Hey, Welcome back! Its the second part of the blog. Let's start from where we left off.
Now that you know the shapes, we can talk about the types of galaxies.
Active Galaxies
Around an estimated number of 10% of the galaxies as we know it in our universe are active galaxies. These types of galaxies have a centre which is 100 times more brighter than the light of all of their stars combined. Astronomers believe that this energy comes from the Supermassive Black Holes in their centres. Gas and dust collect around the black hole to form an accretion disk. The black hole’s gravity compresses and heats the disk, which causes the material to glow. Active galaxies can also be categorized into 2 types. But for that, first we should know what a Radio Galaxy means. A radio galaxy is a galaxy with giant radio emissions well beyond its visible structure. The 2 types of radio galaxies are Radio-loud galaxies and Radio-quiet galaxies. Radio-loud galaxies emit large amounts from both their accretion disk and their jets (they are linear structures which emit large amounts of ionised matter). Radio-quiet galaxies have little-to-no emission from their jets.
Seyfert Galaxies
These types of galaxies are the most common type of active galaxies and exhibit the lowest energies. These galaxies have lower radio luminosities (luminosity means brightness). There are 2 types of Seyfert galaxies. Type I have rapid motion near the accretion disk and type II have much slower motion near the accretion disk.
Quasars
These are also known as the most luminous objects in the whole universe. They are the most luminous type of active galaxy. They produce very powerful jets, and can radiate thousands of times the energy emitted by a galaxy like the Milky Way.
Blazars
We know very little about Blazars but from what we do know is that they produce very powerful jets and light across the electromagnetic spectrum. Their powerful jets point directly at Earth which is why they are the most visible from the Earth, they are the most visible form of active galaxies.
Sometimes, its pretty common that a lot of galaxies can come together to form clusters of galaxies. These galaxies come along together pulling each other apart with the help of their gravitational force and form a galaxy cluster. There are a lot of fun things which can happen in a galaxy cluster, like galaxies randomly smashing into each other, hell lot there are a lot of fun things which happen in 1 galaxy itself like stars randomly dieying or black holes eating things. Sometimes, a lot of celestial objects do not belong to a galaxy or any system, they are just randomly floating around in space. For example-there are some (a very small number) black holes floating around in space, eating up things which come in their way. The largest Galaxy as observed by us in the universe is The Alcyoneus. It is span across 16 Million Light Years. There is huge cluster of galaxies known as The Great Attractor. It is pulling a lot of galaxies including ours towards itself because of its high gravitational pull.
Just a fun fact, galaxies are basically huge star clusters.
Now that we have talked all about galaxies, I still have a small topic remaining to cover in this blog, I know it’s already pretty long but this topic is a very small topic and I cannot write an individual blog about it. That topic is as you might have seen in the title, Star Systems.
Now, I have already told you what star systems are, they are formed when 2 or more stars orbit each other bound by gravitational force. Now there are types of star systems, a star system containing 2 stars is known as a binary star system. If there is no perturbation from other forces and no transfer of mass, like a binary star system is stable. Multiple star systems contain 2 or more stars. This type of system has types depending on the number of stars, such as if there are 3 stars, then it is a triple star system, if there are 4 stars, then it is a quadruple star system and so on. These systems are smaller than open star clusters, which may contain from 100 to 1,000 stars. This type of system can be divided into 2 main types:-
1. Hierarchical System
2. Trapezia
Hierarchical System
These systems have stable orbits and the stars do not interact that much with each other.
Trapezia
These type of systems are usually very young and form close to or within nebulae. They are highly unstable and when they do evolve, they form stable multiple star systems.
Triple Star Systems
These systems contain 3 stars. In this system, each star orbits the centre of mass of the system. Usually, two of the stars form a close binary system, and the third orbits this pair at a distance much larger than that of the binary orbit.
It was a very fun trip exploring the star systems and the galaxies. I don’t have anything much to say, it has already been such a long blog.
By,
Deeparsh Bhanot
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