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WD 1145+017 (also known as EPIC 201563164) is a
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
approximately from
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
of
Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...
. It is the first white dwarf to be observed with a transiting
minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...
orbiting it.


Stellar characteristics

The white dwarf has a mass of 0.6 , radius of 0.012 (1.34 ) and a temperature of 15,020 K, typical for white dwarf stars. It has been a white dwarf for 224 million years. The star's spectrum includes strong absorption lines due to
magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
,
aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
,
silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
,
calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...
,
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and
nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...
. These elements commonly found in
rocky planets A terrestrial planet, tellurian planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate, rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to th ...
are polluting the surface of the star, and would normally be expected to mix through the star and disappear from view after a million years. A circumstellar dust cloud and disk (likely due to disintegrating
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
s, 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 relativistic
precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...
with a period of ~ 5 years) surrounds the star as well. Based on 2018 studies and calculations, it is believed that the star initially was an early
A-type main sequence star An A-type main-sequence star (A) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1.7 ...
with a mass of about , remaining so for an estimated million years. Afterwards, following the exhaustion of hydrogen within its core, it evolved and expanded into a
red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The stellar atmosphere, outer atmosphere is inflated and tenuous, making the radius large and the surface t ...
before eventually ejecting its layers and contracting into a white dwarf, and has gradually cooled over the last million years. This gives the star an estimated total age of around 774 million years. The apparent magnitude of the star, or how bright it appears from Earth's perspective, is about 17. Therefore, it is too dim to be seen with the naked eye.


Planetary system

The supposed planetesimal,
WD 1145+017 b WD may refer to: Arts and entertainment * ''The Walking Dead'' (TV series) * ''Watership Down'' * ''White Dwarf'' (magazine) Businesses and organizations Government agencies * Royal Canadian Air Force Women's Division * War Department ...
, with a 4.5 hour orbit, is being ripped apart by the star and is a remnant of the former
planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
that the star hosted before becoming a white dwarf. It is the first observation of a planetary object being
shredded Shredding, shred, shredder, or shredders may refer to: Equipment * Industrial shredder * Paper shredder * Scrap metal shredder * Woodchipper, or tree shredder Arts, entertainment, and media Films * Shred (film), ''Shred'' (film), a 2008 film by ...
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 the
Kepler space telescope The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...
in its extended ''K2'' 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. An excess of
infrared radiation Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
indicates that there is a dusty disk with a temperature of . Supporting observational data, along with data from the
Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...
, were also found related to dust debris orbiting WD 1145+017.


Similar systems

In September 2020, astronomers reported the discovery, for the first time, of a very massive Jupiter-sized planet, named WD 1856+534 b, closely orbiting, every 36 hours, a tiny
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
star, named WD 1856+534, a left-over remnant of an earlier much larger
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
-like star. This is the first true planet observed to transit a white dwarf, as opposed to the planetesimals transiting WD 1145+017.


See also

*
Disrupted planet In astronomy, a disrupted planet is a planet or exoplanet or, perhaps on a somewhat smaller scale, a planetary-mass object, planetesimal, moon, exomoon or asteroid that has been disrupted or destroyed by a nearby or passing astronomical body or ...
*
List of stars that have unusual dimming periods A list is a set of discrete items of information collected and set forth in some format for utility, entertainment, or other purposes. A list may be memorialized in any number of ways, including existing only in the mind of the list-maker, but ...
* List of exoplanets and planetary debris around white dwarfs Other planetesimals around white dwarfs: * ZTF J0139+5245 * WD 0145+234 * SDSS J1228+1040 b * ZTF J0328-1219


References


External links


EPIC Catalog at MAST
* Harvard ''Center for Astrophysics''

* AstronomyNow
WD 1145+017
* AmericaSpace
WD 1145+017
{{DEFAULTSORT:WD 1145+017 White dwarfs Virgo (constellation) Hypothetical planetary systems