The near-Earth object was thought to be a small threat to Earth’s impact in 2068, but now radar observations have eliminated that.
After its discovery in 2004, asteroid 99942 Apophis was identified as one of the most dangerous asteroids that could affect the Earth. But that impact assessment changed how astronauts observed Apophis and its orbit better determined.
Now, the results from a new radar observation mission coupled with orbit analysis have helped astronauts determine that there is no risk of Apophis affecting our planet for at least a century.
Estimated about 1,100 feet (340 meters) in diameter, Apophis quickly gained a reputation as an asteroid that could pose a serious threat to Earth when astronomers predicted its imminent approach. on 2029. Thanks to observations in addition to the near-Earth (NEO) object, the impact risk in 2029 was again rejected, as well as the potential impact risk in another close way in 2036. Until this month, however, there was still little chance of impact in 2068.
When Apophis flew far away from Earth around March 5, astronomers took the opportunity to use powerful radar observations to accurately estimate the orbit around the sun, allowing them to control with confidence. any risk of impact in 2068 and long after.
These images of the Apophis asteroid were recorded by radio antennas at the Goldstone Deep Space Network facility in California and the Green Bank Telescope in West Virginia. The asteroid was 10.6 million miles (17 million kilometers) away, and has a resolution of 127 feet (38.75 meters) in each pixel. Credit: NASA / JPL-Caltech and NSF / AUI / GBO
“The impact of 2068 is no longer in the capacity scenario, and our calculations do not show any impact risk for at least the next 100 years,” said Davide Farnocchia of NASACenter for Near-Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory in Southern California. “With the help of recent optical observation and additional radar observations, the uncertainty in the Apophis orbit has fallen from hundreds of kilometers to just a few kilometers when projected to 2029. This has greatly improved the experience set in 2029 provides more certainty about future movement, so that we can now remove Apophis from the risk list. “
This animation reveals the orbital path of asteroid 99942 Apophis as it safely moves past Earth on April 13, 2029. The Earth’s gravity goes down slightly along the way as the 1,100-foot (340-meter-wide) object near the Earth comes within 20,000 miles (32,000 kilometers) of the surface of our planet. Dots are the many satellites made by humans orbiting our planet. The movement was accelerated 2,000 times. Credit: NASA /JPL-Caltech
Farnocchia referred to the Sentry Impact Risk Register. Maintained by CNEOS, the record keeps records of the few asteroids whose orbits are brought so close to Earth that impact cannot be denied. With the recent decisions, the Risk Register no longer includes Apophis.
Relying on ground-based optical telescopes and radar to help identify the orbit of all things near Earth to develop long-term risk assessments, CNEOS is measuring high-precision orbits such as support for NASA’s Office of Planning Defense Coordination.
Science Opportunity
To reach the latest Apophis numbers, astronauts turned to the 70-meter (230-foot) radio antenna at the Deep Space Network Communication Center near Barstow, California, to closely monitor Apophis movement. “Although Apophis recently made close contact with Earth, it was still close to 10.6 million miles [17 million kilometers] away. Nevertheless, we were able to get very detailed information about the distance to accuracy of about 150 meters [490 feet], ”Said JPL scientist Marina Brozovic, who led the radar campaign. “Not only did this initiative help us manage the risk of any impact, it set us up for a fantastic science opportunity. ”
This animation shows the path on Earth where Apophis can be seen on April 13, 2029. As the asteroid crosses the Atlantic Ocean, its path turns short from red to gray – and that is the closest time to it. After the nearest approach, the asteroid will move into the sky during the day and will no longer be visible. Cliu: Marina Brozovic / JPL
Goldstone also worked in collaboration with the 100-meter (330-foot) Green Bank Telescope in West Virginia to enable Apophis imaging; Goldstone spread while Green Bank acquired – a “bistatic” test that doubled the strength of the signal received.
Although radar images of Apophis appear pixelated, the images have a resolution of 38.75 meters (127 feet) per pixel, “which is a remarkable resolution, considering that the asteroid was 17 million kilometers away, or about 44 times the speed of the Earth-Moon, ”Brozovic added. “If we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York.”
This animation shows the distance between the asteroid Apophis and the Earth at the time of the closest approach to the asteroid. The blue dots are the many satellites made by humans orbiting our planet, and the pink represents the International Space Station. Cliu: Marina Brozovic / JPL
As the radar team further analyzes their data, they also hope to learn more about the shape of the asteroid. Previous radar observations have suggested that Apophis appears “bilobed,” or peanutlike. This is a very common shape among near-Earth asteroids larger than 660 feet (200 meters) in diameter; at least one in six has two lobes.
Astronomers are also working to better understand the rate of rotation of the asteroid and the axis it spins around (known as its spinning state). That knowledge will allow them to determine which side of the asteroid will face the Earth as it crosses the gravitational field of our planet in 2029, which could change that state and even be spinning. causing an “asteroid earthquake.”
On April 13, 2029, the asteroid Apophis will pass less than 20,000 miles (32,000 kilometers) from the surface of our planet – closer to the distance of a geosynchronous satellite. Through that close 2029 approach, Apophis will be visible to ground observers in the Eastern Hemisphere without the aid of a telescope or binoculars. It is also an unprecedented opportunity for astronauts to get a close look at the memory of a solar system that is now just a scientific curiosity and not an immediate threat to our planet.
“When I started working with asteroids after college, Apophis was the poster child for dangerous asteroids,” Farnocchia said. “We are very pleased to see him removed from the risk list, and we look forward to the science we could find while he was nearby in 2029.”