Asteroid Found In Sun's Glare and Moving to Earth's Path
Source: (
https://bit.ly/3Ds6JeI)
"To date we have discovered two rare Atira/Apohele asteroids,
2021 LJ4 and 2021 PH27, which have orbits completely interior
to Earth's orbit. We also discovered one new Apollo-type Near
Earth Object (NEO) that crosses Earth's orbit, 2022 AP7. Two
of the discoveries have diameters ?1 km. 2022 AP7 is likely the
largest Potentially Hazardous Asteroid (PHA) discovered in about
eight years."
In the abstract of the paper, "A Deep and Wide Twilight Survey
for Asteroids Interior to Earth and Venus," astronomer and lead
author Scott Shepherd, an astronomer at the Earth & Planets
Laboratory of the Carnegie Institution for Science in Washington,
DC, explained three new asteroids have been discovered orbiting
the Sun within or almost within the orbit of Earth. Two are Atira
or Apohele asteroids -- interior-Earth objects (IEOs) whose orbits
have an aphelion (farthest point from the Sun) smaller than Earth's
perihelion (nearest point to the Sun), which is 0.983 astronomical
units (AU). These IEOs are far more rare than the Aten, Apollo
and Amor near-Earth asteroids which are just outside of Earth's
orbit.
"There are likely only a few NEAs 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.
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."
The New York Times is one of the mainstream media sites using
the "Planet Killer" headline to describe the deadly potential of 2022
AP7. Let's start with its size. To put it in perspective, at almost
a mile or 1.5 km in diameter, it dwarfs the 525-foot-wide (160 m)
asteroid moonlet Dimorphos which was bumped recently by NASA's
Double Asteroid Redirection Test (DART) and had its trajectory
altered as a test of our still infantile asteroid deflection system.
Add to that the recent memory of the tiny 66 feet wide (20 meters)
meteorite which exploded in 2013 above the city of Chelyabinsk
in southeastern Russia, shattering windows on thousands
of buildings - that space rock was also hidden by the glare
of the Sun.
Is it time to panic? Do we need a bigger DART?
"Today, AP7 is somewhere between Mars and Jupiter, and given
its five-year orbit, spends most of its time out of our way. When
it next intersects Earth's path, we'll be minding our own business
on the opposite side of the Sun."
Cosmos Magazine gives us a non-mainstream media and more
levelheaded perspective on 2022 AP7. Its path-crossing orbit
currently has it two astronomical units (AU) away from Earth - that's
twice the distance between Earth and the Sun or just under 300
million km or 186 million miles. That still puts it in the near-Earth
category, but calculations show its times crossing through Earth's
orbit in the next 100 years will occur far away from the planet.
However, there is plenty of time after that, and they will be making
further calculations and models to determine if and when 2022
AP7 will live up to its "Planet Killer" nickname.
"Our DECam survey is one of the largest and most sensitive searches
ever performed for objects within Earth's orbit and near to Venus's
orbit. This is a unique chance to understand what types of objects
are lurking in the inner solar system. After 10 years of remarkable
service, DECam continues to yield important scientific discoveries
while at the same time contributing to planetary defense, a crucial
service that benefits all humanity."
To answer that other question most certainly bothering you
yes,
there could be more "Planet Killer" asteroids hiding in the Sun's
glare in an inner-Earth orbit. Scott Shepherd says he's confident
that the Dark Energy Camera (DECam) mounted on the Victor M.
Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory
in Chile, will find them in the 10 minute periods it opens its lenses
to stare at the Sun. Let's hope he's right. SInce they can only be
seen in the twilight, should this be called "The Twiligt Zone"? Or
is that a self-fulfilling prophesy?
In the meantime, it seems like an ironic coincidence that the most
dangerous asteroids may come from the inside of our solar system,
rather than the outer areas. That is the same thing we're finding out
about our own planet - we need to spend more time studying the
oceans and the depths of the mantle where greater dangers to our
planet could lurk. Can they point that DECam at the bottom
of the Pacific?
