The sun may seem eternal, but one day it will die. When one star reaches the end of its life, it may explode into a ball of fury. Others might become less dramatic stellar objects, such as white dwarfs and neutron stars. Both types of stars share similar origins and properties, but they behave differently in a few ways that affect their appearance and surroundings.
During its main life cycle, a star generates light and energy by fusing atoms together. If a star has a mass similar to the sun's, it becomes a hot white dwarf when it runs out of nuclear fuel. Gravity causes it to shrink to about the size of the Earth. Over billions of years, the white dwarf cools off and eventually becomes a black dwarf that's difficult to see.
White Dwarfs in the Neighborhood
Sirus also called the Dog Star, is so bright that its brilliance makes it difficult to see Sirius B, the white dwarf star that's closest to Earth. Sirius B is smaller than Earth, but its gravitational field is 350,000 greater because of the star's mass is 98 percent of the sun's. Gravity is so strong on Sirius B that light leaving it stretches out to longer redder wavelengths.
Neutron Stars: They Weigh a Lot
Stars with masses equal to or greater than 10 times the sun explode as the supernova when they run out of nuclear fuel. If a supernova's remnant is 1.4 to about three times the sun's mass, the remnant becomes a neutron star. Like white dwarfs, neutron stars are dense. But a neutron star is so dense that the equivalent of 1.3 solar masses fits inside an area of a city-sized sphere.
When White Dwarfs Explode
Scientists believe that white dwarf stars may be responsible for type-Ia supernova. Supernova explosions are so bright that you can see them from millions of light-years away. One theory postulates that a white dwarf may extract enough gas from a neighboring star to cause the white dwarf to explode. Another possibility is that two white dwarfs collide creating a single star that has enough mass to explode.
Some white dwarfs produce cosmic rays by spinning at high speeds. Magnetic fields on these stars can be millions of times greater than the Earth's magnetic field. Pulsars are neutron stars that can rotate faster than a blender. Like a lighthouse transmitting light, pulsars emit radio waves that can cross the Earth's path. Often powerful sources of gamma rays, pulsars also have magnetic fields, but those are trillions of times greater than Earth's. Even though scientists think about 1 billion pulsars exist in the Milky Way galaxy, they have only found 2,000.