Last July, C / 2020 F3, nicknamed comet NEOWISE, was visible to the naked eye in the French sky. To spot it, it was enough to observe the claws of the Big Dipper. Will we be able to enjoy such a spectacle this year again?
The object that interests us today is the comet Leonard, cataloged C / 2021 A1, discovered last January by the astronomer Gregory J. Leonard since theMount Lemmon Observatory, in the Santa Catalina Mountains (Arizona).
At the time, it was an extremely weak object of magnitude 19. Remember that the higher the magnitude, the lower the brightness. To better understand, tell yourself that the object was then close to 160,000 times darker than the faintest stars visible to the naked eye.
The comet then placed itself about five astronomical units from the sun, or five times the Earth-Sun distance (149.565 million kilometers), near the orbit of Jupiter. It is at about this distance that methanol (CH3OH) and water begin to wipe off the sublimation process caused by the heat of the Sun. The matter, then solid, turns into gas, hence the presence of a weak tail released by the comet at the time of its first observation.
Visible to the naked eye in December?
According to initial calculations, Comet Leonard is moving in an extremely long and flattened elliptical orbit, moving it away from more than 3,500 AU from the sun (523 billion km). On the other hand, we do know that it will get closer at the end of the year. On December 12, the comet will pass within 34.9 million km of the Earth and less than 92 million km of the sun on January 3, 2022.
For now, we cannot say if this comet will be visible or not to the naked eye, these objects are so unpredictable, but we could expect a magnitude 4. If so, Leonard should be easily seen through binoculars or a small telescope … and hopefully even with the naked eye. Once the Sun has passed, the comet will move away and quickly disappear, bathed in its light.
One of the reasons for optimism is that the object is in a closed orbit and has probably visited the vicinity of the Sun at least once before, some 70,000 years ago.
This is good news insofar as a comet that has never “rubbed” the Sun can develop a surface covered with very volatile matter (carbon dioxide, nitrogen and carbon monoxide). However, these glasses tend to vaporize very far from the sun, so that the objects concerned can display deceptive “bursts” of brightness before quickly darkening.