Astronomers spot ‘planet killer asteroid’

Source: By Rahel Philipose: The Indian Express

A team of astronomers has discovered three massive near-Earth asteroids hiding in the glare of the Sun. Of these, one called 2022 AP7 is believed to be the largest planet killer-sized asteroid to be spotted in nearly a decade, and is “potentially hazardous” to Earth.

According to a study published in The Astronomical Journal, the three asteroids are from a group that is found within the orbits of Earth and Venus. However, they are tough to spot as the brightness of the Sun shields them from telescope observations.

In an interview with CNN, the lead author of the study, Scott S Sheppard, an astronomer at the Earth and Planets Laboratory of the Carnegie Institute of Science in Washington DC, said an asteroid like 2022 AP7 could have “a devastating impact on life as we know it” and could potentially lead to a “mass extinction event”.

So, how did they spot the asteroids?

Since they were concealed by the Sun’s glare, the astronomers conducted their observation during twilight hours — a brief but favourable 10-minute window every night. They used a Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile.

With the high-tech camera, a programme of the US’ National Science Foundation’s (NSF’s) NOIRLAB, they were able to capture large swathes of the sky with immense sensitivity. The camera was originally built to carry out a Dark Energy Survey, conducted by the US Department of Energy and the NSF between 2013 and 2019.

Apart from dealing with the glare of the Sun, the astronomers also had to tackle another major issue — since the asteroids are close to the horizon, they are blurred and distorted by the Earth’s atmosphere.

Asteroids that are further away from the Sun are easier to detect.

What do we know about the asteroids?

Scientists have so far disovered only around 25 asteroids with their orbits within Earth’s orbit.

Of these, Sheppard’s team has now discovered three. “We have found two large near-Earth asteroids that are about 1 kilometre across, a size that we call planet killers,” Sheppard said, speaking about two of the three discovered asteroids. The two — 2021 LJ4 and 2021 PH27 — have orbits that are safely constrained inside the limits of Earth’s orbit. At less than a kilometre in diameter, 2021 LJ4 is the smallest in size. The asteroid, 2021 PH27, is the closest known asteroid to the Sun. Due to this; its surface gets hot enough to melt lead.

What about the 2022 AP7 asteroid?

Among the three asteroids, one in particular stands out — the 1.5-kilometre-wide 2022 AP7 asteroid has an orbit that may someday put it on a collision course with our planet.  At present, researchers have little information about the asteroid, including further details on its possible trajectory and its composition.

Is there an immediate threat to Earth?

At present, the asteroid only crosses the Earth’s orbit while it is on the opposite side of the Sun i.e., when the Sun comes between the Earth and the asteroid. This will continue for several centuries as it takes the asteroid about five years to orbit the sun, according to a CNN report.

An asteroid of this size could have a “devastating impact”, Sheppard said, as the Earth’s atmosphere would be inundated with dust and pollutants for years, preventing sunlight from entering.

Over time, its orbital movement will slowly evolve to be more in sync with Earth’s. As of now, however, Sheppard has said it will “stay well away from Earth”, according to CNN.