An international team of astronomers has just published in ‘The Astronomical Journal’ the hdiscovery of a large asteroid that remained hidden by the glare of the Sun and that could become a threat to Earth.
Cataloged as 2022 AP7, the space rock has 1.5 kilometers in diameter y it is the largest potentially dangerous asteroid detected in the last eight years. Astronomers consider it a ‘planet killer’ because the effects of its impact would cause great devastation and would be felt across multiple continents.
2022 AP7 had not been detected until now because it orbits in the inner solar system, specifically in the region of space that is right between Earth and Venus, and to be able to see anything in that area it is necessary to look directly at the Sun, something extremely difficult due to its great luminosity. Iconic telescopes like James Webb o el Hubblethey never look in that directionsince the brightness of our star would irremediably damage its delicate optics.
For this reason, many of the asteroids that threaten us from that region remain hidden, and sometimes they bring us unpleasant surprises. For example, the famous Chelyabinsk meteorite, which in 2013 exploded right over that Russian city and caused more than a thousand injuries, came precisely from there.
A difficult observation
“To date,” explains Scott S. Sheppard, lead author of the article, “only about 25 asteroids have been discovered with orbits that are entirely within Earth’s orbit due to the Difficulty observing near the glare of the Sun».
The discovery of 2022 AP7, which would be infinitely more damaging than Chelyabinsk if it hit Earth, was only possible thanks to the super-sensitive Dark Energy Camera (DEC) at the Cerro Tololo Inter-American Observatory in Chile, which scans the sky during the hours twilight, when these asteroids can be detected for a short period of time.
And it is that, due to the brightness of the sun, finding asteroids in the inner solar system is a huge and overwhelming challenge. To inspect this area without rendering instruments unusable, astronomers only have two short 10-minute observing windows each night, and they also have to deal with a bright background sky due to glare from the sun. To top it off, such observations are carried out very close to the horizon, which means they have to be made through a thick layer of Earth’s atmosphere, which can blur and distort your observations.
“So far,” Sheppard continues, “in addition to this one we have found two other large near-Earth asteroids that are about a kilometer wide, the ones we call planet killers».
Because these asteroids are so difficult to detect, they are poorly represented in space rock population models of the Solar System. Still, Sheppard believes there are only a few undiscovered ‘planet killers’ left in this hard-to-observe region. According to the astronomer, indeed, most of these unknown asteroids probably follow orbits that always keep them away from our planet.
“It is likely that we only have a few asteroids left to find “Near-Earth asteroids with similar sizes,” Sheppard explains, “and these yet-to-be-discovered large asteroids probably have orbits that keep them inside the orbits of Earth and Venus most of the time.”
potentially dangerous
Currently, astronomers monitor more than 2,200 potentially dangerous asteroids at any given time. Those of more than one km, as is the case of 2022 AP7, are capable of causing widespread destruction that affects the entire planet. but even smaller asteroids would cause a lot of trouble if they fell into densely populated areas. For example, an asteroid only 50 m wide would cause serious damage throughout the city of Madrid if it exploded near the center.
The new research also represents an important step in understand how small bodies are distributed in our solar system. Asteroids further from the Sun than Earth are easier to observe, and thus tend to dominate current theoretical models of asteroid populations. Finding more ‘inner’ asteroids therefore helps to fill that gap while also allowing astronomers to understand how gravitational interactions and heat from the Sun can contribute to their fragmentation.
“Our DECam survey,” says Sheppard, “is one of the most large and sensitive ever made for objects within the orbit from Earth and close to the orbit of Venus. This is a unique opportunity to understand what kinds of objects lie in wait for us in the inner solar system.”