EBLM J0555-57 is a triple star system approximately 670 light-years from Earth. EBLM J0555-57Ab, the smallest

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the system, orbits its primary star with a period of 7.8 days, and at the time of discovery, was 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 Painting, painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's ...

, 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 is a system of two stars that are 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 using a telescope as separate stars, in wh ...

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

Eclipse An eclipse is an astronomical event that 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 ce ...

s, also known as

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1979 film), a 1979 Israeli film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countries in the world * ''Transit'' (2006 film), a 2006 ...

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 those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

, 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 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 Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

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 long ...

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 mass more than two and a half times that of all the other planets in the Solar System combined, but ...

masses, or 0.081

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es. Its radius is 0.08 solar radii (about 59,000 km), 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 nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

, which has an equatorial radius of 60,268 km. The star is about 250 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 , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

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. Th ...

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 possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s using the transit method. Additional properties of the star were determined using Doppler spectroscopy, 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