ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE
16th April 2009
EMBARGOED UNTIL 0001 BST, 21ST APRIL 2009
Ref.: RAS PN 09/23 (NAM 10)


Issued by:
Dr Robert Massey
Press and Policy Officer
Royal Astronomical Society
Mob: +44 (0)794 124 8035
E-mail: rm@ras.org.uk

and

Anita Heward
Press Officer
Royal Astronomical Society
Mob: +44 (0)7756 034 243
E-mail: anitaheward@btopenworld.com

RAS website: http://www.ras.org.uk

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

RAS PN 09/23 (NAM 10, EMBARGOED): LONDON STUDENTS FIND JUPITER-SIZED ODDBALL PLANET

A team of astronomers from University College London (UCL), including undergraduate students, have discovered that an exotic world passes directly in front of the Sun-like star it orbits, revealing for the first time that it is about the same size as Jupiter. And rather than travelling to one of the major observatories in Hawaii or Chile, the students made the discovery with a telescope at UCL's University of London Observatory (ULO) in the capital's northern suburb of Mill Hill.

The work was partly funded by a grant from the Royal Astronomical Society (RAS) and will be presented on Tuesday 21st April at the European Week of Astronomy and Space Science conference by ULO astronomer Dr. Steve Fossey; Ingo Waldmann, a final-year undergraduate and David Kipping, a PhD student working in the field of exoplanet science.

The team were alerted by the exoplanet science website http://www.oklo.org, run by Greg Laughlin of the University of California Santa Cruz. Using infrared space observations, Greg predicted that a planet (HD 80606b) would pass in front of its parent star (HD 80606) in a so-called transit event.

On the evening of 13th February, prompted by his alert, Dr Fossey and five UCL undergraduate observers started monitoring the brightness of HD 80606, and some 10 hours later at just after 4 am they discovered they had found the planet’s transit.

Transit events such as this one are very important because they allow astronomers to pin down a planet's radius, density, and atmospheric composition, and to explore the possibility that their parent stars may harbour other as-yet-undetected planets.

The results have provided astronomers with some of the most precise data yet on the planet's size and density, and the tilt and eccentricity of its orbit: and all with a relatively small telescope operated by UCL undergraduate students from a London suburb. The transit shows that the planet has a radius about the same as Jupiter, despite being about 4 times more massive.

The planet, called HD80606b, is unusual in that it travels in a highly elliptical orbit about its parent star. At its furthest point, it is almost as far from its star as the Earth is from the Sun. But every 111 days it is briefly a scorching 10 times closer to its star than Mercury is to the Sun. A hypothetical observer above the cloud tops of the planet would see its parent star swell to 30 times the apparent size of the Sun in our own sky.

HD80606b now holds the record for both the longest orbital period and most eccentric orbit of all transiting planets and with such extreme variations in heating it presents a fascinating object for further study.

Astronomers world-wide are now planning to follow up future transits of this intriguing world using space- and ground-based telescopes to take a closer look at the planet's characteristics, to try to understand its unusual orbit, and to explore the effect on its atmosphere of its looping, searing encounter with its parent star.

Greg Laughlin was quick to acknowledge the result on his website, “It's certainly been a long time since an observational astronomical discovery of this magnitude has been made from within the London City Limits.”

Team leader Dr Steve Fossey is delighted. "Around the same time we submitted our paper, two other professional teams announced their own observations of the same transit. We are very encouraged that our results compare so favourably with those obtained from bigger European facilities, and that our results constrain tightly the nature of HD 80606b and its unusual orbit."

"For example, spectroscopic observations reported by a French-Swiss team, when combined with our precise measurement of the orbital tilt, indicate that the planet's unusual orbit might be explained by the parent star being a member of a binary system - where the companion star tugs on the planet's orbit over millions of years to leave it in the strange configuration we see today."

In the International Year of Astronomy (IYA2009), it seems appropriate that undergraduate students are making world class discoveries using a relatively small university observatory in an urban setting. Cherry Ng, one of the students who work at Mill Hill, comments, “The project gave me a taste of frontier astronomical research. It has definitely strengthened my resolve to pursue a career in astronomy.”

CONTACTS

Dr Steve Fossey
Mob: +44 (0)7949 802173
E-mail: sjf@ulo.ucl.ac.uk
Tel (office): +44 (0)20 8238 8876
Tel (secretary): +44 (0)20 8959 0421

David Kipping
Mob: +44 (0)7974 396734
E-mail: dkipping@ucl.ac.uk
Tel (office): +44 (0)20 7679 4314

Ingo Waldmann
Mob: +44 (0)7896 320454
E-mail: i.waldmann@ucl.ac.uk

Helene Murphy
Media & PR Officer
University of Hertfordshire
Tel: +44 (0)1707 28 4095
E-mail: h.1.murphy@herts.ac.uk

IMAGES

Images and captions can be found at
http://www.ulo.ucl.ac.uk/news/

Figure 1.

Plan view of the orbit of HD 80606b.
The position of the planet is shown at 1-day intervals, close to the moment of close approach (periastron), where the high eccentricity of the orbit brings the planet 10 times closer to its parent star than Mercury's close approach to our own Sun. The primary transit occurs when the planet moves into the line of sight to the star, as viewed from Earth, and was observed by UCL astronomers and students on the night of Feb. 13/14, 2009.

Credit: S. Fossey (UCL)/G. Laughlin (Univ. California at Santa Cruz)

Figure 2.

The geometry of the transit of HD 80606b on 2009 February 13/14, as viewed from Earth.
The observations made by the UCL team were able to demonstrate that HD 80606b is about the same size of Jupiter, and that the transit was almost grazing - that is, it crossed the line of sight from Earth quite close to the limb of the star. Although it was only possible to capture about 8 hours of the full transit from ULO, it was concluded that the total transit was about 12 hours long.

Credit: G. Laughlin (Univ. California at Santa Cruz)/S. Fossey (UCL).
The ULO news page also includes illustrations for press use made by NASA’s Spitzer Space Telescope team.

MNRAS LETTERS AND PREPRINT

The results appear in a paper accepted publication in MNRAS Letters
http://www3.interscience.wiley.com/journal/118500770/home

S Fossey, I Waldmann & D Kipping, 'Detection of a transit by the planetary companion of HD 80606'. A preprint of the paper is available at http://arxiv.org/abs/0902.4616

FURTHER INFORMATION

ULO home page
http://www.ulo.ucl.ac.uk

UCL news
http://www.ucl.ac.uk/news/news-articles/0903/09030301

Greg Laughlin’s exoplanet science blog
http://oklo.org/?p=320

NOTES FOR EDITORS

EXOCAFE

The undergraduate transit-observing programme at UCL, ExoCafe, is managed by Dr. Fossey, and is supported by grants from the UCL ESCILTA fund and the Royal Astronomical Society.
David Kipping is supported by the Science and Technology Facilities Council (STFC).

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), 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.