Denebola

Denebola (β Leo / β Leonis / Beta Leonis) is the second brightest star in the constellation Leo. It is an A-class star that is about distant from earth, and has a luminosity about twelve times that of the sun. Its apparent magnitude is 2.14. Denebola is a Delta Scuti type variable star, meaning its luminosity varies very slightly over a period of a few hours.

Etymology

Its name is shortened from Deneb Alased, from the Arabic phrase ذنب الاسد ðanab al-asad "tail of the lion", as it represents the lion's tail—the star's position in the Leo constellation. (Deneb in Cygnus has a similar name origin.) On R. A. Proctor's 1871 star chart of the northern hemisphere it was designated Deneb Aleet. To ancient Chinese astronomers, it formed part of the five-star Woo Ti Tsi: the Seat of the Twelve Emperors. In astrology, Denebola was believed to portend misfortune and disgrace.

In Johann Bayer's Uranometria, published in 1603, the star was designated β Leonis; for the second-brightest star in the constellation of Leo. In 1725, John Flamsteed designated this star 94 Leo. (The Flamsteed designation was assigned on the basis of increasing right ascension within the constellation, rather than luminosity.) Additional designations followed as this star was recorded in subsequent star catalogues.

Properties

This is a relatively young star with an age estimated at less than 400 million years. Interferometric observations of this star give a radius that is about 173% that of the Sun. However, the high rate of rotation of this star results in an oblate shape with an equatorial bulge. It has 75% more mass than the Sun, which results in a much higher overall luminosity and a shorter life span on the main sequence.

The surface temperature of Denebola is about 8500 K. It has a high rotation velocity of at least 120 km/s, which is of the same order of magnitude as the very rapidly rotating star Achernar. Compare this to the Sun's more leisurely equatorial rotation velocity of 2 km/s. This star is believed to be a δ Scuti-type variable star that exhibits fluctuations in luminosity of 0.025 magnitudes roughly ten times per day.

Denebola shows a strong infrared excess, which means there must be a debris disk of cool dust in orbit around it. As our solar system is believed to have formed out of such a disk, Denebola and similar stars such as Vega and Beta Pictoris may be good candidate locations for extrasolar planets. The dust surrounding Denebola has a temperature of about . Unsuccessful attempts have been made to image the dust disk, implying that the disk contains much less material than that surrounding Beta Pictoris, which has been imaged frequently.

Kinematic studies have shown that Denebola is part of a stellar association dubbed the IC 2391 supercluster. All the stars of this group share a roughly common motion through space, although they are not gravitationally bound. This implies that they were born in the same location, and perhaps initially formed an open cluster. Other stars in this association include Alpha Pictoris, Beta Canis Minoris and the open cluster IC 2391. In total more than sixty probable members of the group have been identified.