius of the event horizon - Rs (in km)=3M (in solar masses) - Example: o For M=10 M Rs= 30km o For M=20 M Rs=60 km - Nothing, including light, can escape the region within the event horizon hence the name “black hole” How is one to detect a Black Hole? - look for a binary system consisting of a regular star and an invisible object with a mass of at least 3M - [center of mass: is in the middle] - third kepler’s law as formulated by Newton tells us that if you take the size of the orbit cube and the orbital period squared you get the mass o a*3/p*2 = Mpm - from (1) and (2) one can find M and m - also the invisible companion needs to be an intense source of x-rays - stellar wind particles produced by the regular star system are accelerated by the strong gravitational pull near the event horizon and as a result produce x- ray radiation - first discovered in 1971 by
More Less

Related notes for ASTR 1P02

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.