Changes

Like many young, energetic stars, Regular A rotates extremely fast.  At the equator, the star is rotating at 317 kilometers per second, distorting the star significantly.  This tremendous rotary speed gives the star one complete rotation every 15.9 hours. (compared to the Sun's rotation period of 25.38 days).  The equator of the star is much cooler due to the rapid rotation, having a surface temperature of 10,200 K, as opposed to the 15,400 K surface temperature at the poles.<ref name="illinois">http://stars.astro.illinois.edu/sow/Regulus.html</ref>  The rotation period is so quick that if the star rotated only 16 percent faster, [[centripetal force]] would overcome its [[gravity]] and cause the star to break apart.

Like many young, energetic stars, Regular A rotates extremely fast.  At the equator, the star is rotating at 317 kilometers per second, distorting the star significantly.  This tremendous rotary speed gives the star one complete rotation every 15.9 hours. (compared to the Sun's rotation period of 25.38 days).  The equator of the star is much cooler due to the rapid rotation, having a surface temperature of 10,200 K, as opposed to the 15,400 K surface temperature at the poles.<ref name="illinois">http://stars.astro.illinois.edu/sow/Regulus.html</ref>  The rotation period is so quick that if the star rotated only 16 percent faster, [[centripetal force]] would overcome its [[gravity]] and cause the star to break apart.

Regulus A has a binary companion, determined only Spectroscopically.  The companion is only 0.35 AU away and orbits the primary in 40.11 days.<ref>http://adsabs.harvard.edu/abs/2008ApJ...682L.117G</ref> The exact nature of the companion star is unknown, but analysis suggests the star is a low mass white dwarf that is only 30% as massive as the sun (0.3 solar).  This is unusual because according to current theories, white dwarfs should have no less then a minimum mass of 0.55 solar (55 percent the Sun's mass).  One theory is that when the companion evolved off the main sequence into a luminous giant, it loss much of its mass to Regulus A through tidal interaction.<ref name="illinois"/>

Regulus A has a binary companion, determined only Spectroscopically.  The companion is only 0.35 AU away and orbits the primary in 40.11 days.<ref>http://adsabs.harvard.edu/abs/2008ApJ...682L.117G</ref> The exact nature of the companion star is unknown, but analysis suggests the star is a low mass white dwarf that is only 30% as massive as the sun (0.3 solar).  This is unusual because according to current theories, white dwarfs should have no less than a minimum mass of 0.55 solar (55 percent the Sun's mass).  One theory is that when the companion evolved off the main sequence into a luminous giant, it loss much of its mass to Regulus A through tidal interaction.<ref name="illinois"/>

For an [[terrestrial planet|Earth-like]] world to exist with liquid [[water]] on its surface, the hypothetical planet would need to be between 11.9 and 15.5 AU away from Regulus A.  This is equivalent to between the orbits of [[Saturn]] and [[Uranus]] in our Solar System.  Such a planet would take some 22 to 33 years to complete an orbit.

For an [[terrestrial planet|Earth-like]] world to exist with liquid [[water]] on its surface, the hypothetical planet would need to be between 11.9 and 15.5 AU away from Regulus A.  This is equivalent to between the orbits of [[Saturn]] and [[Uranus]] in our Solar System.  Such a planet would take some 22 to 33 years to complete an orbit.