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

@article{Beaulieu2006DiscoveryOA,
  title={Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing},
  author={Jean Philippe Beaulieu and David P. Bennett and P Fouqu{\'e} and A. Williams and Martin Dominik and U. G. J{\o}rgensen and Daniel Kubas and Arnaud Cassan and Ch. Coutures and John G. Greenhill and K. M. Hill and John W Menzies and Penny Sackett and Michael D. Albrow and St{\'e}phane Brillant and John A. R. Caldwell and Johannes J. Calitz and K. H. Cook and Ernesto Corrales and Morgan Desort and Stefan W. Dieters and Dijana Dominis and Jadzia Donatowicz and M. Hoffman and Stephen R. Kane and Jean Baptiste Marquette and R. M. Martin and Petrus J. Meintjes and Karen Pollard and Kailash C. Sahu and Christian Vinter and Joachim Wambsganss and Kristian Woller and Keith Horne and Iain A. Steele and D. M. Bramich and Martin J{\"o}rg Burgdorf and Colin Snodgrass and Michael F. Bode and Andrzej Udalski and Michał K. Szymański and Marcin Kubiak and T. Wickowski and Grzegorz Pietrzyński and Igor Soszyński and Olaf Szewczyk and Łukasz Wyrzykowski and Bohdan Paczyński and Fumio Abe and Ian A. Bond and Tui R Britton and Alan C. Gilmore and John B. Hearnshaw and Yoshitaka Itow and Koki Kamiya and Pam M. Kilmartin and Aarno Korpela and Kimiaki Masuda and Yoshimi Matsubara and Masanori Motomura and Yasushi Muraki and S. Nakamura and Chiho Okada and Kouji Ohnishi and Nicholas J. Rattenbury and T. K. Sako and S. Sato and M. Sasaki and Tomohiko Sekiguchi and Denis J. Sullivan and Paul . J. Tristram and Ph. Yock and Takehiro Yoshioka},
  journal={Nature},
  year={2006},
  volume={439},
  pages={437-440}
}
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. More than 170… 
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