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Celestial objects, including the Sun, Moon, stars, and planets, have been observed for centuries. With the invention of the telescope, new discoveries were made, including the Galilean moons and the elliptical orbits of planets. Modern astronomy has revealed even more objects, such as galaxies and quasars. Google Sky allows anyone to view the night sky online. The word “celestial” captures the wonder of observing these objects.
Celestial objects are things we can find when we view the night sky with a telescope, binoculars, or with the naked eye. Some have been known for centuries, while others are quite recent, revealed only by the most powerful telescopes.
The “standard” celestial objects, ie those known since ancient times, are the Sun and the Moon, the stars visible to the naked eye, and the first six planets, except the Earth, of course. Our ancestors worshiped some of these, such as the Sun and Moon, and attached special significance to the stars, variously describing them as symbols engraved in the sky by the gods, or small holes beyond which was a higher celestial sphere. All stars, planets, and the Sun were thought to orbit the Earth on a fixed shell. Comets were observed from time to time, considered a bad omen.
With the invention of the telescope in the Renaissance, people started to realize that the Sun didn’t orbit the Earth, but vice versa. Galileo Galilei famously observed four moons of Jupiter, which have since been known as the Galilean moons. Thanks to Newtonian physics, it was determined that the orbits of the planets were not actually circular, but rather elliptical. Asteroids and comets were observed, and it was realized that they were space rocks and ice rather than god-sent omens.
Modern astronomy has found a wealth of objects our ancestors could never have dreamed of. More powerful telescopes allow us to observe galaxies, millions of stars, distinguish different classes of stars from each other, and see such exotic celestial objects as quasars. We’ve inferred the existence of black holes, dark matter, and extrasolar planets based on how they affect what we see, and we’ve theorized the existence of bizarre structures like cosmic strings.
In 2007, search engine company Google launched Google Sky, which lets you enter your home coordinates and look at an image of the night sky online, just as it would look on a perfect night. It also allows for zooming, allowing anyone to see celestial wonders without an expensive telescope, although of course, that’s not quite the real thing.
The awe-inspiring connotations of the word “celestial” summarily capture the wonder experienced by humans when they gaze out from our little rock to the great beyond.
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