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  • On the night of January 1, 1801,

  • Giuseppe Piazzi, a priest in Palermo, Italy,

  • was mapping the stars in the sky.

  • Over three nights, he'd look at and draw the same set of stars,

  • carefully measuring their relative positions.

  • That night, he measured the stars.

  • The next night, he measured them again.

  • To his surprise, one had moved.

  • The third night, the peculiar star had moved again.

  • This meant it couldn't be a star at all.

  • It was something new, the first asteroid ever discovered,

  • which Piazzi eventually named Ceres.

  • Asteroids are bits of rock and metal that orbit the Sun.

  • At over 900 kilometers across, Ceres is a very large asteroid.

  • But through a telescope, like Piazzi's,

  • Ceres looked like a pinpoint of light similar to a star.

  • In fact, the word asteroid means star-like.

  • You can tell the difference between stars

  • and asteroids by the way they move across the sky.

  • Of course, Piazzi knew none of that at the time,

  • just that he had discovered something new.

  • To learn about Ceres,

  • Piazzi needed to track its motion across the sky

  • and then calculate its orbit around the Sun.

  • So each clear night, Piazzi trained his telescope to the heavens.

  • Night after night, he made careful measurements

  • until finally, he couldn't.

  • The Sun got in the way.

  • When Piazzi first spotted Ceres, it was here, and the Earth was here.

  • As he tracked it each night, the Earth and Ceres moved like this

  • until Ceres was here.

  • And that meant that Ceres was only in the sky when it was daytime on Earth.

  • During the day, bright sunlight made this small asteroid impossible to see.

  • Astronomers needed to calculate Ceres's orbit.

  • This would let them predict where it was going to be

  • in the vast night sky on any given night.

  • But the calculations were grueling and the results imprecise.

  • Many astronomers searched for Ceres,

  • but not knowing exactly where to look, no one could find it.

  • Luckily, a hardworking mathematician named Carl Friedrich Gauss

  • heard about the lost asteroid.

  • He thought it was an exciting puzzle and went to work.

  • When he realized he didn't have the mathematical methods he needed,

  • he invented new ones that we still use today.

  • He derived a new orbit and new predictions of where to look for Ceres.

  • Hungarian astronomer Baron Franz Xaver von Zach

  • searched for Ceres with Gauss's predictions.

  • After weeks of frustrating clouds,

  • von Zach finally had clear skies on December 31, 1801.

  • He looked through his telescope and finally saw Ceres.

  • We haven't lost track of it since.

  • Today, we've discovered hundreds of thousands of asteroids.

  • Many, including Ceres, orbit the Sun between Mars and Jupiter,

  • while near-Earth asteroids orbit the Sun relatively close to Earth.

  • When we recorded this narration,

  • astronomers had discovered 16,407 near-Earth asteroids,

  • but since we find new asteroids all the time,

  • that number will have grown by hundreds or thousands

  • by the time you watch this.

  • Today, asteroid hunters use modern telescopes,

  • including one in space.

  • Computers analyze the images,

  • and humans check the output

  • before reporting the asteroid observations to an archiving center.

  • Each discovered asteroid has its unique orbit measured.

  • An orbit lets astronomers predict where asteroids are going to be

  • at any given time.

  • Most asteroid trajectories can be predicted for about 80 years

  • though we can calculate where the best studied asteroids will be every day

  • between now and 800 years into the future.

  • We must keep searching for asteroids

  • in case there's one out there on a collision course with Earth.

  • Astronomers don't only search for asteroids, though.

  • They also study them to learn how they formed,

  • what they're made of,

  • and what they can tell us about our solar system.

  • Today, we can do something that Piazzi could only dream of:

  • send spacecraft to study asteroids up close.

  • One spacecraft called Dawn journeyed billions of kilometers

  • over four years to the main asteroid belt.

  • There, it visited Ceres and another asteroid, Vesta.

  • Dawn's stunning images transformed Piazzi's dot of light

  • into a spectacular landscape of craters,

  • landslides,

  • and mountains.

On the night of January 1, 1801,

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B2 H-INT US asteroid orbit night earth sky discovered

The first asteroid ever discovered - Carrie Nugent

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    Evangeline   posted on 2018/04/20
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