On Thursday, October 12, asteroid TC4 will pass within 30,000 miles of the earth — a hair’s-breadth in terms of the vast expanse of the cosmos.
To put it in perspective, the moon orbits Earth at a distance of 250,000 miles.
Spotted by the deep space telescope Pan-STARRS 1 in October 2012, astronomers were able to monitor TC4 for a week before losing sight of it. With their observations, astronomers from the ESA were able to predict the asteroid’s near-earth approach.
Detected again in July of this year by the Very Large Telescope in Chile, NASA, the ESA and other national space agencies have closely monitored its subsequent course towards Earth.
Estimates of TC4’s size range between 30-100 feet. This makes the asteroid roughly the same size as the meteor that entered the Earth’s atmosphere undetected above Chelyabinsk, Russia in 2013. That meteor exploded spectacularly on entry, blowing out thousands of windows and injuring hundreds.
NASA plans to closely observe TC4’s approach, tracking its exact course as it passes so close to Earth offers an invaluable real-life opportunity to test their equipment and theories.
Earth and space-based telescopes will also examine TC4 in order to determine its exact mineral composition. Insights about near-Earth objects gleaned from TC4 will then be incorporated into NASA’s planned Planetary Defense System.
NASA’s Double Asteroid Redirection Test (DART) system remains more conceptual than a reality, but its success will depend on precise real world observations collected during a near pass like TC4’s. DART is a kinetic impactor; after launch it will accelerate towards its target, eventually crashing into it millions of miles from Earth with enough force to divert it off a collision course.
DART’s first live fire test is a planned intercept with the 150-meter diameter “moonlet” of the binary near-Earth asteroid Didymos in October 2022. Colliding at a speed of 6 kilometers per second 11 million kilometers away from Earth, DART should alter the moonlet’ s orbital speed by a fraction of one percent.
At such remote distances, even minor changes in an object’s trajectory should sufficiently divert it from a catastrophic impact with Earth.
While NASA is confident there is no risk of a TC4 impact this time, its close brush with Earth’s gravity will alter its future trajectory in ways that are difficult for existing models to predict. Indeed, astronomers are already examining a potential future TC4 impact in 2050.
According to the Center for Near Earth Object Studies (CNEOS), depending on its exact composition, a TC4 sized asteroid would most likely burn up in Earth’s atmosphere. An asteroid twice its size, though, would likely pass through intact causing significant, if localized destruction.
Predicting the location of a surface impact early and accurately enough to allow evacuations and preparations would prove crucial in such a scenario. Astronomers hope observing TC4 will enhance our understanding and improve the precision of their models.
Photo credit: NASA
