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Hubble, Edwin
An American astronomer who lived from 1889 to 1953. Hubble discovered the expansion of the universe by measuring the red shifts of many galaxies. He also discovered that the recession velocity of a given galaxy is proportional to its distance from the Milky Way. Hubble Space Telescope is named after him.
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Hyades
A cluster of more than 100 stars; the brightest form the V-shaped “face” of Taurus, the bull. It is the nearest major cluster to Earth, at a distance of about 150 light-years.
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Hydra, the Water Snake
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Hydrogen and Helium
Hydrogen is an element, usually in the form of a gas, that consists of one proton and one electron. Hydrogen is the most abundant element in the universe, accounting for about 75 percent of its normal matter, and was created in the Big Bang. Helium is an element, usually in the form of a gas, that consists of a nucleus of two protons and two neutrons surrounded by two electrons. Helium is the second-most abundant element in the universe, after hydrogen, and accounts for about 25 percent of the atoms in the universe. Most of the helium in the universe was created in the Big Bang, but it also is the product of hydrogen fusion in stars.
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