Julian Date: 2459304.18
2020-2021: CIII
THE DAILY ASTRONOMER
Tuesday, March 30, 2021
Exploratorium XXXV: Adophis Misses
Location
99942 Adophis
Time
December 27, 2004
Be careful!
You're now standing on an asteroid that is approximately as long as the Empire State Building is tall. Granted, this little rock serves as a pleasant walking platform. (One can even peer over the edge to see the starfield below.) However, we assume the severe risk of pushing ourselves off the surface merely by taking a single step. Realize that our muscles are accustomed to counteracting the gravitational pull of the entire planet Earth. Here, the surface gravity is a minuscule fraction of Earth's. And,
because every action has an equal and opposite reaction,
the simple act of pressing your foot down would likely propel you upward. You'd then lazily move along a parabolic arc above the asteroid for such a long time you'd likely die of thirst before returning to the surface. So, gentle footfalls, folks.
We're here on the asteroid 99942 Adophis on December 27, 2004 because this tumbling space mountain has made history today. Today (12/27/04). Adophis earned a 4 on the Torino Scale.
Named after Turin (Itay), the location where the previous scale known as the "Near-Earth Object Hazard Index" was revised in 1999, the Torino Scale assigns numbers to outer space objects in accordance to the danger they pose to our planet. For instance, an object with a 0 rating has either no chance or collision or such a small chance that the probability approaches zero. This rating also applies to the innumerable micrometeorites that descend through Earth's skies. While these little motes do strike the planet, they won't collide with its surface. A 1 rating -which isn't much different- refers to an asteroid predicted to make a close pass to Earth without posing any risk of impact.
The ratings 2 - 4 are grouped together under the heading, "Merits attention by astronomers." A 4-rating, the highest yet assigned to any asteroid, refers to a 1% or greater chance of a collision capable of causing regional devastation. Attention by officials may be warranted if the predicted collision is approximately one decade in the future.
On December 27, 2004, 99974 Adophis earned a 4 rating! Around that time astronomers predicted that it had a 2.7% percent chance of hitting Earth on April 13, 2029. For this reason, we've decided to be here on December 27, 2004, when this became the most famous asteroid: the one many feared would bring devastation to Earth! Alas, much to the relief of everyone except, perhaps, for procrastinating tax filers, subsequent observations determined that a 2029 impact was not going to ccur. Some astronomers believed it was possible that Adophis would strike Earth on April 13, 2036 if Adophis happened to pass through a strange little space known as a gravitational keyhole.
A gravitational keyhole is a small region in space where a planet's gravity could alter a passing object's trajectory so as to make a future impact much more likely or even certain. Earth is surrounded by many such little keyholes, some of which are less than a mile in diameter.
Adophis did not venture anywhere close to this keyhole and so a 2036 impact is also highly unlikely. In March 2021, astronomers operating the Goldstone Deep Space Communications Complex refined the orbital calculations of Adophis and concluded that the asteroid will not pose a threat to Earth for at least the next 100 years. Adophis now rates a 0 on the Torino scale and, consequently, will lapse back into obscurity: just another member of the vast community of known asteroids.
Although the improbability of an imminent collision might make us complacent, we shouldn't forget that Earth moves rapidly through a veritable shooting gallery of asteroids. On average an Adophis-sized asteroid strikes Earth about once every 80,000 years. Smaller asteroid collisions are even more frequent, though admittedly still not common. Hopefully, by the time astronomers discover an asteroid that will hit Earth, humans will be able to avert the collision.
We'll wait and see....
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