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Asteroid Apophis is not a threat to Earth for at least 100 years, says NASA

Asteroid Apophis is not a threat to Earth for at least 100 years, says NASA thumbnail

These images of asteroid Apophis were recorded by radio antennas at the Deep Space Network’s Goldstone complex in California and the Green Bank Telescope in West Virginia (Image: NASA/JPL-Caltech and NSF/AUI/GBO)

National Aeronautics and Space Administration (NASA) has ruled out the possibility of a planet-threatening event in 2068. Discovered in 2004 and named after an Egyptian God of chaos, asteroid 99942 Apophis was earlier predicted to pass by uncomfortably close to Earth. However, the new set of data and analysis suggests that the asteroid is not a threat to Earth for at least 100 years.

The new information came to light when astronomers used the asteroid’s flyby on March 5, 2021, as an opportunity to use powerful radar observations to estimate the celestial object’s orbit around the Sun.

“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” Davide Farnocchia of NASA’s Center for Near-Earth Object Studies (CNEOS) said in a statement.

“With the support of 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. This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”

Farnocchia says this “risk list” is the Sentry Impact Risk Table maintained by CNEOS, which includes all the asteroids with orbits close to Earth.

In order to track Apophis’ motion, astronomers used the 70-metre radio antenna at the Deep Space Network’s Goldstone Deep Space Communications Complex near Barstow, California. They also used the 100-metre Green Bank Telescope in West Virginia which showed imaging of Apophis. The two systems were used together in a “bistatic” experiment that doubled the strength of the received signal.

The radar imagery of Apophis may appear pixelated but one pixel covers 38.75 metres which is an impressive feat considering that the asteroid is 17 million km away from Earth. Apart from the asteroid’s orbit, astronomers also hope to learn about its shape with further analysis. The asteroid with a 200-metre diameter is expected to be peanut-shaped, just like most asteroids of this size.

The planet’s next flyby past Earth is estimated to take place on April 23, 2029. It will be 32,000 km away from our planet’s surface and will be visible to the naked eye in the Eastern hemisphere. Before that happens, astronomers wish to understand its rotation rate and the axis it spins around. This will help them understand how it will react to Earth’s gravitational field which can cause asteroid quakes.

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