March 2010 Extra: Supermassive

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.

Interview

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:

• Russ writes in to ask for advice for potential blind amateur astronomers. He says "How hard would it be to get into radio astronomy? Have you heard of a NASA-related radio telescope kit? I would love to listen to the stars and planets, and if I can do this with my wife, who is blind, it would be wonderful."
  Tim explains that there is a NASA-related radio telescope kit as part of Radio Jove - the website contains loads of information on the project, technical requirements and samples of recordings of radio emissions from the Sun and Jupiter. More sounds from space can be heard in a special edition of the Jodcast, the BBC website has a news story on asteroseismology results from the Corot spacecraft including the sounds of three stars and Noreen Grice has written a series of Braille books on astronomy (she also featured in a podcast for the 365 Days of Astronomy in Jan 2010).
• Plans for the new visitor facilities at Jodrell Bank include a building which may be embossed with a contour map of the radio sky. You can view the sky at various wavelengths, including the radio, with Chromoscope.
• Antony Bradbury writes in from Arkansas, USA, to say "Some many years ago, one of your staff gave a talk at my then radio club (Telford and District Radio Society). I wish to recall the data he showed on the radar received at Jodrell Bank during the time of the landing phase of Apollo 11."
  A scan of the original chart recording of the signals received from the Eagle Lander by a radio telescope at Jodrell Bank will be available on our website. Tim also mentioned an interview with Sir Bernard Lovell about Jodrell's involvement with the space race.
• Audra Copeland from New Hampshire, USA, emailed in to say "We were wondering about a specific star that was a very bright color gold. It seemed a lot brighter and larger than the rest around it. Could you possibly shed some light on what it was? A planet or something else?"
  The object was most likely Mars. If you find yourself wondering about objects in the sky, Stellarium is very useful free software to show you what is up and about in the sky at any time and from any location on Earth. If you do find yourself observing Mars you may want to listen to this Mercury Theatre radio broadcast from October 1938 of Orson Welles' adaptation of HG Wells' War of the Worlds.

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