C/2023 A3 - Tsuchinshan-ATLAS

Comet C/2023 A3 (Tsuchinshan-ATLAS) was first detected independently by both the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey in Hawaii and the Tsuchinshan Observatory in China in January 2023, this comet made its closest approach to the Sun, or perihelion, on October 2024.

Upon discovery, C/2023 A3 was located beyond the orbit of Jupiter and was classified as a long-period comet, likely originating from the Oort Cloud—a distant, spherical shell of icy bodies surrounding our solar system. Early photometric observations revealed a relatively large and potentially active nucleus, a trait that could favor strong outgassing activity as the comet approaches the Sun. Spectroscopic studies indicate the presence of volatile compounds, such as water, carbon monoxide, and methane, which could contribute to a bright display as they are vaporized by solar radiation.

Atlas C/2023 A3 has a distinctly elongated orbit, with an inclination of approximately 143 degrees relative to the ecliptic plane, positioning it in a retrograde orbit as it approaches the Sun. Its current orbital parameters predicteded a perihelion distance of about 0.39 AU, situating it just inside Mercury's orbit. This close approach to the Sun caused sublimation, which resulted in a dynamic and highly visible tail. Its journey from the outer solar system to this inner passage is a process taking potentially millions of years. The long orbital period is indicative of its origins in the Oort Cloud, and the comet will likely continue on its elliptical trajectory back into the far reaches of the solar system after this close approach.

In the shown image you can observe an anti tail. Antitails are an optical phenomenon rather than a literal tail pointing toward the Sun. They form under specific conditions of alignment among the comet, Earth, and the Sun. When a comet reaches a particular point in its orbit, the Earth may cross the comet's orbital plane, and the Sun, Earth, and comet align in such a way that dust particles, released previously, appear to "pile up" in a way that points sunward. This is a result of the dust's orbit, which has spread into a thin, fan-like structure that can sometimes project in the opposite direction to the typical tail orientation when viewed from Earth.The illusion of a sunward-pointing tail is due to the line-of-sight effect, where dust particles are distributed along the comet's orbital path. Essentially, the antitail represents particles that are still in orbit around the Sun rather than being blown away by solar wind; their apparent orientation is caused by the observer's viewing angle rather than an actual sunward motion.