Facts about stars
98. Stars are classified by their color, size and temperature. Our Sun is a GV2 type yellow dwarf, and it is a main sequence star. (These main sequence stars are the most common.)
99. Stars are born in nebulae. A nebula is a huge interstellar cloud of gas that consist primarily of hydrogen and helium, and, to lesser extent, dust and other ionized gasses.
Four different planetary nebulae.Via NASA/Chandra Observatory
100. Stars exist in the state that is called plasma, and it is actually the fourth fundamental state of matter.
This is actually the most abundant form of ordinary matter (yes, there is unordinary matter) in the universe, even though we don’t witness it on Earth at all, except in the labs. (Well, and if you cut a grape in half and microwave it. – do not do this at home!)
101. A protostar is a star infant of a sort. This is the name used for a star that is still gathering mass from its parent molecular cloud (Nebula). This is the first stage of the star evolution, and it lasts for about a billion years for stars that are similar in size to our own Sun.
102. Although we see stars as specks of light in the sky, sometimes that speck is not just one star. Binary star systems have two stars instead of one that orbit around each other. The craziest part is that the orbiting objects don’t have to be stars. They can be black holes, neutron stars, white dwarfs, or any other celestial body.
103. Besides binary, there are also other multiple star systems. The most common of these are trinary systems, where three stars orbit around each other.
104. The most complex multiple systems we have discovered are septuple star systems, which means there are 7 star orbiting around each other in a ludicrously complex orbit. To top it off, we found 2 such systems already.
105. Nuclear fusion is a chemical reaction in which two atoms fuse into one. This is the process that is responsible for the huge quantities of energy produced in stars. Stars begin as huge balls of the two lightest elements, Hydrogen and helium, and slowly fuse those into heavier and heavier elements.
106. All the chemical elements up to Iron (28th element) are produced by nuclear fusion in the stars. The Iron is the limit because fusing heavier elements requires more energy than would be produced by the reaction.
107. Since the human beings, animals and plants are mostly made of carbon, oxygen, hydrogen and other fairly light elements mostly produced in stars, there is a tiny bit of a star in each and every one of us. In a way we are all made off star stuff, as Karl Sagan said.
108. Star’s lifespan depends on the amount of fuel it has. Surprisingly, the bigger the star, the shorter it’s life is. This is due to the fact that massive stars produce tremendous amounts of energy, and burn through their fuel reserves quickly.
109. Our Sun has an estimated lifespan of around 10 billion years, and we’re half way through it. When it depletes its reserves it will first become a red giant, before dying out.
110. When stars die (their reserve of fusionable elements is depleted), depending on their size several things can happen:
They become white dwarfs and slowly die out, or they go out in the blaze of glory in a majestic explosion that is called a supernova.
The Early Flash Of An Exploding Star.Via Nasa.gov
111. Supernovae (plural of supernova) are some of the most energetic events in cosmology. They can briefly outshine whole galaxies.
112. The tiniest stars, red dwarfs, might live up to an amazing 10 trillion years, which is almost 800 times the current age of the universe. These stars are also the most numerous.
113. The white dwarfs are the remnants of dead stars. These tiny Earth-sized balls are composed of electrons and can shine for millions of years. The heat and energy they emit is only due to their stored thermal energy (i.e. heat), since no nuclear fusion or any other chemical process is present.
114. Our Sun is to become a white dwarf at the end of its life, after it goes through a red giant phase. When the Sun becomes a red giant, its outer layers will engulf Earth. That won’t be pleasant, I assume.
115. The Sun has the size of around million Earths.
Sun-to-Earth size comparison by John Brady.Via AstronomyCentral.co.uk
116. Sun burns up over four million tons of matter each second in its core. This matter is converted into energy and released in the form of neutrinos and solar radiation.
The Sun has converted over 100 times the mass of Earth into energy so far.
117. The Sun increases its energy production over time, due to heavier elements being used for nuclear fusion. It is estimated that it is 30% brighter now than when it started its main-sequence life.
118. The oldest recorded star is conveniently nicknamed Methuselah. This elderly statesman is estimated to be as old as the universe itself.
This Digitized Sky Survey image shows the oldest star with a well-determined age in our galaxy.Via Wikipedia.org
119. Star colors depend on the temperature of the star. Contrary to what is logical to us, blue is hot and red is cold. This is because the hotter stars emit light on the shorter, more energetic wavelengths, which we see as blue, while the red color is on the opposite side of the color spectrum with longer wavelengths.
120. There are no green stars. Stars that are neither really hot nor cold emit white light that we can see as green when we use certain filters.
121. Neutron stars are the smallest and densest stars that we know of. They are made entirely of neutrons, subatomic particles with no charge, instead of atoms. They are incredibly hot with temperatures of over 600000 Kelvin.
122. Neutron stars can have a radius of about 10 kilometers, but can pack 2 Sun masses in their (comparatively) tiny volume.
A teaspoon of neutron matter from the core would weigh around 10 billion tons, which is similar to the weight of an average Earth mountain.
123. The star nearest to Earth, besides Sun, is Proxima Centauri, 4.2 light years away. To try and understand this distance, here’s a little example:
The space shuttle can reach speeds of 30000 kilometers per hour. If you were to take the shuttle, it would take you around 150000 years to reach our closest neighbor.
124. The black hole is an object so massive and dense that its gravity pull is too strong for even light to escape.
125. Black Holes can be both small and large.
Smallest black holes can be the size of an atom, but hold a mass of a large mountain, while the biggest can be larger than Earth.
126. Supermassive black holes are the largest black holes we know of, and they can have a mass of millions of Suns. In the center of each galaxy is a supermassive black hole, around which the whole galaxy rotates.
127. The Sagittarius A is our galaxy’s very own supermassive blackhole.
It is a large ball with the mass of 4 million Suns and it could fit several Suns, or a few million Earths, in it.
128. The twinkling of the stars is called scintillation. Stars are so far away, that they are actually just points of light, which means that when they reach the Earth, due to the changes of direction (known as refraction), caused by the atmosphere, their light doesn’t reach any single point, including our eyes and telescopes, continuously.
129. Any non-twinkling lights in our sky are either planets from our system, or artificial satellites orbiting Earth. This is because these objects have actual dimensions, so some light always falls on the same place. Really, we can see planets as little discs of light with a sufficiently powerful telescope.
130. Even planets can scintillate though, if we are looking at them when they are low in the sky, near the horizon. This is because the atmosphere is densest in that direction, and there is more of it, so refraction is much higher.
131. Both stars and planets shine steadily, when they are seen from the international space station.
Venus From the International Space Station.Via Nasa.gov
132. Stars do not have uniform composition. Like Earth, and other planets, they have several layers, which have different density, temperature and composition.
133. The surface of a star is called the photosphere. Above it starts the stellar atmosphere- which in turns consists of a Chromosphere and a Corona. Yep, that’s a lot of layers.
134. Photosphere is the layer which we actually see. After it reaches the star’s surface, the energy produced in the star’s interior is finally free to leave and travel through the vacuum of space.
135. Corona is the furthest layer of the Sun, and at the same time the hottest. This effect of inverse temperature has been confusing scientists for decades, and it’s still not fully understood. The corona can only be seen from the Earth during the total eclipse.
136. Heliosphere is the vast magnetic bubble produced by the Sun, which contains our complete solar system, way beyond the orbit of Pluto.
137. Solar flares are sudden and huge flashes that occur on Sun’s surface, but jump out throughout all of the outer layers, usually accompanied by a spectacular coronal mass ejection. Solar flares usually appear in the areas near the active sunspots, due to the intense magnetic fields that appear there.
Solar flares.Via SchoolTutoring.com
138. If there are so many stars in the universe, why isn’t our night sky completely white with the light from all of them? This question is known as the Olber’s paradox.
139. The answer to the Olber’s paradox is twofold:
First, some stars give away light too weak to be seen by naked eye.
Second, and more important, light from many stars hasn’t reached us yet. The speed of light is finite, and the universe is bigger than it is old. (Yeah, that sentence makes sense only in cosmology.)
140. All the stars we see in our night sky are classified into distinct magnitudes. The reason why we perceive stars’ brightness as distinct categories is due to the nature of how brain interprets information we receive with our eyes.
141. This method of star classification was developed in the ancient Greece. Our eyes can see 6 magnitudes, one being the brightest and 6 the faintest. Each magnitude is two times brighter than the next one.
Ok, that’s a lot of information.
But besides stars, planets and galaxies, there are many strange and often unexplained phenomena that we have ran into, over our short space-exploring career.
Which leads us to: