By Paul Rincon
Science reporter, BBC News, Preston
Brown dwarfs are a type of "failed" star
A class of "failed" star called a brown dwarf emits beams of
radiation that are thousands of times brighter than any released by
the Sun.
The brown dwarfs are behaving like an altogether different and
exotic cosmic object called a pulsar.
Pulsars are rotating neutron stars that emit a flashing radio
signal.
When the rotating beams sweep Earth, astronomers detect the radio
pulse, which has been likened to the rotating beacon of a
lighthouse.
Pulsars are created when a massive star explodes in a supernova and
its core collapses into a rapidly spinning neutron star.
Brown dwarfs, on the other hand, are stellar also-rans which lack
the necessary mass to kick-start nuclear fusion reactions in their
cores.
Greg Hallinan from the National University of Ireland in Galway and
his colleagues used the Very Large Array radio telescope in New
Mexico to observe a very cool, rapidly rotating brown dwarf called
TVLM 513-46546.
40-year-old problem
A bright flash from the brown dwarf was observed roughly every two
hours.
All the planets with a magnetic field, including Earth, have bright
radio emission from their magnetic polar regions.
Brown dwarfs are thought to generate their emission in a similar
way to pulsars. But here, the emission is many times brighter than
that from planets. The radio waves are produced above the object's
magnetic poles.
This radio emission requires these brown dwarfs to possess magnetic
fields as powerful as those detected at the most magnetically
active stars.
The periodic pulses detected from brown dwarfs are very similar to
those observed from pulsars. But the whole system is on a much
slower and smaller scale, so it is easier for astronomers to
decipher what is going on.
Link made?
How pulsars produce their radiation has been a problem in
astrophysics for 40 years.
This is because we have little understanding of how hot,
electrified gas, or plasma, behaves in the extreme conditions
present at a pulsar.
Brown dwarfs are now the second class of stellar object known to
produce persistent levels of extremely bright, "coherent"
radiation.
Moreover, this radio signal manifests itself as periodic pulses.
However, in the case of brown dwarfs, both the source conditions
and the emission mechanism are reasonably well understood.
For some time, scientists have wondered if there were similarities
between this type of emission and the periodic radio beams from
pulsars. Observations of TVLM 513-46546 could provide the first
direct evidence for such a link.
Dr Hallinan said: "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.
"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 National University of Ireland astrophysicist presented details
of his work at the Royal Astronomical Society's National Astronomy
Meeting in Preston.
Brown dwarfs are a type of "failed" star
The star is unique and I simply love it 
Taken from :BBC NEWS