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Thomas Bensby. Profile photo.

Thomas Bensby

Senior lecturer

Thomas Bensby. Profile photo.

The first Neptune analog or super-earth with a Neptune-like orbit : MOA-2013-BLG-605LB


  • T. Sumi
  • A. Udalski
  • D. P. Bennett
  • A. Gould
  • R. Poleski
  • I. A. Bond
  • J. Skowron
  • N. Rattenbury
  • R. W. Pogge
  • T. Bensby
  • J. P. Beaulieu
  • J. B. Marquette
  • V. Batista
  • S. Brillant
  • F. Abe
  • Y. Asakura
  • A. Bhattacharya
  • M. Donachie
  • M. Freeman
  • A. Fukui
  • Y. Hirao
  • Y. Itow
  • N. Koshimoto
  • M. C A Li
  • C. H. Ling
  • K. Masuda
  • Y. Matsubara
  • Y. Muraki
  • M. Nagakane
  • K. Ohnishi
  • H. Oyokawa
  • To Saito
  • A. Sharan
  • D. J. Sullivan
  • D. Suzuki
  • P. J. Tristram
  • A. Yonehara
  • M. K. Szymański
  • K. Ulaczyk
  • S. Kozłowski
  • Wyrzykowski
  • M. Kubiak
  • P. Pietrukowicz
  • G. Pietrzyński
  • I. Soszyński
  • C. Han
  • Y. K. Jung
  • I. G. Shin
  • C. U. Lee

Summary, in English

We present the discovery of the first Neptune analog exoplanet or super-Earth with a Neptune-like orbit, MOA-2013-BLG-605Lb. This planet has a mass similar to that of Neptune or a super-Earth and it orbits at 9 ∼ 14 times the expected position of the snow line, a snow, which is similar to Neptune's separation of 11 a snow from the Sun. The planet/host-star mass ratio is q = (3.6 ± 0.7) × 10-4 and the projected separation normalized by the Einstein radius is s = 2.39 ± 0.05. There are three degenerate physical solutions and two of these are due to a new type of degeneracy in the microlensing parallax parameters, which we designate "the wide degeneracy." The three models have (i) a Neptune-mass planet with a mass of Mp = 21-7 +6M orbiting a low-mass M-dwarf with a mass of Mh = 0.19-0.06 +0.05M, (ii) a mini-Neptune with Mp = 7.9-1.2 +1.8M orbiting a brown dwarf host with Mh = 0.068-0.011 +0.019M, and (iii) a super-Earth with Mp = 3.2-0.3 +0.5MM orbiting a low-mass brown dwarf host with Mh = 0.025-0.0004 +0.005M, which is slightly favored. The 3D planet-host separations are 4.6-1.2 +4.7au, 2.1-0.2 +1.0au, and 0.94-0.02 +0.67au, which are 8.9-1.4 +10.5, 12-1 +7, or 14-1 +11 times larger than a snow for these models, respectively. Keck adaptive optics observations confirm that the lens is faint. This discovery suggests that low-mass planets with Neptune-like orbits are common. Therefore processes similar to the one that formed Neptune in our own solar system or cold super-Earths may be common in other solar systems.


  • Lund Observatory - Has been reorganised
  • Department of Physics

Publishing year





Astrophysical Journal





Document type

Journal article


American Astronomical Society


  • Astronomy, Astrophysics and Cosmology


  • Galaxy: bulge
  • gravitational lensing: micro
  • planetary systems




  • ISSN: 0004-637X