Astronomers spot largest potentially hazardous asteroid detected in last eight years AAS_Publishing
1. IntroductionThe small body population in our solar system interior to Earth's and Venus' orbits has not been extensively explored to date because of the difficulty in observing near the glare of the Sun. Twilight observations near Venus' orbit from ground-based Earth telescopes occur at a very high airmass, with a bright sky background, poorer than average seeing, and with the objects of interest being at high phase angles during a short observational window.
Data from the two space missions HELIOS and STEREO indicate the presence of a narrow ring of dust in Venus' orbit . This Venus co-orbital dust ring could come from a population of low-eccentricity stable Venus resonant co-orbital objects . These authors also found that about 8% of an initial population of Venus resonant objects remain stable for the age of the solar system.
Observations were obtained just after nautical twilight ends in the evening and just before nautical twilight begins in the morning. The Sun is usually between about −15 and −12 degrees below the horizon when the images are taken, giving about 10 minutes of observation time each twilight. Images were generally taken at airmasses between about 2.3 and 2.5, near the 23° elevation limit of the telescope.
We find that for the average field with a seeing of about 14, we detected about 50% of artificially implanted objects for mr ∼ 21.3 mag, which is what we take as the overall limiting magnitude of the survey, though different nights had different limiting magnitudes as shown in Table 1 and Figure 5, with some of the best seeing fields reaching nearly 22nd mag in depth.
To understand the orbital behavior of 2021 PH27, we ran a numerical orbital simulation using the SWIFT RMVS4 integrator described by Levison & Duncan and included the planets Mercury, Venus, Earth+Moon , Mars , Jupiter , Saturn , Uranus , and Neptune . The time step of the simulations was 0.1 days. We generated 1000 clones using the JPL covariance matrix of 2021 PH27 from 2022 April 18.
Though 2021 PH27 most likely came from the main asteroid belt, it is possible that it could have originated much closer to the Sun from a possible stable reservoir of small objects in resonance with Venus or even the hypothetical Vulcanoid population, which is a theoretical stable area of small bodies interior to Mercury .
Such a large object with an orbital period of only 5 yr and only a moderate inclination might be expected to have been found earlier by one of the NEO surveys that cover most of the sky exterior to Earth's orbit. Thus either 2022 AP7 has an orbit that aliases Earth's orbit, keeping it usually at a large distance from Earth when in the night sky near opposition, or 2022 AP7 may be brightening as it comes to perihelion from cometary effects.
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