It's the last show before Christmas so the show is a little shorter than usual. First up we bring news of two special video episodes (one about Longitude) that will be out before Christmas. In our interview we talk to Philip Best about galaxies and a new low-frequency telescope named LOFAR. We also bring you some stocking filler ideas and round-up the feedback we've received since the last show via Facebook, Twitter, YouTube, the forum and the website.
Dr Philip Best (University of Edinburgh) starts by telling us about a problem concerning galaxies. With spectroscopic surveys which such as the Sloan Digital Sky Survey (SDSS) we can measure the number of bright and faint galaxies in different patches of the sky. We observe a large number of faint galaxies and a smaller number of bright galaxies but many theories predict that there should be more faint and more bright galaxies than we actually observe.
Fainter galaxies are very small and when the early stars in those galaxies explode as supernovae they can pump enough energy into their environment to heat the surrounding gas enough to prevent new stars from forming. At the bright end, models predict that we should see lots of large blue galaxies with star formation still occuring but we tend to see redder galaxies. So what might be stopping stars from forming in those galaxies? Through our improving understanding of active galactic nuclei - very massive and active black holes at the centre of some galaxies - there are hints that the huge jets from these may be heating the galaxies.
Philip also tells us about the Low Frequency Array (LOFAR) being built in the Netherlands with extensions in other countries around Europe. LOFAR is unlike dish telescopes and is simply a collection of wires and tiny dipoles connected together with powerful computers. Correlating the signals from all the dipoles together can image huge amount of the sky simultaneously. LOFAR observes between 30 and 200 MHz in parts of the electromagnetic spectrum that have had little attention from astronomers in the past. LOFAR will be able to make deep and wide surveys but will also spot sudden, transient, events such as supernovae and gamma-ray bursts. LOFAR is currently under construction and the first station has been operational since 2007. There will be around 50 stations in total and around a third of those should be ready in early 2009 with the rest finished by 2010. In the UK there is one station funded at Chilbolton.
The technology behind LOFAR is also providing some surprising benefits for agriculture with micro-climate observations of potato fields to help fight fungal disease.
It is the time of year when people are trying to think of gift ideas to get the astronomer in their lives so the Jodcast team came up with this fairly inexpensive list of possibilities.
- Dame Jocelyn Bell-Burnell - the discoverer of pulsars who was on the June 2007 edition of the Jodcast - has co-edited a book of poetry named Dark Matter: Poems of Space. Unfortunately, due to high demand it seems to be difficult to get hold of at the moment.
- A Philips Planisphere (or for latitude 35 degrees). You can even save money by using a virtual one or have some entertainment by making your own. Templates are available from the Lawrence Hall of Science (US), the Royal Astronomical Society of Canada (PDF), Discovery Education, or the Starry Lady Astronomy Services (Australia).
- A red LED torch for those night time observing sessions.
- A wooly hat
- A thermos flask
|Interview:||Dr Philip Best and Nick Rattenbury|
|Presenters:||Nick Rattenbury and Stuart Lowe|
|Intro/outro script:||David Ault (with apologies to Clement Clarke Moore)|
|Intro/outro editing:||Fiona Thraille|
|Intro/outro voices:||Nick Rattenbury, David Ault, Stuart Lowe, Megan Argo, Ian Morison, Roy Smits, and Tim O'Brien.|
|Segment voice:||Tess Jaffe|
|Cover art:||NGC 2264 and the Christmas Tree cluster Credit: ESO|