Theta Leonis
Theta Leonis (θ Leo, θ Leonis) is a star in the constellation Leo. It has the traditional names Chertan, Chort and Coxa. With an apparent visual magnitude of +3.324 it is visible to the naked eye and forms one of the brighter stars in the constellation. The distance from Earth can be directly determined from parallax measurements, yielding a value of about 165 light-years (51 parsecs).
This is a large star with 2.5 times the mass of the Sun. The spectrum matches a stellar classification of A2 V, making this a seemingly typical A-type main sequence star. However, the spectrum shows enhanced absorption lines of metals, marking this as a chemically peculiar Am star. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, appears around 12% higher than in the Sun. It is radiating 141 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 9,350 K, literally giving it a white-hot glow.
Theta Leonis is much younger than the Sun, with an estimated age of around 550 million years. It has a moderately high rate of rotation, with a projected rotational velocity of 23 km s−1. Measurements in the infrared band show an excess of emission from the star and its surroundings, suggesting the presence of a circumstellar disk of dust. The temperature of this emission indicates the disk has an orbital radius of 36 AU.
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