Telescopes have a tendency to focus outwards from Earth because of the Sun’s glare. Recent research has shown that Telescopic Surveys can find lots of information if they are prepared to look in the other direction.
Recent surveys have shown that near-Earth object or NEOs are being discovered, including asteroids like we’ve never seen. This could make a significant contribution to our understanding of the history and formations of planets in the Solar System.
Scott Sheppard, an astronomer at the Carnegie Institution for Science Washington DC, reported on NEOs discovered between Earth & the Sun.
Sheppard, in a column published in Science journal, writes “New telescopic studies are braving Sun glare and looking for asteroids towards the Sun at twilight.”
“These surveys have discovered many previously undiscovered asteroids inside Earth.”
These discoveries include the first asteroid known to have an orbit in Venus (named Aylo’chaxnim2020 AV2) and currently the asteroid which has the shortest orbital period (named 2021 PH27).
Although models predicted these asteroids would exist, telescopes such the Zwicky Transient Facility camera from California and National Science Foundation’s Blanco 4-meter telescope telescope in Chile – with the Dark Energy Cameras (DECams) attached – are beginning to actually locate them.
These asteroids are classified according to their orbits: there are the Atiras (with an orbit inside Earth), Vatiras [with orbits internal to Venus], and the hypothetical Vulcanoids (“with orbits inner to Mercury”).
From observations of craters located on moons or planets, it is clear that the number and frequency of NEOs has been stable over the last few billions of years.
NEOs could be replenished through their dynamically unstable orbits (of approximately 10 billion years) or unpredictable movements, as a result of exposure to sunlight.
Sheppard explains that movement is determined by the asteroid’s size, rotation, albedo, distance and distance from Sun. “The smaller and more sun-absorbed asteroids the larger their movement.”
These asteroid discoveries should allow us to better understand how they move and how their numbers have remained stable over extended periods of time. Scientists believe that most NEOs are asteroids dislodged in the main belt that runs between Mars and Jupiter.
Sheppard says that there could be inner reservoirs of NEOs that can provide steady supplies of Atiras as well as Vatiras. They may be able to replace asteroids spinning out into space, colliding with a planet, or getting destroyed by direct contact with the Sun.
The smaller the asteroids the more difficult it is to spot. Scientists estimate that 90% of the NEOs called “planet killers” – those larger than 1 kilometre (0.62 mile) – have been found.
Sheppard says that “the last few undiscovered 1-km NEOs most likely have orbits very close to the Sun, or high inclinations, which keeps them away from the fields for the main NEO Surveys.”
