Green trail, golden leaf! (part 2)

in the last post I was writing about the contest I was one, so check it out if you have not already.

It was pretty cool, and I got surprised at how the kids discussed with me so many things on my presentation.

Those were the questions I mentioned last post:


  1. Name 3 astronauts
  2. What is astronomical unit and what is light year
  3. Name 3 missions (Apollo and other count as 1)
  4. Name 4 constellations that are visible in Czech Republic
  5. Highest mountain in Solar System and where it is
  6. Where do comets come from?
  7. Difference between meteorite, meteor, meteoroid and asteroid.
  8. … (and other)

These were for younger kids and there were two more though I can not remember them..

The first question was normally quite ok, though not always they got 3. Of course most said Armstrong and Gagarin and some people said Vladimír Remek who is the first Czech astronaut.

Astronomical unit is distance from Earth to Sun and light year is the distance the light travels in one year. I thought that those would be very easy but actually to my surprise the kids usually knew what light year is but not AU, though I would guess rather the opposite.

Three missions? Most said Apollo and Sputnik (really, why Sputnik?). Some said the third which was for example Curiosity.

Four constellations are Ursa Major, Ursa Minor, Leo, Orion… and so on, we did not approve parts of constellation like Big Dipper which is just part of Ursa Major.

Olympus Moons on Mars.. few kids new this.

Nobody knew both Kuiper belt and Oort cloud I think and some teams knew one, this was kind of hard I guess.

You already know the difference from one of my posts!

Questions for older kids:


  1. What is afelium and perihelium
  2. Name all Galilean moons and give a small info for one of them
  3. What is HR diagram
  4. (Lot of pictures about life time of star)
  5. Draw the orbit of typicall comet and draw both tails and name one place where they come from.
  6. What is the heaviest element that fuses in core of star.

Afelium: furthest point to Sun. Perihelium: closest point to Sun.
Most people did not know.

Only one group was able to name Europa, Callisto, Ganymede and Io.. most did not know what Galilean moons are.

I already described HR diagram in one post, I really love it though!

There was nebulae, protostar (most people did not recognize it), normal star, red giant, supernova, white dwarf, neutron star and black hole.

Comet has very elliptical orbit and it comes either from Kuiper belt or Oort cloud as I said.
It has two types of tails:

There are two types of tails.

It is iron!





Standard candle

have you ever wondered how do scientists measure distances far away in space? Maybe you have heard about supernova which was found about 11 billions of light years away. The problem is that when something is far away you don`t actually know if what you see is bright or close or dim or far away or the combination of both.

So here comes the standard candle. The standard candle is object in Universe which has always about the same luminosity.
The example of thing that is not standard candle is for example any star since when you are looking at it you don`t know its luminosity since it could be in spectral class O or K  and it could be next to you or far away.

Standard candles are supernovas of type Ia which are the brightest of all supernovas.
First of all I will try to explain what this supernova type Ia is.

This type of supernova is explosion of white dwarf which exceeds the mass of 1.4 the mass of Sun.

How this happens? This white dwarf has to be in binary star system so he can feed on his companion`s gases and get the mass again to trigger fusion. When white dwarf exceeds the Chandrasekhar limit which is 1.4 of Sun`s mass as mentioned above then it explodes in violent explosion called supernova Ia.
Actually it is not so simple because the supernova explodes in what is called “double detonation” which is caused by first explosion happening even before Chandrasekhar limit because of the hydrogen which is fused on the surface on helium (I am going to find out more about this on astronomy stack exchange so I will update it.)

Then the second and main explosion is triggered and the donor, the first star is thrown away from the system by the energy released (1-2*10^44 J).

So the important thing is that supernova works as standard candle because it will be always about the same brightness which is very important because than astronomers can calculate how far away it is because they know how bright this thing is.
Supenovas are used for distances greater than 1,000,000 light years because closer there is not enough of them.


Picture source


What are Black holes?

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 benGPB circling earth.jpgd 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

p.1: Spacetime. (2015, March 5). In Wikipedia, The Free Encyclopedia. Retrieved 18:24, March 19, 2015, from