In particular, recent surveys have revealed NEOs or NEOs, including asteroids that we have not seen before. When it comes to understanding the history of the solar system and the formation of planets, finding and tracking these asteroids can be crucial.
Astronomer Scott Sheppard, of the Carnegie Institution for Science in Washington, D.C., reports some near-Earth objects being found between the Earth and the sun — and the discoveries are still in their infancy.
Sheppard wrote in a column with the latest Sciences magazine.
“These surveys found many previously undiscovered asteroids inside Earth.”
The discoveries include the first asteroid with an inner orbit around Venus (named ‘Ayló’chaxnim 2020 AV2)’, and the asteroid that currently has the shortest known orbital period around the Sun (named 2021 PH27).
While modeling predicted that these asteroids should be present, telescopes like the Zwicky Transient Facility Camera in California and the National Science Foundation’s Blanco 4-meter telescope in Chile—with the attached Dark Energy Camera (DECam)—are now beginning to actually find them.
These asteroids are classified based on their location: we have Atiras (with inner orbits on Earth), Vatiras (with inner orbits to Venus), and hypothetical Vulcanoids (with inner orbits from Mercury).
What we know from observations of craters on planets and moons is that the numbers of NEOs have been constant over the past few billion years.
Given their dynamically unstable orbits (which are about 10 billion years old) and unexpected motions (caused by exposure to the sun), this suggests that NEOs are regenerating in some way.
“Motion depends on the asteroid’s rotation, size, albedo, and distance from the Sun,” writes Sheppard. “The smaller the asteroid and the more sunlight it absorbs, the more it moves.”
These asteroid discoveries should help us understand more about their motion, and how the number of NEOs manage to stay constant over long periods of time. Scientists believe that most NEOs are asteroids that have been ejected from the main belt between Mars and Jupiter.
However, Sheppard points out that there may also be stable internal deposits of NEOs, providing a steady supply of Atiras and Vatiras. These asteroids may be fed and replaced by asteroids that pop out into the wider solar system, collide with a planet, or are obliterated by close contact with the sun.
The smaller the asteroids, the more difficult it is to detect them, of course. Scientists estimate that about 90 percent of the so-called “planet-killer” near-Earth objects have already been found – those that are 1 kilometer (0.62 miles) or more across.
“It is likely that the past few kilometer NEOs have orbits close to the Sun or with high inclinations, which would put them far from the domains of major NEO surveys,” Sheppard wrote.
The perspective was published in Sciences.