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Galaxy - planetpedia

Galaxy

A galaxy is a huge mass of stars, gas and dust, all kept together by the force of gravity, and rotating around a central point. In the Universe there are billions of galaxies. A galaxy can comprise between one billion to 100,000 billion stars.
There are galaxies of different forms and sizes. The elliptic galaxy has old stars and is generally large and bright.

Spiral galaxies have long arms spiralling out from a central nucleus. Those arms contain mainly new stars, and are where new stars may begin. Irregular galaxies do not have an exact formation. They are usually small and rich in gas and dust.
Some spiral galaxies are cut through with a straight bar of stars at the centre with spiral arms branching off at the end. These galaxies are called Barred Spirals.

Quasars

All Quasars are millions of light years away from the Earth. A Quasar looks like a star, but it is widely believed that it is actually the nucleus of a galaxy, with a black hole at the centre.

Black Hole

The explosion of a big star can generate a Black Hole i:e a heavenly body in which the force of gravity is so strong that it does not allow anything to escape, not even light. That is why Black Hole cannot be seen, not even with the most powerful telescope.

The milky Way

The Milky Way is our galaxy. It gets it name because in the starry sky, it appears to the naked eye as a milky-white trail. It is a spiral galaxy, with the Sun and other planets in one of it's arms.
All that we see in the sky with the naked eye belongs to our galaxy, with the exception of three patches which, in fact, are other galaxies.

What How Why

What is a leap Year?

It takes the Earth 365 days and six hours to orbit around the Sun. The Six extra hours cannot be counted on the calander. So, to keep an accurate count, an extra day is added at the end of february every four years.

What How Why

What are the most precious stones?

When the magma cools, the material which it contains solidifies in the form of crystals. Precious stones are crystals with particular characteristics of colour, hardness and the way they can reflect the light. They are used in making jewellery.

What How Why

How is the height of a mountain measured?

To measure the height of mountain, the surface of the sea is taken as the point of reference. The height of the mountain is the distance between the top of the mountain and the surface of the sea.

What How Why

What is an electric current?

An electric current is a passage of electrons from one electrified body to another which is less charged. When too many electrons are generated, they can move.

What How Why

Why does iron go rusty?

Rust forms on the surface of iron objects when they are exposed to the air. It is the product of a chemical reaction called oxidization. The more the object is exposed to the air, the more rapidly rust spreads.

What How Why

How fast can a dog run?

A Greyhound can run at a speed of 64km per hour, a Weimaraner , once used for hunting wolves and wild boar, can reach speed of up to 56 km per hour in a chase. Many breeds of dog which were once bred for hunting are now more common as pets than hunting Dogs.