Homepage

Science Glossary

Previous PageTable Of ContentsNext Page

U

Uhuru satellite

NASA's first X-ray satellite launched in 1970.

Ultra Luminous Infrared Galaxies (ULIRG)

A type of galaxy which is very bright when observed at infrared wavelengths. They were discovered by the IRAS satellite. Astronomers are now investigating the cause of their enormous infrared luminosity.

Ultraviolet light

Region of the electromagnetic spectrum spanning wavelengths from 91.2 nm to 350 nm, wavelengths largely blocked by the Earth's atmosphere.

Ulysses mission

A joint ESA/NASA mission launched in 1990, to explore the region of space above the poles of the Sun. See http://sci.esa.int/ulysses/

Universe

Everything that exists. The size of the observable Universe is determined by the distance light has travelled since the Universe was formed in the Big Bang, 12 - 15 billion years ago.

Uranus

At 19.2 AU away from the Sun, Uranus is the seventh planet in the Solar System and one of the gas giants. Its diameter is four times that of Earth and it has a thick atmosphere composed mainly of hydrogen and helium. Uranus rotates about an axis that is almost perpendicular to the plane in which it orbits the Sun. Hence it appears to be lying on its side. It has at least 20 moons and its surface temperature is typically 58 K.

Previous PageTable Of ContentsNext Page