WASP-49 is a binary star system about 636 light-years (195 parsecs) away in the constellation Lepus. The two stars are separated by 443 AU.[6] The primary is a G-type main-sequence star, with a surface temperature of 5,600 K (5,330 °C; 9,620 °F). WASP-49 is depleted of heavy elements relative to the Sun. It has a metallicity Fe/H index of –0.23, meaning it has 59% the iron level of the Sun.[5]
In 2017, WASP-49b was found to have an extensive sodium envelope.[3] A study in 2019 using data from the Hubble Space Telescope in near-UV found clear absorption features caused by metals, including magnesium and iron. The gaseous magnesium and iron is not gravitationally bound to the planet, but could be magnetically confined to it.[9][10] The sodium layer around WASP-49b could be due to a tidally-heated Io-like exomoon.[11][12] In October 2024, a 5-year study was published indicating that the sodium envelope most likely comes from a distinct body orbiting WASP-49b rather than the star or the planet, although the exact dynamics of the envelope remains to be settled.[13][14]
^Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 –L30. Bibcode:2000A&A...355L..27H.
^ abLendl, M.; Anderson, D. R.; Collier-Cameron, A.; Doyle, A. P.; Gillon, M.; Hellier, C.; Jehin, E.; Lister, T. A.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Smalley, B.; Ségransan, D.; Smith, A. M. S.; Triaud, A. H. M. J.; Udry, S.; West, R. G.; Wheatley, P. J. (2012), "WASP-42 b and WASP-49 b: Two new transiting sub-Jupiters", Astronomy & Astrophysics, 544: A72, arXiv:1205.2757, Bibcode:2012A&A...544A..72L, doi:10.1051/0004-6361/201219585, S2CID54186638
