What are the galaxies?

GALAXIES

A galaxy is a vast group of stars held together by gravity — it is thought that there could be some 2 trillion in our Universe. They are not scattered randomly but exist in clusters, vast distances apart. All the galaxies together take up just two millionths of space.

  1. SIZE Galaxies are huge. The largest are more than a million light-years across (one light-year is the distance that light travels in a year). The smallest, called dwarf galaxies are a few thousand light-years wide. Andromeda measures 220,000 light-years from side to side.
  2. SHAPE A single galaxy is made of billions or trillions of stars arranged in one of four basic shapes: spiral, barred spiral, elliptical, or irregular. Spirals and barred spirals are disc-shaped with arms of stars. In a spiral, such as Andromeda, the arms wind out from a central bulge, while in a barred spiral, they flow from the ends of a central bar of stars. Elliptical galaxies are ball-shaped. Irregular galaxies have no clear shape.
  3. ORBITING STARS Galaxies do not behave like solid objects. Each star follows its own orbit around the centre of the galaxy. Stars in a spiral galaxy typically take a few hundred million years to make an orbit. Those further away take longer than those closest to the core.
  4. SPIRAL ARMS Stars exist throughout a spiral galaxy’s disc. The arms simply stand out because they are full of very bright young stars.
  5. CORE The core of a spiral galaxy typically consists of old red and yellow stars, with a supermassive black hole in its centre. Andromeda’s black hole is as massive as 30 million Suns.
  6. DUST LANES Dense clouds and lanes of dust within the galaxy’s disc hide stars from view.
  7. DWARF GALAXY M110 is one of the dwarf elliptical galaxies that orbit Andromeda. It is held in its orbit by Andromeda’s gravity.

ANDROMEDA GALAXY Andromeda is one of the closest galaxies to our own, the Milky Way. It is a spiral galaxy 2.5 million light-years away from us – the most distant object that can be seen by the naked eye from Earth.

Picture Credit : Google

Leave a Reply

Your email address will not be published. Required fields are marked *