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RAS PN 09/17 (NAM 4): UKIRT astronomers discover local star's cool companion

Last Updated on Monday, 29 March 2010 22:08
Published on Monday, 20 April 2009 00:01
An international team, led by astronomers at the University of Hertfordshire in the UK, have discovered one of the coolest sub-stellar bodies ever found outside our own solar system, orbiting the red dwarf star Wolf 940, some 40 light years from Earth. Dr Ben Burningham of the University of Hertfordshire will present this discovery on Monday 20th April at the European Week of Astronomy and Space Science conference.

ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE
16th April 2009
EMBARGOED UNTIL 0001 BST, 20th April 2009
Ref.: PN 09/17 (NAM 4)

Issued by:

Dr Robert Massey
Press and Policy Officer
Royal Astronomical Society
Mob: +44 (0)794 124 8035
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and

Anita Heward
Press Officer
Royal Astronomical Society
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EWASS meeting press room (20th – 23rd April only)
Tel:
+44 (0)1707 285530, +44 (0)1707 285640
+44 (0)1707 285781, +44 (0)1707 285587

EWASS home page: http://www.jenam2009.eu
EWASS press page: http://www.star.herts.ac.uk/ewass/press [password available on request]
RAS PN 09/17 (NAM 4, EMBARGOED): UKIRT ASTRONOMERS DISCOVER LOCAL STAR’S COOL COMPANION

An international team, led by astronomers at the University of Hertfordshire in the UK, have discovered one of the coolest sub-stellar bodies ever found outside our own solar system, orbiting the red dwarf star Wolf 940, some 40 light years from Earth. Dr Ben Burningham of the University of Hertfordshire will present this discovery on Monday 20th April at the European Week of Astronomy and Space Science conference.

"Although it has a temperature of 300 degrees Celsius, almost hot enough to melt lead, temperature is relative when you study this sort of thing, and this object is cool by stellar standards. In fact this is the first time we've been able to study an object as cool as this in such detail", says Dr Burningham, "the fact that it is orbiting a star makes it extra special".

The object is thought to have formed like a star, but has ended up looking more like Jupiter. It is roughly the same size, despite being between 20 and 30 times as heavy, and when the infrared spectral "fingerprints" of the two objects are compared, their resemblance is striking.

The new object orbits its star at about 440 times the distance at which the Earth orbits the sun. At such a wide distance, it takes about 18,000 years to complete a single orbit.

Too small to be stars, so-called "brown dwarfs" have masses lower than stars but larger than gas giant planets like Jupiter. Due to their low temperature these objects are very faint in visible light, and are detected by their glow at infrared wavelengths.

Modelling the atmospheres of cool brown dwarfs is a complex task, but it is key to understanding what we see when we look at planets that orbit other stars. Models of emitted light from such objects, which are dominated by absorption due to water and methane gas, are sensitive to assumptions about their age and chemical make-up.

In most cases astronomers don't initially know much about the age and composition of brown dwarfs and this can make it hard to tell where the models are right, and where they are going wrong.

"What's so exciting in this case, is that we can use what we know about the primary star to find out about the properties of the brown dwarf, and that makes it an extremely useful find", explains Dr Burningham, "you can think of it as a Rosetta Stone for decrypting what the light from such cool objects is telling us".

The object has been named Wolf 940B, after the red dwarf star that it orbits, which was first catalogued by the pioneering German astronomer Max Wolf ninety years ago.

"Red dwarfs are the most populous stars in the Galaxy, and systems like this may be more common than we know" says Dr David Pinfield of the University of Hertfordshire, "As the generation of ongoing large scale surveys continues, we may discover a pack of Wolf-940B-like objects in our solar back yard."

Wolf 940B was initially discovered as part of a major infrared sky survey - the UKIRT Infrared Deep Sky Survey (UKIDSS) which is being carried out using the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea in Hawaii.

The object was found as part of a wider effort to find the coolest and least luminous bodies in our local Galactic neighbourhood, but it was then found to be a companion to the nearby red dwarf Wolf 940 through its common motion across the sky. The data used to confirm the discovery were obtained using telescopes in Chile, the Canary Islands and Hawaii.

Its temperature was then confirmed using data from the Gemini-North telescope on Mauna Kea. The team's findings will soon be published in the Monthly Notices of the Royal Astronomical Society.

Following its discovery with ground based telescopes, Wolf 940B, has since been observed by the NASA's Spitzer Space Telescope, and the findings from those observations will be published later this year.

"This object is going to continue to provide insights into the processes of cool brown dwarf, and warm planetary atmospheres for some time to come", says Dr Sandy Leggett, of the Gemini Observatory, "finding it was just the first step".

CONTACTS

Inge Heyer, Science Outreach Specialist
Joint Astronomy Centre
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Julia Maddock, Senior Press Officer
Science and Technology Facilities Council
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Fax: +44 (0)1793 442002
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Peter Michaud, Public Information Outreach Manager
Gemini Observatory
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Dr Robert Massey, Press and Policy Officer
Royal Astronomical Society
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Anita Heward, Press Officer
Royal Astronomical Society
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Helene Murphy
Media & PR Officer
University of Hertfordshire
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Science Contacts
Please note that it is best to contact these individuals by e-mail.

Dr Ben Burningham
University of Hertfordshire
Tel: +44 (0)1707 285179
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Dr Andy Adamson
Joint Astronomy Centre
Tel: +1 808 969 6511
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Dr Sandy Leggett
Gemini Observatory
Tel: +1 808-974-2604
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Dr David Pinfield
University of Hertfordshire
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Prof. Gary Davis
Joint Astronomy Centre
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IMAGES


Captions

1. A comparison of the Wolf 940B spectrum and that of Jupiter.

2. UKIRT UKIDSS image of Wolf 940A and Wolf 940B.

3. The Wide Field Camera (long black tube) on the United Kingdom Infrared Telescope on Mauna Kea, Hawaii.

4. The United Kingdom Infrared Telescope on Mauna Kea, Hawaii.

NOTES FOR EDITORS

Light Year

One light year is about 10 million million kilometres or 6 million million miles.

Infrared Light

Infrared wavelengths are longer wavelengths than light waves. They are typically measured in microns, also called micrometres. One micron is one millionth of a metre, one 10000th of a centimetre, or one 25000th of an inch.

UKIRT

The world's largest telescope dedicated solely to infrared astronomy, the 3.8-metre (12.5-foot) UK Infrared Telescope (UKIRT) is sited near the summit of Mauna Kea, Hawaii, at an altitude of 4194 metres (13760 feet) above sea level. It is operated by the Joint Astronomy Centre in Hilo, Hawaii, on behalf of the UK Science and Technology Facilities Council.

UKIRT's technical innovation and privileged position on the high, dry Mauna Kea site have placed it at the forefront of infrared astronomy since its opening in 1979. UKIRT is currently engaged in a world-leading infrared sky survey as well as the type of innovative individual programmes described in this press release. More about the UK Infrared Telescope:
http://outreach.jach.hawaii.edu/articles/aboutukirt/

GEMINI OBSERVATORY

The Gemini Observatory is an international collaboration with two identical 8-metre telescopes. The Frederick C. Gillett Gemini Telescope is located at Mauna Kea, Hawai'i (Gemini North) and the other telescope at Cerro Pachon in central Chile (Gemini South), and hence together they provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space. More about the Gemini Observatory: http://wwww.gemini.edu

THE EUROPEAN WEEK OF ASTRONOMY AND SPACE SCIENCE

More than 1000 astronomers and space scientists will gather at the University of Hertfordshire for the European Week of Astronomy and Space Science (EWASS), incorporating the 2009 Royal Astronomical Society National Astronomy Meeting (RAS NAM 2009) and the European Astronomical Society Joint Meeting (JENAM 2009). The meeting runs from 20th to 23rd April 2009.
 
EWASS is held in conjunction with the UK Solar Physics (UKSP) and Magnetosphere Ionosphere and Solar-Terrestrial Physics (MIST) meetings. The conference includes scientific sessions organised by the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) and the European Space Agency (ESA).

EWASS is principally sponsored by the Royal Astronomical Society (RAS), the Science and Technology Facilities Council (STFC) and the University of Hertfordshire, Hatfield.

THE ROYAL ASTRONOMICAL SOCIETY

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

THE SCIENCE AND TECHNOLOGY FACILITIES COUNCIL

The Science and Technology Facilities Council (STFC) ensures the UK retains its leading place on the world stage by delivering world-class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange partnerships. The Council has a programme of public engagement to inspire students, teachers and the public with UK science.

STFC has a broad science portfolio including Astronomy, Astrophysics and Space Science, It gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European organisation for Astronomical Research in the Southern Hemisphere (ESO) and the European Space Agency (ESA). It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, and the MERLIN/VLBI National Facility, which includes the Lovell Telescope at Jodrell Bank Observatory.

STFC is a partner in the UK space programme, coordinated by the British National Space Centre.

STFC home page
http://www.stfc.ac.uk

Reference

This press release refers to a paper to be published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS) "The discovery of an M4+T8.5 binary system", astro-ph: arXiv:0902.181

Web links

Joint Astronomy Centre - UKIRT
http://www.jach.hawaii.edu/UKIRT/

Joint Astronomy Centre - UKIRT - WFCAM
http://www.jach.hawaii.edu/UKIRT/instruments/wfcam/


Joint Astronomy Centre Press Room
http://outreach.jach.hawaii.edu/pressroom/

Gemini Observatory
http://www.gemini.edu/


Royal Astronomical Society
http://www.ras.org.uk/

Science and Technology Facilities Council
http://www.stfc.ac.uk/