‘Potentially dangerous’ asteroid monster is biggest seen in years : ScienceAlert

‘Potentially dangerous’ asteroid monster is biggest seen in years : ScienceAlert

Astronomers peering into the twilight sky have spotted three previously unknown near-Earth asteroids. One of which is the largest potentially dangerous asteroid discovered in the last eight years.

It is about 1.5 kilometers (nearly 1 mile) in diameter and is in an orbit that may, in the future, bring it close enough to Earth to cause trouble.

The other two asteroids have paths that are completely, and safely, closer to the Sun than Earth’s orbit. That doesn’t make their discovery any less exciting, adding to an inventory of elusive objects that will allow us to better characterize the population of near-Earth objects.

Most of the minor planets in the Solar System – objects in direct orbit around the Sun that are neither planets nor comets – have been discovered at orbital distances greater than Earth. There’s the asteroid belt between Mars and Jupiter, the Kuiper Belt beyond Neptune where Pluto resides, and a bunch of other rocks like Greek and Trojan asteroids that share planetary orbits.

Not much has been discovered about the minor planets closer to the Sun, and for a very good reason. We must look toward a large, bright star whose blinding light makes small, faint asteroids pretty well undetectable. This means that we are more likely to find objects when we look away from the Sun in a direction that faces the outer Solar System.

To have a chance of spotting an inner Solar System asteroid, astronomers must wait until the twilight hours at dawn and dusk, when the Sun’s glow is mostly below Earth’s horizon, providing enough light to illuminate the inner asteroids that may be sweeping through space.

A research team led by astronomer Scott S. Sheppard of the Carnegie Institution for Science conducted such a search of large swathes of the sky closer to the Sun than Earth and Venus, leading to some exciting discoveries.

One was 2021 PH27, an asteroid with the shortest orbit of any asteroid found to date, just 113 days. Then there’s 2021 LJ4, which also circles the Sun entirely within Earth’s orbit. Both are known as Atira asteroids.

“So far we’ve found two large near-Earth asteroids that are about 1 kilometer in diameter, a size we call planet killers,” says Sheppard.

“There are probably only a few near-Earth asteroids of similar sizes to be found, and these undiscovered large asteroids likely have orbits that keep them within the orbits of Earth and Venus most of the time. Only about 25 asteroids with orbits completely in The Earth’s orbit has been discovered until now because of the difficulty of observation near the Sun’s glow.’

The third asteroid, 2022 AP7, is known as the Apollo asteroid. These are asteroids that have elliptical paths that take them from space closer to the Sun and beyond Earth’s orbit. With crossing our orbit, Apollo asteroids like 2022 AP7 could come close enough to our planet to risk a collision, winning them a classification of “potentially dangerous”.

There are over 2,000 potentially hazardous asteroids (the largest of which is about 7 kilometers in diameter) that we fortunately know about. If we know about them, we can model their trajectories and calculate if and when they are likely to come within dangerous range of Earth. With enough notice, we might be able to do something about it, like crash a spaceship into their surface to divert their course.

The discovery of new Atira asteroids is also important. Our understanding of the population of the Solar System’s smallest planets is based primarily on an inventory of space rocks at the farthest point. Having a better idea of ​​what’s in the inner Solar System can tell us more about the dynamics of the Solar System – how asteroids are transported to different regions, as well as more accurate models of the system’s evolution over time.

“Our DECam survey is one of the largest and most sensitive searches ever undertaken for objects within the orbit of Earth and near the orbit of Venus,” says Sheppard. “This is a unique opportunity to understand what kinds of objects are hidden in the inner Solar System.”

Interestingly, despite being more sensitive to smaller objects, the survey revealed a greater number of larger asteroids – those at least one kilometer across. This could mean that smaller asteroids are less stable in the inner Solar System or more prone to disintegration in the intense thermal and gravitational environment closer to the Sun.

It may just be that smaller asteroids are harder to spot, though. This makes an excellent case for more sensitive investigations in the future.

The paper describing the three asteroids has been published in The Astronomical Journal.

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