Glossary main content.


all-sky survey
A telescope scan of the entire sky from Earth's vantage point.

A rocky or metallic body smaller than a planet that orbits a star.

asteroid belt
The region of the Solar System where most of the asteroids orbit. The asteroid belt lies between the orbits of Mars and Jupiter.

brown dwarf
An astronomical object with a mass in the range between a planet and a star (greater than 1.3 percent and less than 8 percent the mass of the Sun). Brown dwarfs have a brief phase of weak nuclear fusion of deuterium (heavy hydrogen), but they never become hot enough in their cores to fuse hydrogen, as stars do.

Of or relating to the Universe as a whole.

The Universe regarded as a whole, including all matter, energy, and space.dataInformation, often in the form of measurements or observations, which can be analyzed.

electromagnetic spectrum
The complete array of electromagnetic radiation (light). In order of increasing wavelength (decreasing frequency and energy), the spectrum ranges from gamma rays through X-rays, ultraviolet light, visible light, infrared radiation, microwaves to radio waves.

A relatively massive assembly of stars, interstellar clouds, and dark matter bound together by gravity.

infrared (IR)
Invisible electromagnetic radiation (light) with wavelengths longer than red light and shorter than microwaves. Infrared light occupies the spectral band extending from 0.75 to about 200 micrometers.

The emission of energy.starA self-luminous body held together by its own gravity and with a central temperature and pressure sufficient to generate nuclear energy.

ultraluminous galaxy
A very bright galaxy that emits nearly all of its energy in the far-infrared (infrared light of longer wavelengths).

ultraviolet (UV)
Invisible electromagnetic radiation (light) with wavelengths shorter than violet light and longer than X-rays. Ultraviolet light occupies the spectral band extending from 300 nanometers down to about 10 nanometers.

visible light
The portion of the electromagnetic spectrum corresponding to the visible colors, with wavelengths longer than ultraviolet light and shorter than infrared radiation. Visible light occupies the spectral band extending from 300 nanometers to about 750 nanometers.

The distance between successive wave crests, or troughs. Light of different wavelengths has different properties, such as color.