How to Weigh a Supermassive Black Hole?

An artist's impression of a black hole.Black Holes

Black holes are known to exist at the centres of most galaxies, including our own Milky Way.  The masses of those black holes are correlated to many of the properties of their host galaxies, which strongly suggests that galaxies and black holes evolve together.  Measuring their masses and comparing them in a variety of different galaxies is crucial to the understanding of the interactions between the two components.

Only a few super-massive black holes have so far been estimated.  This may be done by calculating how much faster the closest stars rotate around the black hole compared to those that are further away. 


New Method for Supermassive Weighing

Published in the journal Nature, a scientific team led by Dr Timothy Davis of the European Southern Observatory has proposed a new method for measuring the mass of supermassive black holes.

Whereas most estimates previously rely on taking an average of the random motion of stellar objects around them, Davis et al. 2013 focus on the cold, dense gas masses, emitting radiation in the microwave frequency range of the electromagnetic spectrum, because the motion of the ionized gas particles can be tracked more accurately.


In A Lenticular Galaxy Far, Far Away…

The research involves NGC4526, a lenticular galaxy in the Virgo cluster, and maps the movements of carbon monoxide (CO) gas molecules at various distances from the galaxy’s central black hole.  It concludes that this particular black hole has a mass estimate of up to 900 billion trillion trillion tonnes.  This is massive, even for stellar objects on this scale.  Until now, black holes are found to be fairly small, both in mass and size.  Most are typically smaller than our Solar System, for galaxies that are billions of time bigger.

NGC4526’s has a mass that is 450 million times that of the Sun!

Over 100 hours of observations were spent using the Carma telescope array in California.  The next generation of telescopes can now be used to make observations directly into the microwave range.  In the future, the same kind of observations could be carried out  in a mere ten minutes, using new instruments like ALMA.

Download the article: 1301.7184v1.pdf