EBLM J0555-57 is a

triple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''st ...

approximately 670 light-years from Earth. The system's discovery was released on July 12, 2017. EBLM J0555-57Ab, the smallest

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

in the system, orbits its primary star with a period of 7.8 days, and currently is the smallest known star with a mass sufficient to enable the fusion of hydrogen in its core.

System

EBLM J0555-57, also known as CD−57 1311, is a triple star system in the constellation

Pictor Pictor is a constellation in the Southern Celestial Hemisphere, located between the star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's easel"). ...

, which contains a

visual binary A visual binary is a gravitationally bound binary star system that can be resolved into two stars. These stars are estimated, via Kepler's third law, to have periods ranging from a few years to thousands of years. A visual binary consists of two st ...

system consisting of two sun-like stars separated by 2.5": EBLM J0555-57Aa, a magnitude 9.98 spectral type F8 star, and EBLM J0555-57B, a magnitude 10.76 star. No orbital motion has been detected but they have almost identical radial velocities and are assumed to be gravitationally bound. Component A of the system is itself an

eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...

(EBLM J0555-57Ab orbiting EBLM J0555-57Aa).

Eclipse An eclipse is an astronomical event which occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ...

s, also known as

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...

s in the context of planetary searches, have been detected in the near

infrared 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 ...

, with brightness drops of 0.05% during the eclipse. The shape and duration of the transits allow the radii of the two stars to be determined. A full solution of the orbit gives a period of 7 days and 18 hours, with a low

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.09, an almost edge-on

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 89.84°, and a

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

of 0.08 AU.

EBLM J0555-57Ab

EBLM J0555-57Ab has a mass of about

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

masses, or 0.084

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

es. Its radius is 0.084 solar radii (about ), comparable to

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

, which has an equatorial radius of 60,268 km. The star is about 290 times more massive than Saturn. Current stellar models put its mass at the lower limit for hydrogen-burning stars. EBLM J0555-57Ab was discovered by a group of scientists at the

University of Cambridge The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209, the University of Cambridge is the List of oldest universities in continuous operation, wo ...

associated with the EBLM project (Eclipsing Binary, Low Mass), using data collected by the

WASP A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

project. WASP (''Wide Angle Search for Planets'') is searching for

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

s using the

transit method Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its parent star. For e ...

. The findings were released on July 12th, 2017, though the exact date of the discovery is unknown. Additional properties of the star were determined using

Doppler spectroscopy Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in ...

, to measure the periodic radial velocity variation of the primary star due to the gravitational influence of its companion. EBLM J0555-57Ab is the smallest hydrogen burning star currently known.

References

External links

Smallest ever star discovered by astronomers
University of Cambridge {{DEFAULTSORT:EBLM J0555-57 J05553262-5717261 Durchmusterung objects Triple star systems Eclipsing binaries Pictor F-type main-sequence stars TIC objects

System

EBLM J0555-57Ab

See also

References

External links