Apophis poses no threat to Earth for at least next 100 years
Radar observations of asteroid Apophis in early March allowed scientists to determine that it has no chance of hitting Earth in the next 100 years.
With a diameter of about 370 meters, the near-Earth object 99942 Apophis, was believed to pose a slight risk of hitting Earth in 2068, but the new radar observations have completely ruled out the possibility of any such impact.
Apophis closely approaches Earth in roughly every eight years or so. Soon after its discovery in 2004, it caused some concerns when initial observations suggested it had 2.7% chance of impacting Earth in 2029.
The asteroid will pass exceptionally close at a distance of just 31,643 kilometres from Earth’s surface on 13 April 2029. For comparison, Moon’s average distance from Earth is 380,000 kilometres.
Despite such a close flyby, 2029 strike was eventually ruled out by scientists, as was the potential impact risk posed by another close flyby in the year 2036.
However, since at that stage Apophis’ orbit and characteristics were not known in greater details, so the possibility of a strike for future flybys remained unclear.
But, gradually its orbit became better determined as astronomers continuously tracked and observed Apophis while it moved through the space.
In 2020, on the basis of its “Yarkovsky acceleration” measurements, scientists determined the asteroid’s “2068 flyby” the most dangerous of all known flybys.
Yarkovsky acceleration is a force that effects the orbital motion of asteroids/meteoroids. It is caused by Sun, when it heats up the objects, generating a small but significant amount of thrust.
In Apophis’ case scientists found that Yarkovsky acceleration is generating a drift of 170 meters per year. That means at the rate of 170 m/year, Apophis is drifting from its expected position in its path.
The other major factor affecting Apophis’ orbit is “2029 flyby”. At that insanely close approach, Earth’s gravity will affect the asteroid’s path.
With these two factors in check, scientists performed more calculations to measure Apophis’ orbit. The results showed an impact chance of one in 150,000. But, given the size of asteroid and considering how much damage it could cause, one in 150,000 is still concerning.
When on 5 March 2021, Apophis came within 16.9 million kilometres of Earth, this gave scientists a rare opportunity to refine its path around the Sun with more accurate precision.
Scientists than added this new data to the previous calculations, ultimately ruling out any impact risk in 2068 and long after. In short, Earth is now safe from Apophis for at least next hundred years.
In order to arrive at these latest Apophis calculations, scientists needed to precisely monitor its motion. So for that, they used 70-meter radio antenna at NASA’s Deep Space Network’s (DSN) Goldstone facility.
According to scientists, even though Apophis’ recent close approach from Earth was at about 16.9 million kilometres away, yet they were able to acquire its location to an incredibly precise distance of 150 meters.
Goldstone facility also operated in a collaboration with the 100-meter Green Bank Telescope located in West Virginia, in order to obtain imaging of Apophis asteroid.
The Goldstone facility was transmitting a radar signal while Green Bank Telescope was receiving the reflection.
Although the resulting radar imagery appears pixelated, but still have a resolution of about 38.75 meters per pixel, which is an outstanding resolution, given the fact that Apophis was 16.9 million kilometres away.
As explained by scientists, with a binocular as powerful as this radar, one can read a dinner menu at a restaurant in New York while sitting in Los Angeles.
This new imagery will boost our understanding about the asteroids. The further analysis of new observations will help scientists to explore more about the asteroid’s shape. Previous observations have suggested that Apophis could have a peanut-like shape.
Scientists also want to learn about Apophis’ rotation rate and its spin state. This will help them to calculate the orientation Apophis will have with Earth as it flies by in 2029. This close encounter could change the asteroid’s spin state or could even cause “asteroid quakes” on its surface.
On 13 April 2029, at its closest approach, Apophis will be at 31,643 kilometres away from Earth, which is closer than the distance of geosynchronous satellites.
At this distance, Apophis will be visible to the unaided eye from some areas of Australia, western Asia, Africa, and Europe.
Originally published at https://theabsolutecosmos.blogspot.com.