Colour of stars indicate their age, surface temperature, size and chemical make-up.
Colour of stars indicate their age, surface temperature, size and chemical make-up. Contributed

DARK SKIES: Understand how stars are born

STARS are born in molecular clouds called nebulas.

They consist of huge amounts of cosmic dust, hydrogen, helium, iron and plasma.

As the nebula compresses this matter under extreme pressure and temperature, hydrogen is fused into helium, also know as nuclear fusion.

When the core temperature rises significantly in the tens of billion degrees Celsius, it is known as the Critical Mass.

So when hydrogen is fused into helium at a very fast rate under extreme temperature and pressure, stars and planets can be formed. Blue/white stars are the hottest, simply because they are converting hydrogen into helium faster, leading to huge amounts of energy.

The average life of most stars is 20 million years.

Stars come in various colours, which indicate its age, size, temperature and chemical make-up.

While the blue supergiant stars like Rigel in Orion, Sirius in Canis Majoris, Canopus in Carina and Spica in Virgo are the brightest and hottest, yellow and red stars are middle-age and dying.

To compare our Sun's diameter to say, Rigel, our Sun is a pebble to a beach ball. And while the Sun's surface temperature is 6000C, compared to Rigel's based on current Spectra analysis, it's much hotter.

Our daytime star, the Sun, is the only one we have to give us life on this planet.

It puts out a lot of energy.

So much so, if were able to harness the Sun's total energy output in one second, it would power the entire world 24/7, for 115,000 years, compared to Rigel, which would be in the millions of years.

So while it takes millions of years to form into a star, it takes even longer to die and this is when it gets interesting.

As we age through life, our bodies and minds slow down and we die.

In stellar evolution, however, as a star depletes its hydrogen fuel, the star moves into the yellow stage like our Sun.

Billions of years later, their colour changes to orange and finally deep red, like Antares in Scorpio, Alderbran in Taurus, Regulus in Leo and Betelgeuse in Orion.

By this time, the star's core collapses on itself, as gravity has now overtaken pressure and one of three things can happen

1. The star explodes as a Supernova;

2. Blows out half of its mass into Space creating a stellar 'smoke-ring' called a planetary nebula; or

3. Into a possible black hole where its gravity is so strong not even its own light can escape.

By taking the spectra of stars, astronomers can gauge the star's chemical make-up, age, size and surface temperature as compared to the 'new kid on the block', our Sun.