Space
How Hot Is the Sun?
NASA puts the Sun's core at about 15 million °C and its surface at 5,500 °C, yet its outer corona reaches 2 million °C. Here is why, and how the heat is made.
Space
Planets, moons, stars and the missions that study them, explained with data and images from NASA and other space agencies.
Space
Why Is Pluto Not a Planet?
Pluto was reclassified as a dwarf planet in 2006 because it has not cleared its orbit of other objects, one of three tests the IAU set for a planet.
Space
How Far Away Is the Moon?
The Moon is about 384,400 km (238,855 miles) from Earth on average. Learn why the distance changes, how lasers measure it and how fast it is growing.