Quick Glossary

The distance light travels in one year, about 9.46 trillion kilometers

The range of wavelengths of electromagnetic radiation

The increase in wavelength of light from distant objects, indicating they are moving away

A cloud of gas and dust in space, where stars are born

A planet that orbits a star outside our solar system

A region of space where gravity is so strong that nothing can escape

The boundary around a black hole beyond which nothing can escape

The explosive death of a massive star

A massive system of stars, gas, dust, and dark matter held together by gravity

A rocky object orbiting the Sun, smaller than a planet

An icy body that releases gas and dust, forming a tail when near the Sun

The path an object takes around another object due to gravity

The Sun and all objects that orbit it, including planets, moons, asteroids, and comets

The leftover radiation from the Big Bang, visible as microwave light

Invisible matter that makes up about 27% of the universe

A mysterious force causing the universe to expand faster