What is a galaxy? What galaxy does the Earth belong to?
Our solar system includes a planet named Earth. Where is the solar system located? That is a tiny part of our Milky Way Galaxy.
Galaxy is an enormous collection of dust and gas and millions of stars with their solar systems. Gravity holds a galaxy together. The Milky Way galaxy also contains a black hole supermassive in its middle.
You can see other stars of the Milky Way when you gaze up into the sky. You can see dusty lines of the Milky Way if it is dark and far from the lights of cities or houses.
But there are other galaxies than our own. We can’t count all of them yet. Hubble’s Space Telescope studied a tiny patch of space over 12 days, finding 10,000 galaxies of different sizes, colours, and shapes. Scientists believe there may be up to 100 billion galaxies within the universe.
Some galaxies have spiral shapes like ours. The arms are curved and make them look like pinwheels. Some galaxies have smooth oval shapes. These galaxies are called elliptical. There are galaxies which are not spirals or ovals. These galaxies have a blob-like appearance and irregular shapes. Each of these galaxies emits light from its stars.
Some galaxies are too close to each other and crash into one another. Someday, the Milky Way will bump into Andromeda. But don’t worry. That won’t occur for five billion years. Even if the event happened tomorrow, it’s unlikely that you would notice. The galaxies are spread so far apart at their ends that they bump into one another, but the solar systems and planets don’t even come close.
Satellite Galaxy: What is it?
The Milky Way Galaxy is a vast collection of stars. Hundreds of billions of stars surround the galaxy’s centre. Did you know other things are even larger orbiting the Milky Way centre? It’s not the only galaxy that orbits it!
The stars in these less massive galaxies are impressive and revolve around their centre. But the galaxies themselves, as well as everything within them, also orbits our galaxy. As if the galaxy we live in is our sun, and all those galaxies around it are planets. They are called “satellite galaxies.”
What are they, and where can you find them?
It has many satellite galaxies. The largest is called the Large Magellanic Cloud. The Large Magellanic Cloud is 163,000 light years away and about 1/100th of the Milky Way’s size. This galaxy is not spiral-shaped like ours. Scientists believe the Milky Way, and possibly other galaxies, are warping and pulling it.
There are only two candidates for the closest satellite galaxy regarding distance. Astronomers call one group of stars a dwarf galaxy. The other is close enough to our galaxy that they are still debating whether it’s part of it or its own.
The Sagittarius Dwarf Spheroidal Galaxy is the galaxy that astronomers have unanimously named. About 50,000 light years away, it is located in the Milky Way’s centre. Like a rotating top, it orbits above and below our disk.
There is another galaxy that’s even closer than our Milky Way. It’s a cluster of star-like objects called by some the Canis Major Dwarf Galaxy. It is estimated to contain around one billion stars. The Milky Way is close enough to it that the centre of our galaxy is closer than the Milky Way’s edge. About 25,000 light years away.
How does one galaxy begin and end?
Scientists disagree on whether the Canis Major star cluster is a dwarf galaxy or its galaxies. They think it’s just a large area of stars far away but still a part of our Milky Way. The massive gravitational force of our Milky Way has brought this group of stars very close. That could happen to other satellite galaxies around the region. One day, they could merge into a larger Milky Way Galaxy!
