Sirius: Brightest Star in Earth’s Night Sky

Sirius, also known as the Dog Star or Sirius A, is the brightest star in Earth’s night sky. The name means “glowing” in Greek — a fitting description, as only a few planets, the full moon and the International Space Station outshine this star.

Because Sirius is so bright, it was well-known to the ancients. But the discovery of a companion star, Sirius B, in 1862 surprised astronomers. The star that you can see with the naked eye is called Sirius A, or sometimes just Sirius. (In this article, we will clearly state when we are talking about Sirius B.)

Sirius B is 10,000-times dimmer than Sirius. It’s so dim, and therefore so difficult to see from Earth, that astronomers couldn’t estimate its mass until 2005, thanks to data from the Hubble Space Telescope.

The constellation Orion and Sirius, the brightest star in the night sky, can be spotted in this shot, taken by’s Megan Gannon in front of the MDM Observatory’s 2.4-meter Hiltner telescope atop Kitt Peak in the Arizona desert on March 17, 2014. (Image credit: Megan Gannon)

How to spot Sirius