As if we needed another reminder of how much we have to learn about the galaxy, now comes word that an entirely new kind of cosmic object has been identified. Working with the Parkes radio telescope in eastern Australia, a multi-national team has found a type of neutron star that is all but undetectable most of the time, while occasionally releasing a single burst of radio waves. The time interval between bursts has thus far been observed to vary between 4 minutes to 3 hours.
Detection of these objects — called Rotating Radio Transients — is a formidable challenge due to the sporadic nature of their emissions. “These things were very difficult to pin down,” says Dr Dick Manchester, a member of the research team and a veteran pulsar hunter who works for CSIRO, Australia’s Commonwealth Scientific and Industrial Research Organisation. “For each object we’ve been detecting radio emission for less than one second a day. And because these are single bursts, we’ve had to take great care to distinguish them from terrestrial radio interference.”
That’s no easy challenge, and it leads the team to conclude that the objects, eleven of which have been identified so far, are indicators of a much larger population, perhaps a few hundred thousand in the Milky Way. The more studied and better understood form of pulsars, emitting regular radio pulses up to hundreds of times per second, are probably far outnumbered by the new objects.
Centauri Dreams note: It’s hard to use the term ‘conventional’ when describing pulsars, which is why I avoided it above. But the kind of pulsar we’re familiar with results from the supernova explosion of a massive star, leaving a collapsed core perhaps ten miles in diameter that is largely made up of neutrons. Such pulsars spin at enormous rates; a pulsar, known as PSR J0205+6449, for example, presently rotates 15 times every second. But the rotational rate slows as the pulsar ages, and after a few million years, such a pulsar will lose the energy needed to generate its radio and x-ray emissions.
How these newly identified objects fit in with the standard pulsar model will be interesting to follow. The paper is McLaughlin, Lyne, Lorimer et al., “Transient radio bursts from rotating neutron stars,” Nature 439 (16 February 2006), pp. 817-820. An abstract is here, and Nature.com also offers a helpful background article.