When stars get to the end of their lives, they swell up and fall together again, throwing off their outer layers. If a star is heavy enough, it will explode in a supernova. So most of the material that we’re made of comes out of dying stars, or stars that died in explosions. And those stellar explosions continue.

The six most common elements of life on Earth (including more than 97% of the mass of a human body) are carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus.

Most common elements in living things are carbon, hydrogen, nitrogen, and oxygen. These four elements constitute about 95% of your body weight.

These chemical building blocks are also the basis for all living organisms on Earth. While living organisms contain a number of different elements, some elements are found in greater abundance in living organisms. These elements are oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus.

Almost 99% of the human body mass consists of six main elements; namely: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphor; 65–90% of each cell in the body is composed of water, as such, oxygen and hydrogen are among the main constituents of the human body.

Andreas Vesalius

Sagan

The largest known star in the universe is UY Scuti, a hypergiant with a radius around 1,700 times larger than the sun.

Most of us are familiar with the saying, made popular by astronomer Carl Sagan, folk singer Joni Mitchell, and countless inspirational posters and billboards—We are stardust. Yet, how do we know that we’re stardust?

From Wikipedia, the free encyclopedia. Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as “stellar nurseries” or “star-forming regions”, collapse and form stars.

The Wolf-Rayet star WR 102 is the hottest star known, at 210,000 K.

A star is born when atoms of light elements are squeezed under enough pressure for their nuclei to undergo fusion. All stars are the result of a balance of forces: the force of gravity compresses atoms in interstellar gas until the fusion reactions begin.

There are new Stars Forming Near the Core of the Milky Way Despite the Harsh Environment. The central core of our galaxy is not a friendly place for star formation, and yet new observations have revealed almost four dozen newly-forming systems.

Stars are born when large gas clouds collapse under gravity. When it eventually dies, it will expand to a form known as a ‘red giant’ and then all the outer layers of the Sun will gradually blow out into space leaving only a small White Dwarf star behind about the size of the Earth.

Stars die because they exhaust their nuclear fuel. Once there is no fuel left, the star collapses and the outer layers explode as a ‘supernova’. What’s left over after a supernova explosion is a ‘neutron star’ – the collapsed core of the star – or, if there’s sufficient mass, a black hole.

When the helium fuel runs out, the core will expand and cool. The upper layers will expand and eject material that will collect around the dying star to form a planetary nebula. Finally, the core will cool into a white dwarf and then eventually into a black dwarf. This entire process will take a few billion years.

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.

We estimate at about 100 billion the number of galaxies in the observable Universe, therefore there are about 100 billion stars being born and dying each year, which corresponds to about 275 million per day, in the whole observable Universe.