VLT NACO image, taken in the Ks-band, of GQ Lupi. The feeble point of light to the right of the star is the newly found cold companion. It is 250 times fainter than the star itself and it located 0.73 arc second west. At the distance of GQ Lupi, this corresponds to a distance of roughly 100 AU. North is up and East is to the left.
GQ Lupi b has a spectral type between M6 and L0, corresponding to a temperature between 2,050 and 2,650 kelvins.[2] Located at a projected distance of about 100 AU from its companion star, giving it an orbital period of perhaps about 1,200 years, it is believed to be several times more massive than Jupiter. Because the theoretical models which are used to predict planetary masses for objects in young star systems like GQ Lupi b are still tentative, the mass cannot be precisely specified — models place GQ Lupi b's mass anywhere between a few Jupiter masses and 36 Jupiter masses.[2] At the highest end of this range, GQ Lupi b could be classified as a small brown dwarf, but at the lowest end of this range, it could be classified as an extremely large Jupiter-like exoplanet rather than a brown dwarf.
As of 2006, the International Astronomical Union Working Group on Extrasolar Planets described GQ Lupi b as a "possible planetary-mass companion to a young star."[8] GQ Lupi b is listed as a "confirmed planet" as of 2020.[9]
Accretion disk
Emission by hydrogen in the near-infrared (paschen beta) was first detected in 2007 with the Very Large Telescope (VLT). This was interpreted as a sign of accretion of material from a disk.[10] Additionally H-alpha emission was detected with Hubble.[11] H-alpha was also detected with the Magellan Telescope, but the disk was not detected with ALMA.[12] An analysis of additional VLT data showed a mutual inclination with the circumstellar disk of 84 ± 9°. This hints to a turbulent formation of the disk around GQ Lupi b. The researchers suspect the disk to be in a transitional stage in which satellites (similar to exomoons) opened a gap within the disk, indicating a late stage of the disk. The accretion rate was estimated to be 10−6.5MJ/year.[13] A study from 2023 with additional VLT data found the emission line to be variable on timescales of several months to decades. The observations were consistent with magnetospheric accretion.[14] Mid-infrared observations with JWST MIRI did not show any silicate features from the disk. This indicates grain growth and dust settling. Additionally the disk could have an inner cavity that is larger than allowed by sublimation.[15]
^ abcdAstrometric and photometric monitoring of GQ Lupi and its sub-stellar companion, Ralph Neuhäuser, Markus Mugrauer, Andreas Seifahrt, Tobias Schmidt, and Nikolaus Vogt, Astronomy and Astrophysics484, #1 (2008), pp. 281–291. doi:10.1051/0004-6361:20078493. Bibcode:2008A&A...484..281N
