~astro-craze~

As what I have shared with you in previous post, white dwarf arises from when small stars, (those which reach up to eight times as massive as our SUN!!), reach the end of their long evolutions.

These ancient stars are known incredibly dense. A teaspoonful of their matter would weigh as much as AN ELEPHANT! Amazing isn’t it? I wonder how The Universe can hold these enormous elements together..

Stars, like our sun, it fuse hydrogen in their cores into helium.White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel. This is what I meant by end of it’s evolution.

Eventually, over tens or even hundreds of billions of years, a white dwarf cools until it becomes a black dwarf, which emits no energy. Because the universe's oldest stars are only 10 billion to 20 billion years old there are no known black dwarfs yet! I hope it will be discovered soon as I am really interested to know how it looks like.

But not all white dwarfs will spend many millennia cooling their heels. Those in a binary star system may have a strong enough gravitational pull to gather in material from a neighboring star.

Other than white dwarf, in the Universe, there is such thing known as Red Dwarf as well. Unlike white dwarf, Red dwarfs are very low mass stars with no more than 40% of the mass of the Sun.

Consequently they have relatively low temperatures in their cores and energy is generated at a slow rate through nuclear fusion of hydrogeninto helium. And they transport their energy from core to the surface by convection, which is totally different from the white dwarves.Convection occurs because of the interior part of Red Dwarf, has higher density compared to the temperature. As a result, energy transfer viaradiation is decreased, and instead convection is the main form of energy transport to the surface of the star.

As red dwarfs are fully convective, helium does not accumulate at the core and, compared to larger stars such as the Sun, they can burn a larger proportion of their hydrogen before leaving the main sequence. As a result, red dwarfs have estimated lifespans longer than the estimated age of the universe, and stars with less than 0.8 solar masses have not had time to leave the main sequence. The lower the mass of a red dwarf, the longer the lifespan.

It is believed that the lifespan of these stars exceeds the expected 10 billion year lifespan of the sun by the third or fourth power of the ratio of their masses to the solar mass; thus a red dwarf with 0.1 solar mass may continue burning for 10 trillion years. As the proportion of hydrogen in a red dwarf is consumed, the rate of fusion declines and the core starts to contract. The gravitational energy generated by this size reduction is converted into heat, which is carried throughout the star by convection.

One mystery which has not been solved as of 2009 is the absence of red dwarf stars with no metals. Metals here as in like Hydrogen or Helium. Unlike all the other Stars, which they have at least one type of metal, Red Dwarf has none.

In The Big Bang theory, which was my first post in this blog, it predicts the first generation of stars should have only hydrogen, helium, and trace amounts of lithium. Hmmmmm.. Another mystery.. This is why I love the knowledge about the Stars and stuff, fun!

for more info, log on to

-science.nationalgeographic.com/.../white-dwarfs-article.html

news.nationalgeographic.com/.../100525-science-space-planets-tilted-orbits-stars/