Now, it’s time to look even further, into deep space. It is complex and filled with galaxies.
Different Galaxies
In deep space, we will encounter a whopping 2 trillion galaxies so we’d have to learn about them.
There are many types of galaxies: Lenticular galaxies, elliptical galaxies, spiral galaxies and irregular galaxies. Each of them has distinct properties.
Lenticular Galaxies
Lenticular galaxies is a type of galaxy between spiral galaxies and elliptical galaxies. They have a large disc but not spiral arms. An example is NGC 5866, which looks like this:
Spiral Galaxies
Spiral galaxies have spiral arms, and are density waves of a them. They indicate the active forming of stars because they need to keep themselves on every rotation. They are also filled with hot OB stars so they are brighter than the rest of the galaxy. Some spiral galaxies are disrupted so they only have a spiral arm.
Spiral galaxies are also very common — they account for about half of the galaxies in the Universe!
Elliptical Galaxies
Elliptical galaxies don’t contain spiral arms, just a big circle. They almost don’t create stars anymore and maintains the shape for billions of years. So, they contain mostly of low-mass stars, but they can be so massive. The largest galaxy, IC 1101, is an elliptical galaxy. It has a whopping 100 trillion stars! That is more massive than the Milky Way and the Andromeda Galaxy combined.
Despite they can be large, they can be very small too. Messier 32, a dwarf elliptical galaxy, its diameter is just 6,500 light years, over twenty times smaller than the Milky Way!
Notable Galaxies
We can start looking out of the Local Group, to the majority of galaxies. There are about 2 trillion galaxies in the Observable Universe, which is too much for a single webpage.
Messier 81 and 82 are in the same group, and they are a galactic 11,500,000 light years away. The special one is Messier 82 because it looks like a thick disk with two wide axes. It is a starburst galaxy, and it is famous for its ridiculously high rate of star-forming.
A bit further, it is Centaurus A, or NGC 5128. It is the closest active galaxy, only at a distance of 13,000,000 light years away. It has a weird shape that looks like both an irregular galaxy and an elliptical galaxy.
Zoom out further, there are the Antennae Galaxies. It is one of the closest interacting galaxies. It is about 45 million light years away, and it has a weird shape because they are 2 galaxies.
Even more, there is Messier 87, 55 million light years away, which is famous for a captured central black hole. It is also a radio galaxy, consisting of about a trillion stars. Interestingly, only a small amount of its luminosity is from stars.
Deep Space
There are a lot of galaxies, even more than 2 trillion, in deep space. They are billions of light years away, and the Universe is constantly expanding. That means some of them have already exceeded our current limit of observations.
The most distant known galaxy is GN-z11, and it’s predicted to be 32 billion light years from Earth currently. The Universe is 13.8 billion years old and light didn’t even arrive here, but the Universe expands, making them much farther than expected. It’s one of the oldest galaxy known, forming very soon after the big bang.
And there are a lot of amazing things out there. This includes a weird, starfish-shaped galaxy (NGC 6240), galaxies with ‘eyes’ as their core (NGC 2936) and even a really nebulous galaxy (3C 348). Also, there are a lot of massive black holes far away. The most massive black hole known is TON 618, which weighs 66 billion solar masses.
Also, there are some luminous stars discovered millions of light years away. One example is NGC 2363-V1, located in NGC 2366, an irregular dwarf galaxy. It is brighter than Eta Carinae, which is the most luminous star in the Milky Way. A blue supergiant, called Icarus, is located billions of light years away from Earth. Moreover, It is detected by gravitational lensing.