February 2014 Extra: Exotic

In the show this time, Prof. Paul Crowther tells us about the most massive stars in the universe, Dr. Ian Harrison talks to us about his work with weak lensing at JBCA in this month's JodBite, and your astronomical questions are answered by Dr. George Bendo in Ask an Astronomer.

JodBite with Dr. Ian Harrison

Dr. Ian Harrison is a postdoctoral researcher in cosmology at the Jodrell Bank Centre for Astrophysics, and in this interview he tells us about weak gravitational lensing of radio galaxies. Weak lensing studies measure the bending of distant light around dark matter, helping to determine the large-scale structure of our Universe. They take place mostly at optical wavelengths (see previous JodBite with Dr. Joe Zuntz), but here Ian discusses his involvement in Super-CLASS, a survey using the e-MERLIN array of telescopes to make radio observations of weak lensing. Such a study is independent of optical measurements, and paves the way for surveys by future telescopes such as the Square Kilometre Array. Ian talks about the hope that weak lensing will tell us more about the history and fate of the Universe, and also discusses his previous work - using a technique called extreme value statistics with the largest galaxy clusters to investigate the standard cosmological model.

Interview with Prof. Paul Crowther

Prof. Paul Crowther from Sheffield University talks about massive stars in the Milky Way and other star-forming galaxies. He explains about how these massive stars form, how they die and why the upper mass limit remains controversial.

Ask an Astronomer

Dr. George Bendo answers your astronomical questions:

• Inspired by the last episode, Steve Armen asks: "Since gravitational waves distort space-time, would it not be possible to measure time being warped instead of looking for mechanical change in the length of the laser beam?"
• The next question, from Sean Mulcahy, is: "Most stars are in binary systems, but our own sun is more unusual as it's on its own. I've heard it said that it could be part of a binary system, but that we just haven't detected our partner yet. What's the current thinking on this idea?"
• Finally, Mark C in Belfast asks: "Can you tell me what are the brightest planets as viewed from the other planets? So, if I were standing on Mars, would Jupiter be the brightest thing in my sky apart from the Sun? Or would the Earth or Venus be brighter because they are closer to the Sun and therefore reflect more Sunlight? What about way out at Neptune? Would Uranus, Saturn or Jupiter be the brightest?"

Odds and Ends

The first evidence that asteroids have a highly varied internal structure had been found using very precise observations of the near-Earth asteroid Itokawa. By measuring the rate of change of its spin due to the YORP effect, it was inferred that the two parts of the asteroid’s peanut shape have different densities. A schematic view of the strange peanut-shaped asteroid Itokawa.

NASA's Lunar atmosphere exploration module LADEE has sent back pictures of the surface of the moon and of the starfield surrounding the instrumet. The satellite takes roughly a picture a minute to establish the spacecraft's orientation, which is essential information for the various scientific instruments on board.

An international team of astronomers has made a very unusual observation of a neutron star, showing a jet shooting out in an unexpected direction. The neutron star has been ejected from a supernova remnant called the Lighthouse Nebula at over 1000 kilometres per second, and is emitting a pulsar wind as it goes. Pulsar winds involve streams of charged particles beamed along the rotation axis of a neutron star as it spins rapidly; they have been observed before, but always in jets that are aligned with the neutron star's direction of travel. Gamma-ray, X-ray and radio observations of this jet, however, show it coming out at right angles to the motion of the neutron star, leading the discoverers to suspect that 'exotic physics' was at play in the supernova explosion. The jet also displays a twisted shape, which could be due either to precession (wobbling of the neutron star as it spins) or to instability in the jet itself.

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