Facts About Stars: Top 9 Amazing Things
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| Photo: skyandtelescope.org |
Stars are luminous spheres made of plasma – a superheated gas threaded with a magnetic field. They are made mostly of hydrogen, which stars fuse in their cores. That process releases energy, which pushes against the weight of the outer layers of the star and keeps it stable. The energy is also released as heat and light, which are radiated out to space. Stars are the main components of galaxies and were among the first objects to form in the early universe.
Science has uncovered a lot about our solar system but we are only on the brink of understanding the sheer capacity of the universe and beyond. Adults and children both enjoy the beauty and mystical qualities of the night sky and the more you learn about our vast solar system the more curiosities and questions are provoked.
The next time you are stargazing share some of these fun facts with your kids to get them excited about astronomy at any age.
1. The Sun is the closest star
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| Photo: universetoday.com |
Okay, this one you should know, but it’s pretty amazing to think that our own Sun, located a mere 150 million km away is an average example of all the stars in the Universe. Our own Sun is classified as a G2 yellow dwarf star in the main sequence phase of its life. The Sun has been happily converting hydrogen into helium at its core for 4.5 billion years, and will likely continue doing so for another 7+ billion years. When the Sun runs out of fuel, it will become a red giant, bloating up many times its current size. As it expands, the Sun will consume Mercury, Venus and probably even Earth.
2. What color can stars be?
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| Photo: lovethenightsky.com |
The color of any star is a mix of different wavelengths of light, ranging from high-energy, short-wavelength blue, and violet light emitted by the hottest materials, to lower-energy, longer-wavelength red and orange emitted by cooler gases. White stars represent an even balance between the two.
3. Stars are made of the same stuff
All-stars begin from clouds of cold molecular hydrogen that gravitationally collapse. As the cloud collapses, it fragments into many pieces that will go on to form individual stars. The material collects into a ball that continues to collapse under its own gravity until it can ignite nuclear fusion at its core. This initial gas was formed during the Big Bang and is always about 74% hydrogen and 25% helium. Over time, stars convert some of their hydrogens into helium. That’s why our Sun’s ratio is more like 70% hydrogen and 29% helium. But all stars start out with 3/4 hydrogen and 1/4 helium, with other trace elements.
4. Stars are black bodies
A black body is an object that absorbs 100 percent of all electromagnetic radiation (that is, light, radio waves, and so on) that falls on it. A common image here is that of a brick oven with the interior painted black and the only opening a small window. All light that shines through the window is absorbed by the interior of the oven and none is reflected outside the oven. It is a perfect absorber. As it turns out, this definition of being perfect absorbers suits stars very well! However, this just says that a blackbody absorbs all the radiant energy that hits it, but does not forbid it from re-emitting the energy. In the case of a star, it absorbs all radiation that falls on it, but it also radiates back into space much more than it absorbs. Thus a star is a black body that glows with great brilliance!
5. Mass = temperature = color
The color of stars can range from red to white to blue. Red is the coolest color; that’s a star with less than 3,500 Kelvin. Stars like our Sun are yellowish-white and average around 6,000 Kelvin. The hottest stars are blue, which corresponds to surface temperatures above 12,000 Kelvin. So the temperature and color of a star are connected. Mass defines the temperature of a star. The more mass you have, the larger the star’s core is going to be, and the more nuclear fusion can be done at its core. This means that more energy reaches the surface of the star and increases its temperature. There’s a tricky exception to this: red giants. A typical red giant star can have the mass of our Sun and would have been a white star all of its life. But as it nears the end of its life it increases in luminosity by a factor of 1000, and so it seems abnormally bright. But a blue giant star is just big, massive, and hot.
6. How many stars are there in the universe?
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| Photo: Wikipedia |
Brace yourself for some big numbers. Astronomers believe there are probably somewhere between 10 sextillions (21 zeros) and 1 septillion (24 zeros) stars in total. That’s based on recent discoveries that there are a lot more tiny, faint stars lurking in large galaxies than previously thought, and some educated guesswork on the total number of galaxies themselves.
7. Most stars come in multiples
It might look like all the stars are out there, all by themselves, but many come in pairs. These are binary stars, where two stars orbit a common center of gravity. And there are other systems out there with 3, 4, and even more stars. Just think of the beautiful sunrises you’d experience waking up in a world with 4 stars around it.
8. How Stars Die
| Stars may “live” longer than humans do – ranging from tens of millions to billions of years – but eventually, they, too, come to the ends of their lives. The manner of a star’s death depends on the mass it had after it finished forming. Stars with masses similar to the Sun die much differently from stars that have 7 or more solar masses. Yet, the process of star death starts out the same for all stars: they run out of fuel. For much of its life, a star fuses hydrogen to make helium. When that runs out, then the star fuses helium, and then carbon. Each level of fusion releases more energy, which heats up the star. |
In sun-like stars, the increased heating causes them to swell up to become giant stars. Any nearby planets are enveloped by the expanding star. Eventually, the outer stellar atmosphere blows away, creating an expanding cloud of gas around the star. This is called a “planetary nebula”. What’s left of the star itself slowly shrinks and cools. Eventually, the dying star becomes a white dwarf.
When stars die, all the elements they created in their cores are scattered to space, to become part of interstellar clouds of gas and dust. Those chemical elements are seed materials for new generations of stars, planets, and life.
9. And they’re very far
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| Photo: telusworldofscienceedmonton.ca |
With so many stars out there, it’s amazing to consider the vast distances involved. The closest star to Earth is Proxima Centauri, located 4.2 light-years away. In other words, it takes light itself more than 4 years to complete the journey from Earth. If you tried to hitch a ride on the fastest spacecraft ever launched from Earth, it would still take you more than 70,000 years to get there from here. Traveling between the stars just isn’t feasible right now.
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