You thought the brightest star was Polaris, right? Or maybe one of the stars in Orion? No! Sirius – “Dog Star” – never gets the recognition it deserves. It is by far the brightest star in the night sky, shining at magnitude 1.4. This puts it in brightness only behind our Moon, Jupiter and Venus.
Even fewer people know that Sirius also shines in all the colors of the rainbow.
Sirius is so it is clear that it is sometimes mistaken for a planet. Maybe that’s why it’s often overlooked. Or maybe because the constellation in which Sirius is located is rather dim.
Canis Major, now visible in both hemispheres, consists of 10 stars – Adhara, Aludra, Amadioha, Atakoraka, Furud, Mirzam, Muliphein, Sirius, Unurgunite, and Wezen – though none is as bright as Sirius or the nearby star Orion.
Sirius and Orion: hunting dog
Another reason most people don’t immediately know where Sirius is may be that it follows Orion, easily the most famous constellation of all. It’s a bit ironic because Sirius now hovers beneath the “hunter” in the southeast – as seen from the northern hemisphere – as darkness falls.
In Greek mythology, Sirius was associated with the god Orion and was considered a hunting dog – hence his constellation Canis Major translates as “big dog” and is called “dog star”.
How to find Sirius
As night falls, you can use the stars of Orion’s Belt to find Sirius. Find the three belt stars – Mintaka, Alnilam and Alnitak – and descend towards the eastern horizon. Sirius is just south of Orion and is the brightest star in this region of the sky. It’s really easy to find.
Sirius is an important star. It is just 8.6 light years from the solar system and is part of the fifth closest star system to the sun. About twice as massive as the Sun, this blue-white main sequence star is one of the hottest stars in the night sky.
Sirius is not one star
However, he is not really alone.
Sirius is a binary star whose blue-white giant is accompanied by a faint white dwarf (remnants of stars similar to our Sun). The two stars orbit each other every 50 years.
It may seem strange, but up to 85% of the stars are in binary systems, and some in triple or even multiple systems.
Sirius as a “rainbow star”
Sirius is also one of the few stars worth putting a telescope on. Not to see its white dwarf companion (you’d need a huge telescope for that), but for its brilliant colors. Stars twinkle because we see their light slightly bent by the turbulent air in our planet’s atmosphere.
The easiest way to see its colors is to focus the telescope on it and then touch the telescope. You will receive an image similar to the one above, taken by Sirius photographer and astrophotographer Steve Brown from North Yorkshire, UK, who regularly tweets photos of Sirius and uploads astro videos to his YouTube channel.
This is best done when Sirius is relatively low in the sky. However, because it’s so close and so bright, its more intense light is split into a spectrum by Earth’s turbulent atmosphere, so it appears in all the colors of the rainbow when it’s low. As it rises higher, it becomes brighter and whiter.
So go out and find Sirius – the brightest star in the night sky – and you’ll always be looking for it every time you spot Orion’s belt.
I wish you clear skies and wide eyes.