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 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
The brightest star visible from any part of Earth is Sirius in the constellation Canis Major the Greater Dog. Sirius is sometimes called the Dog Star. Most people in the Northern Hemisphere notice Sirius in the southeast – south – or southwest on evenings from winter to mid-spring. February evenings are a grand time to see it. It’s also fun to spot Sirius as it ascends in the east before dawn on late summer mornings.
Although white to blue white in color, Sirius might be called a rainbow star, as it often flickers with many colors.
The brightness, twinkling and color changes sometimes prompt people to report Sirius as a UFO!
In fact, these changes are simply what happens when such a bright star as Sirius shines through the blanket of Earth’s atmosphere. The varying density and temperature of Earth’s air affect starlight, especially when we’re seeing the star low in the sky.
The shimmering and color changes happen for other stars, too, but these effects are more noticeable for Sirius because Sirius is so bright.
As seen from around the world, Sirius rises in mid-evening in December. By mid-April, Sirius is setting in the southwest in mid-evening.
Sirius is always easy to find. It’s the sky’s brightest star! Plus, anyone familiar with the constellation Orion can simply draw a line through Orion’s Belt to find this star. Sirius is roughly eight times as far from the Belt as the Belt is wide.
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