A huge asteroid has the chance – albeit a tiny one – to collide with Earth in 2068, as a new analysis of the object shows.
Scientists say they have measured for the first time how a phenomenon known as “Yarkovsky acceleration” affects the orbit of the space rock – “99942 Apophis” after an ancient Egyptian “god of chaos” – as it orbits the sun, according to research presented at the 2020 virtual meeting of the American Astronomical Society’s Planetary Science Division.
Astronomers first discovered Apophis in June 2004 during observations made by the Kitt Peak National Observatory in Arizona.
It is estimated that the object has a diameter of more than 1,100 feet, which is almost as tall as the Empire State Building in New York City.
Since its discovery, scientists have closely observed the object, which is expected to make a number of approaches to Earth over the next century and beyond.
Originally, it looked as if the asteroid might have an uncomfortably high probability – 2.7 percent – of hitting Earth in 2029 or perhaps 2036.
Later observations of the space rock’s trajectory have shown that this is no longer possible, although Apophis will still pass so close to Earth on April 13, 2029 that it will be visible to the naked eye and even closer to our planet than some spaceships in orbit.
“We have known for some time that an impact on Earth is not possible while approaching Earth in 2029,” said Dave Tholen, an author of the latest research from the University Institute of Astronomy Hawaiʻi, who was part of the team that first discovered Apophis, in a statement.
The observations also suggested that Apophis’s close approach in 2068 would probably have no effect either.
Tholen said, however, that observations from the Subaru telescope on Mauna Kea in Hawai’i earlier this year showed how “the Yarkovsky Effect” had caused the asteroid’s orbit to deviate from its standard orbit by about 550 feet per year, which “is sufficient to keep the impact scenario of 2068 in play”.
The Yarkovsky Effect refers to a small but significant force that affects the orbits of asteroids and similar bodies in space. When these objects are heated by sunlight, they eventually release some of this energy, which creates a tiny amount of thrust.
Over long periods of time, this effect can lead to significant changes in the orbits of these objects. And in the case of Apohis, the effect affects the probability of an impact on Earth in 2068.
“Taking Yarkovsky into account, the scenario of an impact in 2068 is still in play. Small, but not zero,” Tholen told Gizmodo.
NASA’s Sentry Risk Table currently lists Apophis as the third highest threat to our planet among known near-Earth objects, with a probability of 1 in 150,000 that an impact could occur on April 12, 2068, although this figure does not take into account the latest findings.
The researchers say that the probability of an asteroid hitting the Earth is likely to change over time as more observations are made. In any case, astronomers will know long before the year 2068 whether an impact is likely.
If the asteroid collides with Earth, “it could wreak havoc on a continental scale, but not global annihilation,” Davide Farnocchia, another author of the research from NASA’s Jet Propulsion Laboratory, told Tekk.tv earlier.
An impact with an object of this size occurs on Earth only about once in 80,000 years, according to a calculator created by researchers at Imperial College London in the UK and Purdue University.