The announcement by NASA scientists that they have finally found another solar system similar to our own is the fulfillment of an age-old quest in astronomy.
Astronomers now definitely know that there are more planetary systems, and some are even in our cosmic backyard.
In a sense, this discovery continues the revolution which was started by Copernicus and Kepler and Galileo, in which Earth (and then the sun) lost its special place as the center of the universe.
At a recent press conference, NASA (National Aeronautics and Space Administration) astronomers said they found five planets around 55 Cancri, a sun-like star that lies 41 light years away in the constellation of Cancer.
The philosopher Epicurus wrote in the fourth century B.C. that "there are infinite worlds both like and unlike this world of ours."
In the 13th century, Albertus Magnus posed the question, "Do there exist many worlds, or is there but a single world?" Magnus went on to say, "This is one of the most noble and exalted questions in the study of Nature."
The heretic Giordano Bruno, who was burned at the stake in 1600, held the view that "innumerable suns exist, and innumerable Earths revolve about these suns."
It was the philosopher Immanuel Kant who made the strongest case for exoplanets, as these planets have come to be known. In his theory of the heavens in 1755, a time when only six planets were known, Kant advanced the idea that there were planets in the solar system beyond Saturn and that planets were not confined just to our solar system.
"Our planetary system has the sun as its central body, and the fixed stars which we see are, in all probability, centers of similar systems," Kant wrote.
The first of Kant's prediction was proven true during his lifetime. In 1781, William Herschel, a German musician and astronomer who had emigrated to England, stumbled upon a faint, hazy object that moved in a planet-like orbit beyond Saturn. It was named Uranus.
This caused a lot of excitement about planet hunting, and amateur astronomers trained their telescopes onto the night sky in the hope of finding more.
While cataloging the planets in our own Solar System was difficult, searching for planets beyond our Solar System was even more complex.
The separation between stars is immense and measured not in miles but in light kyears (a light year is almost six trillion miles). As a consequence, even planets around nearby stars, a few light yars away, are incredibly faint.
Planets produce no light of their own, but they reflect their parent suns. The voyage across interstellar space so diminishes the reflected light that it becomes almost impossible to take images of such planets.
It was only in 1995 that the first planet beyond the Solar System was observed. As our telescopes have improved, more of these extremely faint exoplanets have come into view.
As of today, astronomers have counted roughly 260 exoplanets around nearby stars; most of these are relatively large, about the size of Jupiter.
There is a lot of excitement surrounding the 55 Cancri discovery because astronomers realize that one of the planets lies in the so-called habitable zone; an area around the star where temperatkures are such that water can exist.
Scientists maintain that the presence of water increases the possibility of finding life. This particular planet is almost the size of Saturn, so probably too large to sustain life as we know it; however, it may posses large moons that are Earth-like.
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