A team of astronomers, led by Phil Lucas of Hertfordshire University in the UK, have discovered what is currently the coldest star-like object. The object, called UGPS J0722-05, is also of particular interest because it is one of our closest neighbours. The result is published in The Monthly Notices of the Royal Astronomical Society. UGPS J0722-05 is a cold brown dwarf; these small Jupiter-sized objects are hard to find as they are very faint, and they become fainter, and so even harder to find, with decreasing temperature. UGPS J0722-05 was identified as the only possible brown dwarf in a search of over 600 million sources detected in the plane of our Galaxy by the UK Infrared Telescope (UKIRT) as part of the UKIRT Infrared Deep Sky Survey (UKIDSS). Read more
Title: The discovery of the T8.5 dwarf UGPS J0521+3639 Authors: Ben Burningham, P.W. Lucas, S. K. Leggett, R. Smart, D. Baker, D. J. Pinfield, C. G. Tinney, D. Homeier, F. Allard, Z. H. Zhang, J. Gomes, A. C. Day-Jones, H.R.A. Jones, G. Kovacs, N. Lodieu, F. Marocco, D. N. Murray, B. Sipocz
We have carried out a search for late-type T dwarfs in the UKIDSS Galactic Plane Survey 6th Data Release. The search yielded two persuasive candidates, both of which have been confirmed as T dwarfs. The brightest, UGPS J0521+3639 has been assigned the spectral type T8.5 and appears to lie at a distance of 7-9 pc. The fainter of the two, UGPS J0652+0324, is classified as a T5.5 dwarf, and lies at an estimated distance of 28-37 pc. Warm-Spitzer observations in IRAC channels 1 and 2, taken as part of the GLIMPSE360 Legacy Survey, are available for UGPS J0521+3639 and we used these data with the near-infrared spectroscopy to estimate its properties. We find best fitting solar metallicity BT-Settl models for Teff = 600K and 650K and log g = 4.5 and 5.0. These parameters suggest a mass of between 14 and 32 MJup for an age between 1 and 5 Gyr. The proximity of this very cool T dwarf, and its location in the Galactic plane makes it an ideal candidate for high resolution adaptive optics imaging to search for cool companions.