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September 2014 Extra: Almost

September 2014 Extra

In the show this time, Dr Jane Greaves talks to us about planet formation and the PEBBLES project, Prof Ben Stappers tells us about a 'transformer' pulsar in this month's JodBite, and your astronomical questions are answered by Dr Adam Avison in Ask an Astronomer.

JodBite with Prof Ben Stappers

Professor Ben Stappers discusses a recent press release about the discovery of a 'transformer' pulsar that recently switched from emitting radio waves to sending out gamma-rays. As its switch-off was observed with Jodrell Bank's Lovell Telescope, so its reappearance was seen by NASA's Fermi observatory. The pulsar is spinning at 600 times per second and appears to have accreted material from a companion star in a tight orbit with it, which is a well-known scenario that gives the fastest-rotating pulsars their extraordinary speed. As Ben explains, we may be catching the system in the last phase of an accretion process that lasts for millions of years, and, with luck, we may be able to watch it see-saw between its radio and gamma-ray states. Along with a small handful of other neutron stars, this pulsar shows that the radio waves, associated with a strong magnetic field, and the gamma-rays, coming from an accretion disc of hot material, are not normally visible at the same time. Ben explains how the twin observations may help us to understand the processes by which material accretes onto neutron stars in such extreme conditions, and even to constrain the rigidity of the exotic matter within pulsars.

Interview with Dr Jane Greaves

Dr Jane Greaves studies star and planet formation at the University of St Andrews. After being interviewed by the Jodcast five years ago, she returns to talk about the the progress of the PEBBLES project, which is looking at the thermal radio emission from discs of pebble-sized fragments of material around young stars in order to understand how they may one day coalesce into planets. She describes how PEBBLES uses the e-MERLIN array to peer closely into these discs, and discusses how it can be used with results from other instruments, such as ALMA, to build up a better picture of the processes of planet formation. She also speaks about using old data to make new discoveries about the composition of the dwarf planet Pluto just below its surface, and looks forward to what the New Horizons mission will tell us about the beginnings of our own Solar System when it explores the mysterious region beyond Neptune.

Ask an Astronomer

Dr Adam Avison answers your astronomical questions:

Odds and Ends

2014 RC, an asteroid around 20 metres in diameter, proved mostly harmless when it passed within 35,000 kilometres of the Earth's surface on the 7th of September. However, a piece of it may have produced a crater in Nicaragua - but then again, maybe not. No fireball or shock wave were observed, unlike in Chelyabinsk in 2013. The asteroid, which came closer than geostationary satellites to the Earth, was visible to small telescopes as it zipped by.

Saturn's outermost ring, known as the F ring, looks very different now to what it did 30 years ago. Scientists comparing images taken by the Voyager probes and the Cassini spacecraft, taken 30 years apart, have found that the morphology of Saturn's F ring has changed, probably due to large, rocky moonlets crashing in and out of it.

The European Space Agency shared a selfie taken by the Rosetta spacecraft. The image was actually taken with the Comet Infrared and Visible Analyser (CIVA) on the lander, named Philae. While the image is good for publicity, it was also part of a practical set of tests of all of the spacecraft's instruments before Philae lands on Comet 67P/C-G. The photo and more information are available here.

Show Credits

JodBite:Prof Ben Stappers and Mark Purver
Interview:Dr Jane Greaves and Mark Purver
Ask An Astronomer:Dr Adam Avison and Indy Leclercq
Presenters:George Bendo, Indy Leclercq and Mark Purver
Editors:Indy Leclercq and Mark Purver
Segment Voice:Tess Jaffe
Website:Indy Leclercq and Stuart Lowe
Producer:Indy Leclercq
Cover art:Artist's impression of the J1023 pulsar before and after its radio emission vanished. CREDIT: NASA/Goddard Space Flight Center

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