Amateur astronomers help keep tabs on White Dwarf overdue for massivestarquake (Forwarded)

Press and Media Relations
University of Warwick
Coventry, UK

For further information please contact:

Dr Boris Gänsicke, Department of Physics
University of Warwick
02476 574741

Gary Poyner, 0121 605 3716
http://www.garypoyner.pwp.blueyonder.../varstars.html

Peter Dunn, Press and Media Relations Manager
Communications Office, University of Warwick

22 May 2007

Amateur astronomers help keep tabs on White Dwarf overdue for massive
starquake

Researchers at the University of Warwick have enlisted a world wide team
of amateur / semi-professional astronomers to keep watch on one of the
fastest spinning white dwarf stars ever found. The star is long overdue
for a major eruption that will increase its brightness a thousand fold.

The University of Warwick researchers, led by Dr Boris Gänsicke, first
discovered the star in 2005. Known as HS2331+3905, it is 260 light years
away in the constellation of Andromeda. It belongs to the class of objects
called white dwarfs, which are the burnt out cores of stars like our Sun.
HS2331+3905 is roughly the size of the Earth, but weighs about 170000
times more. While the Earth rotates around its axis once per day,
HS2331+3905 does so in only 67 seconds, and its surface is pulsating every
five minutes. As if that wasn't dramatic enough the researchers have
discovered that it sits in particularly turbulent surroundings that should
cause it to erupt once every ten to twenty years, increasing in brightness
a thousand fold. The next such eruption is decades overdue and could
happen at any time.

The white dwarf is slowly stripping material from a nearby small companion
star that is orbiting around it. That material is building up in an
increasingly hot disc surrounding the white dwarf. When the temperature of
the disc reaches a critical value, the equivalent of a pressure valve
opens and pours the hot material onto the surge of the White Dwarf. During
this eruption, the star will brighten by a thousand fold for a month or
two, and then slowly fade into oblivion. These cataclysmic events should
happen roughly every few decades but the Warwick team have now been able
to piece together observation records for that part of the sky stretching
back to the 1950's which show no sign of an eruption over that period.

When the eruption does come it will obviously be a dramatic event for that
star system, but it will also catapult it from its usual dim state into
the reach of everybody equipped with a pair of binoculars. The University
of Warwick researchers have thus recruited a team of gifted amateur
astronomers to keep watch on the star and sound the alert if they see a
sign of brightening of HS2331+3905. Once this happens, the astronomers
will swing their large telescopes on the ground and in space to study the
eruption in all details.

One of that network of dedicated amateurs is Gary Poyner in Birmingham who
specialize in observing variable stars. He owns a number of sophisticated
telescopes and in 2000 he was awarded the British Astronomical Steavenson
Award for "Outstanding contribution to Observational Astronomy".

He said: "The prospect of catching this object undergoing a rare outburst,
is motivation enough for amateur observers like myself to continue
monitoring the field on every possible occasion. Although too faint to
see whilst in it's quiescent state, the long periods of looking at 'empty
space' will eventually be rewarded once HS2331+3905 finally undergoes the
outburst which will cause a ripple of excitement though both amateur and
professional astronomical communities alike".

[NOTE: Images supporting this release are available at
http://www2.warwick.ac.uk/newsandeve...ronomers_help/
]