Sirius Star
Sirius star
Sirius is so bright that it can even be seen during the day in some areas.
Sirius Facts
  • Sirius is a two star system 8.6 light years from Earth.
  • It consists of the main sequence star Sirius A and its small white dwarf companion Sirius B.
  • White dwarfs are the core remains of stars that have exhausted their fuel and shed their outer layers.
  • Sirius B is the closest white dwarf star to Earth.
  • The force of gravity on Sirius B is 350,000 stronger than on Earth, meaning 3 grams of matter (roughly a sugar cube) would weigh 1,000 kilos (2,200 pounds)!
  • Sirius A is known as a main sequence star, meaning like the sun it produces energy by fusing hydrogen atoms in its core.
  • Sirius is the brightest star in the night sky and the nearest that can be seen without the aid of a telescope.
  • Sirius B has a highly elliptical orbit around its larger companion.
  • The derivation of the name Sirius is from the ancient Greek word for glowing, the star was also known to ancient Egyptians 4,000 years ago.

Sirius A and Sirius B
Sirius A with its small white dwarf companion Sirius B on the right.
Sirius Radius
Sirius A has a radius of 740,000 miles (1.2 million km), which is 71% larger than the radius of the sun, Sirius B has a radius of only 3,650 miles (5,900 km) which makes it slightly smaller than planet Earth!
Sirius Mass
Sirius A has twice the mass of our sun, despite Sirius B being similar in size to Earth it has almost the same mass as the sun, making it an incredibly dense object.
Sirius Temperature
Sirius A is estimated to have surface temperatures of around 10,000C (18,000F), almost twice as hot as the sun, Sirius B has surface temperatures of around 25,000C (45,000F), which is almost five times as hot as the sun.

Sirius Statistics

Also Known As: Alpha Canis Major, the Dog Star

Distance From Earth: 8.6 light years
Constellation: Canis Major

Sirius A Star Type: Class A - Main sequence white star
Sirius B Star Type: White Dwarf

Sirius A Mass: 2.02 x Sun
Sirius B Mass: 0.98 x Sun

Sirius A Luminosity: 25 x Sun
Sirius B Luminosity: 3% of Sun

Sirius A Diameter: Approx 1.5 million miles (2.4 million km) - 171% x Sun
Sirius B Diameter: Approx 7,300 miles (11,800 km) - 92% x Earth

Sirius A Temperature: Approx 10,000C (18,000F)
Sirius B Temperature: Approx 25,000C (45,000F)

Age of System: Approx 240 million years old

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