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Brown dwarf
Brown dwarfs were originally called black dwarfs, a classification for dark substellar objects floating freely in space which were too low in mass to sustain stable hydrogen ... > more -
Extraterrestrial life
Extraterrestrial life is life that may exist and originate outside the planet Earth, the only place in the universe currently known by humans to support life. Its existence is currently purely ... > more -
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against (and hence obscuring a small portion of) the solar disk. During ... > more -
Light-year
A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in a vacuum in one year. While there is no authoritative decision on which year is ... > more -
Gravitation
Gravity is a force of attraction that acts between bodies that have mass. Gravity is the reason for the very existence of the earth, the sun and other celestial bodies; without it matter would not ... > more -
Great Red Spot
The Great Red Spot is a persistent anticyclonic storm on the planet Jupiter, 22 degrees south of the equator, which has lasted at least 340 years. The storm is large enough to be visible through ... > more -
Multistage rocket
A multistage (or multi-stage) rocket is, like any rocket, propelled by the recoil pressure of the burning gases it emits as it burns fuel. What characterizes it as "multi-stage" is that it ... > more -
Solar flare
A solar flare is a violent explosion in the Sun's atmosphere with an energy equivalent to tens of millions of hydrogen bombs. Solar flares take place in the solar corona and chromosphere, heating ... > more -
Comet Hale-Bopp
Comet Hale-Bopp was probably the most widely observed comet of the 20th century, and one of the brightest seen for many decades. It was visible to the naked eye for a record 18 months, twice as long ... > more -
Transit of Venus
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and the Earth, obscuring a small portion of the Sun's ... > more
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