HIP 99770 b

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HIP 99770 b
HIP 99770 b.png
Subaru Telescope detection of HIP 99770 b
Discovery
Discovered by Currie et al. [1]
Discovery site Subaru Telescope
Discovery dateNovember 30, 2022
Direct imaging
Orbital characteristics [2]
15.7+3.5
−1.0 AU
Eccentricity 0.31+0.06
−0.12 [3]
47+14
−4 years
Inclination 151.3+8.4
−12.0 °
279°+72°
−269°
2,465,218+3,763
−771 JD
250°+68°
−218°
Star HIP 99770
(29 Cygni)
Physical characteristics
1.056 [2] RJ
Mass 13.1+4.8
−5.2 [2] MJ
Temperature 1,300 [2] K
Spectral type
L8 [3]

    HIP 99770 b is a directly imaged planet [1] [2] [4] or a brown dwarf [3] orbiting the A-type star HIP 99770 (29 Cygni), detected with Gaia/Hipparcos precision astrometry and high-contrast imaging. [5] HIP 99770 b is the first joint direct imaging + astrometric discovery of a companion and the first companion discovered using precision astrometry from the Gaia mission. [1]

    Contents

    Discovery

    HIP 99770 b was discovered by a team led by Thayne Currie, Mirek Brandt, and Tim Brandt using the Subaru Telescope on Mauna Kea. The Subaru data utilized the observatory's extreme adaptive optics system, SCExAO, to correct for atmospheric turbulence and the CHARIS integral field spectrograph to detect HIP 99770 b at 22 different near-infrared wavelength passbands from 1.1 microns to 2.4 microns. It was also detected at longer wavelengths using the NIRC2 camera on the Keck Observatory. [1]

    Characteristics

    The orbit of HIP 99770 b has been measured using both absolute astrometry of 29 Cygni as measured by Gaia and Hipparcos, [1] and its relative astrometry (location with respect to the host star) from from VLTI/GRAVITY [3] and SCExAO/CHARIS. [2] The most recent orbital solution give an orbital period of 47 years, a semi-major axis of 15.8  astronomical units, an orbital eccentricity of 0.29, and an inclination of 151°. [2] As the host star is significantly more luminous than the Sun, HIP 99770 b receives roughly as much light as Jupiter receives from the Sun. [1] Atmospheric modelling give a temperature of about 1,300  K and a radius of 1.056 RJ. [2] With a spectral type of L8, [3] HIP 99770 b lies at L/T transition for substellar objects, from cloudy atmospheres without methane absorption to clear atmospheres with methane absorption. The companion is likely intermediate in cloudiness between older, more massive field brown dwarfs and young L/T transition exoplanets like HR 8799 d. [1]

    The mass of HIP 99770 b straddles the deuterium burning limit, and as of such it has been considered a super-Jupiter. [3] Its mass has been measured to be as low as 13.1 MJ [2] and as high as 17 MJ. [3] The deuterium burning limit, roughly 13 MJ, is often used to separate planets from brown dwarfs, and is adopted by the International Astronomical Union's Working Group on Extrasolar Planets (WGEP). While it would imply that HIP 99770 b is likely a brown dwarf, its orbital eccentricity and mass ratio (mass divided by the mass of the host star) are better consistent with values for directly imaged planets than brown dwarfs, while also the opposite that it is more eccentric than most directly imaged planets was already claimed [3] and its relatively low orbital separation suggests it may have formed in a protoplanetary disk. Furthermore, the WGEP explicitly notes that its definition is not a normative statement and may evolve with the discovery of new objects, and recent papers show that the deuterium burning limit depends on time, metallicity, and helium abundance, is exhausted in a few tenths of a million years, and has virtually no effect on object formation, [1] while it is still the conventional choice of classifier between planets and brown dwarfs. [3]

    See also

    References

    1. 1 2 3 4 5 6 7 8 Currie, Thayne; Brandt, G. Mirek; Brandt, Timothy D.; Lacy, Brianna; Burrows, Adam; Guyon, Olivier; Tamura, Motohide; Liu, Ranger Y.; Sagynbayeva, Sabina; Tobin, Taylor; Chilcote, Jeffrey; Groff, Tyler; Marois, Christian; Thompson, William; Murphy, Simon J. (April 14, 2023), "Direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star", Science, 380 (6641): 198–203, arXiv: 2212.00034 , Bibcode:2023Sci...380..198C, doi:10.1126/science.abo6192, ISSN   0036-8075
    2. 1 2 3 4 5 6 7 8 9 Bovie, Danielle; Currie, Thayne; Morsy, Mona El; Lacy, Brianna; Kuzuhara, Masayuki; Chilcote, Jeffrey; Tobin, Taylor; Guyon, Olivier; Groff, Tyler (September 2, 2025), "Multi-band Spectral and Astrometric Characterization of the HIP 99770 b Planet with SCExAO/CHARIS and Gaia", The Astronomical Journal, arXiv: 2509.02665
    3. 1 2 3 4 5 6 7 8 9 Winterhalder, T. O.; Kammerer, J.; Lacour, S.; Mérand, A.; Nowak, M.; Stolker, T.; Balmer, W. O.; Marleau, G.-D.; Abuter, R.; Amorim, A.; Asensio-Torres, R.; Berger, J.-P.; Beust, H.; Blunt, S.; Bonnefoy, M. (June 27, 2025), "Orbit and atmosphere of HIP 99770 b through the eyes of VLTI/GRAVITY", Astronomy & Astrophysics, arXiv: 2507.00117 , doi:10.1051/0004-6361/202554766, ISSN   0004-6361
    4. ↑ "HIP 99770 Overview". NASA Exoplanet Archive.
    5. ↑ Andrew Jones (April 17, 2023), "Giant exoplanet found, imaged directly thanks to star-mapping data (photos)", Space.com

    Further reading

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