When you look at the night sky, you see spots like twinkling stars, the moon, and clouds. Those tiny celestial bodies we call stars are giant luminous spheres made from a mixture of gasses. Our naked eyes view that shines with edges, and yet humans tend to draw stars with five edges instead of spherical ones.
We can only see a very small number of stars from the billions of trillions of stars without using special equipment.
After the Big Bang phenomenon, the molecular clouds of hydrogen gas would clump together with other elements. The gravitational pull of the hydrogen gas molecules would attract other gasses to fuse. These gaseous clouds continue to pull each other closer and shrink to form a mass. When these gasses fuse, they emit energy outwards and create a gaseous pressure to keep the mass stable. Over time, the mass grows to become a spherical clump called a baby star or protostar, which is extremely hot.
When the gasses release atomic energy, they create light, which makes them shine. This gaseous pressure stops the star from collapsing under its weight. Together, they create a fine balance to keep the star stable.
So, at night, when we see stars twinkling, it’s the radiation from nuclear reactions happening in them. Depending on the size of the star, the nuclear reaction or burning of fuel takes place. All stars are made from the same stuff – mostly hydrogen and some helium, besides other elements. Sun is the closest star to the Earth, and even that, too, is mainly made from hydrogen and helium.
Fusion reaction is the longest phase in a star’s life, changing its temperature, luminosity, and size in the process. A star’s death starts when it runs out of fuel – hydrogen atoms to fuse with helium. So, it loses the energy released outwards, and the gaseous pressure drops to make the star unstable.
The outer layer explodes like a supernova, releasing enormous amounts of energy. The inner core turns into a white dwarf star, carrying remnants that cool over time and stop emitting light.
The red dwarf stars are the most common type of stars with temperatures lower than the Sun. They burn their nuclear fuel so slowly that their age can live on for a long time. Meanwhile, the stars that couldn’t make it are called brown dwarf stars, and they lack enough mass to initiate any form of nuclear fusion.
The temperature of the star and its color are directly connected. Also, it’s directly connected to the star’s size, but there’s an exception. Typically, the color of the stars indicates how hot they are. For instance, the hottest star will appear blue. As the temperature of the star drops, its color gradually shifts from blue to yellow to red. It also indicates its size since the star burning hot and appearing blue will have massive amounts of nuclear fuel to burn.
However, the red giant stars can be an exception, for they can be as large as the Sun and still not have enough fuel to burn. The burn rate is directly proportional to its size—huge stars burn more fuel rapidly to generate energy that keeps them stable. That said, those large stars also have a shorter life than the tiny ones with a slower burn rate.
Ancient cultures often saw the stars forming patterns resembling people, animals, or popular objects. These patterns looked like a dot-to-dot puzzle that you could connect with a line to make a shape. The pattern depicting a shape is called a constellation, not a group of stars. So, several popular constellations, like Andromeda, Ursa Major, Ursa Minor, Gemini, Orion, and others, are still visible at night in clear sky.
Astronomers continue to discover stars that have evolved over the years and those that are near extinction. They still use constellation names for such stars and meteor showers. While you can only see some parts of constellations at night, a consumer-grade telescope can help you explore stars that far away.