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  • Writer's pictureKGB

Regulus. A Royal Double Star.

Hello again. Terrible weather equates to no new deep sky image taken for a few weeks. So, I thought we would have a look at a famous star, which just happens to be a famous double star as well. As you have probably guessed by the title of this blog post, the star is Regulus, located in the constellation of Leo the Lion.

Graphic showing the constellation of Leo.

Regulus is the brightest star in the constellation of Leo and is also designated as Alpha Leonis and 32 Leonis. Visually, with the naked eye Regulus appears to be one star, but a telescope clearly shows it's double nature. Indeed, Regulus is actually a quadruple star system composed of 4 stars, organised into 2 pairs. The entire system lies approximately 79 light years from Earth. Regulus has an actual luminosity of about 160 times that of our sun and has an estimated diameter of about five times that of our home star. Additionally, Regulus is not only one of the 21 brightest stars in the sky, but it possesses a practical importance as one of the principal stars having been used by sailors ever since the beginning of navigation to determine their place at sea. Regulus has a magnitude of about 1.4 and cannot be missed with the naked eye. It is a hot blue-white main sequence star and is probably around 1 billion years old. As regards its royal status, it has been known from the remotest times as one of the 4 royal stars regarded by the ancient Persian monarchy which were supposed long ago to rule over the four quarters of the heavens. Regulus signified Spring and the other three seasonal "royal stars" are Antares in Scorpius (summer), Fomalhaut in Piscis Austrinus (autumn) and Aldebaran in Taurus (winter).

Regulus and its close companion (bright star to the left) as imaged by me, the author, on January 18th 2024.

Now, if you look closely at my image, you can see a very faint patch of light below and to the left of Regulus. This is actually Leo 1, which is a dwarf galaxy. At about 820,000 light years distant, it is a member of the Local Group of galaxies and is thought to be one of the most distant satellites of our Milky Way galaxy. It was discovered in 1950 by Albert George Wilson on photographic plates which were taken with the 48-inch Schmidt camera at Palomar Observatory. Leo 1 is located only 12 arc minutes from Regulus and for that reason, the galaxy is sometimes called the Regulus Dwarf. Studies of Leo 1 suggest that there is almost certainly a black hole of three million solar masses in the center of the galaxy! This is significant, as it is the first time this has been seen in a dwarf spheroidal galaxy. Leo I's black hole has a mass comparable to the mass of the Milky Way's black hole, Sagittarius A. There is also a very small spiral galaxy in the image designated IC 591 (see below), to the far left of Regulus.

To finish this post, I thought I would show you this image, above, of my actual plate solve of the Regulus area. A plate solve is an astrometric solution of your original image. The software looks at your image and tells you the actual objects that you have captured in your image. This service is free at Of course, you have to have your own image for this to work. I hope you have enjoyed this blog/post and as usual any comments are welcome good or bad. See you next time. Until then, keep safe..

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Feb 18
Rated 5 out of 5 stars.

Super interesting


Kez Bloor
Kez Bloor
Feb 18
Rated 5 out of 5 stars.

Very informative 🚀

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