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One or more bound planets per Milky Way star from microlensing observations


Cassan, A and Kubas, D and Beaulieu, J-P and Dominik, M and Horne, K and Greenhill, JG and Wambsganss, J and Menzies, J and Williams, A and Jorgensen, UG and Udalski, A and Bennett, DP and Albrow, MD and Batista, V and Brillant, S and Caldwell, JAR and Cole, AA and Coutures, C and Cook, KH and Dieters, S and Prester, DD and Donatowicz, J and Fouque, P and Hill, KM and Kains, N and Kane, S and Marquette, JB and Martin, R and Pollard, KR and Sahu, KC and Vinter, C and Warren, D and Watson, RD and Zub, M and Sumi, T and Szymanski, MK and Kubiak, M and Poleski, R and Soszynski, I and Ulaczyk, K and Pietrzynski, G and Wyrzykowski, L, One or more bound planets per Milky Way star from microlensing observations, Nature, 481, (7380) pp. 167-169. ISSN 0028-0836 (2012) [Refereed Article]

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Copyright Statement

Copyright 2012 Macmillan Publishers Limited

DOI: doi:10.1038/nature10684


Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17–30% of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002–07) that reveals the fraction of bound planets 0.5–10 AU (Sun–Earth distance) from their stars. We find that 17+6-9% of stars host Jupiter-mass planets (0.3–10 MJ,where MJ = 318 M and M is Earth’s mass). Cool Neptunes (10–30 M) and super-Earths (5–10 M) are even more common: their respective abundances per star are 52+22-29% and 62+35-37%. We conclude that stars are orbited by planets as a rule, rather than the exception.

Item Details

Item Type:Refereed Article
Keywords:astronomy, planetary sciences
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Stellar astronomy and planetary systems
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Beaulieu, J-P (Dr Jean-Philippe Beaulieu)
UTAS Author:Greenhill, JG (Dr John Greenhill)
UTAS Author:Cole, AA (Professor Andrew Cole)
UTAS Author:Dieters, S (Dr Stefan Dieters)
UTAS Author:Hill, KM (Dr Kym Hill)
UTAS Author:Warren, D (Mr David Warren)
UTAS Author:Watson, RD (Dr Bob Watson)
ID Code:78625
Year Published:2012
Web of Science® Times Cited:385
Deposited By:Mathematics and Physics
Deposited On:2012-07-10
Last Modified:2022-07-13

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