Experimenting CLIL: school subjects in English / Science

The Life Cycle of a Star (1)

Namaskara guys!

Now you know how to say “hello” in Kannada, a language spoken in the southern India.

Ok, apart from this I’m going to talk to you about the very long and troubled life of a star. I’ll try to do it in two or three posts don’t worry, and I hope to do it right. =)

Our universe is still an enormous  mystery also for the astronomers and astrophysicists that spend their life studying it.

A few days ago, while I was watching a documentary, I decided to find out more and to understand what stars actually are… Let’s STARt then 😉

In the immensity of the universe, as a product of the great explosion of the Big Bang, billions of particles float under the action of gravitational fields. When some of these particles concentrate together (reaching the density of about 10.000 particles/cm³) they form a Nebula. 

A nebula is usually composed of Hydrogen (90%), plasma and other gases, but surely, seen in pictures, they are something… divine! Fluffy and colorful twinkling clouds that create fabulous figures. These are for example the Orion, Carina and Cat’s Eye nebulas.

Orion Nebula

Carina nebula

Cat's Eye Nebula

Thanks to gravity, an area in the Nebula can coagulate more, with the consequential production of heat and the increase in temperature. In its centre a Protostar is coming to life, and it immediately starts to produce infrared radiations that allow telescopes to capture them.

Thermonuclear reactions in the star nucleus, however, seldom inhibit the force of gravity, so the star keeps collapsing until the temperature reaches the level of about  10,000,000° Kelvin,  Hydrogen starts to fuse in Helium, producing the necessary energy to contrast the gravitational force, and the newborn Star reaches its balance. In the core, temperature and pressure reach the level of about, respectively, 15 million degrees Kelvin and 5 billion atmospheres, and plasma particles have an extremely high kinetic energy.

This stage is called Main Sequence and is the phase in which the celestial body usually lives the 70% of its life. Our Sun, for example, started this stage about 5 billion years ago and will be there for other 5 billion years.   In its core temperature and pressure reach the level of about, respectively, 15 millions degrees Kelvin and 5 billion atmospheres, and plasma particles have an extremely high kinetic energy.

This is an H-R (Hertzsprung-Russell) graph that shows the relationship between the absolute magnitudes (brightness) and the Spectral Type (temperature) of stars. You can see a curved line in the middle of the chart that represents all the stars in the main sequence.

 Now… our star has some hydrogen to burn…  let’s leave it alone.

Let’s wait until it’s done with it. 🙂 Ryder

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