26 Lift up your eyes and look to the heavens:
Who created all these?
He who brings out the starry host one by one
and calls forth each of them by name.
Because of his great power and mighty strength,
not one of them is missing.
Isaiah 40:26 New International Version (NIV)
- Stars are formed when clouds of gas are pulled together by gravity. As the gas particles are squeezed closer and closer together, they warm up. Eventually, they are pressed together so closely and tightly that they begin to join up, giving off energy in nuclear fusion: the cloud has become a star.
- Stars are objects in turmoil. Stars differ in size, brightness and colour. What’s more, they evolve over time. Most stars will get brighter as they move through their life cycle, until they run out of fuel in their core, at which point many of them fluff up to produce a huge ‘giant’ star.
- The giant phase does not last forever. A mid-sized star that became a giant is likely to blow off its outer layer as a cloud of gas, leaving a small white dwarf behind. Larger super giants undergo cataclysmic explosions called supernovas, generating heavy elements and leaving a neutron star or black hole.
- Supernovas can be detected on the Earth because they produce immense bursts of light. A star that is usually much too far away to be seen suddenly becomes visible from the Earth. What appears to be a new star is seen in the sky. Supernovas can be so bright that they are briefly visible in the daytime. As the supernova subsides, the result is a vast swirl of stellar debris called a nebula. The best known of these is the Crab Nebula, the remainder of a supernova seen on Earth in 1054 and recorded by Chinese astronomers. With modern telescopes, we can detect supernovas in galaxies outside the Milky Way, and because particular types of supernova have similar brightness, they are used as ‘standard candles’ to measure the distance to galaxies.