April 2007 NUI Galway astronomers make important pulsar discovery

Researchers at the Centre for Astronomy, NUI Galway have made an important discovery regarding brown dwarfs which has revealed that these "failed stars" can possess powerful magnetic fields and emit lighthouse beams of radio waves thousands of times brighter than any detected from the Sun.

The team of Gregg Hallinan, Stephen Bourke and Caoilfhionn Lane; scientists based at the Armagh Observatory; and US researchers in New Mexico and Arizona, has discovered that the brown dwarfs are behaving like pulsars, one of the most exotic types of object in our Universe.

"Brown dwarfs tend to be seen as a bit boring – the cinders of the galaxy. Our research shows that these objects can be fascinating and dynamic systems, and may be the key to unlocking this long-standing mystery of how pulsars produce radio emissions," said Mr Hallinan who presented his findings at a recent meeting of the Royal Astronomical Society in Preston, UK.

Since the discovery of pulsars 40 years ago, astronomers have been trying to understand how the rotating neutron stars produce their flashing radio signals. Although there have been many attempts to describe how they produce the extremely bright radio emissions, the vast magnetic field strengths of pulsars and the relativistic speeds involved make it extremely difficult to model.

The researchers have found that brown dwarfs are now the second class of stellar object observed to produce this kind of powerful, amplified (coherent) radio signal at a persistent level. The emissions from the brown dwarfs appear to be very similar to those observed from pulsars, but the whole system is on a much slower and smaller scale, so it is much easier to decipher exactly what is going on. Importantly, the mechanisms for producing the radio emissions in brown dwarfs are well understood, as they are almost identical to the processes that produce radio emissions from planets.

Dr Aaron Golden, lecturer at the Department of Information Technology, who supervised the group said: "The observations that yielded this discovery involved the use of some of the world s finest astronomical facilities, but it was sheer hard work and focussed, inspired analysis that have put astronomical research at NUI Galway on a global stage.

"I think it is particularly important to stress that such world class research being lead by astronomers at NUI, Galway is a testament to the quality and ability of our postgraduate students on campus, and a vindication of the University s recent decision to approve the setting up of the Centre for Astronomy."

Mr Hallinan added; "It looks like brown dwarfs are the missing step between the radio emissions we see generated at Jupiter and those we observe from pulsars".

The group is now planning a large survey of all the known brown dwarfs in the solar neighbourhood to find out how many are radio sources and how many of those are pulsing. If a large fraction of brown dwarfs are found to pulse, it could prove a key method of detection for these elusive objects.