Wolf 424
Encyclopedia
Wolf 424 is a binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 system comprising two red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....

 stars at a distance of approximately 14.2 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....

 from the Sun. It is located in the constellation Virgo
Virgo (constellation)
Virgo is one of the constellations of the zodiac. Its name is Latin for virgin, and its symbol is . Lying between Leo to the west and Libra to the east, it is the second largest constellation in the sky...

, between the stars ε Virginis
Epsilon Virginis
Epsilon Virginis is a star in the constellation Virgo. It has the traditional name Vindemiatrix, which comes from Greek through Latin and means Grape Gatherer....

 and δ Virginis
Delta Virginis
Delta Virginis is a red giant star in the constellation Virgo. It also has the traditional name Auva.It has a spectral type of M3-III, and an magnitude of 3.38, bright enough to be seen with the naked eye...

.

The close binary nature of this star was discovered by Dutch American astronomer Dirk Reuyl
Dirk Reuyl
Dirk Reuyl was a Dutch American physicist and astronomer. He was the cousin of astronomer Peter van de Kamp.-Life:He was awarded his Ph.D from Utrecht University in Utrecht, Netherlands. He came to the United States a few years before his cousin Peter van de Kamp. He joined the staff at McCormick...

 in 1941, based upon an elongation of the star found in photographs. The two stars in the Wolf 424 system orbit about each other with a semi-major axis
Semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...

 of 4.1 AU and an eccentricity of 0.3. The stars have an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

 of 15.5 years and have a combined apparent magnitude of about 12.5.

Wolf 424A is a cool main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....

 star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 of approximately 0.14 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...

es (147 Jupiters
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....

) and a radius of 0.17 solar radii. Its companion, Wolf 424B, is a cool main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...

 red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....

 star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 of approximately 0.13 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...

es (136 Jupiters
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....

) and a radius of 0.14 solar radii. They are two of the dimmest objects within 15 light years of the Sun. In 1967, it was discovered that both are flare star
Flare star
A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to magnetic reconnection in the atmospheres of the stars. The brightness increase is...

s that undergo random increases in luminosity. The system has been designated
Variable star designation
Variable stars are named using a variation on the Bayer designation format of an identifying label combined with the Latin genitive of the name of the constellation in which the star lies...

FL Virginis, and may experience sunspot activity. The stars may undergo variation in the level of flare activity over periods lasting several years.

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