Planet finder catches a comet (Forwarded)

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Dr Robert Massey
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Anita Heward
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NAM 2008
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CONTACTS

Dr Henry Hsieh
Astrophysics Research Centre
School of Mathematics and Physics
Queen's University Belfast
University Road
Belfast BT7 1NN
UK
Tel: +44 (0)28 9097 3692

Professor Alan Fitzsimmons
Astrophysics Research Centre
School of Mathematics and Physics
Queen's University Belfast
University Road
Belfast BT7 1NN
UK
Tel: +44 (0)28 9097 3124

EMBARGOED UNTIL 0001 BST, 2 April 2008

Ref.: PN 08/21 (NAM 12)

Planet finder catches a comet

Last October, astronomers all over the world were astounded when the
normally very faint Comet Holmes erupted in the largest outburst for more
than a century. Speaking at the RAS National Astronomy Meeting in Belfast
on Wednesday 2 April, Queen's University Belfast astronomer Dr. Henry
Hsieh will describe how a UK telescope was in the right place at the right
time to capture the first images of this once-in-a-lifetime event.

The SuperWASP-North facility on the island of La Palma was built by UK
scientists to discover planets around other stars. The 8 cameras that make
up the system operate robotically, automatically scanning large areas of
the sky each night. By coincidence, at 2339 GMT on the evening of 24
October 2007, it was pointing towards Comet 17P Holmes.

"By the time SuperWASP spotted the comet, it had already brightened by a
factor of 1000," explains Dr. Hsieh. "But this was still almost 3 hours
before anyone else noticed it." (That honour belongs to amateur astronomer
Juan Antonio Henriquez Santana who saw the eruption from Tenerife).

Over the next 2 hours the comet continued brightening, until SuperWASP
could no longer accurately measure it -- it was too bright for the
cameras!

Comets are bodies orbiting the Sun composed of frozen gases and
microscopic solid particles in a small solid nucleus. When they come close
to the Sun, they heat up and some of the icy material turns to gas,
producing characteristic tails. But during this outburst, Comet Holmes
released a large amount of its material all at once.

Two days after the eruption began, sunlight reflecting from the ejected
material had made the comet one million times brighter than it was
originally making it easily visible to observers across the northern
hemisphere.

Dr. Hsieh comments: "Over the next few weeks, SuperWASP continued to
observe Comet Holmes as the cloud of dust and gas surrounding the 3-km
diameter nucleus of the comet steadily expanded. By 31st October, the
cloud was already 900,000 km across or more than twice the distance from
the Earth to the Moon.

"Using our SuperWASP observations, we measured the speed of expansion of
the outer edge of this cloud to be over 1500 km per hour and by 17
November measured the size of the cloud to be more than 2 million km
across -- much larger than the Sun."

Two weeks after the outburst, SuperWASP captured an added bonus -- the
faint and delicate tail of the comet composed of the gas released from the
nucleus. As astronomers watched over the next few weeks, this tail
gradually faded and moved away from the comet.

Although many images were gathered by astronomers around the world, the
precise cause of the outburst is still a mystery. All they know right now
is that it happened once before -- in 1892 -- and may well happen again.

IMAGES AND ANIMATIONS

Images and animations of Comet Holmes from SuperWASP,
http://star.pst.qub.ac.uk/~hhh/holmes/

FURTHER INFORMATION

* SuperWASP
http://www.superwasp.org
* Astrophysics Research Centre, Queen's University Belfast
http://star.pst.qub.ac.uk
* STFC home page
http://www.stfc.ac.uk

NOTES FOR EDITORS

The SuperWASP-North facility is operated by the WASP consortium, which
consists of representatives from Queens University Belfast, the University
of Cambridge (Wide Field Astronomy Unit), Instituto de Astrofisica de
Canarias, the Isaac Newton Group of Telescopes (La Palma), the University
of Keele, the University of Leicester, the Open University, the University
of St Andrews and the South African Astronomical Observatory.

The SuperWASP-North and -South instruments were constructed and are
operated with funds made available from consortium universities and the UK
Science and Technology Facilities Council. SuperWASP-North is located in
the Spanish Roque de Los Muchachos Observatory on La Palma, Canary Islands
which is operated by the Instituto de Astrofisica de Canarias (IAC).

The RAS National Astronomy Meeting (NAM 2008) is hosted by Queen's
University Belfast. It is principally sponsored by the RAS and the Science
and Technology Facilities Council (STFC). NAM 2008 is being held together
with the UK Solar Physics (UKSP) and Magnetosphere, Ionosphere and
Solar-Terrestrial (MIST) spring meetings.