Something strange is happening to this year’s most anticipated skywatcher comet.
Astronomers first discovered what was dubbed Comet Leonard in January 2021, and soon sky watchers were eagerly anticipating the months of December and January, when the comet was due to pass first Earth, and then the Sun. But by late November, observers noticed something strange. The comet It should get brighter as it gets closer to the sun – and it does, but apparently only because it gets closer to it Earth, not because she has become naturally brighter.
Instead, it appears to be fading away.
“That’s not great news. The comet should be brighter and brighter,” Quanzhi Ye, a University of Maryland astronomer who specializes in comets, told Space.com. “If it doesn’t get brighter, it’s something wrong, but we don’t know exactly what it is at this point.”
Related: Comet Leonard will light up the sky this month – here’s how to see it
Based on what they’ve seen of past comets, scientists worry that Comet Leonard’s strange dimming means the ice ball may be doomed. In the past, some comets that crashed even when they were flying close to the sun – It was the first sign something was going on.
“Why fading away, there are all kinds of hypotheses,” Yi said. “The simplest and most obvious is that something unhealthy happens to the comet.”
The most likely hypothesis, he said, is that Comet Leonard is already splitting, or that it will begin to do so soon. But other factors can be blamed. For example, a comet may run out of ice until the sun evaporates, although Yi thinks that is unlikely. “It seems too much of a coincidence,” he said.
However, it is too early to consider Comet Leonard to be mortal.
The pictures I saw from this morning [Dec. 7], the comet still looks fine – technically it looks good. But the intrinsically fading trend still continued, Ye said. And time will tell, we don’t know at this point.
The first sign of a doomed comet, Yi said, is that it’s losing its ionic tail, a stream of charged particles flowing from the comet in the direction opposite to the sun. This feature can disappear within a few hours of the comet crash.
Comet Leonard will approach its closest approach to Earth on Sunday (12 December); Perigee, or its closest approach to the sun, comes on January 3. Although the Sun’s influence will diminish after January 3rd, a comet is not necessarily safe even if it survives for a long time.
“Comets do all kinds of weird things,” Yi said. “Sometimes they disintegrate before they reach perihelion, and sometimes afterwards, and there are hypotheses that comets can disintegrate when they are farther from the sun. So we won’t know until we see that happen.”
Yi pointed out that there are many factors that can break up a comet. Sure, the gravitational pull of the Sun or a large planet could tear it apart, but a comet’s core could explode, too. If comet material evaporates just the right way, it can speed up the comet’s spin so dramatically that the ice ball flies to pieces.
And if Comet Leonard crashes, scientists may never know what the culprit is. “It is usually difficult to determine the dominant driver for individual comets,” Yi said.
Should skywatchers panic?
Even if Comet Leonard meets an early end, there is still plenty of time to see it in the sky. There is usually a delay between the time a comet begins to disintegrate and when it fades as seen from Earth, Yi said.
“Normally it will take a few days before you can see the comet dramatically change and fade and things,” he said. “We must continue to achieve something very bright next week, simply because it takes time for a comet to disintegrate completely.”
Comet Leonard will be visible in the late morning as it approaches Earth until December 12. After that, it will disappear for a few days, hidden by the glare of the sun, before making its way onto the evening sky by December 17. For more details about the discovery of Comet Leonard, visit Sky Watch Guide.
Yi said he hasn’t been able to see Comet Leonard yet because of cloudy weather, but he’s hoping to do so next week. While he is interested in what comets can tell scientists about the early days of the solar system, he values the show just as much.
“It’s fun to watch and it’s beautiful for bright comets,” he said. “It’s great to see them in the night sky.”