White dwarf

From Conservapedia

White Dwarf Stars photographed by the Hubble Space Telescope.

A White dwarf is a star that is the remnant core of a star that has completed fusion in its core. The sun will become a white dwarf. White dwarfs are typically composed primarily of carbon, have about the radius of the earth, and do not significantly evolve further. Where a star ends up at the end of its life depends on the mass it was born with. Stars that have a lot of mass may end their lives as black holes or neutron stars. A low and medium mass star (with mass less than about 8 times the mass of our Sun) will become a white dwarf. A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars.

White Dwarf Stars in M4

Observations of White Dwarfs

There are several ways to observe white dwarf stars. The first white dwarf to be discovered was found because it is a companion star to Sirius, a bright star in the constellation Canis Major. In 1844, astronomer Friedrich Bessel noticed that Sirius had a slight back and forth motion, as if it was orbiting an unseen object. In 1863, the optician and telescope maker Alvan Clark spotted this mysterious object. This star was later determined to be a white dwarf. This pair are now referred to as Sirius A and B, B, being the white dwarf. The orbital period of this system is about 50 years.

The Hubble Space Telescope, with its 2.4 meter mirror and advanced optics, has been successfully viewing white dwarfs with its Wide Field and Planetary Camera. In August of 1995, this camera observed more than 75 white dwarfs in the globular cluster M4 in the constellation Scorpius. These white dwarfs were so faint that the brightest of them was no more luminous than a 100 watt light bulb seen at the moon's distance. M4 is located 7,000 light years away, but is the nearest globular cluster to Earth. It is also approximately 14 billion years old, which is why so many of its stars are near the end of their lives.