The Life Cycle of a Star The Horsehead Nebula – one of the most famous pictures in astronomy

This is the Orion Nebula or M42 This is the Orion Nebula or M42. It is the nearest bright nebula to us and can be seen with the naked eye. Its brightness led to it being the first nebula ever photographed (in 1882) and its proximity (1500 light years) means that we know more about it than any other star-forming region. It is also in a very active stage of star formation and it is perfectly placed for us to explore the intimate details of the birth of stars. A Nebula (plural nebulae) is a stellar nursery. It is a region of dust and gas where new stars are born.

The Sun formed 4.5 billion years ago, as the solar system coalesced from a cloud of gas and dust. The Sun will run out of fuel in about 5 billion (5,000,000,000) years. When this happens it will expand to form a red giant and engulf Mercury and Venus in the process. The sun is a main sequence star. This is the longest, most stable period of a star’s life. It converts hydrogen to helium in its core, generating heat and light.

Betelgeuse (pronounced "beetle juice") is a red giant in the constellation of Orion. It is over 600 million miles in diameter (almost 1,000 times bigger than the Sun but cooler than the Sun). If Betelgeuse were at the center of our Solar System, it would extend beyond the orbit of Jupiter. It is 520 light-years from Earth. A stars expands as it grows old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright; this is a red giant.

This white dwarf is known as Shapley 1 It is about 1000 light years away from Earth. When a red giant collapses, its outer layers shed off and what remains is white dwarf (a very hot, dense star).

The brightest star in this picture is the first supernova to be visible to the unaided eye for almost 400 years. It occured in a region rich in young, blue stars and it was one of these which destroyed itself. The location of the supernova in the Large Magellanic Cloud (LMC) means that it can only be seen from the southern hemisphere. A supernova is the death of a large star. It is a spectacular explosion

A black hole can be created when a giant star undergoes a supernova. A common type of black hole is the type produced by some dying stars. A star with a mass greater than 20 times the mass of our Sun may produce a black hole at the end of its life. Black holes are objects so dense that not even light can escape their gravity, and since nothing can travel faster than light, nothing can escape from inside a black hole. A black hole can be created when a giant star undergoes a supernova.