What is it?
Asteroid 3200 Phaethon, discovered in 1983, is named for its close proximity. Phaethon was a Greek mythology figure who almost burned Earth because he drove a chariot of fire too close.
The asteroid is best known for being the parent body of the Geminid meteor shower, but NASA also calls it a mystery because they have several theories as to why it produces meteors, but they're not sure which is correct.
Is it going to be at a safe distance?
Absolutely. Though the asteroid itself is classified as potentially hazardous, this particular fly-by is at a safe distance of almost 6.5 million miles, scientists say.
"Since this is about 27 times the Earth-moon distance, any claim suggesting this pass by 3200 Phaethon is dangerous is both false and misleading," according to EarthSky.
Nonetheless, it's much closer to Earth than Venus, as EarthSky's chart shows.
What'll happen when 3200 Phaethon sweeps past Earth? https://t.co/5CpskSEcL8— EarthSky (@earthskyscience) December 10, 2017
Mysterious rock-comet - parent body of this week's Geminid meteor shower - will brush closely past Earth on Dec 16, just days after the Geminids' peak.
Will 2017 be a fantastic year for the Geminids? pic.twitter.com/epQopF1USW
Why is it called 'potentially hazardous?'
The asteroid has this classification because it is large enough to be threatening and has the potential to pass by Earth at a very close distance.
"This 'potential' to make close Earth approaches does not mean a PHA will impact the Earth. It only means there is a possibility for such a threat," NASA explains on its website.
Why is Saturday special?
Of the known near-Earth Potentially Hazardous Asteroids, 3200 Phaethon is the third largest, according to NASA's jet propulsion lab.
The lab has been and will be observing the asteroid for the days surrounding its approach, taking advantage of its proximity to obtain radar images in hopes of creating a 3D model.
Saturday marks the closest the asteroid will come to Earth since its discovery, and it won't come this close again until 2093, when it's expected to pass within 2 million miles of Earth.
How do I watch?
The asteroid can't be seen with the naked eye, according to EarthSky, but it can be viewed through a backyard telescope.
It will be visible by telescope for weeks, but the best time to watch is 6 p.m. ET on Saturday.
Here's a look at where it will appear in the sky.
How to see 3200 Phaethon: https://t.co/UtAa3J5EMr— EarthSky (@earthskyscience) December 14, 2017
This is the parent object of tonight's Geminid meteor shower: https://t.co/khb8mWRjK5
Meteors are easy to see, but you can't see 3200 Phaethon with the eye alone. But backyard telescopes can pick it up. pic.twitter.com/t6BycfTfEa
You can also watch a livestream on virtualtelescope.eu.