Life as a Star

Stars light up the entire night sky. They light up nebulae and the galaxies’ dark arms making them glow, they gather in superb clusters, some of which can be seen with the naked eye, they grow planets around them, and sometimes they create and maintain life :) 

Young solar system (artist's impression)
Young solar system (artist's impression)

Before its birth, the Sun was nothing more than a bunch of gas and dust floating through the interstellar space. Driven by its own gravity, the mass of gas and dust starts to collapse in a very smooth inward spiral. The same movement can be observed in the water flowing out of a sink when you pull its plug. It is a “silly” discovery that in fact helped in the understanding of hydrodynamics and its mechanical similarities to the mechanics of the electromagnetic field.

Million years later, huge amounts of gas (mostly hydrogen) have had gathered into one dense body. High pressure exerted by gravity, the most important ingredient of this recipe, causes the gas ball to increasingly gain heat and the star to start shining (the protostar phase). When the core temperature reaches ten million degrees Celsius, the magic happens: in the very center of the ball, electrons of hydrogen atoms are ripped off from their orbits around their nuclei, and the first hydrogen atoms combine to form helium (process called nuclear fusion). In this process, a very small portion of matter transforms into energy while the hot helium starts to shine for the first time... The star ignites. The remaining mass of gas and dust finds itself on orbit around the newborn star, and the birth of a new solar system begins. 

Given its mass, the new star experiences great gravitational pressure that tends to compress it even more than it already is. In order to avoid collapse, to become stable, the star must provide an opposing force to balance the gravitational pressure and maintain itself in a harmonious equilibrium. That “force” is the temperature, which - according to the ideal gas law - if enough, it holds the star stable. So the problem of the dying stars is not the lack of hydrogen but the lack of very high temperature.

White dwarfs / Black dwarfs

When the star will have consumed most of its hydrogen, it will transform into a different object, depending on its mass. A star with a medium or even smaller mass will burn all of its “fuel” and consequently, its core will start to contract. Inside it, new reactions occur: this time the helium atoms combine to form carbon. Meanwhile, in the outer layers, the remaining hydrogen is fused, process that will make the dying star bigger and red (red giant). In this phase, its outer layers will be thrown into space forming planetary nebula. When there will be no helium left in the core, it will contract again, becoming even denser and small as a planet, but the reactions inside it will no longer have enough power to keep the star burning. It will continue to “peacefully” radiate the remaining heat (in which phase the star is called a white dwarf) and slowly cool down until it will become a cold dark dwarf star. 

The Star Sirius A and its faint white dwarf companion, Sirius B
The Star Sirius A and its faint white dwarf companion, Sirius B

Although the universe is 13,7 billion years old, no black dwarf has been discovered by now, the oldest known white dwarf star still radiating a temperature of few thousands degrees Kelvin.

Stars with huge masses are most likely to end their life collapsing under their own gravitational force (called gravitational collapse) becoming red giants and finally supernovae (exploding stars). Experiencing a greater pressure than a white dwarf would, the helium atoms in the center of such a star will form an iron core instead of carbon one, so dense that after the explosion it will either form a neutron star or, if the star’s mass was very big, a black hole. 

Pulsar
Pulsar

Neutron Stars and Black Holes

Both the neutron star and the black hole are fantastic objects. The neutron stars are so dense that they crush the atoms inside them and consist mostly of neutrons. They have the mass of a normal star but only 15-18 miles in diameter and rotate so fast that electromagnetic beams are emitted at their magnetic poles. The neutron stars’ magnetic axes do not necessarily coincide with their rotation axes, creating thus the lighthouse effect: from a point in universe, the neutron star looks like it pulses (hence their pseudonym – Pulsars), but only if the electromagnetic beam is emitted in its direction.

The baby black holes are even denser objects with great mass and only few kilometers in diameter, that deform the space-time so hard that they “absorb” everything that passes by them, including light and even their own light. Massive black holes can achieve masses comparable to million solar masses and most of them can be found in the center of galaxies. The Quasi-Star Radio Sources (also called quasars), the most bright and distant objects in the universe, are galaxies with huge black holes in their center. The matter around such black hole is absorbed with such a speed that the friction of the collapsing matter inside it shines more than anything in the universe. The quasars are products of the early universe and none of them really exists now, but we can still see the light coming from them.

Binary systems / Double stars

Some stars “live” in binary systems: two stars, which round a common mass center. They are called double stars and their combined gravitational forces keep each other on orbit. Sometimes, the two stars can be optically close only, but more than 60% of the stars of the universe are double stars physically. There also can be triple systems or even multiple ones. Some of the binary systems can consist of a star and a black hole, but the most spectacular ones are those consisting of two neutron stars. They rotate so fast that they create gravitational waves propagating in the space-time continuum. When one of the stars of a binary system dies, the other is thrown away on a straight trajectory. If the its speed is very high, they heat the interstellar gas in their way and create a shockwave similar to what happens to the water in front of a moving boat. These stars can travel at 550-1,000 km/s.

A couple of interesting facts

  • A star does not have a solid nor a liquid surface as we tend to believe when we see photos or when we look through a telescope or special sunglasses. The Sun’s surface looks sharp because we are way too far away from it to see that the whole star is made of very hot gas only.
  • As the hydrogen fuses into helium, the quantity of helium continuously grows, thus making the star shine even brighter. Scientists estimated that a star’s brightness increases by 10% every billion years. They also estimated that our Sun is four billion years old, which means that now is 40% brighter than it initially was, and will continue to shine for another ten billion years.

Size comparison
Size comparison
Betelgeuse is a red giant in the Orion constellation
Betelgeuse is a red giant in the Orion constellation
Nebulas, star nurseries
Nebulas, star nurseries
The M3 glubular cluster
The M3 glubular cluster

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Comments 24 comments

Petra Vlah profile image

Petra Vlah 6 years ago from Los Angeles

You wrote a very informative and most interesting hub with plenty of scientific explanations that will give people an idea about this complex and ongoing process. It is way over my head in terms of understanding the full importance of the well researched data, but a fascinating read nevertheless.

.


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Thanks for your kind words, Petra. I try not to go into too much detail, to keep it short, simple and interesting in the same time, Teleenciclopedia style :) Thanks again!


Victoria West profile image

Victoria West 6 years ago from Toronto

Great hub!


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Hi, Victoria, thanks for reading my hub and for your comment! I'm glad you liked it :)


prasetio30 profile image

prasetio30 6 years ago from malang-indonesia

As a teacher I really like this hub. I found useful information about various types of star. I'll share this information to my student. I think they will love this. Very informative. Life as a star and always shining everyday. Thank you very much. Two thumbs up for you. I rate this one.

Prasetio


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Prasetio, I'm very glad you found my hub usefull, this is what I hope for everytime I publish a new one. Thank you!


lucky1000 profile image

lucky1000 6 years ago

great hub nice word use


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Thank you, lucky :)


Nell Rose profile image

Nell Rose 6 years ago from England

Hi, Daniel, what I love about your writing is that it explains everything in a way that even the most difficult parts are so easy to understand, great stuff, I love anything to do with Space! nice to see you, nell


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Thank you Nell, nice to see you too!


RunAbstract profile image

RunAbstract 6 years ago from USA

Very absorbing article. The photos are wonderful. It is a pleasure to read such well researched and thought out material.

Tends to make me feel so small in the vastness of it all. Which isn't a bad thing!

Thank you!


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Thank you, RunAbstract!

We are small all right, but what really *scares* me is the infinite, and me being a part of it :)


Mr. Happy profile image

Mr. Happy 6 years ago from Toronto, Canada

Stephen Hawkin has a new book coming out I think soon (if it isn't out already) titled "The Grand Design". Seemed quite interesting after seeing an interview about it. It talks about similar things as your blog here.


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Stephen Hawking is absolutely amazing. He can write only one character at a time and still has the patience to write books. I'm glad I'll have the chance to read about how his view of the universe changed in the last decade.

Thanks for stopping by!


epigramman profile image

epigramman 6 years ago

...this is perhaps the most definitive hub on stars I've ever seen which is ironic because the stars are infinite - are they not? ...... but just the same - anyone who can write and put together a hub like this is truly a geniune star in my book!!! Bravo - may you see your shooting star and make a wish!


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Hi epigramman,

Thank you so much for your words, it's an honor!


prasetio30 profile image

prasetio30 6 years ago from malang-indonesia

I learn much from this hub. I give my big attention to outer space subject. I'll bookmark this one and I'll show this to my student. Thank you very much. ~prasetio


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Hi prasetio30,

Thanks again for your interest in this hub!


TeamSTM profile image

TeamSTM 6 years ago

I am an Astronomy Buff and I really enjoyed your HubPage here!! When I was a kid the Constellations intrigued me very much, as well as looking through a telescope in the Summer-time!

Thanks for your "Life as a Star" HubPage!!!


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Hello, TeamSTM! I've always been fascinated by nebulae and galaxies, now I don't know if there's anything I'm not interested in about the universe and our world. Thanks for your comment!


rafken profile image

rafken 6 years ago from The worlds my oyster

Once again, a very good job.


Daniel V. profile image

Daniel V. 6 years ago from Romania Author

Hi rafken, thanks again for stopping by!


RunAbstract profile image

RunAbstract 5 years ago from USA

I love your facts! But even more... I love the hints of fasination you gave me!

Thanks!


Daniel V. profile image

Daniel V. 5 years ago from Romania Author

Thank you so much, RunAbstract!

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