‘Asteroid found hiding in sun’s glare may one day hit Earth’
ASTRONOMERS HAVE discovered a giant asteroid hiding in the glare of the sun that might one day cross paths with Earth
The 0.9-mile-wide (1.5 kilometers) asteroid is the largest potentially hazardous
asteroid spotted in the past eight years and astronomers have dubbed it a “planet
killer” because the effects of its impact would be felt across multiple
continents. The asteroid, named 2022 AP7, managed to avoid detection for so
long because it orbits in the region between Earth and Venus.
To spot space rocks in this area, astronomers have to look in
the direction of the sun, and that is notoriously difficult due to the sun's
luminosity. For example, flagship telescopes such as the James Webb Space Telescope and the Hubble Space Telescope never look toward the sun,
as the star's brightness would fry their sensitive optics.
Because of that, astronomers have only a limited understanding
of the nature of asteroids lurking in this region, and sometimes, surprises may
happen.
In 2013, a much smaller asteroid, only 66 feet wide (20 m),
arrived from the direction of the sun completely without warning. That asteroid
exploded above the city of Chelyabinsk in southeastern Russia, shattering
windows on thousands of buildings.
"Only about 25 asteroids with orbits completely within
Earth's orbit have been discovered to date because of the difficulty of
observing near the glare of the sun," Scott S. Sheppard, an astronomer at
the Earth and Planets Laboratory of the Carnegie Institution for Science and
the lead author of the paper describing the new discovery, said in a statement.
The discovery of 2022 AP7, which
would be much more damaging than Chelyabinsk if it were to hit Earth, was only
possible thanks to the supersentive Dark Energy Camera (DEC) at the Cerro
Tololo Inter-American Observatory in Chile, which scans the sky during twilight
hours when these asteroids can be detected within two 10-minute periods each
day.
"So far we have found two large
near-Earth asteroids that are about 1 kilometer [0.6 miles] across, a size that
we call planet killers," Sheppard said.
Because the inner solar system asteroids are so hard to detect,
they are underrepresented in models of the overall solar system space rock population. However,
Sheppard believes that only a few unknown “planet killers” are left in this
difficult-to-observe region. The good news is that most of these unknown
asteroids likely follow orbits that keep them safely away from Earth.
“There are likely only a few (Near
Earth Asteroids) with similar sizes left to find, and these large undiscovered
asteroids likely have orbits that keep them interior to the orbits of Earth and
Venus most of the time,” Sheppard said.
In addition to the potentially
threatening 2022 AP7, astronomers discovered two other smaller space rocks in
DEC observations, one of which is the closest to the sun ever seen. Because of
its close proximity to the star at the center of the solar system, this
asteroid, named 2021 PH27, experiences the largest effects of general
relativity among all solar system objects, the scientists said in the
statement.
According to Albert Einstein's general theory of relativity, massive
objects warp spacetime, which can affect the motion of other objects in their
vicinity. These effects, which are very minor, can be observed as
irregularities in the orbits of planets and asteroids that cannot be explained
by Newtonian physics. Luckily, both, 2021 PH27 and the
third asteroid, named 2021 LJ4, follow orbits that don't intersect with that of
Earth.
Astronomers currently monitor over
2,200 potentially hazardous asteroids, space rocks that orbit dangerously close
to Earth and are wider than 0.6 miles (1 km). Such asteroids are of the
greatest concern as they would cause widespread destruction, potentially
affecting the entire planet. However, even much smaller asteroids would cause a
lot of trouble if they were to fall into densely populated areas. For example,
an asteroid only 160 feet wide (50 m) would cause damage over the entire city
of London if it were to explode above the city's center.
Fortunately,
astronomers are able to calculate asteroid trajectories for centuries into the
future and there are currently no known space rocks that should have us
worried. And by the time such a rock appears, the global space community hopes
to have tools in their hands to protect the planet.
In September, NASA's Double Asteroid Redirection Test (DART) mission
successfully changed the trajectory of the 525-foot-wide (160 m) asteroid
moonlet Dimorphos which orbits around its 2,560-foot-wide (780 m) parent rock,
Didymos. The success of this first-of-its-kind experiment suggests that as long
as we know early enough, we may be able to keep pesky asteroids at bay. (By
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