A total of 566 people from 41 countries have gone into space. 12 of them walked on the moon. By the way, a full NASA space suit costs $12,000,000.

The sun, like other stars, is a ball of gas. It is made of 91.0% hydrogen and 8.9% helium. The sun's core is about 2500 times hotter than its surface. The sun's temperature is 9,941°F, which is equal to 5,505 °C.

A satellite is a star or other object that orbits around a larger object. Jupiter is so massive that it has 79 moons.

Neptune has the coldest overall average temperature, and Uranus has the coldest temperature ever recorded. Pluto is categorized as a dwarf planet and not a regular planet since it is much smaller, but Pluto was the planet furthest away from the sun and also the coldest.

Pluto has way more frozen water than scientists initially thought. It was discovered on February 18th, 1930.

A light-year is a unit of distance the light travels in one human year. The calculation is as follow: multiply the number of seconds in one year by the distance that light travels in one second (186,282 miles or 299,792 km). The result: one light-year is about 5.88 trillion miles (9.5 trillion km).

Asteroids are pieces of rock and debris believed to be from long, destroyed planets.

Mercury is the nearest planet to the sun and the most cratered planet in the solar system. It's also the smallest planet in our solar system. Mercury has an orbital period of 88 days.

It takes Venus longer to turn once on its axis than to complete one orbit (cycle) of the sun. Meaning a day on Venus is longer than one year on earth.

Mars is slower and more distant from the Sun. Thus, a full circuit takes 687 Earth days (which is one Mars year). The tallest mountain in the solar system is located on mars.