EF Eridani
Encyclopedia
EF Eridani is a variable star
of the type known as polars
, AM Herculis
stars, or magnetic cataclysmic variable stars. Historically it has varied between apparent magnitude
s 14.5 and 17.3, although since 1995 it has generally remained at the lower limit. The star system consists of a white dwarf
star with a substellar massed former star in orbit
.
in orbit around the white dwarf is a star which lost all of its gas to the white dwarf, except what remains, a 0.05 solar mass
ball, which is too small to continue fusion
, and does not have the composition of a super-planet
, brown dwarf
, or white dwarf. There is no category for such a stellar remnant.
It is theorized that 500 million years ago, the white dwarf started to cannibalize its partner, when they were separated by 7 million km. As it lost mass, the regular star spiralled inward, until now they are separated by a mere 700,000 km.
Another former star orbits the pulsar PSR J1719-1438.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
of the type known as polars
Polar (cataclysmic variable)
A Polar is a type of cataclysmic variable binary star system with a very strong magnetic field.In most cataclysmic variables, matter from a main-sequence companion star is gravitationally stripped by a white dwarf star in the form of an accretion disk. In polar systems, the magnetic field of the...
, AM Herculis
AM Herculis
AM Herculis is a red dwarf variable star located in the constellation Hercules. This star, along with the star AN Ursae Majoris, is the prototype for a category of cataclysmic variable stars called polars, or AM Her type stars.-History:...
stars, or magnetic cataclysmic variable stars. Historically it has varied between apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
s 14.5 and 17.3, although since 1995 it has generally remained at the lower limit. The star system consists of a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
star with a substellar massed former star in orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
.
EF Eridani B
The substellar massSubstellar object
A substellar object, sometimes called a lump, is an astronomical object whose mass is smaller than the smallest mass, approximately 0.08 solar masses, at which a star can sustain hydrogen fusion...
in orbit around the white dwarf is a star which lost all of its gas to the white dwarf, except what remains, a 0.05 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
ball, which is too small to continue fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
, and does not have the composition of a super-planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
, brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
, or white dwarf. There is no category for such a stellar remnant.
It is theorized that 500 million years ago, the white dwarf started to cannibalize its partner, when they were separated by 7 million km. As it lost mass, the regular star spiralled inward, until now they are separated by a mere 700,000 km.
Another former star orbits the pulsar PSR J1719-1438.
See also
- AM HerculisAM HerculisAM Herculis is a red dwarf variable star located in the constellation Hercules. This star, along with the star AN Ursae Majoris, is the prototype for a category of cataclysmic variable stars called polars, or AM Her type stars.-History:...
- Cataclysmic variable starCataclysmic variable starCataclysmic variable stars are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state...
- Nova-like star
- Polar (cataclysmic variable)Polar (cataclysmic variable)A Polar is a type of cataclysmic variable binary star system with a very strong magnetic field.In most cataclysmic variables, matter from a main-sequence companion star is gravitationally stripped by a white dwarf star in the form of an accretion disk. In polar systems, the magnetic field of the...
- Variable stars
- Stellar remnants
- PSR J1719-1438, a star system with a planetary-mass former star in orbit around a compact star
- PSR J1719-1438 b, a planetary-mass former star that was eroded by its binary star partner