In the show this time, Dr Adam Deller tells us about a new high-resolution radio survey, Peter Schemmel talks about experimenting with the orbital angular momentum of light in this month's JodBite, and your astronomical questions are answered by Dr Mark Purver in Ask an Astronomer.
JodBite with Peter Schemmel
Peter Schemmel is a PhD student at the Jodrell Bank Centre for Astrophysics, conducting experiments to investigate the orbital angular momentum (OAM) of light. He explains the physical meaning of light with orbital angular momentum, and discusses how researchers are developing ways to detect it at low (microwave) frequencies. As Peter explains, telescope receivers may one day measure the orbital angular momentum of the light they collect, in order to gather new information about astronomical objects.
Interview with Dr Adam Deller
Dr Adam Deller, a radio astronomer at ASTRON in the Netherlands, talks to us about a new very-high-angular-resolution radio survey called mJIVE. The survey makes use of an technique called Very Long Baseline Interferometry (VLBI), which combines measurements from telescopes that can be separated by thousands of kilometres to form images with an angular resolution of a few milli-arcseconds (around a millionth of a degree!) at a frequency of 1.4 GHz. He explains how such a high-resolution survey has recently been made possible thanks to a technique that drastically reduces the volume of data by looking only at pre-selected regions. Finally, he talks about some early results with mJIVE, most notably the discovery of new candidate gravitational lenses.
Ask an Astronomer
Dr Mark Purver answers your astronomical questions:
- Matt asks: "Is there a lower limit to the frequencies of electromagnetic radiation that are usable or detectable with current equipment? Is there a lower limit to how low a frequency can exist?"
Mark talks about how the plasma frequencies of the Earth's atmosphere and the interstellar medium impose lower limits on the frequencies of radiation that can reach our telescopes.
- Peter Baxter says: "If you entangled a pair of particles near a black hole, and one of the particles fell into the black hole and the other one didn't, would you be able to observe the properties of the particle that escaped? Wouldn't the properties of both particles, such as their spin, be destroyed when one particle was crushed by the black hole?"
Mark refers to the debates over the meaning of entanglement, the destructive properties of black holes and the characteristics of black holes as defined by the 'no-hair theorem'.
Odds and Ends
India launched its first mission to Mars on 5 November 2013. The Mars Orbiter Mission (MOM), also known as Mangalyaan, entered a highly elliptical orbit around the Earth ahead of six engine thrusts designed to swing it ever higher before flinging it off towards the Red Planet. Although the fourth of these thrusts did not lift the spacecraft as high as expected, spare fuel allowed the problem to be resolved with an extra boost that was executed after this episode of the Jodcast was recorded. MOM, which cost just $72 million (£45 million), will encircle Mars in 10 months' time and probe the Martian atmosphere, investigating why the planet lost its water.
During a five-hour spacewalk on the International Space Station, Russian cosmonauts handed over the Olympic torch as part of the torch relay for the Sochi 2014 Winter Games. This is the first time an Olympic torch has been taken out into open space, although Olympic torches have travelled aboard spacecraft twice before.
The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite fell to Earth south of South America on 11 November 2013. The satellite had been orbiting Earth since March 2009, performing highly precise measurements of variations in the Earth's gravitational field. To do this, the satellite needed to orbit the Earth at an altitude of 260 km, which was low enough that it encountered some drag from the upper portion of the Earth's atmosphere. The satellite had used propellant to keep it in orbit, but it ran out of propellant on 21 October and finally (and ironically) succumbed to gravity this month.
|JodBite:||Peter Schemmel and Mark Purver|
|Interview:||Dr Adam Deller and Indy Leclercq|
|Ask An Astronomer:||Dr Mark Purver|
|Presenters:||George Bendo, Libby Jones and Mark Purver|
|Editors:||Adam Avison and Mark Purver|
|Segment Voice:||Mike Peel|
|Website:||Mark Purver and Stuart Lowe|
|Cover art:||The phase pattern of light with 'mode 1' orbital angular momentum. CREDIT: Peter Schemmel, JBCA|