Sun-Universe

The Place of the Sun in the Universe

Everybody knows his address on the Earth: state, city, street number of the house. And what would our address be on a cosmic scale? Imagine that a sensible being from a far-away world wishes to send you a message. How would you explain him your address in the Universe?

Let’s begin with the “address” description upwards, from small to big, from known to unknown.

    A schematic picture of our galaxy. With an arrow is
shown the place of our Solar System: around 26 500 light
years from the center of the galaxy and around 100 light
years from its equatorial plane. The Sun rotates on an
almost circular orbit around the center of the Galaxy with a
speed of 220 km/sec and makes a full rotation for around
200 million earth years.

We live on the third planet of the Solar System, called Earth. But we can use this address only for contacts with other planets, rotating around the Sun. It is enough to go only a ten billion kilometers away and we won’t be able to see the Earth with any telescopes any more. That is why we will have to give the address of the Sun. Our daily luminary is just an ordinary insignificant star. There are millions like it. Together with not a very big group of stars ( to which belong almost all stars seen with naked eye on the sky) it is a part of the star cloud called “ Local System”. This cloud (of stars) is situated in one of the spiral sleeves of our Galaxy.

The name Galaxy originates from the Greek word “gala” (“milk”). We see the Milky way as a grayish lights on the sky. But with the help of telescopes the lights turn into numerous separate stars, which taken together form the Galaxy. It has the form of a convexo-convex lens. From its centre come out several spiral-like sleeves of stars.

The main data about the Galaxy themselves speak about this gigantic sky island, to which belongs our Sun as well.

The Galaxy has a diameter of nine-ten-a hundred thousand light years. In the central part, where the nucleus is situated the thickness of the lens reaches 10 000 light years, but then it diminishes; in the area of the Sun it is around 2000 light years, getting thinner and thinner towards the end. The whole Galaxy includes around a 150 billion stars, the main part of which ( 90-95%) is situated in its equatorial plane. There are also situated the main clouds of intergalactic gas and dust.

Besides of the flat system, the galaxy also consists of a spherical system made explicitly of old star formations, to which belong comparatively small number of stars.

Our Solar System is situated in the outskirts, in a part, poor of stars. The Sun is 26 500 light years away from the centre of the Galaxy and around a hundred light years from its equatorial plane. It rotates around the centre of the Galaxy on an almost circular orbit with the speed of 250 km/second, making a full rotation ( = a galactic year) for about 200 million Earth years.

All other stars also rotate with different speeds on different orbits around the nucleus of the Galaxy, just the way that the planets rotate around the Sun.

Our Galaxy has two satellites- smaller star island ( of some ten billions of stars) with irregular shapes, called the Big and Small Magellan Islands. They are around a 100-120 000 light years away from the Galaxy. They are visible only from the Southern hemisphere.

But the Galaxy, to which we belong is not at all alone in the Universe. At a distance of around a million and a half light years from us is situated another spiral Galaxy, similar to ours (even a bit bigger) called the Andromeda Nebula (because it can be seen in the Andromeda constellation).

There are also billions of visible Galaxies, some with spiral, others with oval, still others with irregular shapes. All of them together form the biggest known formation- the Metagalaxy.

It is known that our Metagalaxy grows bigger. Science is still unable to tell us of what and how many Metagalaxies the Universe consists, whether they become bigger or smaller, how far away they are from us. But they all, together with our Metagalaxy build the ever-lasting and endless Universe.