Asteroids!

Legend says, Phaethon, son of the Greek god of the sun Helios, once drove his father’s chariot after begging for it. Unwillingly, the god concealed only to witness how his decision proved fatal as his inexperienced son almost set the Earth on fire.

Phaethon is also the name of a small 3-mile-wide asteroid orbiting the Sun and discovered back on October 11, 1983 by NASA’s Infrared Astronomical Satellite. This small rock body that follows a 523-day orbit around our star would be unremarkable if it was not for two things: proximity and meteors.

The irregular chunk of rock is classified as “potentially hazardous” by NASA. This means Phaethon has the potential to make close approaches to the Earth and is of a size large enough to cause significant damage—the asteroid that arguably wiped out the dinosaurs was around 6-mile wide. Last Saturday, December 16, it passed within 6.4 million miles from Earth—around 27 times the distance between the Earth and the Moon—on its way to the Sun. It will not pass that close again until December 14, 2093, when it will pass within “just” 1.8 million miles from Earth.

Furthermore, Phaethon may be responsible for the Geminid meteor shower—named after the constellation from where the meteors appear to spring, Gemini—as its orbit matches well the path of the shower. Meteor showers are the result of Earth crossing the orbit of a comet and the stream of debris it leaves behind. As the debris speeds through the atmosphere it glows. Because of this, some scientists believe Phaethon might be the remnant of a comet that no longer has an active nucleus of ice and dust heating up as it gets close to the Sun.

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Artist’s illustration of the asteroid Oumuamua, the first interstellar object ever known to visit our solar system. Credits: M. Kornmesser/European Southern Observatory

But Phaethon is not the only asteroid that has been in the news recently. For the first time ever, a team from the Pan-STARRS observatory has detected an asteroid that appears to have originated from outside the solar system as it approached it from above the plane of our system. The unusual interstellar object, named Oumuamua—in Hawaiian, messenger from afar arriving first—is significantly elongated, less than a quarter-mile in size and moves remarkably fast.

At the end of the day, asteroids may be both a danger and an opportunity. From the possibility of a collision to the fascinating idea that they could be mined to fuel space exploration. Moreover, their study may tell us about the origins of our solar system and help us understand the origin of life.

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