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March 2010 Extra: Supermassive

March 2010 Extra

In this show we talk to Dr Robert Dunn about supermassive black holes and X-ray binary systems. Tim answers your astronomical questions, and we round-up the feedback we've received since the last show.


Dave talked to Dr Robert Dunn about his research in two fields: Supermassive Black Holes in Galaxies, groups and clusters, and Black Hole X-ray binary systems.

Comparing high resolution X-ray images of Clusters (which shows lots of high temperature gas) with the radio emission resulting from jets coming from the supermassive black hole at the centre shows that the radio emitting plasma pushes the high temperature gas out of the way. The radio plasma forms bubbles inside the X-ray gas. This is a unique way to inject mechanical energy into the centre of the cluster - which is good; as the gas is emitting X-rays, it is cooling, and so should condense onto the central galaxy and form stars. However, this condensation isn't observed, and the energy from the supermassive black hole is about right to heat up the gas sufficiently. Also we find these active supermassive black holes in clusters where we need to have energy injected. This process also works in groups and galaxies, and effects the evolution of the galaxy.

Black hole X-ray binaries are black holes of about 10 times the mass of our Sun in a binary system with another star. This star is a donor for material falling onto the black hole, which forms an accretion disc. These objects are usually detected when they brighten in the X-ray band - an outburst. During these outbursts, the emission from the disc (black body) dominates over a non-thermal powerlaw component. However, the evolution of the spectrum with the luminosity over time is hysteretical, the disc decays before the powerlaw component recovers.

Ask an Astronomer

Tim answers your questions:

Odds and Ends

New Jodcast videos should be coming soon! A video about the Chinese Space Programme that was filmed at the Museum of Science and Industry should be up soon and later in the year we will have videos from a team of students at Salford University

Wonders of the Solar System is now showing on BBC 2 with Professor Brian Cox. It is available on iPlayer and should be in the States later on this year.

Show Credits

Interview:Dr Robert Dunn and Dave Ault
Ask An Astronomer:Dr Tim O'Brien
Presenters:David Ault and Jen Gupta
Editor:Iain McDonald
Segment voice:Mike Peel
Website:Stuart Lowe
Cover art:Artist's concept of a growing black hole in a quasar Credit: NASA/JPL-Caltech

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