Scientists are able to estimate the age of the Universe by looking for the oldest stars and by measuring the rate of expansion of the Universe.
The Life Cycle Of Stars
Stars undergo a life cycle based on the composition of the gases within them. As stars age the amount of hydrogen in the star changes, therefore changing the color and brightness of the star.
- Stars start out in giant clouds of dust called a nebula. Gravity forces the dust to bunch together. As more and more dust bunches up. Once the center gets hot enough, nuclear fusion will begin and a young star is born.
- Once a star, it will continue to burn energy and glow for billions of years. This is the state of the star for the majority of its life and is called the "main sequence". During this time a balance is met between gravity wanting to shrink the star and heat wanting to make it grow bigger. The star will remain this way until it runs out of hydrogen.
- When the hydrogen runs out, the outside of the star expands and it becomes a red giant.
- Eventually the core of the star will start to make iron. This will cause the star to collapse. What happens to the star next depends on how much mass it had (how big it was). The average star will become a white dwarf star. Larger stars will create a huge nuclear explosion called a supernova. After the supernova it may become a black hole or a neutron star.
Pillars of Creation
The Pillars of Creation are two 4-light-year-tall columns 7,000 light years from Earth. The “Pillars of Creation,” are one of the most iconic images ever taken by the Hubble telescope, but might have been long ago torn apart by a distant explosion more than a thousand years ago.
Around 6,000 years ago, a blast wave from a nearby supernova likely crashed into them, grinding them down and washing them away in concert with the young stars. But we won’t be able to watch them dim and disappear until the year 3015 (give or take). You see, the Pillars live 7,000 light-years away from Earth. The light we see from them — the light that Hubble Space Telescope scientists used to make the new image — departed from the nebula in the year 4985 B.C.E., traveled at the speed of light toward us, and arrived here 7,000 years later. We thus see the nebula as it looked 7,000 years ago.
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Stars undergo a life cycle based on the composition of the gases within them. As stars age the amount of hydrogen in the star changes, therefore changing the color and brightness of the star.