Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted April 11, 1998)

Are there two types of blackhole? One is like the Cygnus X-1, and the other is a super massive blackhole in the active galactic nuclei?

The Answer

Thank you for contacting our Ask an Astrophysicist service. The only real difference between these two kinds of black hole is size. A black hole in an X-ray binary will only be a few times as massive as the sun. A black hole at the center of an active galaxy can be millions of times as massive as the sun. It can get so big because the density of matter in a galactic center is high so there is lots of matter for it to accrete.

Both kinds of black hole can have an accretion disk. Usually most of the radiation we detect comes from the accretion disk. The accretion disk of a super-massive black hole will be much larger than that of one in an X-ray binary. This means that the radiation that we detect varies on a much longer timescale (days instead of milliseconds).

Damian Audley
for Ask an Astrophysicist

Previous question
Main topic
Next question

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

DVD Table of Contents
Educator's Index