Astronomy is a natural science that is the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies), the

physics, chemistry, mathematics, and evolution of such objects, and phenomena that originate outside the atmosphere of Earth, including supernovae explosions,

gamma ray bursts, and cosmic background radiation. A related but distinct subject,

cosmology, is concerned with studying the universe as a whole.

Astronomy is not to be confused with

astrology, the belief system which

claims that human affairs are

correlated with the positions of celestial

objects. Although the two fields share a

common origin they are now entirely

distinct.

A star-forming region in the Large Magellanic Cloud, an irregular galaxy.

A giant Hubble mosaic of the Crab Nebula, a supernova remnant

Sub-Fields of Observational Astronomy:Radio astronomy

Infrared astronomyOptical astronomy

Ultraviolet astronomyX-ray astronomy

Gamma-ray astronomyFields not based on the electromagnetic

spectrumAstrometry and celestial mechanics

Galileo-Galilei

The most important astronomer of all time turns out to be the Italian spearhead of the Scientific Revolution, Galileo. Galileo was, in a sense, a lucky astronomer. To put it simply, he was fortunate to be alive when the

telescope was invented (around 1607 AD). He caught wind of this amazing new device, and quickly made his own refracting telescope. This gave him absolutely unprecedented access to information on the heavens– and

he was the first to capitalize on it. While military leaders across Europe were using the spyglasses to watch their enemies at sea, Galileo turned his telescope to the sky and discovered secrets that had lay waiting for

millennia.

Because Galileo lived and worked at such an opportune time, he is considered by most to be the father of modern observational astronomy (not to mention the father of modern physics). Many aspects of his life lend

themselves to this title. He was the first to lay eyes on the Rings of Saturn (though they looked more like handles from his perspective), and he also discovered and named various moons of Jupiter. He was also the

first to observe sunspots, which was rather significant, because it was then believed by the church that the sun was perfect and without blemishes of any kind.

Hipparchus

Widely believed to be the greatest astronomer of antiquity, Hipparchus can easily be viewed as a sort of founding father of astronomy. His most important contribution to the field was the first known star catalogue,

which historians think he was inspired to construct after viewing a supernova. This star catalogue was later used extensively by Ptolemy in

his astronomical observations. His other contributions include important findings on the positions and motions of the moon and Sun. Using

trigonometry – a subject for which he is basically credited for inventing –he was able to measure the distance to the moon during a solar eclipse. He is also known for creating the method by which a star’s brightness is

measured, a system still in use today.

Edwin Hubble

Hubble is credited with discovering galaxies outside of our own Milky Way. Although the race to solve this mystery had contributions from many different scientists, it was Hubble’s observations through the Hooker telescope, around the year 1923, that proved to the scientific

community that there was more to outer space than the Milky Way. In essence, with one finding, Hubble ballooned the Universe from a galaxy of about a hundred thousand light years across, with approximately one

hundred billion stars, to an indefinite expanse of intergalactic space, billions of light years across, and with a seemingly infinite amount of

stars.

Johannes Kepler

Kepler was a German astronomer and was the first to fully explain the motion of the

planets of our solar system.

William Herschel

A fascinating side-note to his astronomical career was the fact that Herschel built his own reflecting

telescopes. He used his self-made telescopes to observe binary systems of stars, in which two stars

orbit around a common center of gravity in a bound system. Johannes KeplerKepler was a German

astronomer and was the first to fully explain the motion of the planets of our solar system.

ASTRONOMY

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