Most comets are brightest as they approach the sun at the shortest distance. However, sky lovers will find it hard to capture any comet at that moment because the sun’s glare and horizon conceal them. Comet Leonard (C/2021 A1) is perhaps an exception to the rule.
The ‘story’ behind Comet Leonard
Comet “Leonard” is named after Gregory J. Leonard, a senior research specialist and an astronomer, who initially discovered it on Jan. 3 at the Mount Lemmon Infrared Observatory, located in the Santa Catalina Mountains, nearly 17 miles northeast of Tucson, Arizona.
The comet has appeared dim since its first detection, challenging amateur telescopes despite approaching both the sun and the Earth at a close distance. However, this December is unique. Scientists have estimated that Leonard would shine brightly for a short period, Space.com reported.
Around 35,000 years ago, the icy ball was located at its elongated elliptical orbit’s far end (aphelion), about 3,500 astronomical units distant from the sun, at a temperature barely above absolute zero. One astronomical unit (AU) equals the average distance of the Earth from the sun: 92,955,807 miles (149,565,894 kilometers).
Comet Leonard starts to “act” weird
Although Leonard is getting closer to the sun, it’s not getting brighter as expected but seems to be fading instead.
Quanzhi Ye, an astronomer at the University of Maryland specializing in comets, told Space.com. “If it’s not getting brighter, then something’s wrong, but we don’t know exactly what at this stage.”
Based on previous comets’ researches, scientists are afraid that Comet Leonard’s strange dimming may be a sign of its possible end.
Ye supposed that there are several hypotheses behind Leonard’s fading; the comet encountering something unhealthy is the simplest and most obvious one.
According to the astronomer, the highest possible hypothesis is that Leonard is already splitting up, or it will start that process.
Although the fading trend shows no sign of ceasing, Ye stated that it’s too early to determine Leonard a goner. He said: “Time will tell; we don’t know at this point.”
Leonard will start its closet Earth access on Sunday, Dec. 12, then vanish for a few days, concealed by the sun’s glare, before returning to the evening sky as a special guest by Dec. 17. It will reach its perihelion-closest access to the sun on Jan. 3.
Although the sun will diminish its influence after Jan. 3, the comets safety is not ensured even if it survives that long.
“Comets do all sorts of weird things,” Ye explained. “Sometimes they disintegrate before reaching perihelion, sometimes after, and there are even hypotheses saying that comets can disintegrate when they’re farther out from the sun. So we won’t know until we see it happen.”
Ye also stated that it’s also challenging to identify “the dominant driver” for an individual comet if a break-up happens. Besides, even if Leonard experiences an early end, sky lovers still have the opportunity to observe it in the skies thanks to a delay between the beginning of the separating process and its fading, watching from Earth.
“Usually, it will take a few days before you can see the comet dramatically change and fade and stuff,” he said. “We should be still in for something pretty bright next week, simply because it takes time for the comet to fully disintegrate.”