Your Night Sky for May 13, 2020

Regulus, the Little King

The bright star Regulus is in the constellation Leo the Lion and is actually the brightest star in that region of the sky. In early spring it's in the east, now it's becoming high overhead, and by the beginning of summer it will be in the west. It's actually along the ecliptic where the Sun, moon and planets travel along.

When you look at Leo the Lion you will see a backward question mark with Regulus at its bottom. This makes up the head and front quarters of Leo and is called "The Sickle." What makes Regulus so prominent is the fact that it's actually 4 stars that circle around each other. Only the main one is visible with unaided vision, and the others require a strong telescope to observe them.

This bright star is very conspicuous in the evening sky shortly after sunset. The star we see is Regulus "A." It's about 75 LY away, and is a bright blue white star. Its surface temperature averages about 21,970 degrees and is much hotter than our Sun which is 9,941 degrees. It's about four times larger than our Sun, so it's huge! Its rapid rotation makes its equatorial region bulge, so it looks like an egg.

Regulus "B" is a cool orange dwarf that's only o.8 times the mass of our Sun. It's half as bright with a temperature of 8.333 degrees. Its companion Regulus "C" is 1/3 the mass of our Sun and is a red dwarf. The fourth star is thought to be a closely orbiting white dwarf. It hasn't really been explored. So when you look at the evening sky, check out Leo the Lion the King of Beasts to observe Regulus.

Also in the evening when you see the bright planet Venus, you should be able to observe Mercury below it. Venus has been starting to drop down, as Mercury has been rising. By the end of this month, Mercury will be 8 degrees high. Just look in the NW to see them. Hopefully the mountains won't be in your way.

On the 21st they will meet with Mercury only 1 degree below Venus. Then Venus will start to drop down and be out of the night sky by the end of this month. Mercury is on the far side of the Sun and is moving in the opposite direction of Venus. On June 4 it will reach its greatest elongation from the Sun. That's when it will be at greatest viewing. Obviously Venus is brighter at 4.4 degrees as opposed to Mercury at 0.6 magnitudes. But it will be fun to observe them together.





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