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Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing


Beaulieu, J-P and Bennett, DP and Fouque, P and Williams, A and Dominik, M and Jorgensen, UG and Kubas, D and Cassan, A and Coutures, C and Greenhill, JG and Hill, KM and Menzies, J and Sackett, PD and Albrow, M and Brilliant, S and Caldwell, JAR and Calitz, JJ and Cook, KH and Corrales, E and Desort, M and Dieters, S and Dominis, D and Donatowicz, J and Hoffman, M and Kane, S and Marquette, JB and Martin, R and Meintjes, P and Pollard, K and Sahu, K and Vinter, C and Wambsganss, J and Woller, K and Horne, K and Steele, I and Bramich, DM and Burgdorf, M and Snodgrass, C and Bode, M and Udalski, A and Szymanski, MK and Kubiak, M and Wieckowski, T and Pietrzynski, G and Soszynski, I and Szewczyk, O and Wyrzykowski, L and Paczynski, B and Abe, F and Bond, IA and Britton, TR and Gilmore, AC and Hearnshaw, JB and Itow, Y and Kamiya, K and Kilmartin, PM and Korpela, AV and Masuda, K and Matsubara, Y and Motomura, M and Muraki, Y and Nakamura, S and Okada, C and Ohnishi, K and Rattenbury, NJ and Sako, T and Sato, S and Sasaki, M and Sekiguchi, T and Sullivan, DJ and Tristram, PJ and Yock, PCM and Yoshioka, T, Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing, Nature, 439, (7075) pp. 437-440. ISSN 0028-0836 (2006) [Refereed Article]

DOI: doi:10.1038/nature04441


In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M ⊕) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (AU), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars 1-4. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 AU from normal stars. Here we report the discovery of a 5.5 -2.7 +5.5 M ⊕ planetary companion at a separation of 2.6 -0.6 +1.5 AU from a 0.22 -0.11 +0.21 M ⊙ M-dwarf star, where M ⊙ refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory. © 2006 Nature Publishing Group.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the mathematical sciences
UTAS Author:Beaulieu, J-P (Dr Jean-Philippe Beaulieu)
UTAS Author:Greenhill, JG (Dr John Greenhill)
UTAS Author:Hill, KM (Dr Kym Hill)
UTAS Author:Dieters, S (Dr Stefan Dieters)
ID Code:37583
Year Published:2006
Web of Science® Times Cited:478
Deposited By:Physics
Deposited On:2006-08-01
Last Modified:2022-06-03

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