May 1, 2020 | By Gyan | Posted in
A hundred billion galaxies exist in the universe. Each consists of a vast collection of stars, gas and dust. They started life thousands of millions of year ago, slowly forming into distinctive shapes.each galaxy can contain billions of stars. Gravity keeps the stars together and keeps the galaxy in clusters.
Types of galaxies : Most galaxies have a central ball of stars, the nucleus, and many have a flattened disc coming out of this. Astronomers have classified galaxies into three main types based on these features. No one know why galaxies become a particular shape. It may be to do with how fast a galaxy spins and how quickly stars form inside.
About 60 percent of galaxy are ball-shaped collection these galaxies looks like a egg shape formation as I shown in picture.
A hub of older stars is surrounded by a flattened disc with spiral arms containing younger stars. You can check in picture how spiral galaxy looks like our milky way galaxy is a spiral shape galaxy.
Barred spiral :
These galaxies consist of a central bar of older stars with arms containing younger stars coming from the end of the bar. You can see in the picture how this galaxy look like.
About 10 percent of galaxy are irregular. They are collections of stars with no distinctive shape or structure , and do not fit into any of the average galaxy and contain large amounts of gas and dust.
Milky Way Galaxy :
about 500 billion stars make up the spiral-shaped Milky Way. The arm contain young, hot, bright starts; older, dimmer stars make up the nucleus. A thin holo of old stars surrounds our Galaxy. The Sun is in one of the arms, about two-thirds of the way from the centre. It orbits the centre of the Galaxy once every 220 million years
In 1923, the American astronomer Edwin Hubble ( 1889-1953 ) proved that there are galaxy other than the Milky Way. The next year he classified galaxies according to their shape. He went on to the show that galaxy are moving away from each other, and so provided proof that the Universe is expanding.