In the night sky the stars appear to us as tiny dots of light.
But this is only because of their great distances:
In reality, stars are huge spheres of glowing matter, natural nuclear reactors in which nuclear fusion processes take place and release enormous amounts of energy.
Our sun is also a star in astronomical terms.
It only appears so much larger than the stars in the night sky because it is much closer to us than these.
The diameter of the Sun is 1.39 million kilometers – about one hundred times the diameter of the Earth.
On average, the earth is 150 million kilometers away from the sun.
This means that our central star in the Earth’s sky has a diameter of just half an angular degree.
The stars in the night sky are considerably further away from us than the sun.
The distance to our nearest neighbor Proxima Centauri is 4.24 light-years.
One light year is the distance that light travels in one year, about 9.5 trillion kilometers.
No wonder, then, that stars remain point-like objects not only for our eyes but – with very few exceptions – even in large telescopes.
Viewed from the distance of Proxima Centauri, our sun would have an angular diameter of only seven thousandths of an arc second.
By comparison, the Hubble Space Telescope has a resolution of about five hundredths of an arc second.
It would therefore image the sun at the distance mentioned above only as a point.
The stars are shown as circles of different sizes.
The Sun is at its smallest, Sirius is slightly larger, Aldebaran and Rigel are considerably larger, and Betelgeuse is so large that it no longer fits completely into the image.
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 inflate towards the end of their lives to form a so-called red giant.
Such giant stars can reach several hundred times the mass of a star as a “supergiant” and even reach a thousand times the diameter of our Sun.
The largest known star at present is VY Canis Majoris, whose diameter is 1800 to 2100 times larger than our Sun.
In about seven billion years our Sun will also become a red giant, swallowing up Mercury, Venus and probably the Earth in the process.
When the sun has finally used up all its nuclear fuel, it will collapse into a white dwarf.
Such stars, which slowly cool down over billions of years, are only about as large as the Earth, with diameters of several thousand to ten thousand kilometers.
Neutron stars are even smaller.
With a diameter of about 20 kilometers, matter in these final stages of massive stars is as densely packed as in atomic nuclei – one cubic centimeter on a neutron star contains about one billion tons of matter!
Further information about how big the stars are:
https://www.schoolsobservatory.org/learn/astro/stars/class/starsize [Last seen: 01.12.2020]
https://spaceplace.nasa.gov/sun-compare/en/ [Last seen: 01.12.2020]
https://en.wikipedia.org/wiki/List_of_largest_stars [Last seen: 01.12.2020]
https://earthsky.org/space/shedding-light-on-a-stars-mass-limit [Last seen: 01.12.2020]
More topics and articles about stars:
- How to describe a star
- How does a star produce energy?
- How many stars are in the sky?
- The composition of a star
- How stars are classified?
- How long does a star live?
- How to find the locaiton of a star
- How is a star born?
- How big are the stars?
- Star names and their meanings
- What are stars made of?
- What is a shooting star / falling star?
- What types of stars exist?
- What is the definition of a star?
- What is a star?