_(2024-103).png) Artist concept of the aurora in W1935 | |
| Observation data EpochJ2000 EquinoxJ2000 | |
|---|---|
| Constellation | Sagittarius[1] |
| Right ascension | 19h 35m 18.60792s[2] |
| Declination | −15° 46′ 20.8074″[2] |
| Characteristics | |
| Evolutionary stage | brown dwarf |
| Spectral type | ≥Y1[3]+ >Y1[4] |
| Astrometry | |
| Radial velocity (Rv) | −36.9±5.1[5] km/s |
| Total velocity | 42.02±5.33[5] km/s |
| Proper motion (μ) | RA: 290.2±11.6mas/yr[3] Dec.: 43.1±11.5mas/yr[3] |
| Parallax (π) | 69.3±3.8 mas[3] |
| Distance | 47 ± 3 ly (14.4 ± 0.8 pc) |
| Details | |
| W1935A | |
| Mass | 12–39[4] MJup |
| Radius | 0.95±0.14[5] RJup |
| Surface gravity (log g) | 4.7±0.5[5] cgs |
| Temperature | 482±38[5] K |
| Age | 4.5±4.0[5] Gyr |
| W1935B | |
| Mass | 7–24[4] MJup |
| Temperature | 360–420[4] K |
| Position (relative to W1935A)[4] | |
| Component | W1935B |
| Epoch of observation | 20 September 2022 |
| Angular distance | 172.2+18.7 −7.7mas |
| Position angle | 148.12+2.86 −1.98° |
| Projected separation | 2.48+0.27 −0.11AU |
| Other designations | |
| CWISE J193518.61−154620.7, CWISEP J193518.59−154620.3,[2] W1935[6] | |
| Database references | |
| SIMBAD | data |
CWISEP J1935−1546 (CWISEP J193518.59−154620.3 or Brown Dwarf W1935 or W1935) is a coldbrown dwarf binary[4] orplanetary-mass binary[4] with a mass of 2–20MJ[7] or 6–35MJ[5] and a distance of 14.4parsecs (47light-years).[3]
CWISEP J1935−1546 was discovered in 2019 by Marocco et al. as an extremely cold brown dwarf with a temperature range of 270–360 K (−3–87 °C; 26–188 °F) and a distance of 5.6–10.9 parsecs. It was discovered with the help of the python packageXGBoost, usingmachine-learning algorithms and theCatWISE catalog, as well as theWiseView tool.[7] According to a NASA press release CWISEP J1935−1546 was discovered by thesecurity engineer[8] and citizen scientistDan Caselden.[6] Follow-up observations with Spitzer revealed a very red object with ch1-ch2 of 3.24±0.31 mag.[7] Later Kirkpatrick et al. 2021 showed a temperature of 367 ± 79 K (93.9 ± 79.0 °C; 200.9 ± 142.2 °F) and a parallax of69.3±3.8mas (14.43+0.84
−0.75 parsec) for this object. Thespectral type was estimated to be later thanY1.[3] Observations withJWST found strong signatures ofmethane,carbon monoxide,carbon dioxide,water vapor andammonia in the atmosphere of this brown dwarf. The abundance ofhydrogen sulfide was measured, but the researchers don't mention its detection.Phosphine is undetected and the researchers only provide upper limits.[5]
Using JWST MIRI imaging it was discovered that CWISEP J1935−1546 is a binary of two Y-dwarfs, only the second discovered Y-dwarf binary afterWISE J0336−0143. The researchers did aPSF-subtraction, revealing that it required two sources to successfully subtract the object in F1000W and F1280W filter images. The two objects are separated by2.48+0.27
−0.11 AU and assuming a circular orbit the orbital period would be 16–28 years. The mass ratio is quite low with q=0.55–0.62.[4]
At the 243rd meeting of theAAS it was announced that W1935, showsemission ofmethane. This is attributed to heating of the upper atmosphere by anaurora around W1935. Impacts of electrons with molecular hydrogen createstrihydrogen cation (H+
3) ingas giants with an aurora. Emission from H+
3 was not detected in W1935, likely due the higher density of the brown dwarf, which leads to a shorter lifetime of H+
3. Aurorae were discovered in the past around hotter brown dwarfs withradio telescopes. TheSolar System planetsJupiter andSaturn have an aurora because of interactions with the stellar wind and with particles from activemoons, such asEnceladus andIo. The researchers propose that the aurora around W1935 is caused by either unaccounted internal processes or by external interactions with interstellar plasma or a nearby active moon. The researchers also announced that W1935 has a temperature inversion that is either caused by the aurora or has to do with internal energy transport. These results were later published in April 2024.[6][5] The discovery of the companion W1935B allows for the alternative scenario that the companion and not the primary has the methane emission or that mechanisms in presence of the companion drive plasma formation. Observations with NIRSpec could detect periodicity of the methane emission, which could help identify which component produces the emission. Possible stable orbital configurations of an exomoon could be idenified by tracing the orbit of the Y-dwarf binary.[4]
