ALBERT

Description: The 'hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only approximately 0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94 days and a mass of ten Jupiter masses (10 M(Jup)), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 10(6), as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hellier, Coel -- Anderson, D R -- Cameron, A Collier -- Gillon, M -- Hebb, L -- Maxted, P F L -- Queloz, D -- Smalley, B -- Triaud, A H M J -- West, R G -- Wilson, D M -- Bentley, S J -- Enoch, B -- Horne, K -- Irwin, J -- Lister, T A -- Mayor, M -- Parley, N -- Pepe, F -- Pollacco, D L -- Segransan, D -- Udry, S -- Wheatley, P J -- England -- Nature. 2009 Aug 27;460(7259):1098-100. doi: 10.1038/nature08245.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK. ch@astro.keele.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19713926" target="_blank"〉PubMed〈/a〉

Description: Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gillon, Michael -- Jehin, Emmanuel -- Lederer, Susan M -- Delrez, Laetitia -- de Wit, Julien -- Burdanov, Artem -- Van Grootel, Valerie -- Burgasser, Adam J -- Triaud, Amaury H M J -- Opitom, Cyrielle -- Demory, Brice-Olivier -- Sahu, Devendra K -- Bardalez Gagliuffi, Daniella -- Magain, Pierre -- Queloz, Didier -- England -- Nature. 2016 May 2;533(7602):221-4. doi: 10.1038/nature17448.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut d'Astrophysique et de Geophysique, Universite de Liege, Allee du 6 Aout 19C, 4000 Liege, Belgium. ; NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas, 77058, USA. ; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. ; Center for Astrophysics and Space Science, University of California San Diego, La Jolla, California 92093, USA. ; Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK. ; Astrophysics Group, Cavendish Laboratory, 19 J J Thomson Avenue, Cambridge, CB3 0HE, UK. ; Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27135924" target="_blank"〉PubMed〈/a〉