Which is big sun or stars

How big are stars?

In the night sky, the stars appear to us as tiny points of light. But that's only because of their great distances: in truth, stars are huge spheres of glowing matter, natural nuclear reactors in which nuclear fusion processes take place and release enormous amounts of energy.

From an astronomical point of view, our sun is also a star. It only appears so much larger than the stars in the night sky because it is much closer to us than they are. The diameter of the sun is 1.39 million kilometers - around a hundred times the diameter of the earth. On average, the earth is 150 million kilometers from the sun. This means that our central star in the earthly sky has a diameter of just half an angular degree.

The stars of the night sky are considerably farther away from us than the sun. The distance to our closest neighbor, Proxima Centauri, is 4.24 light years. A light year is the distance that light travels in one year, about 9.5 trillion kilometers. So it's no wonder that stars remain point-like objects not only to our eyes, but - with very few exceptions - even in large telescopes. Viewed from a distance of Proxima Centauri, our sun would have an angular diameter of only seven thousandths of an arc second. For comparison: the Hubble space telescope has a resolution of around five hundredths of an arc second. It would therefore only depict the sun as a point at the distance mentioned.

Many stars are bigger than our sun

Of course, not all stars are the same size. The size of a star depends on its mass: the more matter it contains, the larger it is. In addition, the size of a star changes over time. Many stars expand into what is known as a red giant towards the end of their life. Such giant stars can reach hundreds of times the massive stars as "supergiant" even a thousand times the diameter of our sun. The currently largest known star is VY Canis Majoris, the diameter of which exceeds our Sun by 1800 to 2100 times. Our sun will also become a red giant in about seven billion years, devouring Mercury, Venus and probably also the earth.

When the sun has finally used up all of its nuclear fuel supply, it will collapse into a white dwarf. With a diameter of a few thousand to ten thousand kilometers, such stars, which have cooled slowly over billions of years, are only about the size of the earth. Neutron stars are even smaller. With a diameter of around 20 kilometers, in these final stages of massive stars the matter is as tightly packed as in atomic nuclei - one cubic centimeter on a neutron star contains around one billion tons of matter!