“Twinkle twinkle little stars…” is the first poem every child is taught. These balls of hot gas have always captured everyone’s attention, regardless of their age or interests. It is a star (our home star- the Sun) that is responsible for light as well as life on our planet.
As it is said in the title, there is more to the stars than their twinkle, in fact, stars do not really twinkle, however it may look like from here. Let’s clear another misconception, if you are not a science nerd, you definitely do not know enough about stars. To countermand this, here are 10 facts and figures about the billions of stars in the observable universe that will help you understand them better.
1. Not all stars are the same
Not all stars are same. There are several different types of stars in the universe that differ in mass, size, lifespan and so on ranging from red dwarfs, brown dwarfs, hyper giants and supergiants. They are also divided by their temperatures and luminosities. Amongst all these, red dwarfs are the most common stars. Their life period extends for more than 100 billion years. As they age red dwarfs get dimmer and dimmer, until they vanish. On the other hand, giant stars like hyper giant and super giant explode into a glaring supernova.
2. Size of a star
From where we stand, the Sun looks massive but the other stars in the sky seem tiny in comparison. This is not just a trick our eyes play on our mind. The cosmic truth is that the universe is filled with stars of all sizes. Red hyper giants are the largest stars in the universe while our home star is a red dwarf, whose lifespan is billions of years. The biggest star in the observable universe can absorb even the orbit of Saturn if replaced with the Sun.
3. More massive in size = shorter life span
There is something more interesting than the fact that if you stack 1420 sun in a line, it will be equal to the diameter of the biggest star in the universe. For stars, being more massive than the other is not beneficial. In fact, the lower the mass of a star, the longer is its life. A low mass star can go through their fuel for trillions of years without running out, whereas the giants go through their energy ferociously, decreasing their overall life.
4. 200,000,000,000,000,000,000,000
This is the number of stars scientists estimate are in the observable universe. Even in our own Milky Way, there are 300-400 billion stars and if you talk about the galaxies, the number is around 500 billion. These are the estimate numbers from the observable universe. There may be a thousand billion more galaxies yet to be discovered. If you calculate these, the number of stars in the universe is unfathomable.
5. You can only see 9000 stars in a night sky
We have all heard the phrase that you can see a million stars in the night sky, especially on a clear day. However, next time you listen this, you can be a know-it-all and correct them that there are only about 9000 stars that can be seen from Earth. Moreover, the number of stars that you can see with a naked eye is even less. Roughly 2000 stars are visible to a naked eye. To see the rest, you need to use a telescope.
6. An average star is 1 to 10 billion years old
Stars are celestial bodies that can live on forever; well, if you compare a human life to theirs. A star can live on for a billion to 10 billion years or even longer. However, the smaller the size of a star, the large is its life expectancy. Even our home star, which is about 5 billion years old, still has same years left of its life.
7. The closest star is 4.2 light-years away from Earth
The Sun looks like the closest star to earth. But this is only because of its size. The closest star is called Proxima Centauri, which is 4.2 light years away. This means that it will take 4 years and 2 months to make the journey from Earth. Moreover, the distance between the stars is giant. It will take about 70,000 years to reach the stars even in the fastest spacecraft available on Earth.
8. The different colours of stars
The sky’s view from the Earth on a dark and clear night is just white stars shining brightly. However, not all stars are same in colour. They range from red, blue, green, orange, brown, yellow and white depending on their temperature. The cool stars are brown while the hottest stars are blue. They change from blue to red as they cool down, which is confusing as we generally associate red with hot and blue with cold.
9. Our home star is not yellow in colour
Ask the colour of the sun and you’ll hear the same answers mostly. To the people who are unaware, Sun seems a bright yellow or an orange star. But the eyes can lie. Our home star is actually a ‘green star’ or rather a ‘green-blue star’, just like the Earth. It is from the influence of its surroundings that it looks yellow from the surface of the Earth.
10 The most famous stars
While there are 200,000,000,000,000,000,000,000 (approx.) in the observable universe, some stars are more famous than the others. Their popularity can depend on their size, mass, colour, location and so on. For us, the Sun is the most important one as it keeps us alive. However, there are also stars like UY Scuti, which is a red super giant with a radius of 2.4 billion kilometres or the Betelgeuse, which is the 10th brightest and 9th largest star known to us in the observable universe. Other famous stars include WOH G64, RW Cephei, VY Canis Majoris, HD 143183, and many others.
