After scientists expected its demise for a year, Leonard’s Comet, the brightest comet of 2021, has finally disintegrated. But its tumultuous journey to the sun has caused excitement among astronomers.
Comet C/2021 A1, generally referred to as Leonard’s Comet, began breaking apart after passing the sun on January 3, 2022 at perihelion, which occurs when a comet is at its closest to the sun.
Post-perihelion, the comet has lost its nucleus and its temporary atmosphere. The outermost layer of the once powerful comet has disintegrated.
The name “Leonard’s Comet'' honors astronomer Gregory Leonard of the Catalina Sky Survey in Arizona, who discovered the comet on January 3, 2021 – exactly one year before its perihelion. When discovered, the bright rock was approaching orbit with Earth and Venus, but was still far away.
When a comet approaches the sun, the nucleus becomes especially heated, ultimately leading to the release of gas and dust. The nucleic residual creates an atmospheric layer about the comet, known as the coma.
Comets are known for their unpredictability; however, astronomers have synthesized repeating trends in comets, which they refer to as “normal behavior.” The general principles for this include consistent brightness levels, a fully round shape on the head of the comet, and the most obvious, staying on its projected pathway.
Ultimately, a comet’s unpredictability depends on its behavior, namely its brightness and physicality. Cometary scientists and astronomers alike found that – when behaving – a comet that travels from any given point in respect to the inner solar system will “become 16 times brighter” than before.
This general rule derives from myriad observations, including that of Leonard’s Comet, with which astronomers detected a different pattern.
The bright comet initially demonstrated normal behavior until around late November 2021 when amateurs began suspecting that the comet was disintegrating, arguing that the brightness was fading. Suspicions only grew stronger when the comet’s nucleus started showing abnormal activity. It was losing its round shape. The nucleus is commonly observed from the coma’s thick, external surface. Lastly, the comet appeared to be veering off course, which is also indicative of eroding.
But they were all wrong.
Luckily, on December 2, 2021, these theories were debunked by the Central Bureau for Astronomical Telegrams, the official international site for details regarding transient astronomical affairs. The organization issued Electronic Telegram #5077, which refuted all preceding allegations.
The closer the comet was to the sun, the more the brightness would fluctuate. The tail, in particular, formed a unique structure, revealing the sun’s influence on its nucleic pattern. Consequently, the comet would be closely examined by both experts, professionals, and even amateurs.
Months later, the comet’s death was officially confirmed. In February of 2022, Edith Cowan University Professor Martin Masek captured new pictures of Leonard’s Comet, mainly observing a lack of central condensation. Fellow observers, too, noticed the comet’s deterioration, referring to the comet as a “ghostly streak.”
Comet C/2021 A1 Discoverer Gregory Leonard wrote in an email on March 16, 2022: “C/2021 A1’s legacy will likely be the spectacular outburst-induced displays of its ion tail structures. Otherworldly and astonishing are the only descriptions that come to mind when I began viewing the images being posted online by a handful of dedicated expert astrophotographers, particularly after December 19, 2021, when the comet began undergoing strong periodic outburst activity.”
Hopefully, in the near future, we can discover equally fascinating comets in the sky.
[Sources: EarthSky.org; Smithsonian Magazine; space.com]