Marking the end of the constellation Leo the Lion’s tail is mag. +2.1 star Denebola (Beta (β) Leonis), its name coming from the Arabic danab al-asad, ‘tail of the lion’.
Denebola is 36 lightyears away, and is 1.6 times larger and 15 times more luminous than our own Sun.
It has the spectral type A3Va, which means it is a slightly more luminous than average main sequence star (the ‘Va’ part) which appears white in colour ( the ‘A3’ part).
Denebola has 1.73 times more mass than the Sun, but its most interesting and extreme variation is in regards to its spin rate.
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Where our Sun rotates at a rather leisurely 2km/s, Denebola spins 64x faster at 128km/s.
This is fast enough to cause the star to bulge at the equator into an oblate spheroid.
In contrast, the slow rotation of the Sun results in one of the most perfect spheres known in nature.
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Viewed in infrared, Denebola shows an excess of radiation, hinting at the existence of a disc of debris in orbit around it.
This circumstellar disc may be the nursery for a forming solar system, although no planets have yet been identified within it.
Detailed analysis of the disc suggests that it extends 5 to 55 AU from the star.
The highest concentration of material appears around the 39 AU mark, with a temperature of 120K. Amazingly, structure has been detected within the circumstellar disc.
There appears to be a 2 AU hole and a hot 600K dusty ring 4–6 AU in diameter.
Have you observed or photographed Denebola? Share your observations and images with us by emailing contactus@skyatnightmagazine.com
This guide appeared in the March 2019 issue of BBC Sky at Night Magazine