Which is the Brightest star in Earth's night sky ?

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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.

constellation Canis Major

It's  in the constellation Canis Major, brightest star in the sky. The bright planet Venus is also up before dawn now. But you'll know Sirius, because Orion's Belt always points to it.

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. 

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.

Sirius appears bright because of its intrinsic luminosity and its proximity to the Solar System. At a distance of 2.64 parsecs (8.6 ly), the Sirius system is one of Earth's nearest neighbours. 

Sirius is gradually moving closer to the Solar System, so it will slightly increase in brightness over the next 60,000 years. 

After that time, its distance will begin to increase, and it will become fainter, but it will continue to be the brightest star in the Earth's night sky for the next 210,000 years.

Sirius A is about twice as massive as the Sun (M☉) and has an absolute visual magnitude of +1.42. It is 25 times more luminous than the Sun but has a significantly lower luminosity than other bright stars such as Canopus or Rigel. 

According to NASA, Sirius has a mass that's two times that of Earth's sun. If the star were placed next to our sun, Sirius would outshine it more than 20 times over.

How to spot Sirius

Sirius is highly visible in the Northern Hemisphere's winter night sky, because the star has a high luminosity, or intrinsic brightness, relativeto other stars, and because it's relatively close to Earth (8.6 light-years away).

 (Image credit: SkySafari App)

Winter brings another opportunity to see starlight from a range of eras. Sirius, the brightest star in the night sky, Meanwhile, the two brightest stars of Orion are distant but shine so brightly because they emit much more light. Betelgeuse is an old, red supergiant star 500 light-years away. It may already have exploded in a supernova blast, but we won't know about it until the light arrives! Blue Rigel is about as bright as Betelgeuse but sits 860 light-years away

The brightest star in Earth's night sky, Sirius, hovers over a burial mound, called the Leeburg tumulus, in a new image by project nightflight. (Image credit: project nightflight)

Used as :

The heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians, mostly in the Southern Hemisphere, the star marked winter and was an important reference for their navigation around the Pacific Ocean.

Source : Wikipedia , Space.com

Read also : Sun and the Fraunhofers lines