Dull brown dwarf stars may not outshine the sun in terms of light, but they win hands down with radio emissions, writes Yvonne Cunningham
Scientists at NUI Galway have discovered a "cosmic missing link" which may be the key to solving the 40-year-old mystery of pulsars.
Researchers from Galway and Armagh, in collaboration with scientists in the US, have discovered that brown dwarfs, which used to be considered pretty dim, in fact emit beams of radiation thousands of times brighter than any detected from our sun.
Brown dwarfs and pulsars emit invisible radio waves in similar ways, a fact which Gregg Hallinan, part of the Galway team, reckons is crucial to understanding pulsars.
"Like black holes, pulsars are among the most exotic things in the universe and we can use complex computer modelling to map the behaviour of brown dwarfs - which are well-understood - onto pulsars, which are not," he says.
Brown dwarfs, first discovered in the 1960s, are objects with masses bigger than a typical planet but smaller than a typical star. Unlike our sun, they aren't big enough to burn hydrogen which means they don't emit much visible light. This makes them very hard to find.
There are as many brown dwarfs as there are stars in the sky, according to Hallinan. There is probably a brown dwarf less than four light years away from earth which would make it closer to us than the nearest star. Hallinan even believes there could be one even closer to us - they just haven't found it yet.
These brown dwarfs are really failed stars that were too small to get hot enough to burn hyrdorgen. The do, however, emit bright bursts of radio waves. "Dead stars are very much alive," states Hallinan.
And it is these radio bursts that make brown dwarfs so interesting to scientists. They emit radio waves in a similar way to pulsars but the whole system is on a much slower and smaller scale, so it is easier to decipher what's going on.
Pulsars are super dense remnants of stars that have exploded. They are considered "exotic" as scientists don't know much about them, they can only guess at what they do.
The next step for the NUI Galway and Armagh Observatory team is to survey the sky to find more brown dwarfs. They will do this using the Very Large Array (VLA) radio astronomy observatory in New Mexico, as well as the US Naval Observatory, the Vatican Observatory and Merlin in the UK.
The VLA in New Mexico "is the best equivalent to Hubble [space telescope] in radio" says Hallinan. And the NUI co-ordinated group has been the top users of the VLA in the world.
The VLA featured in the film Contactstarring Jodie Foster.
This kind of research could also help in the search for life on other planets.
"One of the prerequisites for a planet to support life is that it has a magnetic field so that it is protected from harmful radiation," explains Hallinan.
All the magnetised planets, including Earth, emit extremely bright radio emissions from their magnetic polar regions.
Jupiter can produce radio emissions at low frequencies that are brighter than those detected from the sun.
So, if astronomers become expert at detecting radiation from brown dwarfs, this will help them when they go looking for radio waves from planets outside our solar system.
The research team, supervised by Aaron Golden, lecturer at the Department of Information Technology at NUI Galway, includes five researchers in the university's Centre for Astronomy, two core researchers in Armagh as well as collaborators throughout the world. All the work is co-ordinated by NUI Galway.
The project has been running for four years and is supported by Science Foundation Ireland under its Research Frontiers Programme, by the Higher Education Authority's Programme for Research in Third Level Institutions, and the Irish Research Council for Science, Engineering and Technology. Fresh SFI funding will enable the project to continue for a further three years.