On January 16, 1862, Alvan Clark, an American astronomer and telescope maker, discovered Sirius B, the first white dwarf.
Sirius, also known as α Canis Majoris or the brightest star in the night sky, has a luminosity 22 times that of the Sun. However, this is not a record in the world of stars. Sirius’ high apparent brilliance is due to its relative proximity. Sirius is visible from all regions of the Earth except for the northernmost areas. It is located 8.67 light-years away from the solar system and is one of the closest stars to us.
In 1844, Friedrich Bessel proposed that Sirius was a binary star system. In 1862, Alvan Clarke discovered a companion star orbiting Sirius, which is sometimes referred to as Sirius A. The two stars orbit around a common center of mass at a distance of about 20 astronomical units with a rotation period close to 50 years. In 1915, astronomers at Mount Wilson Observatory determined that Sirius B was a white dwarf, making it the first white dwarf to be discovered. It is interesting to note that Sirius B must have been significantly more massive than Sirius A in the past, as it had already left the main sequence during evolution.
According to modern research, Sirius is estimated to be around 230 million years old (with estimates varying from 200 to 300 million years). Initially, Sirius was composed of two blue-white stars of spectral class B: one component (Sirius B) had a mass of 5 solar masses, while the other (Sirius A) had a mass of 2 solar masses. Sirius B burned through and became a red giant before shedding its outer shell, leaving it in its current white dwarf state. Its mass is now slightly less than that of the Sun, while Sirius A’s mass remains about twice that of the Sun.
