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Issued by: Inge Heyer, Public Information Officer Images, notes, and contact details appear below. 29 January 2010 UKIRT Astronomers Discover Cool Stars in Nearby SpaceAn international team, led by British astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii, have discovered what may be the coolest sub-stellar body ever found outside our own Solar System. This object is technically known as a brown dwarf but what has excited astronomers is its very peculiar colours, which actually make it appear either very blue or very red, depending on which part of the spectrum is used to look at it. The object is known as SDSS1416+13B and it is in a wide orbit around a somewhat brighter and warmer brown dwarf, SDSS1416+13A. The brighter member of the pair was detected in visible light by the Sloan Digital Sky Survey. By contrast, SDSS1416+13B is only seen in infrared light. The pair are located between 15 and 50 light years from the Solar System, which is quite close in astronomical terms. "This is the fourth time in three years that UKIRT has made a record breaking discovery of the coolest known brown dwarf, with an estimated temperature not far above 200 degrees Celsius", says Dr Philip Lucas of the University of Hertfordshire’s School of Physics, Astronomy and Mathematics. "We have to be a bit careful about this one because its colours are so different than anything seen before, that we don't really understand it yet. The colours are so extreme, that this object will keep a lot of physicists busy trying to explain it." SDSS1416+13B was first noticed by Dr Ben Burningham of the University of Hertfordshire as part of a dedicated search for cool brown dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS). The object appeared far bluer at near-infrared wavelengths than any brown dwarf seen before. A near-infrared spectrum taken with the Japanese Subaru Telescope in Hawaii showed that it is a type of brown dwarf called a T dwarf, which has a lot of methane in its atmosphere. The methane causes large gaps in the spectrum at certain wavelengths. Dr Burningham soon noticed that a previously observed brighter star (SDSS1416+13A) which appears close by in the UKIDSS discovery image, was also a brown dwarf. Team member Dr Sandy Leggett of Gemini Observatory then used the orbiting Spitzer Space Telescope to investigate SDSS1416+13B at longer wavelengths. She measured its colour at mid-infrared wavelengths, which are thought to be the most reliable indicator of temperature, and found that it is the reddest known brown dwarf at these wavelengths by some margin. Comparison with theoretical models of the brown dwarf atmospheres then provided a temperature estimate of about 500 Kelvin (227 degrees Celsius). "The fact that it is a binary companion to a warmer brown dwarf that also has an unusual spectrum is helping us to fill in some some gaps in our understanding", says Dr Burningham. "It seems likely that both brown dwarfs are somewhat poor in heavy elements. This would be consistent with the pair being old, which in turn implies a high gravity for both dwarfs, which can further enhance the unusual colors seen for both dwarfs." Professor Gary Davis, Director of the UKIRT, noted that the discovery of brown dwarfs in large numbers is one of the key objectives of the UKIDSS survey programme. "The harder we look in the infrared, the more of these objects we find, and because they are failed stars, they allow us to probe the unexplored realm between stars and gas-giant planets. This discovery is just one more in a stunning sequence of recent successes by UKIRT in detecting these very cool objects." The team's findings have been accepted for publication in the Monthly Notices of the Royal Astronomical Society. Images
UKIRT UKIDSS near-infrared image of SDSS1416+13AB (left panel) and the Spitzer+UKIDSS mid-infrared image (right panel). Credit: JAC/UKIRT, Spitzer Space Telescope, University of Hertfordshire.
Subaru near-infrared spectrum of SDSS1416+13B, taken with the IRCS spectrograph. The almost total absence of light at wavelengths between 1.7 and 2.5 microns reflects the low metal content and high gravity at the surface of the brown dwarf, and results in its very blue near-infrared colour. These same physical properties enhance the brightness in the mid-infrared, and so the colour flips to red when the near-infrared is compared with data from the Spitzer Space Telescope. Credit: Subaru Telescope (NAOJ), University of Hertfordshire
The Wide Field Camera (long black tube) on the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. Credit: UKIRT/JAC.
The United Kingdom Infrared Telescope on Mauna Kea, Hawaii. Credit: UKIRT/JAC.
The Subaru Telescope (NAOJ) on Mauna Kea, Hawaii. Credit: Subaru Telescope (NAOJ).
Artist rendition of the Spitzer Space Telescope in its heliocentric orbit. Credit: Spitzer Space Telescope.
Notes for EditorsLight YearOne light year is about 10 million million kilometres or 6 million million miles. Infrared LightInfrared 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. Visible light has wavelengths around half a micron, while the observations reported here were at wavelengths of about 2 microns. Brown DwarfA brown dwarf is a small, faint, cool object (often called "failed" star) that, unlike the Sun and other stars, does not have sufficient mass to achieve hydrogen fusion in its core. With mostly slow gravitational contraction as an internal energy source, a brown dwarf gradually cools down as it radiates energy away into space over billions of years. Brown dwarfs exist in the mass range between about ten times that of Jupiter and one-twelfth the Sun's mass (which marks the boundary between these dwarfs and hydrogen-burning stars). The low temperatures and small sizes of brown dwarfs combine to make them both very faint and red in color. Most of their radiation is in the infrared, and therefore is not detectable to either the human eye or conventional optical detectors. Detectors sensitive to longer infrared wavelengths, such as those used at UKIRT, are capable of observing these objects in unique ways. The spectrum of a brown dwarf is characterized by large wavelength regions from which almost no light is seen because it is being absorbed by water, methane and other molecules in the object's atmosphere. The details of these absorption patterns depend sensitively on the star's temperature. UKIRTOne of the world's largest telescopes dedicated solely to infrared astronomy, the 3.8-metre (12.5-foot) United Kingdom 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/ Subaru Telescope (NAOJ)The Subaru Telescope is Japan's premier optical-infrared telescope operated by the National Astronomical Observatory of Japan. Located on Mauna Kea on the island of Hawaii, the telescope, with an effective aperture of 8.2 m, is also one of the world's largest and most technologically advanced telescopes. Through the open use program astronomers throughout the world have access to Subaru's excellent image quality. Spitzer Space TelescopeThe Spitzer Space Telescope is a space-borne, cryogenically-cooled infrared observatory capable of studying objects ranging from our Solar System to the distant reaches of the Universe. Spitzer is the final element in NASA's Great Observatories Program, and an important scientific and technical cornerstone of the Astronomical Search for Origins Program. University of HertfordshireThe University of Hertfordshire is an ambitious and entrepreneurial university in the United Kingdom. It offers excellence in teaching, learning and research and puts students at the heart of its activities. It is a model of a 21st century university, international, business-facing and business-like in its approach – making it distinctive in an ever changing higher education environment. The University of Hertfordshire has over 2,700 staff and a student community of 23,000, including more than 2,000 international students from over eighty-five countries. For more information, please visit, www.herts.ac.ukScience and Technology Facilities CouncilThe Science and Technology Facilities Council is an independent, non-departmental public body of the Office of Science and Innovation which itself is part of the Department of Innovation, Universities and Skills. It was formed as a new Research Council on 1 April 2007 through a merger of the Council for the Central Laboratory of the Research Councils (CCLRC) and the Particle Physics and Astronomy Research Council (PPARC) and the transfer of responsibility for nuclear physics from the Engineering and Physical Sciences Research Council (EPSRC). We are one of seven national research councils in the UK. The Science and Technology Facilities Council is government funded and provides research grants and studentships to scientists in British universities, gives researchers access to world-class facilities and funds the UK membership of international bodies such as the European Organisation for Nuclear Research, CERN, the European Space Agency and the European Southern Observatory. It also contributes money for the UK telescopes overseas on La Palma, Hawaii, Australia and in Chile, the UK Astronomy Technology Centre at the Royal Observatory, Edinburgh and the MERLIN/VLBI National Facility. Media ContactsPlease note that it is best to contact these individuals by email.
Science ContactsPlease note that it is best to contact these individuals by email.
ReferenceThis press release refers to a paper to be published in the Monthly Notices of the Royal Astronomical Society Web links
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