Asteroid 99942 Apophis has been considered one of the most dangerous asteroids with the potential to impact Earth since its discovery in 2004. Now, scientists have revised that opinion after an accurate analysis of the asteroid’s orbit.
Previous predictions noted that the 1,110-foot-wide asteroid might be too close for comfort in 2029, 2036, and might have a slim chance of impacting Earth in 2068.
During that distant flyby, astronomers used radar observations to better monitor the asteroid’s orbit around the sun. Their results allowed them to rule out any risk of the asteroid impacting Earth in 2068. Previous concerns about 2029 and 2036 had already been shelved due to improved predictions and research.
“An impact of 2068 is no longer in the realm of possibility, and our calculations show no risk of impact for at least the next 100 years,” said Davide Farnocchia, a navigational engineer and researcher at the Center for Near Object Studies at NASA Earth (CNEOS), in a statement.
“Supported by recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029,” Farnocchia said. “This vastly improved knowledge of its position in 2029 provides more certainty of its future move, so now we can remove Apophis from the risk list.”
The CNEOS Center maintains a hazard list, tracking asteroids with orbits that bring them closer to Earth, close enough to cause concern about a possible impact. Scientists at the center use radars and telescopes to study near-Earth objects and understand the dangers they can pose to the planet.
The CNEOS Center is managed by NASA’s Jet Propulsion Laboratory in Pasadena, California.
To observe Apophis and remove it from the hazard list, astronomers used the Deep Space Network’s Goldstone radio antenna near Barstow, California. This dish is one of only three in the world that allow communications with spacecraft in deep space. The scientists also relied on a collaboration with the Green Bank Telescope in West Virginia.
“Although Apophis recently approached Earth, it was still nearly 10.6 million miles away,” JPL scientist Marina Brozovic said in a statement. “Still, we were able to acquire incredibly accurate information about its distance to the nearest 150 meters (490 feet). This campaign not only helped us rule out any risk of impact, it prepared us for a wonderful scientific opportunity.”
While the images appear blurry, the resolution is quite strong considering that the asteroid was about 17 million miles away, or 44 times the distance between Earth and the Moon, at the time.
“If we had binoculars as powerful as this radar, we could sit in Los Angeles and read the dinner menu at a restaurant in New York,” Brozovic said.
The data from this observation will help scientists learn more about the shape and speed of rotation of the asteroid. The current belief is that Apophis is shaped like a peanut.
Although Apophis poses no risk for the next century, it will encounter Earth’s gravitational field during its flyby on April 13, 2029, and will pass within 20,000 miles of the Earth’s surface. That’s closer than satellites orbiting the Earth and 10 times closer than the Moon.
Apophis will be visible to people in the eastern hemisphere with the naked eye, without the need for telescopes or binoculars. And astronomers will have the opportunity to study the asteroid closely.
“When I started working with asteroids after college, Apophis was the model for dangerous asteroids,” Farnocchia said. “There is some satisfaction in seeing that it was removed from the risk list, and we are eager to learn the science that we could discover during its next approach in 2029.”