 Alight curve for WD 1145+017 showing a dimming event, adapted from Xuet al. (2019).[1] The green dots are the data points and the blue line is the best fit model from the Xuet al. paper. | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 | |
|---|---|
| Constellation | Virgo[2] |
| Right ascension | 11h 48m 33.62972s[3] |
| Declination | +01° 28′ 59.4204″[3] |
| Apparent magnitude (V) | 17.24±0.02[4] |
| Characteristics | |
| Evolutionary stage | White dwarf |
| Spectral type | DB[5] |
| Astrometry | |
| Proper motion (μ) | RA: -43.664mas/yr[3] Dec.: -4.027mas/yr[3] |
| Parallax (π) | 6.8534±0.0907 mas[3] |
| Distance | 476 ± 6 ly (146 ± 2 pc) |
| Details | |
| Mass | 0.63±0.05[6] M☉ |
| Radius | 0.012±0.001[4] R☉ |
| Luminosity | 0.0088±0.0021[4] L☉ |
| Surface gravity (log g) | 8.07±0.07[6] cgs |
| Temperature | 15,020±520[6] K |
| Age | 774±130[6] Myr |
| Other designations | |
| WD 1145+017,EPIC 201563164[5] | |
| Database references | |
| SIMBAD | data |
WD 1145+017 (also known asEPIC 201563164[5]) is awhite dwarf approximately 476light-years (146parsecs) fromEarth in theconstellation ofVirgo. It is the first white dwarf to be observed with atransitingminor planet orbiting it.[7][8][9]
The white dwarf has a mass of 0.6M☉, radius of 0.012R☉ (1.34R🜨) and a temperature of 15,020K, typical for white dwarf stars. It has been a white dwarf for 224 million years.[6][10] The star's spectrum includes strong absorption lines due tomagnesium,aluminium,silicon,calcium,iron andnickel. These elements commonly found inrocky planets are polluting the surface of the star, and would normally be expected tomix through the star and disappear from view after a million years.[10]
A circumstellar dust cloud and disk (likely due to disintegratingasteroids, located at 97 to 103 R_wd, and emitting thermal IR radiation) surrounds the star. In addition, a circumstellar gas disk (located ~ 25 to 40 R_wd, and undergoing relativisticprecession with a period of ~ 5 years) surrounds the star as well.[1][11]
Based on 2018 studies and calculations, it is believed that the star initially was an earlyA-type main sequence star with a mass of about2.48±0.14 M☉, remaining so for an estimated550±100 million years.[6] Afterwards, following the exhaustion of hydrogen within its core, it evolved and expanded into ared giant before eventually ejecting its layers and contracting into a white dwarf, and has gradually cooled over the last224±30 million years. This gives the star an estimated total age of around 774 million years.[6][12]
The apparent magnitude of the star, or how bright it appears from Earth's perspective, is about 17.[4] Therefore, it is too dim to be seen with the naked eye.
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ~0.000016 M🜨 | ~0.0054 | 0.187454(4) | — | ~90° | ~0.03 R🜨 |
| Dusty disk | 0.5?AU | — | — | |||
The supposed planetesimal,WD 1145+017 b,[13] with a 4.5 hour orbit, is beingripped apart by the star and is a remnant of the formerplanetary system that the star hosted before becoming a white dwarf.[8][9] It is the first observation of a planetary object beingshredded by a white dwarf. Several other large pieces have been seen in orbit as well. All the various larger pieces have orbits of 4.5 to 4.9 hours. Rocky material is raining down onto the star, and showing up in the star's spectrum. The system was detected by theKepler space telescope in its extendedK2 mission. Though the system was not a target of interest, it was within the field of view of observing sessions, and analysis of the observed data revealed the system.[14][15][16][17]
An excess ofinfrared radiation indicates that there is adusty disk with a temperature of 1,150 K (880 °C).[10] Supporting observational data, along with data from theChandra X-ray Observatory, were also found related to dust debris orbiting WD 1145+017.[18]
In September 2020, astronomers reported the discovery, for the first time, of a very massiveJupiter-sized planet, named WD 1856+534 b, closely orbiting, every 36 hours, a tinywhite dwarf star, namedWD 1856+534, a left-over remnant of an earlier much largerSun-like star.[19][20][21] This is the first true planet observed to transit a white dwarf, as opposed to the planetesimals transiting WD 1145+017.
Other planetesimals around white dwarfs:
