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An unusual horned comet notable for a series of outbursts, nicknamed the “devil’s comet,” will make its closest approach to Earth on Sunday around 3 a.m. ET.
Although the comet has not been visible to people in the Northern Hemisphere since the first week of May, skygazers in the Southern Hemisphere have a better chance of seeing the faint object through binoculars or a telescope.
Exactly why the dynamic comet takes a shape that draws comparisons to the Millennium Falcon spacecraft from the “Star Wars” films while being explosively active is still a mystery to scientists. But the celestial body only completes one orbit around the sun about every 71 years, similar to Halley’s Comet, making the chance to study it up close a unique opportunity.
Since the comet will not pass by Earth again for decades, collective observations by astronomers could provide important insights into its true nature and behavior.
Officially known as Comet 12P/Pons-Brooks, the celestial object made its closest pass to the Sun on April 21, coming within 74.4 million miles (119.7 million kilometers) of our star.
The comet will make its closest pass to Earth on Sunday, but will be more than 230 million kilometers from our planet and will not pose a risk. For reference, the sun is 93 million miles (149 million kilometers) away from Earth.
The comet peaked in brightness in late April and has been steadily fading for three to four weeks, said Dr. Dave Schleicher, an astronomer at the Lowell Observatory in Arizona.
“For people below the equator, the coming weeks and months could be the first good chance to see this thing since the 1950s,” says astronomer Dr. Teddy Kareta, a postdoctoral fellow at Lowell.
Two prolific explorers, Jean-Louis Pons and William Robert Brooksindependently observed the Devil’s Comet — Pons in 1812 and Brooks in 1883. But the comet likely made many trips around the sun over thousands of years, long before astronomers thought of comets as anything other than “something strange in the atmosphere,” Schleicher said. said.
Astronomers estimate the massive comet has a diameter of between 10 and 20 kilometers, Kareta said.
The rare visitor has a green appearance that is typical of most comets, because they contain diatomic carbon molecules that absorb sunlight and emit a color that appears green from our perspective, Schleicher said.
A series of cosmic eruptions
Pons-Brooks recently caught the attention of astronomers after exhibiting intriguing behavior that caused the comet to take on a horned appearance and drift through our solar system.
The comet has experienced a number of outbursts over the past eight months, emitting gas and dust. While such releases are not unusual in comets, and a crescent or Pac-Man shape has been observed in other comets, it’s hard to say what’s normal for Pons-Brooks.
“I would say it’s somewhat unusual given the number of eruptions it’s had,” Schleicher said. “On the other hand, it’s not like you have good records from the past that really let you know what’s typical. And I suspect, given the fairly large number of eruptions that have occurred over the last eight months, that this is very clearly a common occurrence for Pons-Brooks.”
Comets are chunks of dust, rock and ice, essentially frozen remnants from the formation of the solar system. They also contain frozen elements such as carbon dioxide and carbon monoxide.
Comets become warmer and brighter as they approach the sun, and some frozen gases stored in comets don’t have to warm up much before they start turning to vapor, Schleicher said.
“We obviously think the ultimate driver is solar heating,” he said. “The comet is coming in; it has been in the freezer for years. The heat will work its way from the surface to where the carbon dioxide or carbon monoxide ice is.”
Astronomers suspect that Pons-Brooks eruptions occurred over the course of repeated events, with heat vaporizing the material inside the comet, causing pressure to build and break through the surface. Although an explosion of gas wouldn’t be visible in telescopes, the dust it kicks up would cause the kind of events observed from Pons-Brooks, Schleicher said.
Scientists have traced the jets of material observed during the comet’s outburst to two source regions on its surface. Astronomers are puzzled why “the entire surface doesn’t go off like crazy,” Schleicher said.
The observations imply that ice has settled over most of the surface, or that the ice has evaporated, leaving only dirt behind, but astronomers “aren’t entirely sure which of these mechanisms are running the show,” he said.
However, the comet’s outbursts appear to have stopped and the comet has not shown any outbursts since February, Kareta said.
What we can learn from comets
Astronomers have been observing Pons-Brooks in hopes of discovering more details about its rotation rate, or the speed at which comets spin as they move through space. Pons-Brooks has a rotation period of 57 hours, which is longer than expected, and astronomers want to know whether the jets of material released from the comet speed it up or slow it down.
An overlapping series of events likely contributed to Pons-Brooks’s distinctive appearance, but it could also be due to our perspective of the comet, Kareta said.
“These are three-dimensional objects,” Kareta said. “When we take images of the night sky, we take them in a limited number of colors, all flattened in two dimensions. This makes things that make perfect sense to you, when you can go up and walk around and see it from a number of different perspectives, look a lot more complicated than they actually are.
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