WD 1856+534

WD 1856+534

Artist's impression of WD 1856+534 and its planet.
Observation data Epoch J2000      Equinox J2000
Constellation	Draco
WD 1856+534
Right ascension	18h 57m 39.34s[1]
Declination	+53° 30′ 33.30″[1]
Apparent magnitude (V)	17.244±0.046[2]
G 229-20 A
Right ascension	18h 57m 38.4s[2]
Declination	53° 31′ 14.43″[2]
Apparent magnitude (V)	13.15[2]
G 229-20 B
Right ascension	18h 57m 38.33s[2]
Declination	53° 31′ 12.24″[2]
Apparent magnitude (V)	13.23[2]
Characteristics
WD 1856+534
Evolutionary stage	white dwarf
Spectral type	DA[3]
Apparent magnitude (J)	15.677±0.055[1]
Apparent magnitude (H)	15.429±0.094[1]
Apparent magnitude (K)	15.548±0.186[1]
Astrometry
Proper motion (μ)	RA: −240.759±0.148[1] mas/yr Dec.: −52.514±0.143[1] mas/yr
Parallax (π)	40.3983±0.0705[1] mas
Distance	80.737±0.144 ly (24.754±0.044[4] pc)
G 299-20 A
Proper motion (μ)	RA: 256.12 mas/yr[2] Dec.: -52.72 mas/yr[2]
Parallax (π)	40.298 ± 0.024 mas[2]
Distance	80.94 ± 0.05 ly (24.82 ± 0.01 pc)
G 299-20 B
Proper motion (μ)	RA: 241.4[2] mas/yr[2] Dec.: -44.176 mas/yr[2]
Parallax (π)	40.33 ± 0.024 mas[2]
Distance	80.87 ± 0.05 ly (24.80 ± 0.01 pc)
Details[3]
WD 1856+534
Mass	0.576±0.040 M☉
Radius	0.01263±0.00050 R☉
Surface gravity (log g)	7.995±0.065 cgs
Temperature	4860±60 K
Metallicity [Fe/H]	<−8.8[4] dex
Age	6.60±0.48 Gyrs (cooling age) 8 to 10 (total age) Gyr
G 299-20 A[4]
Mass	0.335±0.024 M☉
Radius	0.35±0.02 R☉
Temperature	3,521 K
G 299-20 B[4]
Mass	0.322±0.023 M☉
Radius	0.34±0.02 R☉
Temperature	3,513 K
Position (relative to G 229-20)[4]
Angular distance	~43″
Projected separation	1030+130 −55 AU [4]
Other designations
LP 141-14, LSPM J1857+5330, 2MASS J18573936+5330332, NLTT 47263, TIC 267574918, TOI-1690, WDS J18576+5331C, WISE J185739.62+533032.9
Database references
SIMBAD	data
Exoplanet Archive	data

WD 1856+534 is a white dwarf located in the constellation of Draco. At a distance of about 25 parsecs (80 ly) from Earth, it is the outer component of a visual triple star system consisting of an inner pair of red dwarf stars, named G 229-20. The white dwarf displays a featureless absorption spectrum, lacking strong optical absorption or emission features in its atmosphere. It has an effective temperature of 4,700 K (4,430 °C; 8,000 °F), corresponding to an age of approximately 5.8 billion years.^[4] WD 1856+534 is approximately half as massive as the Sun, while its radius is much smaller, being 40% larger than Earth.^[5]

The white dwarf is known to host one exoplanet, WD 1856+534 b, in orbit around it. The exoplanet was detected through the transit method by the Transiting Exoplanet Survey Satellite (TESS) between July and August 2019. An analysis of the transit data in 2020 revealed that it is a Jupiter-like giant planet with a radius over ten times that of Earth's, and orbits its host star closely at a distance of 0.02 astronomical units (AU), with an orbital period 60 times shorter than that of Mercury around the Sun.

The unexpectedly close distance of the exoplanet to the white dwarf implies that it must have migrated inward after its host star evolved from a red giant to a white dwarf, otherwise it would have been engulfed by its star.^[4] This migration may be related to the fact that WD 1856+534 belongs to a hierarchical triple-star system: the white dwarf and its planet are gravitationally bound to a distant companion, G 229–20, which itself is a binary system of two red dwarf stars.^[4] Gravitational interactions with the companion stars may have triggered the planet's migration through the Lidov–Kozai mechanism^[6][7][8] in a manner similar to some hot Jupiters. An alternative hypothesis is that the planet instead has survived a common envelope phase.^[9] In the latter scenario, other planets engulfed before may have contributed to the expulsion of the stellar envelope.^[10] JWST observations seem to disfavour the formation via common envelope and instead favour high eccentricity migration.^[11]

The planetary transmission spectrum obtained with GTC OSIRIS is gray and featureless, likely because of the high level of hazes.^[12] The transmission spectrum was also obtained with Gemini GMOS. It does not show any features beside a possible dip at 0.55 μm. This feature could be caused be auroral emission at the nightside of the planet. The research find a minimum mass of 0.84 M_J by accounting for the transit geometry of a grazing transit. The researchers also revised the white dwarf parameters and found a total age of 8-10 billion years, in agreement with the system beloning to the thin disk.^[3]

A search with transit timing variations found no additional planets. The search exclude planets with a mass more than 2 M_J with orbital periods as long as 500 days and planets with >10 M_J with orbital periods as long as 1000 days.^[13]

• WD 1145+017, a white dwarf with a transiting disrupted planetary-mass object
• WD J0914+1914, a white dwarf with a disk of debris originating from a possible giant planet
• ZTF J0139+5245, another white dwarf with a disk of debris from a disrupted planetary-mass object
• CWISEP J1935-1546 a free-floating object with aurora emission in the infrared
• List of exoplanets and planetary debris around white dwarfs

• NASA Missions Spy First Possible ‘Survivor’ Planet Hugging White Dwarf Star, Sean Potter, NASA, 16 September 2020
• Planet discovered transiting a dead star, Steven Parsons, Nature News and Views, 16 September 2020

• v
• t
• e

Constellation of Draco

• List of stars in Draco
• Draco in Chinese astronomy

Stars

Bayer	α (Thuban) β (Rastaban) γ (Eltanin) δ (Altais) ε (Tyl) ζ (Aldhibah) η (Athebyne) θ ι (Edasich) κ λ (Giausar) μ (Alrakis) ν (Kuma) ξ (Grumium) ο π ρ σ (Alsafi) τ υ φ χ ψ1 (Dziban) ψ2 ω
Flamsteed	6 7 (Tianyi) 8 (Taiyi) 10 (i) 15 (A) 18 (g) 19 (h) 26 36 39 (b) 42 (Fafnir) 45 (d) 64 (e) 68
Variable	TW AG BY CL CM CX DO V581
HR	3751 4126 4934 5811 6237 6618 (Alruba) 6817 7137 7783
HD	101364 156279 158259 176693 191939
Other	2MASS 1237+6526 2MASS J17554042+6551277 G 240-72 GD 356 Gliese 420 Gliese 625 Gliese 687 GRW +70 8247 Kepler-4 Kepler-10 Kepler-12 Kepler-90 Kepler-296 LP 71-82 Qatar-1 Struve 2398 TOI-1136 WISE 1647+5632

Exoplanets	Orbitar HD 139357 b HD 167042 b Hypatia Kepler-4b Kepler-10b c Kepler-12b Kepler-90e f g h i TOI-1452 b TrES-2b

Star clusters	LAMOST 1

Nebulae	Abell 50 Cat's Eye Nebula

Galaxies

NGC	3147 4121 4125 4236 4319 4345 4513 4589 5678 5777 5866 5866B 5879 5906 5907 5949 5963 5965 5982 5985 6090 6248 6285 6286 6340 6365 6373 6394 6412 6503 6566 6621 6622 6670 6676 6786 6789
Other	3C 249.1 3C 305 3C 319 3C 371 3C 390.3 3C 401 4C +72.26 H1821+643 HFLS3 KKR 25 PGC 39058 UGC 9391

Galaxy clusters	Abell 2218 CL1358+62 Draco Supercluster

Astronomical events	Swift J1644+57 SN 2005B SN 2016aps

Category