The green, horned “Devil Comet” is now visible in the Australian sky, offering a once-in-a-lifetime chance to see a unique celestial body.
The comet – real name 12P/Pons-Brooks – has been nicknamed the Devil’s Comet because eruptions from its nucleus can make it look like it has two horns. More recently, Star Wars fans have called it the Millennium Falcon.
The comet, whose nucleus has a diameter of 34 km, has been compared to Halley’s Comet because it passes by Earth about every 71 years. It also has a green tint due to its molecular structure.
Halley’s Comet appears about every 76 years, and was last visible in 1986, when amateur astronomers flocked outside at night to see it. It is often referred to as the most famous comet because, according to Nasa, it was “the first time astronomers understood that comets can be repeat visitors to our night sky”.
Brad Tucker, an astrophysicist at the Australian National University, said that while the Devil’s Comet is technically visible now, it is difficult to spot – but it will become clearer over the next week or so.
“It’s really low in the sky, but it’s kind of right next to Jupiter, so if you can see Jupiter sitting in the western sky, the comet is close.”
As it gets closer to the Sun, the icy core and gas trail heat up, making it more visible. It will be at its brightest on April 22, just above the horizon, but Tucker says it will be like “a game of cat and mouse” to find it, because then it will compete with a full moon.
“The best day would probably be from around Anzac Day,” he said. “It’s past the full moon, though [the comet’s] still bright and it’s a bit higher… so the 25th, then next weekend.”
Rebecca Allen, associate director of the Space Technology and Industry Institute at Swinburne University of Technology, said it would be visible to the naked eye, but that it might help to spot it first with binoculars or a telescope. She said the comet had been spotted for centuries, so it was a piece of history, but it was also special because of its brightness.
“As it made its journey from the outer solar system, it heated up, so it released more gases,” she said. “There is even a recorded explosion where it jumped dramatically in brightness.
“It’s green because of its diatomic carbon, a very rare form of carbon that’s unstable, so you only get it in very specific environments that don’t have oxygen — like being on a comet.”
It has also been called the “Mother of Dragons” because it is cryovolcanic – a type of volcano that spews water vapor and other materials from the core.
“With the heat, you get this pressure inside the comet and it releases this burst,” Tucker said.
According to Nasa, people once saw comets as “long-haired stars that appeared unannounced and unpredictably in the sky”. Now they are known to be “leftovers” from the Big Bang, consisting of ice and dirt and sometimes called “dirty snowballs”.
Allen said these comets, which have survived eons and traveled from the edge of the solar system, are pulled in and eventually destroyed by the sun’s gravity.
“They’re really individual and if they’re heated by the sun, you just don’t know which ones will break apart,” she said.
“Every time they come in, they lose a little more mass. So there will be a final orbit when it finally breaks up.”
