A green comet with an anti-tail: the secrets of a peculiar phenomenon that can be easily seen

The last time it was visible from Earth, 50,000 years ago, Neanderthals were still living in Europe. It shows off an attractive green and has an anti-tail. And besides, you can almost enjoy it with the naked eye. All these characteristics make the so-called “green comet” (there have been others) a curious event that goes a little beyond the world of amateur astronomers. “Is a hype [excesivo bombo] because now everything is, but the truth is that it’s cool”, acknowledges Javier Armentia, astrophysicist and director of the Pamplona Planetarium. “Not all comets present this “anti-tail”, or rather, this phenomenon that the material leaving the comet remains illuminated is not normally observable; on the other hand, the green color, not being unusual either, is striking”, sums up the specialist. The comet was discovered in March 2022, less than a year ago, by the Zwicky Transient Facility (ZTF), from which its true scientific name is derived: C/2022 E3 (ZTF).

Why is it green? It is not the first time that a green comet is visible from Earth, as This one that NASA picked up in 2009. The green color is produced only in the envelope of its head (called a coma), as a turquoise aura, caused by the reaction of ultraviolet light and carbon dioxide emanating from this space object, as described in This studio of 2021 that tried to explain the phenomenon.

What is that anti-tail? Although he is not the first to wear it either, he also has the peculiarity of having an anti-tail. For example, him famous Hale-Bopp he sported his in its wake in 1997. The twin tails of a comet are often clearly visible, thanks to the fact that the dust trail reflects sunlight and the gas within the other tail ionizes, giving it a faint glow. But the third, the antitail, which appears in the opposite direction to what is expected: an optical illusion that is seen when the Earth crosses the orbital plane of a comet. “At this time, the edge of the comet’s fan-shaped dust tail looks like a point pointing toward the sun,” he explains. SpaceWeather.

Can you enjoy it with the naked eye? About. Walking through the center of a city and looking at the night sky, without further ado, it is unlikely to be seen. The ideal is, as always, to get away from light pollution in rural areas. “It is tiny, and although people are trying to convince that it can be seen, without binoculars or a telescope there is no way. In addition, the moon is waxing and in these next few days there will be more light in the sky and less contrast”, warns Armentia.

“It will pass close to the Polar star on January 30 and close to the bright Capella on February 6, moving with a very fast angular velocity during the days it is closest to Earth,” says astrophysicist Josep Maria Trigo in The Conversation.

NASA recalls that “it should be visible with a telescope and probably with binoculars” observers in the northern hemisphere will find the comet in the early sky, before dawn, as it moves rapidly northwest during January. And it will become visible in the southern hemisphere in early February. Next week will be the ideal to observe it. This comet is not expected to be the spectacle that Comet NEOWISE was in 2020, but it is still an incredible opportunity to make a personal connection with an icy visitor from the far outer solar system.

How close is it? February 1 will be when it gets closest to Earth. The comet reached its perihelion on January 12, 2023, at a distance of 166 million kilometers and the closest approach to our planet, on February 1, will be at a distance of only 42 million kilometers.

You can follow MATTER in Facebook, Twitter and instagramor sign up here to receive our weekly newsletter.