How old is Sirius, How is it SO hot, How come there are two parts to it, why is it known as the White Dwarf?

Question

Sirius (star)

Answer 1

I'm not sure how old Sirius is. It is hotter because it is more massive than our sun, about 2.1 times the mass. The "two parts" are two different stars that orbit Each other. Sirius A is the A0 or A1 class star we see in the sky. Sirius B is a white dwarf star that orbits it at about 20 AU (around the same distance Uranus is from the sun). A white dwarf is a star that has used up all of its fuel in fusion and has collapsed into a small dead star. They still glow with heat left over from when they were active and the heat generated from their collapse. They eventually run out of heat and stop shining, becoming black dwarves but the universe is not old enough for any black dwarves to have formed yet (it takes 10s fo billions of years for this to happen).

The companion white dwarf has about half the mass of our sun and is a bit larger than Earth. It is practically impossible to see from ground-based telescopes because it is so small and faint next to the very luminous Sirius A.

Answer 2

Determining the age of a star is an inexact science, but recent estimates put the age of Sirius at 225 to 250 million years. Sirius is a binary star. The bright star that we see has a much fainter companion, officially known as Sirius B, but sometimes referred to as "the Pup" by amateur astronomers. Sirius B is a white dwarf, which means it is the no longer active remains of a star and glows only because it still retains heat from its days as an active star.

Sirius A is still on the main sequence and is spectral class A1. Being somewhat more than twice as massive as the Sun, Sirius will use up all the hydrogen in its core in another billion years or so, and turn into a red giant.

Answer 3

im not sure exactly how old sirius is but it is soo hot because it is a white dwarf.... white dwarfs are dim stars, but they are the hotter than the sun or any other star..... sirius is located in the bottom left- hand corner of the H-R diagram....

Answer 4

Here's a good write up that should answer your questions. Sirius is actually two and possibly three stars.

http://en.wikipedia.org/wiki/Sirius