Astronomy 1021 Chapter Notes - Chapter 14: Cygnus X-1, Degenerate Matter, Solar Mass
29 May 2018
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Department
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Astronomy 1021
Chapter 14
Do Black Holes Exist?
•Evidence that we can see them b/c see jets ejected from black holes, and accretion disks
surrounding supermassive black holes
•Evidence from objects orbiting black holes- if we see stars that are orbiting something, noticed
stars in the centre of the Milky Way orbiting something, and the mass of that thing was 4 million
MSun, indicates this is a supermassive black hole
•Gravitational Lensing- mass acts as a giant magnifying glass- bend the spacetime around them,
cause background objects to briefly appear brighter
-Ex. galaxy cluster Abell 2218, lights from galaxies get distorted which indicates black holes
•Black holes formed from supernova explosion- neutron degeneracy pressure cannot support itself
against gravity, if iron core is over 2-3 solar masses it forms a black hole
•Formation- mass limit of a neutron star is 2-3 solar masses, as soon as the core exceeds neutron
star limit, gravity overcomes neutron degeneracy pressure and core collapses into black hole; the
more the star collapses, stronger the gravity gets (Einstein)
•Observational Evidence for Black Holes- X Ray binaries- some contain black holes rather than
neutron stars; ex. Cygnus X-1, contains star with 19MSun, the star orbits a companion with
15MSun
