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Alpha Leonis
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The star alpha leonis, Regulus, is the most prominent star in Leo, shining at magnitude +1.36 which makes it the 21st brightest star. The name literally means 'king' and comes from the latin 'rex'.
Regulus lies at a distance of 69 light-years and has an absolute magnitude of -0.7, and a surface temperature of 13,000K. The star has a +7.7 dwarf companion (also a double star), 177 arcseconds away.
Regulus is one of the brightest stars that can be occulted by our solar system planets. Our Moon also occults the star over two `periods` of 18 months during it`s 18.6 metonic cycle.

Picture 816



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Regulus
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Title: The impact of the oblateness of Regulus on the motion of its companion
Authors: Lorenzo Iorio
(Version v2)

The fast spinning B-star Regulus has recently been found to be orbited by a fainter companion in a close circular path with orbital period P_b = 40.11(2) d. Being its equatorial radius R_e 32% larger than the polar one R_p, Regulus possesses a remarkable quadrupole mass moment Q. We investigate the effects of Q on the orbital period P_b of its companion in order to see if they are measurable, given the present-day level of accuracy in measuring P_b. Conversely, we will look for deviations from the third Kepler law, attributed to the quadrupole mass moment Q of Regulus, to constrain the ratio \gamma=m/M of the system's masses.

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Stars are round - that's the received wisdom. But Regulus, the brightest star in the constellation Leo, is shaped like a pumpkin. That's because it is spinning so fast it can barely hold itself together. Now we may know why it whirls so quickly: another star dumped material onto it millions of years ago.
In 2004, astronomers discovered that Regulus's equatorial diameter is 32 per cent greater than its polar diameter. Now Douglas Gies of Georgia State University in Atlanta and colleagues have found it has a faint companion star. The unseen star betrayed its presence through its gravitational pull, which causes Regulus to wobble to and fro.
The companion has a third of the sun's mass, orbits Regulus every 40.1 days and is only 52 million kilometres from it - slightly closer than Mercury is to the sun.

 "I'm 70 to 80 per cent positive that it's a white Dwarf"

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Regulus (α Leo / α Leonis / Alpha Leonis) is the brightest star in the constellation Leo and one of the brightest stars in the nighttime sky. Regulus is approximately 77.5 light years from Earth’s Solar System.

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