It is a blue (very hot) supergiant, over 100 times bigger than the Sun.Īs medium sized stars exhaust their hydrogen content, they expand up to 100 times their original size to become red giants. Rigel is the brightest star in the constellation called Orion and one of the brightest stars in the sky. Massive stars, more than 3 times the mass of the Sun, mostly convert hydrogen into helium.

Stars are powered by nuclear fusion in their cores, mostly converting hydrogen into helium and liberating tremendous amounts of energy.Īcknowledgement: JPL-Caltech National Aeronautics and Space Administration (NASA) Massive star One example of a stellar nursery is the Eagle Nebula.Īcknowledgement: T.A.Rector & B.A.Wolpa, NOAO/AURA/NSF Average starĪn average or medium star is less than 3 times the mass of the Sun.

Nuclear fusion processes begin converting hydrogen into helium. Hundreds of millions of years later in stellar nebulae, the hydrogen gas clouds coalesce and, under gravity, form protostars. Moments after the Big Bang, energy begins to condense into matter, protons and neutrons are formed, and then the first element (hydrogen) is formed. As stars evolved in space after the Big Bang, nuclear reactions occurred that transformed hydrogen and helium, formed as a result of the Big Bang, into the elements as we know them.Ĭlick on each stage of the star life cycle and discover how the elements that we are all made up of were created. “We’re literally the ashes of long dead stars,” says Sir Martin Rees, Professor of Cosmology and Astrophysics, University of Cambridge.

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