1-Saturn would float if you would put it in water.
2-If you would place a pinhead sized piece of the Sun on the Earth you would die from standing within 145 km (90 miles) from it.
3-Space is not a complete vacuum, there are about 3 atoms per cubic meter of space.
4-Only 5% of the universe is made up of normal matter, 25% is dark matter and 70% is dark energy.
5-Neutron stars are so dense that a teaspoon of them would be equal to the weight of the entire Earth’s population.
6-The Sun is 400 times larger than the Moon but is 400 times further away from Earth making them appear the same size.
7-The star Lucy in the constellation Centaurus is a huge cosmic diamond of 10 billion trillion trillion carats.
8-Seasons last 21 years on Uranus while each pole has 42 years of sunlight followed by 42 years of darkness.
9-Venus,on the other hand, does not have any seasons at all.
10-1 year on Mercury consists of less than 2 days on Mercury.
11-There are as many oxygen atoms in a breath as breaths of air in the atmosphere.
12-Helium is the only substance in the universe that cannot be in solid form.It can’t be cold enough.
13-The coldest place in the universe is on Earth. In Wolfgang Ketterles lab in Massachusetts. 0.000000000001 degrees Kelvin.
14-The pistol star is the most luminous star known 10 million times the brightness of the Sun.
15-Saturn’s moon Titan has liquid oceans of natural gas.
16-All the planets are the same age: 4.544 billion years.
17-Earths moon was most likely formed after an early planet named Theia crashed into Earth.
18-8000 stars are visible with naked eye from Earth. 4000 in each hemisphere, 2000 at daylight and 2000 at night.
19-90-99% of all normal matter in the universe is hydrogen.
20-Only 55% of all Americans knows that the Sun is a star.
21-Because of the speed the Sun moves at, solar eclipses can last at most 7 minutes and 58 seconds.
22-Lunar eclipses, however, can last 1 hour and 40 minutes.
23-All the coal, oil, gas, wood and fuel on Earth would only keep the Sun burning for few days.
24-A full moon is nine times brighter than a half moon.
25-When the Moon is directly above your head or if you stand at the equator, you weight slightly less.
26-A single Quasar produce the same amount of energy as 1 trillion suns.
27-Just after the Big Bang, everything in the universe was in liquid form.
28-A planet nicknamed “The Genesis Planet” has been found to be 12.7 billion years old making it the oldest planet found.
29-The shape of the universe looks a lot like a brain cell.
30-Every year, the Moon is moving away from Earth by 3.8 centimeters.
31-The Moon spins around its axis in the same time it goes one lap around the Earth which makes us always see the same side of it.
32-Upsilon Andromeda B also only face one side to its star. One side is hot as lava while the other one is cold below freezing.
33-The average galaxy contains “only” 40 billion stars.
34-While in space astronomers can get taller, but at the same time their hearts can get smaller.
35-Mars surface is cowered with iron oxide (rust).
36-Only half a billionth of the energy released by the Sun reaches Earth.
37-Rogue planets are not bound by any star, brown dwarf or another planet which makes them free-float around the galaxy.
38-Sweeps 10 is the planet with the shortest orbital period found. It orbits its star in only 10 hours.
39-85% of all stars in our galaxy are part of multiple-star systems.
40-Some brown dwarfs have liquid iron rain falling down on them.
41-The light emitting from the Sun is actually 30.000 years old.
42-Of the over 20 million meteors that are observable every day only one or two reach the surface of Earth.
43-The United States have approximately 3.500 astronomers, but over 15.000 astrologers.
44-The closest black hole to Earth is only 1.600 light-years away.
45-There are at least 10^24 stars in the universe.
46-Certain “star quakes” have been found to tear apart the surface of neutron stars.
47-Any free-moving liquid in outer space will form itself into a sphere due to surface tension.
48-The odds of being killed by falling space debris is 1 in 5 billion.
49-Neutron stars can rotate up to 500 times in 1 second.
50-The largest structure found in the universe is the Sloan Great Wall, a super cluster of galaxies 1.37 billion light-years wide.

Very interesting facts from Astronomers & Scientists.. I still could not get it about fact number 18 ? Half of the stars are visible at daylight with naked eye from Earth? Could anyone explain!