From Academic Kids

An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics.

Nicolaus Copernicus.Image provided by Classroom Clip Art (
Nicolaus Copernicus.Image provided by Classroom Clip Art (

Astronomy is generally thought to have begun in ancient Babylon by the Persian Zoroastrian priests (the magi). Recent studies of Babylonian records have shown them to be extremely accurate for the ancient night sky. Following the Babylonians, the egyptians also had an emphasis on observations of the sky.

Mixtures of religious interpretations of the sky, as mythic tales of the gods, led to a duality that we now identify as astrology. It is important to recognize that before about 1750, there was no distinction between astronomy and astrology.

Unlike most scientists, astronomers cannot directly interact with the celestial bodies, and so instead must resort to detailed observation in order to make discoveries. Generally, astronomers use telescopes or other imaging equipment to make such observations.

Famous Astronomers

Astronomer Contribution
Hipparchus and Ptolemy Determined the positions of about 1,000 bright stars, tried to explain the puzzles of astronomy without refuting the commonly believed geocentric model of universe and classified stars by magnitude.
Aristarchus First known person to propound the heliocentric model of universe
Nicolaus Copernicus Reitererated the heliocentric model of universe.
Nasir al-Din al-Tusi This Persian astronomer gave the first extant exposition of the whole system of plane and spherical trigonometry. Made very accurate tables of planetary movements and named many stars. His planetary system was the most advanced of his period and was used extensively until the development of the heliocentric model. Tusi-couple resolves linear motion into the sum of two circular motions. He also calculated the value of 51' for the precession of the equinoxes and contributed to construction and usage of astrolabe.
Galileo Galilei Was the first to use the telescope to observe the sky. Condemned to house arrest for his discoveries by Inquisitional edict, which was lifted 359 years later by Pope John Paul II.
Johannes Kepler Suggested the elliptical orbits of planets, and propounded his Laws of Planetary Motion.
Isaac Newton Published Philosophiae Naturalis Principia Mathematica (1687), containing the "Newton's laws of motion", which are fundamental to mechanical physics, and which explained Kepler's laws of planetary motion. Predicted the orbits of the planets.
Subrahmanyan Chandrasekhar Extensive work on the internal mechanisms of stars, particularly known for determining the effect of special relativity on stars, including being the first to calculate the Chandrasekhar limit, which he did, without a calculator, on a boat journey.
Henrietta Swan Leavitt Catalogued Cepheid variable stars in the Magellanic Clouds, in 1912 discovered the relationship between luminosty and periodicity in Cepheids -- leading to Hertzprung's later work.
Ejnar Hertzsprung determined the distance to several Cepheids, when Cepheids were detected in other galaxies such as the Andromeda galaxy, the distance to those galaxies could then be determined.
Edwin Hubble Discovered the expansion of the universe. (Hubble's Law) The Hubble Orbiting Space Telescope was named in his honor.

See also

There is also a well-known painting by Johannes Vermeer titled The Astronomer, which is often linked to Vermeer's The Geographer. These paintings are both thought to represent the growing influence and rise in prominence of scientific enquiry in Europe at the time of their painting, 1668-69.


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