Space FAQ: Big Questions, Short Answers

In 2006 the IAU defined a planet as a round body orbiting the Sun that has cleared its orbit. Pluto shares its zone with many Kuiper Belt objects, so it became a dwarf planet.

Saturn, with more than 270 confirmed moons as of 2025. Most are tiny, irregular objects only a few kilometres across.

Venus. Its thick carbon dioxide atmosphere traps heat, keeping the surface around 465 degrees Celsius, hotter than Mercury.

Proxima Centauri, about 4.24 light-years away.

Not without heavy protection. Mars has a thin, unbreathable atmosphere, freezing temperatures and high radiation. Future bases would need shelters, oxygen and water from local ice.

We do not know yet. The best places to search are Mars (for ancient microbes) and ocean worlds such as Europa and Enceladus.

About 4.6 billion years, based on the ages of the oldest meteorites.

In orbit they are in continuous free fall around Earth, so they feel weightless even though gravity is still strong there.

Yes. Mercury, Venus, Mars, Jupiter and Saturn are visible to the naked eye at the right times. Venus and Jupiter are often the brightest points in the night sky after the Moon.

Voyager 1, more than 24 billion km from Earth and travelling through interstellar space.