Stars

"Stars"

We're all pretty familiar with stars. We see them on most clear nights as tiny, twinkling pinpricks of light in the sky.A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth.

Stars are the topic of countless poems, stories, and nursery rhymes alike. But just what is a star, exactly?

A star is a luminous ball of gas, mostly hydrogen and helium, held together by its own gravity. Nuclear fusion reactions in its core support the star against gravity and produce photons and heat, as well as small amounts of heavier elements. The Sun is the closest star to Earth.

Where do stars come from?

According to current star formation theory, stars are born as clumps within gigantic gas clouds that collapse in on themselves. The cloud’s material heats up as it falls inward under the force of its own gravity.

When the gas reaches about 10 million K (18 million °F), hydrogen nuclei begin to fuse into helium nuclei, and the star is born. Energy from nuclear fusion radiates outward from the center of the burgeoning star, and gradually halts the gas cloud’s collapse.

"Life Formation of a Star"

THE LIFE CYCLE OF A STAR.

Outlined above are the steps involved in a stars evolution, from its formation in a nebula, to its death as a white dwarf or neutron star. A nebula is a cloud of gas (hydrogen) and dust in space.

How long is the life of a star?

Generally, the more massive the star, the faster it burns up its fuel supply, and the shorter its life. The most massive stars can burn out and explode in a supernova after only a few million years of fusion. A star with a mass like the Sun, on the other hand, can continue fusing hydrogen for about 10 billion years.