Dwarfs

Hi,
I had little pause but now I am coming back.
Today I want to write something about dwarfs because I found them little confusing.
We are talking about dwarfs in Universe not Tyrion.. there are six kinds:

1. Brown dwarf
   
   Brown dwarf is the only one which is not star. It is actually extremely big planet which almost made it for the size of star. This term is used because red dwarfs already existed.
   Scientist are not really sure when it comes  to the difference of planet and brown dwarf. Jupiter would have to be more than 50x larger to be brown dwarf.
2. Red dwarf
   
   Red dwarfs are “cool” stars. For example Proxima Centauri, the closest star is red dwarf. Their mass has to be about 0.08 of Sun to 0.5 of Sun´s mass. Red dwarfs are extremely common in Milky way as most of stars are smaller than Sun. That picture shows red dwarf and it would be more orange if showed from smaller distance.
3. Yellow dwarfYellow dwarf is not really a dwarf. It is star which is about the same size like our Sun. Its temperature on the “top” is about 5000 to 6000 K.
4. Blue dwarfBlue dwarfs are kind of related to red dwarfs because they are just a stage in their live. When red dwarf uses almost all of its hydrogen it will need to equalize with gravity and for that he uses temperature which rises and from red color it will shine in blue. This stage is only hypothetical because red dwarfs lifetime is really long and this could not yet happen.
5. White dwarfWhite dwarfs are stage of all stars which wont make it to neutron stars or black holes. They are about the size of earth but much denser. From white dwarfs supernovas can explode.
6. Black dwarfBlack dwarfs are only hypothetical but it is almost sure that they will happen when time comes. They are the next stage of white dwarfs. Black dwarf should not shine anymore because it is cool. They should be also really hard to detect because of their black color.

   Dragallur

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What is the life cycle of stars?

Hi!
Somehow I wanted to write something from universe… not really I am still sitting in my hometown so here it is:

Well, stars (as our Sun) DO have beginning and end as you probably heard already. It can have different length.
First of all there have to be material. I mean lot of material because as you know our sun is huge. (Sun is bigger that 90% of stars)
This material comes from other stars that are dead now and theirs material probably came up from Big bang.
There are extremely large clouds that are called Molecular clouds. In them is lot of stuff and mostly H2.
If there is enough stuff at one place (it is really dense) it can make up planet which is either stony or made from gas.
If there is enough stuff it will make even larger gas planet than Jupiter or Saturn.
At that point all of this H2 will be pulled toward the center with magnificent force. That will create heat because atoms will be brushing against each other. If there is enough heat termonuclear reaction will occur which will normalize that pull of gravity and whooo! we have new born star!
Termonuclear reaction will change Hydrogen to Helium. Helium is heavier so it will go toward center and just a little bit of Hydrogen will be left on the edges. If the star is enough heavy it will start to change Helium to Carbon or Oxygen (I think). It will continue with couple of rounds until there in the middle is Lead (Pb). Than it will never be able to go forward and the life cycle will kind of end. Few more termonuclear reactions will occur (That is called red giant because it will greatly gain volume and the it will lose it) but then gravitation will win and if that star was small (even like our Sun) White Dwarf will be the END.
White dwarf is only really dense and hot piece of stuff.
If it was heavier.
Neutron star (made of only neutrons) will be the next stage. It extremely dense thing with tremendous gravitational field.
The last thing which can happen is Black hole, you can read about them in one of my first posts, they are absolutely awesome!

Dragallur
PS: if white dwarf gains again enough mass because of some stuff from space it can heavily explode into Supernova

What are really bright objects in universe?

Today in my 3rd post I would like to tell you something about two kinds of objects (from universe) which are very bright.

First one is quasar and blazar. As far as i know they are probably same thing but from different angle of view. They are very bright and in middle of them are black holes (if you want to read something about BH then read my second post).

When stars or lot of stuff (dust) around hole starts to accelerate toward the black hole, lot of heat and radiation will be created because particles in high speed will rub againt each other. This will create massive disk around hole. That is called quasar/blazar and it can be even brighter then our own Galaxy!

Second object is Supernova.
It is created in two ways. I will try to explain only the first one because again, i dont really understand how the second works.
Anyway, imagine you have white dwarf (like our sun when it will be few billions years older). It is object which has such mass like our sun but it is big like Earth. It is shining even that termonuclear reaction does not occur anymore. After some time it will turn to black (cold) dwarf. But if this dwarf gains some mass again and heat inside core will be high enough to create another round of reaction it will violently explode! Picture on the left shows galaxy and that “little” point is actually supernova. It does not shine long time, only for weeks or months.

So those are the two bright objects in our universe. I hope i did not miss something important.
Btw. thanks to people who liked my posts, i really appreciate that.
Dragallur
PS. next time I will probably move to something on the earth!

P.1: Quasar. (2015, March 2). In Wikipedia, The Free Encyclopedia. Retrieved 12:47, March 20, 2015, from http://en.wikipedia.org/w/index.php?title=Quasar&oldid=649527988

P.2: Supernova. (2015, March 17). In Wikipedia, The Free Encyclopedia. Retrieved 12:47, March 20, 2015, from http://en.wikipedia.org/w/index.php?title=Supernova&oldid=651800657

What are Black holes?

Hi,
this is my second post. I would like to say something about my most favourite topic: Black holes. I hope that there won´t be any mistakes so I will not go deep and more complicated stuff.

Black holes are universal objects as you probably already know. Important thing is their size. If you know something about white/black dwarfs and neutron stars you could easily get to right answer about how big are black holes.
You see I said something about dwarfs and neutron STARS. Right, stars. There are not really kind of stars but all of these three objects come from stars like our own Sun!
I will probably make another post for only stars so I will write this short. When gravitation pulls lot of dust from universe together it will have so huge gravitation (like our Sun) that termonuclear reaction will occur. (Jupiter is almost so huge that he would be another small sun if little bigger) This reaction will be able to keep star from falling into itself by gravity. But when fuel (H,He…) runs out it will crush itself under gravity. If it was small white dwarf will be next stage. (That will happen to sun). If gravity pull is very huge electrons won´t be able to hold the force and neutron star will appear (made of neutrons). If it is even larger and strong interaction won´t be enough strong black hole will born!

In black hole there is actually no force to hold it and it will fall into singularity! That is point infinitly dense and infinitly small.
Particles have gravitational pull on other particles. When there is lot of particles, gravitation is very strong and it will start to bend spacetime(P.1).

(Sun does that and stars behind seems to appear somewhere else than they are.) Black holes have such strong pull that even light can not escape, that is why they are black (no light comes to your eye).
Around black hole is event horizont. That is circle which is edge of black hole. Light circles around it. It can not escape but it wont be either sucked by hole.

Long time it was thought that black holes can not decay particles but Stephen Hawking actually came up with Hawking radiation. On this topic I will have to learn something more because I dont really understand how it works. Anyway black hole is actually radiating (lossing mass) and at one point it will explode when strong nuclear force will be again able to fight gravitation. Can happen after 10^66 years.

Surely I forgot to say something but you can ask me in comments.
Please comment this post if there are any mistakes!
Btw. I highly recommend to read The brief history of time by S. Hawking
Dragallur

p.1: Spacetime. (2015, March 5). In Wikipedia, The Free Encyclopedia. Retrieved 18:24, March 19, 2015, from http://en.wikipedia.org/w/index.php?title=Spacetime&oldid=649931558