A comet larger than Mount Everest could become visible to the naked eye in the coming weeks as it continues its first visit to the inner solar system in more than 70 years, astronomers say.
The icy body is a Halley-type comet – meaning it will appear once, or possibly twice, in a lifetime. Indeed, 12P/Pons-Brooks, as it is known, completes its orbit once every 71.3 years, and is due to make its closest approach to the sun on April 21.
While some reports suggest that 12P/Pons-Brooks date back as far as the 14th centuryit is named after the French astronomer Jean-Louis Pons who discovered it in 1812 and the British-American astronomer William Robert Brooks who observed it in 1883 on its next orbit.
Thought to have a core left 30 km (20 miles) in diameterit is classified as a cryovolcanic comet, meaning that it erupts with dust, gases and ice when pressure builds up inside as it is heated.
One such outburst last year caused it to brighten a hundredfold and earned it the sobriquet of “the Devil’s Comet” after the haze surrounding it formed a horn shape.
While the comet – and its green tint – has already been spotted in the night sky experts say it is expected to get even brighter in the coming weeks. “The comet is expected to reach a magnitude of 4.5, which means it should be visible from a dark place in the UK,” said Dr Paul Strøm, an astrophysicist at the University of Warwick.
“The comet is moving from the constellation Andromeda to Pisces. As it does so, it passes bright stars that will make it easier to see on certain dates. In particular, on March 31 12P/Pons-Brooks will be only 0.5 a degree of the bright star called Hamal,” he said.
But Dr Robert Massey, the deputy executive director of the Royal Astronomical Society, said even if the comet brightened, it could still be difficult to see, adding that basic instruments such as small telescopes would help a lot.
“If you have half-decent binoculars, definitely try to look for it with that,” Massey said, adding that apps that map the sky have also been helpful.
The best views of the comet are currently to be found in the northern hemisphere. Massey says those who wanted to catch a glimpse should venture out on a clear night and look low in the west-northwest as dusk draws to a close. “You want to avoid haze, you want to avoid moonlight, you want to avoid light pollution.”
Strøm said that comets, along with asteroids, are often considered the unused building blocks of the solar system, providing insight into the conditions under which they formed.
Massey said there is also satisfaction in seeing a comet that has only been observed a handful of times since its official discovery. “That in itself is quite a nice thing to think about,” he said.
