At night, away from the blinding lights of cities, the sky reveals a fascinating picture of hundreds of stars scattered across constellations and the Milky Way. It seems impossible to count them yourself - the numbers seem fantastic, from millions to billions. But it immediately comes to mind that this is exactly what astronomers should do. So how many stars are really in the sky? Today we will try to determine the exact number.
Stars visible to the eye
We've heard more than once that there are trillions of stars in the visible universe alone. But there is a nuance - not all of them are visible to man. It's all about shine, or stellar size - dim luminaries close by look brighter than very powerful ones in the distance. The smaller the stellar value, the better the star is visible - but there is a limit after which even the sharpest look will not distinguish the star. The bar for the human eye is a star value of +7. The specific value varies between +6 and +8 depending on the visual acuity and darkness of the sky.
As a result, out of all the immense number of stars a man can see in the sky... only 6000! But this is an approximate number. As we already know, the celestial sphere is divided into two hemispheres, each of which can be seen up to 3000 stars. Moreover, part of the stars are near the horizon, where they are very difficult to observe - they are hidden by a dense atmosphere. And also it is necessary to make a correction on a reality where there is no ideally equal horizon. It is constantly complicated by trees, buildings, hills and other irregularities of the landscape, reducing the number of simultaneously visible stars to 2500.
It is an interesting fact that all these obstacles lead to the fact that large observatories are built in the mountains, at a distance from settlements. The atmosphere is not so dense there, and the horizon on the highest mountain is more accessible. Mountains near the sea or the ocean are especially popular: the water surface is probably the only flat horizon in the world.
But even this number is available under ideal observation conditions, i.e. on a dark moonless night. In summer, the sky near the edges is brighter than in winter, and any city lantern creates a light. In the middle of the big city, the number of stars in the sky drops to 200-300. Consequently, the best view of the stars opens only in winter, at a distance of more than 5 kilometers from any settlement or illuminated road.
To see more stars, you have to get very far away.
Stars in the telescope
However, humanity has long found a way to bypass the limitations of its own vision. Many powerful telescopes on Earth and in space push back the visible boundaries of space every day, opening up new stars and galaxies. Even the most ordinary binoculars give an opportunity to see an additional 200 thousand stars. A cheap telescope opens up 10 times more luminaries!
Of course, we cannot see all the stars in the universe. The center of our galaxy is an insurmountable barrier that covers part of the Milky Way from us, and clouds of cosmic dust absorb all but the infrared rays. And while astronomers are struggling - for example, James Webb's telescope will penetrate obstacles that were previously considered insurmountable - the universe remains limited. At least apparently, the maximum distance we can look at is 45.7 billion light-years.
We'll sum up the final score. There are about 100 to 400 billion stars in our galaxy. According to the Hubble telescope, about 100 billion galaxies have now been found, and it is believed that they will soon be found another 100 billion. Our galaxy has traditionally been recognized as an average number of stars - there are both larger and smaller objects.
Let's use the known numbers and count the number of stars in the sky together. We have 100 billion galaxies, each containing 100-400 billion stars. Multiply 1011 by 1011 - we have 1022 stars, 100000000000000000000000000 stars in the sky. And this is only a minimum score! If there are more galaxies or stars, the number will grow by orders of magnitude.
Because of all these conventions and inaccuracies, astronomers rarely make an accurate estimate of the number of stars in the sky. There are simply too many of them, and not everything can be clearly seen and separated from the rest. Especially in remote galaxies, they often look like one dull star.