Astronomers have detected a "planet killer" asteroid which crosses Earth’s orbit and could slowly move closer and closer to us centuries from now.
With a diameter of about 1.1 km to 2.3 km, the asteroid, named 2022 AP7, is the largest object potentially hazardous to Earth to have been discovered in the last eight years, said the team.
It is also likely to be in the top 5 per cent of the largest potentially hazardous asteroids (PHAs) known.
The asteroid was detected by researchers using the Dark Energy Camera in Chile to look for objects within the orbits of Earth and Venus. They described their findings in an article in The Astronomical Journal published in September.
“Our twilight survey is scouring the area within the orbits of Earth and Venus for asteroids,” said lead author Scott Sheppard, an astronomer at the Earth and Planets Laboratory of the Carnegie Institution for Science.
“So far we have found two large near-Earth asteroids that are about 1 kilometre across, a size that we call planet killers,” he said in a statement.
In addition to 2022 AP7, the team also detected two other near-Earth asteroids, called 2021 LJ4 and 2021 PH27, which have orbits that safely remain completely interior to Earth’s orbit and shouldn’t ever come in its path.
Planet killer has ‘no chance to hit the Earth currently’
The term “planet killer” may sound scary but as far as 2022 AP7 goes, it will be staying “well away” from Earth for now, according to Sheppard.
“It has no chance to hit the Earth currently,” he told Euronews Next in an email.
As things stand, 2022 AP7 crosses Earth’s orbit. This makes it a potentially hazardous asteroid, he said.
However, the crossing occurs at a time when the Earth is on the other side of the sun, he explained, adding that this configuration will continue for the foreseeable future.
“Slowly, over time, the asteroid will start to cross Earth’s orbit closer to where the Earth is, but this will be centuries into the future, and we do not know the orbit of 2022 AP7 precisely enough to say much about its dangers centuries from now,” he said.
“But for now, 2022 AP7 will stay well away from Earth”.
The question of how to defend Earth from potential space object collisions recently made headlines when NASA confirmed that the spacecraft it smashed into an asteroid in September had succeeded in nudging the object from its natural orbit.
The DART mission (Double Asteroid Redirection Test) was the first test of a planetary defence system designed to prevent a potential doomsday meteorite collision with Earth and marked the first time humanity altered the motion of a natural body in space.
'It would be a mass extinction event'
If an asteroid 1 km or larger should strike Earth, this would have a devastating impact on life as we know it, said Sheppard.
Dust and pollutants kicked up into the atmosphere would remain there for years, likely meaning that the Earth’s surface would cool significantly from sunlight not getting to the planet, he said.
“It would be a mass extinction event like hasn’t been seen on Earth in millions of years”.
But Jay Tate, director of The Spaceguard Centre in the UK, said he was “not personally losing any sleep” over 2022 AP7.
“The chances of a collision with Earth are very small, and far in the future when we will have hopefully tested and deployed measures to change an asteroid’s path enough to turn a direct hit into a near miss,” he told Euronews Next.
Were a collision to happen, survivors of the impact would probably “slip back into the Middle Ages," Tate said, but he was optimistic recovery would be possible.
“We could expect to lose 25 to 40 per cent of the human population of the planet, but the critical failure will be the essential infrastructure that supports a modern civilisation,” he said.
“However, recovery will be possible assuming that we don't slip into a dystopian chaos”.
Asteroids lurking in the glare of the sun
The three newly announced asteroids are part of an elusive population lurking inside the orbits of Earth and Venus, said the research team. It’s a notoriously challenging region for observations, they said, because asteroid hunters have to contend with the glare of the sun.
But astronomers were able to tackle this by conducting surveys during two 10-minute windows at night.
“There are likely only a few [near-Earth asteroids] with similar sizes left to find, and these large undiscovered asteroids likely have orbits that keep them interior to the orbits of Earth and Venus most of the time,” said Sheppard.
“Only about 25 asteroids with orbits completely within Earth’s orbit have been discovered to date because of the difficulty of observing near the glare of the sun”.
Sheppard said that he and his team were not surprised by their findings, “since we know a few of these planet killer asteroids are still out there yet to be discovered”.
In fact, they expect to find a few more planet killers or larger near-Earth objects (NEOs) over the next year or two.
“To date, we think there are about 1,000 NEOs larger than 1 km in size,” he said, adding that researchers had uncovered about 95 per cent of these over the past decade.