White Dwarfs (Sirius B)

Hello!

When you go to a place, far away from city lights during a clear night, you might see an "ocean" of stars. Many of these stars have different luminosities, sizes and colours. However, even in the darkest regions, you cannot see some stars at all with the naked eye. One of these stars are known as white dwarfs.

White dwarfs or degenerate dwarfs are the remnants of dead stars after it turns into a red giant. They are not formed by supernovae, the process is mostly silent compared to other phenomena. An example of a star that will turn into a white dwarf is the Sun. It will turn into a red giant in 5 billion years, eventually turning into a white dwarf. It is hypothesized that white dwarfs will turn into so-called "black dwarfs" after trillions of years.

Even though we can't see white dwarfs with our eyes, we can actually pinpoint the locations of some, such as Sirius B, a white dwarf which is in a binary star system which consists of the much brighter and bigger Sirius A. Sirius B is also known to be the closest white dwarf to the solar system at around 9 light years.

The picture below shows the Sirius star system, however Sirius B is not shown in the picture due to its low brightness.

Sirius A is the star with the lowest apparent magnitude of -1.46 (it means it is the brightest from the Earth's perspective) but Sirius B has an apparent magnitude of 8.44 despite being the same distance away from the Earth, which makes it visible only to special telescopes. This shows the contrast between the brightness of different stars and star remnants.

White dwarfs, despite being small have very strange properties. Sirius B is as big as Earth but has half the mass of the Sun and also has a surface temperature around 25,000 Kelvin; much hotter than the Sun, which has a surface temperature of around 5000 Kelvin!

Sirius B and other white dwarfs don't have any source of energy so it will slowly cool down until it dies trillions of years later. It's quite a lonely existence being alone or just with another star for trillions of years, isn't it?

Thanks for reading!