Written by: Sakshyam Karna - 26013, Grade IX
Posted on: 19 December, 2022
Like every other thing in this universe, stars also have their life cycle. The stars are formed from stellar nebulae when the gravitational pull becomes too big for it to withstand and it collapses. Then from the force of the collapse the material at the center heats ups and creates a prostar. It slowly heats up more and more and when it has enough heat it becomes a star. There are two types of stars that can be born from a stellar nebula, an average star and a massive star. But to learn about white dwarfs we only need to know about the average stars. These stars have a small amount of energy and they extinguish fast. After a few billion years the star becomes a red giant and grows to 800% of its original mass and starts burning fast for about 2 billion years. Then it runs out of gas and becomes a white dwarf. Red dwarfs and other smaller stars are unable to develop into red giants. They just exhaust all of their hydrogen, turning into a faint white dwarf in the process. No red dwarfs have yet evolved into white dwarfs due to the fact that it takes them trillions of years to exhaust their fuel, which is much longer than the universe's age of 13.8 billion years.
When stars like our sun have used up all of their fuel, what is left are white dwarfs. They are low and medium mass stars' final detectable stage of development and are dense, dim stellar corpses. According to NASA, a low or medium mass star with a mass less than around 8 times that of the sun will eventually turn into a white dwarf while the majority of large stars will eventually go supernova. According to astronomers, the Milky Way's stars will eventually turn into white dwarfs in about 97% of cases. Despite being far smaller in size than our sun, a white dwarf is similar to Earth in terms of carbon and oxygen mass, according to New Mexico State University (NMSU). Red dwarfs and other smaller stars are unable to develop into red giants. They just exhaust all of their hydrogen, turning into a faint white dwarf in the process. No red dwarfs have yet evolved into white dwarfs due to the fact that it takes them trillions of years to exhaust their fuel, which is much longer than the universe's age of 13.8 billion years.
When a star runs out of fuel, the fusion process no longer pushes the star outward, and the star collapses inward on itself. According to Cosmos, the astronomy encyclopedia from Swinburne University in Australia, white dwarfs have around the same radius as Earth but roughly the mass of the sun. They are only surpassed in density by neutron stars and black holes, making them some of the densest objects in space. NASA estimates that a white dwarf's surface has a gravity 350,000 times greater than Earth's. In other words, a person weighing 150 pounds (68 kilograms) on Earth would weigh 50 million pounds (22.7 million kg) on a white dwarf's surface.
