2. Our planets: Mercury
Mercury is the planet that is closer to the Sun. The temperature on the surface of Mercury is minus 190 to plus 430 Celsius.
Mercury has no atmosphere and about Moon’s size.

3. Venus
The temperature on the surface of Venus is 480 Celsius. It is the hottest planet in our solar system.
The pressure on the surface is 90 bar, like 900 meters under the sea!

4. Our Earth
Our planet is in the right distance from the Sun, so water can be liquid on its surface. This and the atmosphere makes Earth friendly to life.
The Moon is a big satellite, just 4 times smaller than the Earth. That helps the axis of the Earth to keep a stable tilt.

5. Earth and the Moon

6. Mars
The temperature on Mars is minus 87 to minus 20 Celsius. The atmosphere of the planet is very thin. Mars is red, because of the iron oxide on the surface. The size of Mars is the half of the Earth’s size.
There is ice under the surface and on the 2 poles.

7. The asteroid's belt
This belt contains thousand asteroids. Some are hundreds of kilometers big, but they are still to small to have a spherical shape. The asteroids are gravity bounded with Jupiter.
Asteroids collisions can make them dangerous for our Earth. Earth’s water came from asteroids falling on our planet over 4 billion years ago.

8. Jupiter
Jupiter is the largest planet of our solar system. This giant gaseous planet is 100 times bigger than the Earth.
Jupiter is very far from the Sun (800 millions km). The temperature on the planet’s surface is minus 180 Celsius.
Jupiter has more than 70 moons.

9. Io
Io is one of Jupiter’s 4 big satellites. The other 3 are Ganimidis, Europi and Kalisto.
There are many volcanoes on Io, and we can observe a lot of eruptions. The tidal forces from Jupiter make these volcanoes active.

10. Saturn
Saturn is also a giant gaseous planet, just a little bit smaller from Jupiter.
Saturn’s rings are very impressive, they contain mostly small pieces of ice.
This giant planet has also more than 60 moons.

11. Titan
Titan is Saturn’s largest moon. This moon has a thick atmosphere and like the water cycle on Earth, a methane cycle!
It is raining liquid methane, and we can observe methane lakes on the Titan’s surface.

12. Uranus and Poseidon
These 2 planets are the most distant of our solar system. Their atmospheres contains a lot of methane, so they appear blue and green. Both planets are not visible with the naked eye, so the astronomers discovered them after the invention of the telescopes.

13. The planets in the sky
The planets in the night sky are very bright and we can find them in a belt that we call ecliptic plane.
Also the Moon and the Sun are in the ecliptic.
Venus is the brightest planet of the sky.

15. Stars and planets
Stars are thousand times larger than planets. Stars fuse hydrogen into helium in their cores, so they produce energy.
Our Sun contains the 99% of our solar systems mass.
The diameter of the Sun is km (Earth km).

16. Our solar system .

17. A very important picture of our Earth

18. The comets
The comet’s origin is a belt very far from the Sun (Oort’s cloud). They contain a lot of ice. The ice is melting when they came close to the Sun.
The tails of the comets are very impressive.

20. Eclipses
When the Moon is in frond of the Sun there is a total solar eclipse, and we can observe the chromosphere and the corona of the Sun.
When the Moon is in the shadow of the Earth there is a total Moon eclipse.

21. Total Moon eclipse

22. Total Sun eclipse

23. The exoplanets
We have discovered more than 4000 planets around other stars.
The most of these planets are gaseous giants, but we can hardly see smaller planets with our telescopes.
We also discovered some Earth- like planets in the right distance to they stars, so they can contain liquid water.

25. Interstellar nebula
Interstellar nebula contain molecular hydrogen and a small amount of heavier elements. Small parts of these nebula collapse when gravity is getting strong enough. This is the way the stars are formed.
Water and more complex molecules are in these nebulas, enriching the future stars and planets

27. Open star clusters
Neighboring newborn stars usually form clusters. After the stars begins to fuse the hydrogen in their cores, their strong winds despair the remaining gas between them.
After millions of years the clusters dissolve into individual stars.
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28. Planetary nebula
Planetary nebula are remains of stars with the mass of the Sun. They are the outer parts of a dead star, called white dwarf.
Planetary nebula contains complex molecular, which will enrich the future stars and planets.

30. Globular nebula
Globular nebula are many billions years old. They look like small galaxies and contain more than a million of stars.
They are placed in the halo of the Galaxy, so they are tens of thousands light years away.

31. The Galaxies
Galaxies contains hundreds of billion of stars. They contains also much of interstellar gas. Every galaxy has a halo of dark matter, 10 times more massive than its visible matter!
In some galaxies thousand of stars are forming every year. (1 per year in our Galaxy)
All the stars we can see in the sky belong to our Galaxy.

32. Galaxy clusters
Galaxies also form clusters. Our Galaxy belongs to the Virgin cluster.
In the center of every galaxy cluster is a big elliptical galaxy.
Our galaxy is a spiral galaxy

34. Telescopes
In astronomy we use very large telescopes. We also use special telescopes for all the wavelengths, from gamma ray to radio waves.
The largest telescopes on Earth are placed in very dry and dark places. There are also telescopes in space, because our atmosphere do not allow gamma and X-rays, ultraviolet and infrared light to reach the Earth’s surface.
Some people have astronomy as a hobby. These amateur astronomers help a lot in astronomy publishing, and some of them support the work of the professional astronomers.

46. Astronomy helps us to see the big picture