Very large space rocks that fly within 4.6 million miles (7.5 million kilometers) of Earth’s solar orbit are known as potentially hazardous asteroids. (Image credit: Mark Garlick/Science Photo Library/Getty Images)
A large asteroid, approximately the length of more than 14 Central Bank Towers, is nearing Earth. However, unlike the planet-killed comet in the recent movie “Don’t Look Up,” this stony asteroid is expected to zoom safely and harmlessly past Earth on January 18th, 2022.
The asteroid – (7482) 1994 PC1 – was discovered on August 9th, 1994, by astronomer Robert McNaught at the Siding Spring Observatory in Coonabarabran, Australia. It is classified as a Potentially Hazardous Asteroid due to its size and relatively close known flybys of our planet. However, astronomers discovered earlier images from other observations that date to September 1974. An asteroid of this size strikes Earth approximately every 600,000 years. However, with 47 years of observations, the asteroid’s orbit is well established.
On January 18th, 2022, its closest approach to Earth is expected at 5:51 PM AST (21:51 UTC). This approach will be the closest for this asteroid for at least the next 200 years for which astronomers have calculated its orbit.
The speeding asteroid will pass 1.2 million miles (1.93 million km) from Earth, or about 5.15 times the Earth-moon distance. That’s a very safe distance, yet close enough to observe easily with a small backyard telescope.
According to EarthSky, the huge space rock is traveling at 43,754 miles per hour (19.56 kilometers per second) relative to Earth. The considerable speed will enable amateur astronomers to spot the fast asteroid. It will appear as a point of light, similar to a star, passing in front of background stars throughout the evening. Asteroid (7482) 1994 PC1 will shine at around magnitude 10. An object at 10th magnitude is a decent target for observers using a 6-inch or larger backyard telescope from a dark sky site.
How to see it
Sky enthusiasts using a small telescope pointed at the correct time and location might be able to spot asteroid (7482) 1994 PC1. For North America and those in the Caribbean, observers with backyard telescopes have the best opportunity to see the huge asteroid hours after the January 18th close approach. You should be able to detect the space rock’s motion thanks to its size and proximity. When the asteroid passes close to fixed background stars, the movement will be more noticeable.
Another good technique for spotting (7482) 1994 PC1 is to attach a camera to the telescope and take exposures of 30 to 45 seconds. An image exposed for several seconds shows the space rock’s motion as a streak of light, while shorter exposures reveal the asteroid as a point of light that appears in different locations in the images. Point the camera and telescope at a reference star or object in the trajectory of the asteroid. Using an app like Night Sky can help you find reference stars.
How common is this?
Asteroids are space rocks that are leftovers of the early solar system when our neighborhood was filled with objects like it. Tens of thousands of asteroids exist, but only a subset of them pass close enough to Earth to be termed near-Earth objects (NEOs). The 7482 (1994 PC1) flyby is thus very typical of the several dozen or so typical Earth flybys reported by media every year.
Any asteroids or comets (which can be very loosely defined as icy space rocks that are trailed by a tail) that come within 1.3 astronomical units (120.9 million miles, or 194.5 million km) qualify as NEOs, NASA says.
The agency had a mandate from the U.S. Congress to seek and report at least 90 percent of all NEOs 460 feet (140 meters) and larger by the end of 2020, following up from an earlier request to find even larger objects.
NASA recently launched a mission called Double Asteroid Redirection Test (DART) that will seek to alter the path of an asteroid’s moonlet in the fall of 2022. Another mission, called OSIRIS-REx (Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer), is en route from asteroid Bennu with a sample, which may help with future asteroid composition studies and aid defense measures.
As for seeking out new asteroids, NASA aims to put a dedicated mission into space by 2026, called NEO Surveyor. The agency says that in the decade after launch, NEO Surveyor should meet the Congressional request to seek out 90 percent of all NEOs 460 feet (140 meters) and larger.
Is this the largest asteroid to miss Earth?
Asteroid (7482) 1994 PC1, at approximately 1.3 kilometers wide, will pass 1.2 million miles (1.93 million km) from Earth, or about 5.15 times the Earth-moon distance. However, the largest near-miss occurred on September 1st, 2017, when 3122 Florence (1981 ET3) flew by Earth with an estimated size between 2.5 miles and 5.5 miles wide, and it will make another pass again on September 2nd, 2057.