Leonard’s comet is fading and behaving strangely

(ORDO NEWS) — Something strange is happening with this year’s most anticipated comet.

Astronomers first noticed Leonard’s comet in January 2021. Skywatchers eagerly awaited December and January, when the comet would first pass the Earth and then the Sun. But by the end of November, observers noticed something strange. The comet should get brighter as it gets closer to the Sun, but only because it gets closer to the Earth, and not because it becomes inherently brighter.

Instead, she seems to disappear.

“This is not good news. The comet should be getting brighter and brighter,” said Kwangji Ye, a comet astronomer at the University of Maryland. “If it doesn’t get brighter, then something is wrong, but at this stage we don’t know exactly what it is.”

Based on what they’ve seen from previous comets, scientists fear that Comet Leonard’s strange darkening means the ball of ice may be doomed. In the past, some comets that fell apart disappeared even as they flew closer to the Sun – this was the first sign that something was happening.

“Why it disappears, there are all kinds of hypotheses,” – said Ye. “The simplest and most obvious of these is that something unhealthy is happening to the comet.”

The most likely hypothesis, he said, is that Leonard’s comet is already disintegrating, or that it will start soon. But there could be other factors to blame. For example, a comet may simply run out of ice, which is unlikely. “It seems like too much of a coincidence,” he said.

However, it is still too early to call Comet Leonard dead.

“In the images I saw this morning [Dec 7], the comet seems to be doing well – morphologically, it looks normal. But the internally fading trend is still ongoing,” Ye said. “Time will tell, we don’t know that at the moment.”

The first sign that a comet is doomed is that it is losing its ion tail – a stream of charged particles directed away from the comet in a direction opposite to the Sun. This feature can disappear within a few hours after the comet decay.

Comet Leonard will come closest to Earth on Sunday (December 12); its perihelion, or closest approach to the Sun, is January 3, 2022. Although the star’s influence will weaken after January 3, the comet will not necessarily be safe even if it lasts that long.

“Comets do all sorts of weird things,” Ye said. “Sometimes they decay before reaching perihelion, sometimes after, and there are even hypotheses that say comets can decay when they are further from the Sun. So we won’t know until we see how that happens.”

There are several factors that can destroy a comet. Of course, the gravitational pull of the Sun or a large planet can tear it apart, but the heart of a comet can also explode. If the comet’s material does not vaporize in the right way, it can accelerate the comet’s rotation so dramatically that the ball of ice will shatter into pieces.

And if Leonard’s comet does decay, scientists may never know who the culprit was. “It is usually difficult for individual comets to determine what force helped them disappear,” Ye said.

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