WASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars

D.R. Anderson, A. Collier Cameron, C. Hellier, M. Lendl, T.A. Lister, P.F.L. Maxted, D. Queloz, B. Smalley, A.M.S. Smith, A.H.M.J. Triaud, D.J.A. Brown, M. Gillon, M. Neveu-Vanmalle, F. Pepe, D. Pollacco, D. Ségransan, S. Udry, R.G. West, P.J. Wheatley

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We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31M; 1.46R) in a 4.9-day, near-aligned (λ = 12.7 ± 4.2) orbit around CD-24 102 (V = 10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91M; 1.21R) in a 3.4-day, near-aligned (λ = 8 ± 18) orbit around a V = 12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7 Gyr and 6000 ± 100 K for WASP-20; 5 Gyr and 6100 ± 150 K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars' spins via tidal dissipation.
Original languageEnglish
Article numberA64
Number of pages8
JournalAstronomy & Astrophysics
Early online date24 Feb 2015
Publication statusPublished - Mar 2015


  • Planetary systems
  • Stars: individual: WASP-20b
  • Stars: individual: WASP-28b


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