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VHS 1256–1257 Exoplanet System

A young triple brown dwarf system with roaring dust storms //

VHS J125601.92–125723.9, or more simply VHS 1256–1257, is a real exoplanet system located 69.0 light-years away in the constellation Corvus. It is a young system of 140 million years with an inner brown dwarf binary and an outer companion. The binary objects—named VHS 1256–1257 A and VHS 1256–1257 B—are thought to be near-identical, each weighing around 74 Jupiter masses and a little below the threshold to become a star. The pair are fairly hot with a modelled temperature of 2620 K and an M7.5 spectral type. They circle each other every 7.3 years on highly eccentric orbits—in fact, the highest ever seen in low-mass binaries.

VHS 1256–1257 b is a companion of spectral type L7 discovered around the twin hosts in 2015. It is likely a third brown dwarf that follows an incredibly long ~16,000-year orbit with an average distance of 350 AU. Its path is also eccentric, and may even be going retrograde (in the opposite direction) relative to its parent bodies. In comparison, Neptune orbits the Sun at a mere 30 AU. There is some uncertainty surrounding the mass and size of VHS 1256–1257 b. Recent modelling suggests a 60% chance that it possesses 16 times the mass and 1.22 times the radius of Jupiter with a temperature of 1194 K, though other parameters have been proposed.

VHS 1256–1257 b is a prime candidate for atmospheric studies. It displays wild brightness fluctuations over a matter of hours and holds the second-highest variability ever seen in a brown dwarf, pointing to a highly turbulent atmosphere of patchy clouds. But these are a far cry from the water clouds on Earth, instead being composed of a gritty mix of silicate. The conditions could be best imagined as a churning storm of superheated dust ranging from a fine smoke-like mist to larger sand-sized grains. Other compounds like water vapour, methane, carbon monoxide and carbon dioxide have also been detected in the swirling giant. Vertical mixing causes carbon monoxide to rise from lower and hotter layers and methane to sink down, forcing the upper atmosphere into a chemical disequilibrium. Overall, VHS 1256–1257 b is an exciting target for improving our understanding of atmospheric dynamics and brown dwarf evolution.

In this simulation, features of the VHS 1256–1257 system are replicated from existing data wherever possible or inferred in cases of knowledge gaps:

• VHS 1256–1257 b is most widely reported to have a 22.04 h rotation period, but this is a rough estimate and has been called into question.
  
• The magnetic field strength of the inner binary VHS 1256–1256 AB has been modelled at a powerful 1700 gauss. The authors of the same paper also suggest a strength of 100 gauss for VHS 1256–1257 b.
  
• Temperature simulation has been turned OFF to replicate the objects' real-life temperatures. Universe Sandbox has its own model for brown dwarf heating and its values are higher than reported in scientific literature. You may switch it back on via Sim > Temperature.
  
• This stimulation has accurate and functional orbits, but trail mode is recommended due to display limitations of orbit mode in circumbinary systems. Lastly, VHS 1256–1257 b would appear to move slowly at the default simulation speed but keep in mind the long timescales at work: even at 2 year/sec, one full orbit requires over 2 h of real-life time!

A special mention to @Gluestick_55 for suggesting this system.

2MASS J12560215-1257217, SIPS J1256-1257, VHS J125601.92-125723.9, WISE J125601.96-125723.9, ** SJM 1, TIC 2470992, WDS J12560-1257A, Gaia DR3 3526198184723289472, ** SKF 2542A, VHS J1256-1257, WDS J12560-1257Aa,Ab, Gaia DR2 3526198184723289472

• Dupuy, T.J., Liu, M.C., Evans, E.L., Best, W.M., Pearce, L.A., Sanghi, A., Phillips, M.W. and Bardalez Gagliuffi, D.C., 2023. On the masses, age, and architecture of the VHS J1256− 1257AB b system. Monthly Notices of the Royal Astronomical Society, 519(2), pp.1688-1694.
  
• Gauza, B., Béjar, V.J., Pérez-Garrido, A., Osorio, M.R.Z., Lodieu, N., Rebolo, R., Pallé, E. and Nowak, G., 2015. Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601. 92-125723.9. The Astrophysical Journal, 804(2), p.96.
  
• Guirado, J.C., Azulay, R., Gauza, B., Pérez-Torres, M.A., Rebolo, R., Climent, J.B. and Osorio, M.Z., 2018. Radio emission in ultracool dwarfs: The nearby substellar triple system VHS 1256–1257. Astronomy & Astrophysics, 610, p.A23.
  
• Miles, B.E., Biller, B.A., Patapis, P., Worthen, K., Rickman, E., Hoch, K.K., Skemer, A., Perrin, M.D., Whiteford, N., Chen, C.H. and Sargent, B., 2023. The JWST Early-release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 μm Spectrum of the Planetary-mass Companion VHS 1256–1257 b. The Astrophysical journal letters, 946(1), p.L6.
  
• Stone, J.M., Skemer, A.J., Kratter, K.M., Dupuy, T.J., Close, L.M., Eisner, J.A., Fortney, J.J., Hinz, P.M., Males, J.R., Morley, C.V. and Morzinski, K.M., 2016. Adaptive optics imaging of VHS 1256–1257: A low mass companion to a Brown dwarf binary system. The Astrophysical Journal Letters, 818(1), p.L12.
  
• Zhou, Y., Bowler, B.P., Apai, D., Kataria, T., Morley, C.V., Bryan, M.L., Skemer, A.J. and Benneke, B., 2022. Roaring Storms in the Planetary-mass Companion VHS 1256-1257 b: Hubble Space Telescope Multiepoch Monitoring Reveals Vigorous Evolution in an Ultracool Atmosphere. The Astronomical Journal, 164(6), p.239.
  
• Zhou, Y., Bowler, B.P., Morley, C.V., Apai, D., Kataria, T., Bryan, M.L. and Benneke, B., 2020. Spectral Variability of VHS J1256–1257b from 1 to 5 μm. The Astronomical Journal, 160(2), p.77.