Astro Glossary

Eta Carinae

One of the Milky Way’s most impressive star systems, about 8,000 light-years away in the southern constellation Carina. It probably consists of two stars, each of which is many times as massive as the Sun. The stars are surrounded by a thick, dusty nebula that makes it impossible to see one of the stars. The larger star is unstable and has erupted several times over the last few centuries, most recently in 1843, when it grew brighter than every other star in the night sky except Sirius. This star is expected to end its life as a supernova.

European Astronomy and Space Program

Evening Star

A name for the planet Venus when it appears in the evening sky. It outshines all of the other stars and planets in the night sky. The name also occasionally is applied to Jupiter, the second-brightest point of light in the night sky.

ExoMars

ExoMars is a European space mission to study Mars and to develop the technology and capabilities for future landers and rovers. Scheduled for arrival at Mars in October 2016, it consists of the Trace Gas Orbiter, which will hunt for evidence of methane and other compounds that could be produced by living organisms, and the Schiaparelli lander, which will operate for a day or two before its batteries die. The lander will help the European Space Agency plan for ExoMars 2020, which include a rover.

Exoplanet

A planet that orbits around a star other than the Sun.

Expansion of the Universe

Experimental Aircraft and Test Pilots

Explorer Missions

NASA’s longest-running series of spacecraft, with more than 75 successful missions. Explorer 1, launched January 31, 1958, was the first successful American satellite. Other Explorers have studied the solar wind, Earth’s magnetic field, the “afterglow” of the Big Bang, the ultraviolet glow of distant galaxies, and many other subjects.

Extinct Constellation

An extinct constellation is one that is no longer recognized an official constellation by astronomers. In the early 20th century, astronomers created a list of 88 official constellations, each with its own boundaries. All other constellations were discarded. Many other constellations had been abandoned long before then, however. Astronomers split Argo Navis, which represented the ship that carried Jason and the Argonauts, into three smaller constellations. European astronomer created dozens of new constellations from the late 1500s through the early 1800s, either to populate the southern sky, which wasn't visible from most of Europe, or to fill in blank regions between ancient constellations. Many of those constellations survived, but many others did not. The list includes Apes, the bees; Cerberus, a three-headed serpent in the hands of Hercules; George's Harp, which honored England's King George III, a patron of astronomy; and many others.

Extinction Events