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September 2011 Extra: Cactus

September 2011 Extra

In this show, we talk to Dr Andrew Strong about the high-energy Universe. Dr Tim O'Brien answers your questions and we report on some astronomical odds and ends.

Interview with Dr Andrew Strong

Dr Andrew Strong studies some of the highest-energy photons in the Universe - gamma-rays. Here he talks about using the Fermi satellite to detect the gamma-rays emitted when particles known as cosmic rays interact with the interstellar medium. He describes how high-energy observations can be used to to map the magnetic field of the Milky Way and to study very cold, diffuse molecular hydrogen known as dark gas (not to be confused with dark matter). He discusses gamma-rays from compact sources inside and outside our Galaxy and how their measurement can help observatories at other wavelengths, such as the Planck spacecraft. He also explains a recent study of gamma-rays coming from our nearest star, the Sun.

Ask an Astronomer

Dr Tim O'Brien answers your astronomical questions:

Odds and Ends

NASA satellite UARS is expected to make an uncontrolled re-entry into the Earth's atmosphere some time in late September. This hefty bus-sized probe has a 1-in-3200 chance of hitting a person on the ground.

The winners of the 2011 Astronomy Photographer of the Year competition were announced on September 8. The winning photograph is a spectacular image of Jupiter with two of its moons, Io and Ganymede. Images from this year's competition are on display at the Royal Observatory Greenwich until 12 February 2012.

NASA have released new images of three of the Apollo landing sites, taken by the Lunar Reconnaissance Orbiter (LRO). Phil Plait has compared the new LRO image of the Apollo 17 landing site with a photograph taken by the astronauts as they left the Moon on his blog.

Observers at the ESO observatory in La Silla, Chile have discovered fifty new exoplanets using HARPS (High Accuracy Radial Velocity Planet Searcher). Sixteen of these are classified as "super-Earths", which means that they have a mass greater than the Earth but less than that of gas giants such as Jupiter. Included in this discovery are five planets with masses less than five times the mass of the Earth, including one (HD 85512b) which has an estimated mass of 3.6 Earth masses and is orbiting on the edge of the habitable zone.

A massive storm on a brown dwarf has been observed by astronomers at the University of Toronto, Canada. The target brown dwarf (2MASS J21392676+0220226, or 2MASS 2139 for short) had a 30% change in observed brightness over approximately 8 hours - a massive change on such a short timescale - and the astronomers say this is probably due to brighter and darker patches on the object's surface coming into and out of view as it rotates. These patches could be due to a gigantic storm on the object's surface, like a much larger version of the red spot on Jupiter.

Show Credits

Interview:Dr Andrew Strong, Liz Guzman and Mark Purver
Ask An Astronomer:Dr Tim O'Brien
Presenters:Jen Gupta, Libby Jones and Christina Smith
Editors:Jen Gupta, Tim O'Brien and Mark Purver
Producer:Libby Jones
Segment Voice:Liz Guzman
Website:Libby Jones and Stuart Lowe
Cover art:Cutout from an all-sky image, constructed from two years of observations by NASA's Fermi Gamma-ray Space Telescope. CREDIT:: NASA/DOE/Fermi LAT Collaboration

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