Bok Prize for IoA Honours Student

the mouse

It’s a case of cosmic forensics, and the culprit is a Mouse.

Christopher Hales of the Institute of Astronomy at the University of Sydney has been awarded the 2008 Bok Prize for outstanding research in astronomy by an Honours student at an Australian university.

Chris’ project involved the heady task of taking raw, archival observational data spanning 12 years from the VLA (Very Large Array) and turning it into a coherent story. The steep learning curve of reducing and manipulating the data to create useful images was a tough challenge he soon overcame.

According to his cosupervisor, Dr Shami Chatterjee, “Chris showed initiative and persistence throughout the course of his project, and his Honours thesis reflects a great deal of hard work”. This was echoed by the judging panel, who noted that his thesis “was a pleasure to read and showed a solid grasp of the science involved”.

The problem to be tackled was a hit and run investigation. At first glance the nebulous object known as the Mouse, powered by a young pulsar, appeared to be speeding away from a nearby supernova remnant, but what were the circumstances leading up to this situation?

A pulsar is a highly magnetized, rapidly rotating neutron star, weighing more than our Sun but compacted within a radius of only around 13km (our Sun has a radius of around 700 million km). Through an outflow of energetic particles, young pulsars can ‘inflate’ a bubble of shocked gas around them, known as a pulsar wind nebula and of which the Mouse is a classic example.

Neutron stars are formed during a cataclysmic explosion at the end of a massive star’s life, known as a supernova. Given asymmetries in these events, the resulting neutron star can be ‘kicked’ out at supersonic speeds away from the remnant gas cloud. It’s this speed that Chris measured. At a blistering 305km/s, this speed fell into the average range for similar objects.

Chris Hales

Chris was also able to answer the question of how old the pulsar is, to show conclusively that the Mouse system is not at all related to the earlier mentioned nearby supernova remnant, and suggested that the pulsar may be evolving into a magnetar (an exotic neutron star with an extremely high magnetic field).

By analysing the bowshock wave formed in front of this supersonically moving system, Chris was able to estimate the density of the interstellar medium surrounding the Mouse. “I think it’s great that my calculations can tell me the density of a pinpoint in space, 16,000 light years away!”

Chris presented his Honours thesis in a unique, clear, story-telling manner, which impressed the judges. He approached the problem as one of cosmic forensics, and continued by detailing the Case Brief, Case Background, Fingerprinting, Ballistics, a recreation of the Scene of the Crime, and concluding with strong Closing Arguments. His supervisor, Professor Bryan Gaensler, describes Chris as “the ideal student; it was a privilege to supervise him. I expect that he has a very successful career in astronomy ahead of him”

Chris begins a PhD later this year with Professor Gaensler, and will give an oral presentation of this research at the July Scientific Meeting of the ASA in Perth.