VHS J1256 1257 Latitude and Longitude:

Sky map 12h 56m 02.15s, −12° 57′ 21.7″
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VHS J125601.92–125723.9
Observation data
Epoch J2000.0       Equinox J2000.0
Constellation Corvus
Right ascension 12h 56m 02.1337s [1]
Declination −12° 57′ 21.924″ [1]
Apparent magnitude (V) 17.759 ± 0.059 [2]
VHS J1256–1257AB
Spectral type M7.5 ± 0.5 [2]
VHS J1256–1257 b
Spectral type L7.0 ± 1.5 [2]
Apparent magnitude (J) 16.662 ± 0.287 [2]
Apparent magnitude (H) 15.595 ± 0.209 [2]
Apparent magnitude (K) 14.568 ± 0.121 [2]
Radial velocity (Rv)−1.4 ± 4.5 [2] km/s
Proper motion (μ) RA: −272.462±0.574  mas/ yr [1]
Dec.: −190.239±0.501  mas/ yr [1]
Parallax (π)47.2733 ± 0.4731  mas [1]
Distance69.0 ± 0.7  ly
(21.2 ± 0.2  pc)
Details [3]
VHS J1256–1257 AB
Luminosity (bolometric)0.0011±0.0002 (10−2.95 ± 0.07L
Temperature2620±140 [2]  K
Rotation2.0782±0.0004 (A)
2.1342±0.0003 (B) [4]
Rotational velocity (v sin i)75.2+2.7
[5] km/s
Age140±20 [6]  Myr
VHS J1256–1257 b
Mass19±5  MJup
Radius1.13–1.21 [7]  RJup
Luminosity (bolometric)10−4.54 ± 0.07  L
Surface gravity (log g)4.55+0.15
Temperature1240±50  K
Rotation22.04±0.05 h [7]
Rotational velocity (v sin i)13.5+3.6
[5] km/s
Age140±20 [6]  Myr
Orbit [6]
PrimaryVHS J1256–1257 A
CompanionVHS J1256–1257 B
Period (P)7.31±0.02 yr
Semi-major axis (a)1.96±0.03 AU
Eccentricity (e)0.8826+0.0025
Inclination (i)118.7±1.0°
Longitude of the node (Ω)4.4±0.5°
Periastron epoch (T)2021.537+0.015
Argument of periastron (ω)
Position (relative to VHS J1256–1257AB) [2]
ComponentVHS J1256–1257 b
Epoch of observation MJD 55743.067635 (1 July 2011)
Angular distance8.06 ± 0.03
Position angle218.1 ± 0.2°
Observed separation
102 ± 9 AU
Other designations
VHS J1256–1257AB: 2MASS J12560215–1257217, TIC 2470992, SIPS J1256–1257, WDS J12560-1257A, WISE J125601.94–125723.7 [8]
VHS J1256–1257 b: 2MASS J12560183–1257276, TIC 2470993, WDS J12560-1257B, WISEA J125601.66–125728.7 [9]
Database references
Extrasolar Planets

VHS J125601.92–125723.9 (abbreviated to VHS J1256–1257) is a young triple brown dwarf system located in the constellation Corvus approximately 69.0 light-years (21.2 parsecs) from the Sun. [1] The system consists of the equal-mass binary VHS J1256–1257AB and the distant planetary-mass companion VHS 1256–1257 b. [2] [10] In 2022, a continuous radio emission from the radiation belts surrounding VHS J1256–1257 was detected. [11]

VHS 1256–1257 b

Artist's impression of VHS 1256 b in orbit

VHS 1256–1257 b was first identified and documented by the 2MASS survey in 2015. [2] It orbits at a distance of 350+150
AU and has an estimated mass of approximately 19±5 Jupiter masses. [12] [13] [14] [6]

The planet is carbon-rich, with a C/O molar ratio exceeding 0.63, and its temperature has been measured at 1380±54 K. [15] VHS 1256-1257 b's rotation period has been measured to be 22.04 ± 0.05 hours, which is unusually long for substellar objects. [16] [17]


Observations with Hubble Wide-Field Camera 3 near-infrared time-series spectroscopic observations showed that VHS 1256 b varied with 19.3% at 1.1 and 1.7 μm over 8.5 hours. With the 1.27 μm filter the amplitude was even higher at 24.7%. [17] This is the largest amplitude for any substellar object as of 2022, placing it in the mid-infrared. [16] [18] Later studies with the Hubble space telescope have yielded even higher brightness variability of 33-37% without a definite period, indicating a presence of both spots and waves. [19]

Atmospheric composition

The atmosphere of VHS 1256 b is in a chemical disequilibrium. [18] Carbon monoxide naturally reacts with hydrogen molecules in the atmosphere of brown dwarfs, forming methane and water molecules. The reaction works in both ways, meaning that methane reacts with water and releases hydrogen and carbon monoxide. At higher temperatures and lower pressure the reaction is tilted towards carbon monoxide and at lower temperatures and higher pressure the reaction is tilted towards methane. At equilibrium a cold brown dwarf or planet should have a high concentration of methane and a low concentration of carbon monoxide. [20] The presence of carbon monoxide and depleted methane in the spectrum of VHS 1256 b compared to equilibrium atmospheric models suggests atmospheric mixing. The vertical mixing causes carbon monoxide to rise from lower and hotter atmospheric layers and methane to sink into these lower layers, forcing the upper atmosphere in chemical disequilibrium. [18]

Water and carbon monoxide have both been detected in the atmosphere. [21] The JWST observed the planet in 2022 by taking spectra at a wavelength of 1-20 μm with the instruments NIRSpec and MIRI. The team analysing the data found water vapor, methane, carbon monoxide, carbon dioxide, sodium, potassium and silicate clouds within the atmosphere of VHS 1256 b. The direct detection of silicate clouds is the first such detection reported for a planetary-mass object. The silicates are thought to be made of small amorphous silicate particles. The silicate feature in VHS 1256 b closely matches the silicate feature in the L4.5 brown dwarf 2M2224-0158, detected with Spitzer. The grain size and composition of the silicate clouds in VHS 1256 b will be modelled in the future. [18]

The VHS J1256–1257 planetary system [6]
(in order from star)
Mass Semimajor axis
( AU)
Orbital period
( years)
Eccentricity Inclination Radius
b 11.8±0.2  MJ 360+110


  1. ^ a b c d e Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv: 2208.00211. doi: 10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d e f g h i j k Gauza, Bartosz; Béjar, Victor J. S.; Pérez-Garrido, Antonio; Zapatero Osorio, Maria Rosa; Lodieu, Nicolas; Rebolo, Rafael; et al. (May 2015). "Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9". The Astrophysical Journal. 804 (2): 18. arXiv: 1505.00806. Bibcode: 2015ApJ...804...96G. doi: 10.1088/0004-637X/804/2/96. S2CID  118735358. 96.
  3. ^ Dupuy, Trent J.; Liu, Michael C.; Magnier, Eugene A.; Best, William M. J.; Baraffe, Isabelle; Chabrier, Gilles; et al. (April 2020). "The Parallax of VHS J1256-1257 from CFHT and Pan-STARRS-1". Research Notes of the AAS. 4 (4): 54. arXiv: 2004.05180. Bibcode: 2020RNAAS...4...54D. doi: 10.3847/2515-5172/ab8942. S2CID  215744970. 54.
  4. ^ Miles-Páez, Paulo A. (2021). "Detection of photometric variability in the very low-mass binary VHS J1256-1257AB using TESS and Spitzer". Astronomy & Astrophysics. 651: L7. arXiv: 2004.05180. Bibcode: 2021A&A...651L...7M. doi: 10.1051/0004-6361/202141203. S2CID  235694454.
  5. ^ a b Bryan, Marta L.; Benneke, Björn; Knutson, Heather A.; Batygin, Konstatin; Bowler, Brendan P. (December 2018). "Constraints on the spin evolution of young planetary-mass companions". Nature Astronomy. 2 (2): 138–144. arXiv: 1712.00457. Bibcode: 2018NatAs...2..138B. doi: 10.1038/s41550-017-0325-8. S2CID  119421455.
  6. ^ a b c d e Dupuy, Trent J.; Liu, Michael C.; Evans, Elise L.; Best, William M. J.; Pearce, Logan A.; Sanghi, Aniket; Phillips, Mark W.; Bardalez Gagliuffi, Daniella C. (2023), "On the masses, age, and architecture of the VHS J1256−1257AB b system", Monthly Notices of the Royal Astronomical Society, 519 (2): 1688–1694, arXiv: 2208.08448, Bibcode: 2023MNRAS.519.1688D, doi: 10.1093/mnras/stac3557
  7. ^ a b Zhou, Yifan; Bowler, Brendan P.; Morley, Caroline V.; Apai, Dániel; Kataria, Tiffany; Bryan, Marta L.; Benneke, Björn (August 2020). "Spectral Variability of VHS J1256-1257b from 1 to 5 μm". The Astronomical Journal. 160 (2): 77. arXiv: 2004.05168. Bibcode: 2020AJ....160...77Z. doi: 10.3847/1538-3881/ab9e04. S2CID  215745742. 77.
  8. ^ "VHS J1256-1257 -- Low-mass star (M<1solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 1 July 2021.
  9. ^ "VHS J1256-1257B -- Brown Dwarf (M<0.08solMass)". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 July 2021.
  10. ^ Stone, Jordan M.; Skemer, Andrew J.; Kratter, Kaitlin M.; Dupuy, Trent J.; Close, Laird M.; Eisner, Josh A.; et al. (February 2016). "Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System". The Astrophysical Journal Letters. 818 (1): 5. arXiv: 1601.03377. Bibcode: 2016ApJ...818L..12S. doi: 10.3847/2041-8205/818/1/L12. S2CID  118504775. L12.
  11. ^ Climent, J. B.; Guirado, J. C.; Zapatero Osorio, M. R.; Zakhozhay, O. V.; Pérez-Torres, M.; Azulay, R.; Gauza, B.; Rebolo, R.; Béjar, V. J. S.; Martín-Pintado, J.; Lefèvre, C. (2022), "Radio emission in a nearby, ultra-cool dwarf binary: A multifrequency study", Astronomy & Astrophysics, 660: A65, arXiv: 2201.12606, Bibcode: 2022A&A...660A..65C, doi: 10.1051/0004-6361/202142260, S2CID  246431037
  12. ^ Rich, Evan A.; Currie, Thayne; Wisniewski, John P.; Hashimoto, Jun; Brandt, Timothy D.; Carson, Joseph C.; et al. (October 2016). "Thermal Infrared Imaging and Atmospheric Modeling of VHS J125601.92-125723.9 b: Evidence for Moderately Thick Clouds and Equilibrium Carbon Chemistry in a Hierarchical Triple System". The Astrophysical Journal. 830 (2): 10. arXiv: 1607.06007. Bibcode: 2016ApJ...830..114R. doi: 10.3847/0004-637X/830/2/114. S2CID  119221162. 114.
  13. ^ Miles, Brittany E.; Skemer, Andrew J.; Barman, Travis S.; Allers, Katelyn N.; Stone, Jordan M.; et al. (December 2018). "Methane in Analogs of Young Directly Imaged Exoplanets". The Astrophysical Journal. 869 (1): 11. arXiv: 1810.04684. Bibcode: 2018ApJ...869...18M. doi: 10.3847/1538-4357/aae6cd. S2CID  113400693. 18.
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  19. ^ Zhou, Yifan; Bowler, Brendan P.; Apai, Dániel; Kataria, Tiffany; Morley, Caroline V.; Bryan, Marta L.; Skemer, Andrew J.; Benneke, Björn (2022), "Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space Telescope Multi-epoch Monitoring Reveals Vigorous Evolution in an Ultracool Atmosphere", The Astronomical Journal, 164 (6): 239, arXiv: 2210.02464, Bibcode: 2022AJ....164..239Z, doi: 10.3847/1538-3881/ac9905, S2CID  252734903
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External links