Back in 2004, an asteroid was discovered and named 2004 MN4. It’s over 300 meters across, and at the time of the discovery, the calculated orbit caused much concern, as it seemed to bring the asteroid on a potential impact trajectory with Earth in 2029. Headlines, of course, went wild with sensational headlines, referring to 2004 MN4 as a “killer asteroid” and generally scaring the bejeezus out of the general population.

The team that discovered 2004 MN4 was composed of Roy Tucker, David Tholen, and Fabrizio Bernardi, and they used the Kitt Peak National Observatory in their search. They are also responsible for naming this small body Apophis. Now, I could get into the mythology about the name, but, let’s face it, the show Stargate SG-1 was still popular at the time, and a couple of the discoverers were fans. Since Apophis was the Big Bad for a couple of seasons, and he was always bent on the conquering and destruction of Earth’s human population, naming this potential impactor after him sounded like a good idea.

Just how big was the possibility of a collision with Earth in 2029 at the time of the discovery? Less than three percent. And that chance went down to zero once scientists started going through older images and refining Apophis’ orbit. Honestly, it’s hard to believe that we’re closer to that potential impact (remember, it’s not actually going to hit Earth) than we are to the discovery. Of course, as we saw last year, media coverage ignores asteroids when they’re no longer a threat, which means the scary stories stay in the public’s collective consciousness.

I still get asked about Apophis routinely.

But there is a secondary issue with Apophis in that it had a chance of passing through a “gravitational keyhole” that could change the orbital trajectory enough to become a threat in a 2036 pass. That, too, is no longer predicted to happen based on even further refined orbital calculations. The next potential close pass is 2068.

So why is Apophis in the headlines again? Headlines that are once again being a bit ridiculous. Demon asteroid. God of Chaos asteroid. Most intimidating asteroid. Jumbo. Well, Apophis had a close-ish pass of Earth last week, coming within 15 million kilometers and, more importantly, giving astronomers an opportunity to observe the asteroid and make even more refined calculations. 

Starting on March 3 and continuing through March 14th, the Green Bank Telescope has teamed up with NASA’s Goldstone to collect even more observations of Apophis. Planetary defense is a hot topic in the space world these days, and as Green Bank’s recent press release states: Predicting if there is a real chance of impact, decades ahead of time, gives scientists the opportunity to take action to manipulate the orbit of Apophis to avoid a collision in the future.

You see, that 2029 pass is still going to be, as a colleague said, “spicy” since Apophis will pass between the orbits of the Earth and Moon at about 32,000 kilometers and actually be at the same distance as some spacecraft in their orbits. So it’s important to understand as much as possible about Apohis’ orbit, and Green Bank’s observations are crucial. The telescope is using a bistatic radar, bouncing signals off the asteroid from Goldstone that are then collected by Green Bank’s dish. And since it’s all done in radio wavelengths, no one has to wait for nightfall.

Near-Earth asteroids like Apophis, who are considered to have some level of potential impact threat, are why missions like the upcoming Double Asteroid Redirection Test, or DART, are of vital importance. While the current threat calculations for Apophis are close to zero, they are not zero. And there are a lot of asteroids out there. Being able to deflect an asteroid even slightly could be the technology needed to save life on Earth from another Chixculub event.

Nonetheless, headlines can be misleading, and the bottom line is that Apophis is not a threat to life as we know it. Not now, and not in 2029. But we’ll keep updating you as NASA and other teams get more data.

More Information

Green Bank Observatory press release

NASA In Depth article