Science Dictionary

Do you know what a meteor is, or what scientists mean when they are talking about cryogenics? Our collection of science terms explains the meaning of some of the most common scientific ideas.

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Barnard, Edward Emerson

Barnard, Edward Emerson (1857-1923), was a United States astronomer. He discovered 16 comets, Jupiter's fifth satellite, and many dark nebulae.

Hubble, Edwin P.

Hubble, Edwin P. (Powell) (18891953), a United States astronomer. Hubble revolutionized astronomy by showing that the universe is much larger than had been previously believed and by providing observational evidence for the theory of an expanding universe.

Eudoxus of Cnidus

Eudoxus of Cnidus (NY duhs or kuh NY duhs) (400 B.C.?-350 B.C.?) was a Greek astronomer who made important contributions to the field of geometry.

Pease, Francis Gladheim

Pease, Francis Gladheim (1881-1938), a United States astronomer and optician. Pease made photographic and spectrographic studies of the moon, the planets, star clusters, and nebulae.

Francis Graham Smith

Smith, Francis Graham (1923-) is a British astronomer and one of the leading authorities on radio astronomy, the branch of astronomy that studies celestial bodies by measurement and analysis of the electromagnetic radiation they emit in the wavelength range from 1 mm to 30 mm.

Hoyle, Sir Fred

Hoyle, Sir Fred (1915-2001), a British astronomer, noted for research on the development of stars.

Fred Lawrence Whipple

Whipple, Fred Lawrence (1906-) was an American astronomer who was the first to suggest that the nucleus of a comet resembled a “dirty snowball.” His research led to insights regarding the behavior of meteors and the nature of the upper atmosphere and helped establish the modern view of comets.

Friedrich Wilhelm August Argelander

Argelander, Friedrich Wilhelm August (1799-1875) was a Finnish-German astronomer and professor of astronomy who compiled the Banner Durchmusterung, a catalog which recorded the positions and magnitudes of 324,198 stars of the northern celestial hemisphere.

Friedrich Wilhelm Bessel

Bessel, Friedrich Wilhelm (1784-1846), a German astronomer, was the first to measure stellar parallax, an apparent change in a star's position as a result of the earth orbiting the sun.

Davidson, George

Davidson, George (1825-1911), a United States geographer and astronomer. He was born in Nottingham, England, and came to the United States in 1832.

Hale, George Ellery

Hale, George Ellery (1868-1938), a United States astronomer. He was a pioneer in the field of astrophysics, which uses the techniques of physics to study the physical qualities of the sun and other stars, and was especially noted for his studies of the sun.

Kuiper, Gerard Peter

Kuiper, Gerard Peter (1905-1973), a Dutch-American astronomer. An authority on the earth's moon, he directed the research on selection of sites for the manned moon landings of 1969-72.

Schiaparelli, Giovanni Virginio

Schiaparelli, Giovanni Virginia (1835-1910), was an Italian astronomer. He is best known for his studies of Mars, begun in 1877, in which he described in detail the Martian canals.

Shapley, Harlow

Shapley, Harlow (1885-1972), a United States astronomer. His studies of stars in globular clusters and of Cepheid variable stars led to a new understanding of the structure of the universe.

Helen Sawyer Hogg

Hogg, Helen Sawyer (1905-1993) was an American-born Canadian astronomer. She became known for her research on variable stars —stars whose light regularly varies in brightness because of their pulsating atmospheres.

Russell, Henry Norris

Russell, Henry Norris (1877-1957), a United States astronomer. About 1913 he and Ejnar Hertzsprung independently noted certain relationships between stars that resulted in the Hertzsprung-Russell Diagram, a method of classifying stars.

James Bradley

Bradley, James (1693-1762), an English astronomer, discovered the aberration of starlight that provided the first direct proof that the earth revolves around the sun, and the nutation, or nodding motion, of the earth's axis.

Jocelyn Bell Burnell

Bell Burnell, Jocelyn (1943-), a Northern Irish astronomer, discovered the first four pulsars, neutron stars that emit pulses of radiation with a high degree of regularity.

Adams, John Couch

Adams, John Couch (1819-1892), was a British astronomer and one of the discoverers of the planet Neptune.

Flamsteed, John

Flamsteed, John (16461719), an English astronomer. Flamsteed was appointed the first astronomer royal, in 1675, and Greenwich Observatory was built for him in 1676.

Joseph Hooton Taylor Jr.

Taylor, Joseph Hooton, Jr. (1941-) is an American astrophysicist and radio astronomer acclaimed for discovering the first binary pulsar, a system of two collapsed stars that emit tremendous energy as they rotate rapidly around one another.

Fraunhofer, Joseph von

Fraunhofer, Joseph von (1787-1826), a German optician and physicist. He was the first to make a careful study of the dark lines that appear in the solar spectrum, and these lines (and similar ones from other sources) were named in his honor.

Tsiolkovsky, Konstantin Eduardovich

Tsiolkovsky (or Ziolkovsky), Konstantin Eduardovich (1857-1935), a Russian rocket pioneer who is generally regarded as the father of space travel.

Maarten Schmidt

Schmidt, Maarten (1929-) is a Dutch astronomer. He identified the starlike objects now known as quasars.

Mitchell, Maria

Mitchell, Maria (1818-1889), a United States astronomer. Her birthplace was Nantucket, Massachusetts.


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