‘Potentially dangerous’ monster asteroid largest seen in years : ScienceAlert

‘Potentially dangerous’ monster asteroid largest seen in years : ScienceAlert

Astronomers peering into the twilight sky have found three previously unknown near-Earth asteroids. One of them is the biggest and potentially dangerous an asteroid discovered in eight years.

It measures roughly 1.5 kilometers (almost 1 mile) in diameter and is in an orbit that could bring it close enough to Earth in the future to pose a problem.

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

The majority small 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’s. In between is the asteroid belt mars and JupiterThe Kuiper belt beyond Neptune that houses Pluto, and a bunch of other rocks, like the Greek and Trojan asteroids that share planetary orbits.

Fewer planets have not been discovered closer to the Sun, and for a very good reason. We have to look towards a big, bright star, whose blinding light makes the small, dim asteroids quite invisible. 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 to spot an inner Solar System asteroid, astronomers need to wait for dawn and dusk when the Sun’s glare is mostly below Earth’s horizon, providing enough light to illuminate inner asteroids that might be moving through space.

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

One was 2021 PH27, the asteroid with the shortest orbit of all asteroids found at only 113 days. Then there’s 2021 LJ4, which also orbits the Sun entirely within Earth’s orbit. Both are known as Atira asteroids.

“So far we have found two large near-Earth asteroids about 1 kilometer in diameter, the size we call planet killers,” Sheppard says.

“There are probably only a few near-Earth asteroids of similar sizes left to find, and these large undiscovered asteroids probably have orbits that keep them inside the orbits of Earth and Venus most of the time. Only about 25 asteroids with orbits completely inside Earth’s orbit have been discovered to date because difficulty in observing near the glare of the Sun.”

The third asteroid, 2022 AP7, is known as an Apollo asteroid. These are asteroids that have elliptical paths that take them from space closer to the Sun to outside the Earth’s orbit. By crossing our orbit, Apollo asteroids like 2022 AP7 could come close enough to our planet to risk collision, earning they are classified as “potentially dangerous”.

They are over 2,000 potentially hazardous asteroids ( of which the largest is about 7 kilometers in diameter) that we fortunately know about. If we know about them, we can model their orbits 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, for example crash a spacecraft into their surface to divert their course.

It is also important to discover the new Atira asteroids. Our understanding of the Solar System’s minor planet population is primarily based on the inventory of space rocks in the far reaches. 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 for objects within Earth’s orbit and near the orbit of Venus” Sheppard says. “This is a unique opportunity to understand what kinds of objects lurk in the inner solar system.”

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

However, it could be that smaller asteroids are harder to detect. This makes a great case for more sensitive surveys in the future.

A paper describing the three asteroids was published in The Astronomical Journal.

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