This article first appeared on ntv.de
The green comet is approaching the earth. And the chances of seeing him increase. You haven't seen it yourself yet, says Monika Staesche, director of the planetarium at the Insulaner and the Wilhelm Foerster Observatory in Berlin, to ntv.de. Because a blanket of fog and clouds is currently hanging over the capital. But she knows from a colleague who saw the comet as a small dot about a week and a half ago: When you see it, you can definitely see the distinctive green of the tail star.
At the moment the comet called C/2022 E3 ZTF is flying towards the earth coming from the sun. It will be closest to our planet on February 1st and is also the best time to see it. However, most likely in dark areas, says Staesche. You should also have binoculars or a telescope with you, it will be difficult with the naked eye. A telescope with a large field of view (field of view) is also advisable, because it makes it easier to discover the comet, says Staesche. Observatories are also a good address.
The early morning of January 31 is particularly good for observing the green comet because the moon will set after 4 a.m. This is just increasing and disturbs the observation at night with its light. In the days that follow, it becomes increasingly difficult: February 4th is full moon and Earth's satellite is in the sky all night. Only from February 8th in the evening hours will there again be a chance of an undisturbed comet search, whereby C/2022 E3 ZTF will then have lost some of its brightness.
Where to look? The comet will be visible in the northern sky in late January/early February, between the well-known constellation of the Big Dipper and North Star. There are also tips on how to find the tail star in the sky on the website of the Association of Star Friends.
And the weather has to play along too. But that's exactly the biggest uncertainty factor at the moment: "The deep foothills are repeatedly thwarting the friends of the cosmic sky spectacles. Especially at the end of the month," says ntv weather expert Björn Alexander. According to the current status, there are only good chances for a cloud-free view of the sky in the south-west of the country. "Otherwise the weather computers see plenty of clouds."
If you still catch the green comet: The sight should be a little different than you might expect. Some remember the comet Neowise, whose long tail could be seen in the sky with the naked eye in the Corona summer of 2020. But C/2022 E3 ZTF looks more like a foggy patch at the moment. "It's quite high in the night sky, but it doesn't have a long tail like other comets," says Staesche. The reason: C/2022 E3 ZTF flies almost vertically towards the earth, "so we look almost exactly at its head". Its tail is more or less hidden behind it.
But why is this comet actually green? "The color of a comet depends on the substances it is made of," explains Staesche. In the case of the green comet, it is ethyne (acetylene), a hydrocarbon that is released as a gas by solar radiation. Ethine consists of two carbon and two hydrogen atoms. It is gradually decomposed by the energy of sunlight - when the two carbon atoms are separated, the green glow is created. "However, it is only a short-term effect, which is why the entire comet does not glow green, but only its head," says Staesche.
If you miss the green comet, that's probably it for now: it won't return to Earth for about 50,000 years. After its rendezvous with Earth, it flies past Mars into the outer solar system - towards its probable origin, the Oort Cloud. This is an assumed region that lies about halfway between the sun and the nearest fixed star. There are very likely many more large chunks of ice like him out there. "When a neighboring star approaches, its gravity is enough to give some of these chunks a nudge and make them fly towards the sun," says Staesche. These are the comets that you can admire in the night sky every year.