Huge Near-Earth Asteroid Could Be the End of Us in About 400 Years

3200 Phaethon: the second largest near-Earth asteroid identified to date. NASA

One of the most dangerous near-Earth asteroids recently whizzed past our planet at just 27 times the distance between Earth and the moon, and we discovered that it's even larger than previously believed. In fact, the asteroid, known as 3200 Phaethon, is now recognized as the second largest space rock to threaten our planet, according to a NASA press release.

The good news is, 3200 Phaethon's close trajectory means that we can map out its path with a high degree of accuracy for about the next 400 years — and we're safe, for now. After 400 years, though, that could change.

Aside from its intimidating size, 3200 Phaethon is also interesting in that it's the parent body for the annual Geminids meteor shower of mid-December. Its close orbit around the sun at perihelion is also peculiar, more closely resembling that of a comet than an asteroid; it has thus been referred to as a "rock comet."

Caught on camera

The remarkably egg-shaped asteroid was caught on camera thanks to the Arecibo Observatory Planetary Radar in Puerto Rico, and its diameter was measured at about 3.6 miles, which is about 0.6 miles bigger than previous estimates.

"These new observations of Phaethon show it may be similar in shape to asteroid Bennu, the target of NASA's OSIRIS-REx spacecraft, but more than 1,000 Bennus could fit inside of Phaethon," said Patrick Taylor, one of the scientists working on the measurements.

The new data is a reminder of just how important it is to have the Arecibo Observatory back up and running again in the aftermath of Hurricane Maria. The facility represents the most powerful astronomical radar on the planet, and it's ideal for getting the most accurate measurements of the shape, size, and rotation of asteroids, as well for determining their trajectory and threat-level to our planet.

In order for any space object to get classified as hazardous, it has to be large enough, and it to pass close enough to our planet to warrant concern. 3200 Phaethon crosses the orbits of Mercury, Venus and Mars, as well as Earth, making it especially menacing. Its close pass to the sun can also cause a comet-like dust tail to form.

If this asteroid ever does end up on a collusion course with us, at least we'll have plenty of time to study how the impact might play out, and hopefully conceive of a way to thwart it. Even so, its presence is an ominous reminder that space can be a dangerous place, and that impacts are inevitable over the long arc of time.