‘Planetkiller’ near-Earth asteroid spotted, largest in 8 years

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Astronomers have spotted three nearby terrestrial asteroids lurking undetected in the sun’s glare. One of the asteroids is the largest potentially dangerous object on Earth discovered in the past eight years.

The asteroids belong to a group found in the orbits of Earth and Venus, but they’re incredibly difficult to spot because the sun’s brightness shields them from telescope observations.

To avoid the sun’s glare, astronomers seized the opportunity to conduct their observations during the brief twilight window. An international team spied on the space rocks while using the Dark Energy Camera located on the Víctor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile.

Their findings were published Monday in The Astronomical Magazine.

One of the asteroids, called 2022 AP7, is 1.5 kilometers (0.9 mi) wide and has an orbit that could put it on Earth’s path in the future, but it’s hard for the scientists to know. when.

“Our twilight survey searches the area within the orbits of Earth and Venus for asteroids,” lead study author Scott S. Sheppard, an astronomer with the Earth & Planets Laboratory at the Carnegie Institution for Science, said in a statement.

“So far we have found two large near-Earth asteroids with a diameter of about 1 kilometer, a size we call planet killers.”

The other two asteroids, 2021 LJ4 and 2021 PH27, are on much safer orbits that pose no risk to Earth.

However, astronomers are intrigued by 2021 PH27, as it is the closest known asteroid to the Sun. As the space rock gets closer to our star, its surface reaches temperatures high enough to fuse lead.

Astronomers hunting asteroids face quite a challenge if they want to find space rocks in the inner solar system – including Mercury, Venus, Earth, Mars and the main asteroid belt. To avoid the harsh light of the sun, they only have two 10-minute windows each night to sweep the area with ground-based telescopes.

During twilight, astronomers still face the complications of a clear sky in the background due to the sun. And to search the inner solar system, their telescopes have to focus close to the horizon, which means looking through Earth’s thick atmosphere and its blurring effects.

If it sounds complicated for ground-based telescopes, observations of the inner solar system are impossible for space telescopes like Hubble and James Webb, because the sun’s heat and intense light could fry their instruments. the star.

The wide-angle capabilities of the Dark Energy Camera allowed astronomers to overcome their observational challenges and to view vast expanses of the night sky in great detail.

“Large areas of the sky are needed because the inner asteroids are rare, and deep images are needed because asteroids are faint and you’re fighting the clear twilight sky near the sun and the distorting effect of Earth’s atmosphere,” Sheppard said. . “DECam can cover large areas of the sky to depths not achievable with smaller telescopes, allowing us to go deeper, cover more sky and explore the interior of the Solar System in ways that have never been done before.”

Near-Earth objects are asteroids and comets with orbits that place them within 30 million miles (48.3 million kilometers) of Earth. Detecting the threat of nearby terrestrial objects that could cause serious damage is a primary focus of NASA and other space agencies around the world.

There are currently no asteroids directly impacting Earth, but more than 27,000 near-Earth asteroids of all shapes and sizes exist.

While NASA recently proved it can successfully change the motion of an asteroid in space with September’s Double Asteroid Redirection Test of DART mission, astronomers must first find space rocks that pose a threat to our planet. Instruments such as the Dark Energy Camera, as well as future space observatories such as the Near Earth Object Surveyorcan locate previously unknown asteroids.

Studying and understanding asteroid populations will also help scientists learn the distribution and dynamics of space rocks — such as how the sun’s heat can fracture and fragment them over time.

“Our DECam search is one of the largest and most sensitive searches ever conducted for objects within Earth’s orbit and near Venus’ orbit,” Sheppard said. “This is a unique opportunity to understand what types of objects lurk in the inner solar system.”