An unusually large comet is making an appearance in the sky this spring, a once-in-seven-decades phenomenon that delights professional and amateur astronomers.
On March 10, Šarūnas Kazlauskas knew this would be the night. He packed up a camera and headed out of the city. He then spent an hour and a half photographing the sky.
The time in the cold paid off in spades as he captured the extremely rare comet 12P/Pons-Brooks. This celestial body comes close to Earth once every 71 years.
“Trying to understand the scales and distances of the objects in the photo makes you think about your own insignificance in the context of the universe, the uniqueness of our planet and life, and makes you reflect on your life choices and values – it’s a very pleasant feeling, and I highly recommend it,” the photographer tells LRT.lt.
Comet approaching Earth
According to Vidas Dobrovolskas, an astrophysicist at Vilnius University’s Faculty of Physics, 12P/Pons-Brooks is still approaching the Sun, so the comet’s brightness will increase. In April, it will be at its brightest and can then be seen with the naked eye.
“The comet will be closest to the Sun, and at the same time at its brightest, visible with the naked eye in the sky, on April 21. But it should still be visible through binoculars in May,” says the scientist.
In May and June, however, the comet could be difficult to see because of short and bright nights. By the end of the summer, the comet will be far enough from the Sun and the Earth to be visible only through telescopes. The next time Comet 12P/Pons-Brooks will approach the Earth is in 71 years.
It is one of the most active comets in the Solar System, says Dobrovolskas, with a few cryovolcanoes erupting from its depths from time to time, which can suddenly increase its brightness by a factor of ten.
“As the comet’s nucleus rotates on its axis, the sun’s rays heat up the surface, and if there is even a small crack in the surface, the deeper accumulations of water, ammonia, and various gases gush out in a powerful stream. Then the comet suddenly shines ten times brighter for a day or two.
“Since last autumn alone, astronomers have recorded five such flashes of Comet Pons-Brooks,” says Dobrovolskas.
When and where to look
Casual observers will be able to see the comet with the naked eye next month, but for now, it is only visible through a telescope.
Kazlauskas says that to capture it in a photo, one needs to observe a number of factors. First, it has to be a clear night, one must get away from city lights and know where to look in the night sky.
“First of all, I had to wait for a clear, moonless night,” says the amateur astronomer about his experience photographing the comet.
“On 10 March, I started looking for a location away from the city to escape the light pollution. In this case, I went north of Vilnius towards Molėtai, as the comet is orbiting in the north-western sky. After searching for a while for a place with an open horizon to the north-west, [...] I camped on a hill by the roadside and started preparing my equipment. [...] I knew [the comet] would be very close to the Andromeda galaxy, which is easy to find in the sky, so I pointed my lens at it and easily found the comet.”
Equipment is also important for capturing a good image.
“Since the comet is not very bright at the moment, a good photo requires a motorised mount that compensates for the rotation of the Earth, in other words, it follows the comet’s movement in the sky. This allows for long exposure and highlights the features of the comet and other celestial bodies,” says Kazlauskas.
Everest-size comet
Comet 12P/Pons-Brooks is a sizeable body, with many media headlines noting that its size exceeds Mount Everest.
“The nucleus of Comet 12P/Pons-Brooks is one of the largest, with a diameter of around 30 km, while typical comet nuclei have a diameter of around one kilometre,” says Dobrovolskas.
However, even though the comet is large and inexorably approaching Earth, the scientist reassures that there is no chance of it colliding with our planet.
“Comet 12P/Pons-Brooks takes 71 years to circle the Sun, even reaching the orbit of Neptune and getting close to Venus. However, there is no risk of collision with the planets, including Earth, because the comet’s orbit around the Sun is almost exactly perpendicular to the plane of motion of the planets, inclined by 74 degrees,” he said.
Time capsules
Dobrovolskas says that both 12P/Pons-Brooks and other comets are witnesses to the formation of the Solar System, and their study is particularly important for understanding more about how the planets were formed.
“The material that makes up the nuclei of comets has changed very little since the early stages of the Solar System. Together with asteroids, comets are like time capsules that can ‘tell’ astrophysicists about the conditions that existed when planets formed,” says the scientist.
In addition to studying comets with telescopes from the surface of the Earth, scientists are also sending spacecraft to the nuclei of comets.
“Last time, it was the European Space Agency’s Rosetta mission where a spacecraft studied comet 67P/Churyumov-Gerasimenko at close range from 2014 to 2016,” the researcher recalls.
Comets may also hold the key to the origins of life on Earth.
“Comet nuclei brought very large quantities of water, as well as a variety of organic materials when they collided with Earth 4.5-4.0 billion years ago. It is thought that the material brought by comets may have facilitated the emergence of life on Earth,” concludes Dobrovolskas, a researcher at Vilnius University’s Faculty of Physics.
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