The Time Now > Astronomy > Stars, nebulae and star clusters

Stars, nebulae and star clusters

We all are made of starstuff. The atoms of some of the elements that comprise our bodies were created in the depths of stars. What we are is literally the stuff of the cosmos –atoms that have been recycled many times before they came together to make us. Stars are born, live out their lives, and die. And when some of them die, they die very violently –in a cosmic cataclysm called a supernova. Others die gently, slowly, quietly. Their remains –gas and dust– are strewn across the galaxies to be recycled into other stars, other planets, possibly even other life?

Read below to help you become acquainted with stars, nebulae, and star clusters.


Night sky with amazing stars
Night sky with amazing stars. © iStockphoto/EpicStock

A star is a massive sphere of very hot, glowing gas, mostly hydrogen and helium. The whole is maintained by gravity. A star shines because of a process in its interior called nuclear fusion, basically a nuclear burning. It differs from a planet which light is produced by reflection.

The nearest star from Earth is the Sun. The Sun is so hot, that we can compare it to a hydrogen bomb, constantly undergoing a great nuclear reaction. As the Sun, all the stars constantly release a huge amount of energy.

The photo on the right represents the Milky Way galaxy, many stars can be seen on this amazing New Zealand night sky, as they are not obscured by any atmospheric phenomena.


The Helix Nebula
The Helix Nebula. © iStockphoto/MKonrad

Nebulae is the plural of nebula, which means "cloud" in latin. Nebulae are interstellar clouds of gas -mostly hydrogen, helium- and dust.

The Helix Nebula, shown on the left picture, also known as The Helix, NGC 7293, or Caldwell 63, is one of the closest to Earth large bright planetary nebula. It is located 700 light-years away in the constellation Aquarius, one of the oldest of the recognized constellations along the zodiac -the sun's apparent path.

The Hubble Space Telescope has taken recent images of the Helix Nebula.

Star clusters

Messier 13, the great globular cluster in Hercules constellation
Messier 13, the great globular cluster in Hercules constellation. © iStockphoto/MKonrad

Star clusters are groups of stars, also known as star clouds, which are gravitationally bound.

There are several types of star clusters.

Globular clusters, also simply known as globular, are star clusters concentrating approximately ten thousand to one million very old stars. They are very tightly bound by gravity and orbit as a satellite. They are around 150 globular clusters known in the Milky Way, and more still undiscovered. Messier 13 shown on the right is a famous globular cluster.

Open clusters, also known as galactic clusters, concentrate a maximum of a few thousands stars. These stars have a similar age and a very close composition. Some of them are visible without instruments, only with the naked eye, such as Pleiades open star cluster. Many others will need binoculars or telescopes.

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