Site Glossary

energy transmitted by photons across the electromagnetic spectrum.

The complete range of electromagnetic radiation, arranged by wavelength or frequency.

an oval-shaped closed curve with two foci.

A rounded galaxy made mostly of older stars with little gas or dust.

A spectrum containing bright lines produced by excited atoms or ions.

Choosing a mathematical relationship suited to the available information and motion conditions.

a visual representation of the uncertainty or variability associated with a data point or measurement.

the minimum initial speed required to escape a body's gravitational influence without further propulsion.

The boundary around a black hole beyond which escape is impossible.

a planet orbiting a star outside our Solar System.