Scientists discover hidden ‘planet-killer’ asteroids in an elusive part of the solar system

Astronomers carefully scan the sky to asteroids that veer into the vicinity of Earth’s solar system. Butsome are masked.

Most asteroids – rubble leftovers from the formation of our solar system around 4.6 billion years ago – orbit the sun between Mars and Jupiter. Millions exist there. But in the inner solar system, asteroids are obscured by the sun’s blinding glare.

Now, a new study of space rocks in regions around the orbits of Venus and Mercury has spotted sizable asteroids in this elusive zone. One is nearly a mile wide, the type of “planet killer” rock that would decimate life on Earth. Fortunately, these rocks currently pose no danger to our planetnor will they for the foreseeable future – although over centuries, if not much longer, one of the asteroids’ orbits may change and potentially pose a threat.

To find these rocks, scientists must scan the sky at dusk (at dawn and dusk). They only have 10 minutes. At dusk, for example, they have a narrow viewing time after the sun has faded, but before that sun-facing sky disappears below the horizon.

“You don’t have a lot of time,” Scott Sheppard, an astronomer at the Carnegie Institution for Science, told Mashable. Sheppard led the new research on these twilight asteroid discoveries, which was recently Posted in The Astronomical Journal.

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A powerful telescope is needed to find these rocks. At 7,200 feet in Chile, scientists attached a camera, called the Dark Energy Camera, to a 4-meter (13-foot) wide telescope. It’s the largest camera on such a large telescope, Sheppard explained, and it can see large swaths of the sky. (Previously, astronomers used it to search really deep space objectsbeyond Pluto.) In a single image, scientists can see a region of sky encompassing about 11 full moons, as opposed to their twilight viewing capabilities of about two full moons.

So far, they’ve spotted three “Near-Earth Asteroids,” or NEAs. This doesn’t actually mean that they are literally “near” Earth, like the moon. It means they are relatively closebecause space is huge. These are rocks whose orbit can sometimes pass within 30 million kilometers of the Earth’s orbit around the sun (not necessarily the Earth itself), explains NASA.

The 4-meter Víctor M. Blanco Telescope is used to detect asteroids at dusk.
Credit: CTIO / NOIRLab / NSF/ AURA / D. Munizaga

The designation also does not mean that they are a threat. No known asteroids over 460 feet in diameter will threaten the Earth over the next century. Basically, the chances of a major impact in our lives are, to our knowledge, extremely low, Eric Christensen, the director of the Catalina Sky Survey in Arizona, searching for nearby asteroids, said Mashable earlier this year. As Mashable reported:

Impacts from objects about 460 feet in diameter occur every 10,000 to 20,000 years, and a “dinosaur killer” impact from a rock about half a mile in diameter or more occurs on time scales of 100 million years. Although something smaller can certainly surprise us, like the unexpected football-field-sized asteroid that has traveled only 40,000 miles of the Earth in 2019. That’s why it’s essential to watch. We may not be able to move away a rock that is approaching our planet – it’s an ambitious space business that takes years of planning – but we can brace for an impact and get people out of the way.

However, two of the three newly revealed asteroids are indeed “planet killer” in size. They probably came from the main asteroid belt, where most asteroids live. Near-Earth asteroids are in eccentric orbits that are stable for about a million years, Sheppard explained. But as they interact with the gravity of neighboring planets, their orbits can change. Eventually, they will most likely be ejected into the outer solar system.

“There is no danger.”

The largest of these objects, 2022 AP7, is expected to pass very close to Venus – a few thousand miles away – over the next 1,000 years. It could potentially hit Venus, although that probability remains low. “It’s unlikely to happen, but you never know,” Sheppard noted. Someday in the future, 2022 AP7 may also move into Earth’s orbit path. That’s why this colossal rock also deserves the designation of “Potentially Hazardous Asteroid” (meaning it’s over 460 feet wide and orbits within 4.6 million miles of orbit). or the Earth’s path around the sun.)

But that day, if it ever comes, is not anytime soon. This possibility is of the order of centuries or millennia. “There is no danger,” Sheppard stressed. “There are no interactions with Earth for the foreseeable future.”

Unfortunately, this reality won’t stop some news sites from running misleading and alarmist headlines about newly discovered space rocks, like, I’m not kidding: “Massive ‘planet-killer’ asteroid discovered – and it’s headed for we.” It makes no sense. In fact, whenever a news site or social media entity warns that an asteroid is “heading our way”, ignore it. These blatant efforts only seek to get your clicks. These dubious stories are published weekly. Yet NASA Literally Never Issued a Warning About a Threatening, Incoming Asteroid. If ever a space rock becomes a threat, NASA, the White House and political leaders will be involved.

To protect humanity from asteroid strikes, astronomers and planetary defense experts want to know where most near-Earth asteroids are heading. If it is projected that one day – perhaps decades or centuries from now – we will come unnervingly close to Earth, then we can do something about it. “You have to know what’s going to happen, when it’s going to happen, and how hard it’s going to hit,” Christensen told Mashable. Even a smaller asteroid, around 100 to 170 feet in diameter, could destroy a place like Kansas City, which is home to half a million people. Thus, surveys for large and “small” rocks are vital.

a chart showing the discoveries of asteroids near Earth

A chart showing near-Earth asteroid discoveries
Credit: NASA / Center for Near Earth Object Studies

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With enough time (years), Nasa recently proved that we have the ability to slightly alter the trajectory of an asteroid, and thus save the Earth from a potential disaster. The space agency recently crashed a vending machine-sized spacecraft into a stadium-sized asteroid. The science-fiction-like endeavor, called DART, or Double Asteroid Redirection Test, was a successful mission to see how civilization could alter the trajectory of a menacing asteroid, should one find itself on a collision course with our planet.

Of the largest class of near-Earth space rocks – those 1km wide or more – astronomers estimate they have found about 95% of them. They are not threatening. By November 2022, they had located 857. That means there are still 20 to 50 of these “planet killer” asteroids. Astronomers would like to find more, just to be safe. It means peering into the twilight sky.

“We didn’t find them all,” Sheppard said.

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