Stars are the beacons of light of the Universe, and without them, life wouldn’t exist. Our Sun is a star, and the Universe is filled with billions of them!
Key Facts & Summary
- Stars are celestial objects just like planets; however, they are a ball of plasma held together by their own gravity.
- Stars are born from interstellar mediums, such as molecular clouds of gas and dust.
- If an interstellar medium is rich in materials, stars can grow up to enormous proportions; however, their lifespan is limited because of this.
- When a star dies, it either explodes as a supernova or becomes a black hole or neutron star.
- If the star explodes, it releases a lot of materials into space, which, over time, can lead to the creation of other stars and even planets or moons.
- Gravity pulls the swirling gas and dust together, and when it reaches the right temperature, the star is born.
- In our Milky Way galaxy alone, there are billions of stars!
- Stars are classified based on their temperature. Letters are assigned to them as an indication of their hotness.
- Letters such as O, B, A, F, G, K, and M, are used in this classification.
- The hottest is the letter designation O, while M is the coldest. Our Sun, for example, is a G-type star.
- Many other types of classifications exist for stars, but this is the most simple one to keep in mind.
- Stars are also classified based on their physical characteristics.
- Here are some types of stars – red giant stars, blue giant stars, yellow dwarfs (our Sun), orange dwarf, red dwarfs, blue giants, red giants, blue supergiant stars, red supergiant stars, yellow supergiants stars, white dwarfs, neutron stars, black dwarfs, black holes, or brown dwarfs.
- Other classifications can include hypergiant stars or yellow supergiant stars.
Stars for Kids
In our galaxy, the Milky Way, there are millions and millions of stars, but there are also millions and millions of galaxies. Can you believe how many are actually out there? Let’s see what exactly are stars and how many types of stars are there!
What Exactly are Stars?
Stars are enormous celestial bodies, mostly made up of hydrogen and helium. They are several times bigger than planets. For example, our Sun is more than 109 times bigger in diameter than Earth, and over 1.3 million Earth’s could fit inside of it!
Not all stars are tens or hundreds of times bigger than planets. For example, white dwarf stars can be the same size as Earth but hundreds of times heavier!
Some stars are even smaller than Earth, such as neutron stars, which can be as little as 20 kilometers / 12 miles in diameter. Our Earth is 12,742 km / 7,917 mi in diameter, and as such, a planet can be more than 600 times bigger than certain stars, such as neutron stars, but planets weigh less, despite the difference in size.
Black holes, don’t they might not look like it, are also stars. They are considered dead stars, though. Either way, stars are the building blocks of galaxies and, practically, life.
We are made out of stardust since every element in the Universe is created within a star’s core before it explodes into a supernova. Most of the star’s material is blown off into space, and in time, it comes together again to create and shape something new, even planets and moons.
What are the Seven Types of Stars?
The Universe is filled with innumerable stars, and since humanity began to observe and classify them, we have currently concluded that there are seven types of stars:
* O-type stars (the hottest stars) – blue color – more than a million times brighter than Sun
*B-type stars – blue color – hundreds to thousands of times brighter than Sun
*A-type stars – blue color – tens of times brighter than Sun
*F-type stars – blue to white color – brighter than our Sun
*G-type stars (like our Sun) – white to yellow color - bright
*K-type stars – orange to red color - faint
*M-type stars (the coldest stars) – red color - faint
Stars are classified based on their spectra – the elements which they absorb, and their temperature. O-type stars are the hottest, and they are rare; however, M-type stars are the coldest, and they are quite common.
Main Sequence Stars
Main-sequence stars are stars similar to our Sun. They convert hydrogen to helium in their cores, and the majority of the stars are in this classification, including dwarf stars, yellow dwarf stars, and red dwarf stars.
Giant and Supergiant Stars
Giant and supergiant stars can be both young and very old stars. These types of stars are several times bigger than our Sun, often cooler, but brighter than our Sun. Some of them are blue giants, red giants, red supergiants, or blue supergiants. These stars expand as their hydrogen and helium supplies are depleted.
Dead stars are usually the cores of stars, which were exposed after their outer layers were blown off, or worse, they collapsed. We have white dwarf stars, brown dwarf stars, neutron stars, pulsars, or black holes in this category.
What is a Star Made of?
Stars are made out of huge amounts of hydrogen and helium. They produce light and heat from the nuclear reactions within their cores. They also have small amounts of other elements, so it depends on what star you are analyzing.
Fun Kids Facts About Stars
- Capella is a G-type star just like our Sun. It is located in the constellation of Auriga.
- The giant star VY Canis Majoris is between 250,000 to 500,000 times brighter than our Sun. It is around 2,000 times bigger than our Sun as well.
- In around 5 billion years or so, our Sun will become a red giant star. This will happen as its hydrogen and helium supplies will deplete.
- Proxima Centauri is among the closest stars to Earth (apart from the Sun). It is located at around 4.2 light-years away from us.
- Planets orbit around stars; however, stars can orbit around other stars as well. They are known as binary stars.
- The most powerful explosion is produced when a star explodes into a supernova.
- The majority of stars are red dwarf stars.
- Stars have life cycles based on their initial mass.
- When we look into the night sky, we can see between 2,000 to 2,500 stars at once.
Size and Comparison
The smallest stars are neutron stars, which can be as little as 20 kilometers / 12 miles in diameter. Our Sun, has 1.3 million km / 0.8 million mi in diameter, however, it is considered a medium-sized star.
The biggest stars can be thousands of times bigger than our Sun. For example, one of the biggest stars currently known, VY Canis Majoris, is around 2,000 times bigger than our Sun, and there are even bigger stars out there!
What is the Brightest Star in the Night Sky?
Apart from our Sun, the brightest star in the night sky is Sirius. Sirius is also the brightest star in the constellation of Canis Major. There are stars brighter than Sirius out there, however, Sirius is located much closer to us, hence it appears brighter.
Why Do Stars Twinkle?
Some stars have variations in brightness over a period of time. They get fainter and fainter, and then they begin to shine brighter and brighter. However, stars twinkle because of our Earth’s atmosphere.
Turbulences, or the movement of air, may affect the light we perceive from a star to get slightly bent, hence, it creates this illusion that the star twinkles.
What Color is the Hottest Star?
The hottest stars in the Universe are typically blue in color. They are O-type stars, and they are several times hotter than our Sun. 10 Lacerta, for example, is an O-type star, and its average surface temperatures are around 36,000 K. This means it is more than 6.2 times hotter than our Sun, which has temperatures of 5,778 K.
White dwarf stars, on the other hand, are even hotter. They can reach temperatures of up to 100,000 K, or more than 17 times hotter than our Sun. Some white dwarfs are even hotter than this.
- Stars are the beacons of light of the Universe, and without them, life wouldn’t exist. They are enormous celestial bodies, mostly made up of hydrogen and helium.
- Stars are several times bigger than planets, however, some stars, such as neutron stars, are several times smaller than planets.
- The hottest stars are blue in color, while the coldest are red.
- Stars can be classified as O, B, A, F, G, K, and M-type stars. O-type stars are the hottest, and biggest, while M-type stars are the coldest.
- Planets orbit around stars, however, stars can orbit around other stars as well. They are known as binary stars.
- Stars have different evolution stages based on their composition and mass. Stars like our Sun, for example, will turn into red giant stars, and will become several times bigger as they expand.