Remember that asteroid they discovered back in 2004 that they used to scare everyone to death, claiming that it would just might impact our planet in a few years and cause massive damage to the Earth? Well, it's back in the news, because it's here. And that asteroid, designated 99942 Apophis, will do a friendly fly-by on Jan. 9.
Why friendly? Because on this go-round, it will pass within some 9 million miles from the Earth, according to NASA. Not particularly close, but close enough in this and in future flybys that the near Earth asteroid was designated a "Potentially Hazardous Asteroid." The initial concern was never that it would hit us sooner but later.
When Apophis (named after the Egyptian demon Apep (Apophis in Greek) the Uncreator, purveyor of darkness and chaos, and the nemesis of Ra the Sun God) was first discovered, calculations pointed to a good possibility of the massive asteroid slamming into the Earth in 2029. With a few years and more accurate calculations made through observation, the chances have grown considerably less. And still, current calculations put the asteroid passing close to the Earth in 2029. But there is a certain portion of space that Apophis could fly through that would set the Earth up for a very close flyby on April 13, 2036. In fact, it could soar through -- inside geosynchronous orbit distance -- at about 21,000 miles above the Earth.
And yet, scientists cannot be completely certain that the asteroid will maintain that kind of distance due to something called as the "Yarkovsky Effect," a process whereby the heating and cooling of the surface of the asteroid as it rotates in its orbit past the Sun affects the space rocks orbit. Deviations caused by the Effect could alter the asteroid's path, resulting in the asteroid passing closer to or farther away from the Earth during each pass.
If Apophis were to actually collide with Earth, it could potentially do great damage. It's size -- 270 meters (855 feet) in width -- and speed could produce an impact equal to 510 megatons, according to NASA. In comparison, the Tunguska Incident (in Russia) was a 3-10 megaton impact and it flattened trees for over 800 miles, was equal to about a thousand Hiroshima-sized atomic bombs, and would have destroyed a large metropolis. Apophis would do roughly 50 times as much damage if it impacted on land and would cause a massive tsunami (resulting in untold amounts of catastrophic damage) if it crashed into an ocean.
In the meantime, scientists will observe and measure and calculate. And hope that the Yarkovsky Effect does not push Apophis closer to future collision course with the Earth.
The flyby can actually be observed from the Earth via large telescopes (but, unfortunately, not your common back yard variety). For those without the mechanical means to view, the Slooh Space Camera will track the near-Earth asteroid online on Jan. 9 and 10.