Comet Tsuchinshan-Atlas on the 12th/13th October can be seen with the naked eye

Potsdam. Of course, Jörg Weingrill, an employee of the telescope control and robotics department at the Leibniz Institute for Astrophysics Potsdam (AIP), will also be lying in wait. He also wants to catch a glimpse of the comet Tsuchinshan Atlas, which was only discovered by a Chinese observer on January 9, 2023 and was named after him. “So far it is not visible in the evenings, but on October 12th and 13th it should be visible right after sunset,” said Weingrill. The best observation time is on Saturday and Sunday at 6:30 p.m., looking west a hand’s breadth above the horizon line.

Why are we only really seeing the comet this weekend?

In order to see a comet from Earth with the naked eye, three conditions are required: The celestial body must be close to the Sun, but also close enough to the Earth. Its orbit must be such that after sunset it is both illuminated by the sun and comes into our field of vision, so that we are not turned away from it at night.

In this respect, Tsuchinshan Atlas, which astronomers have named C/2023 A3, actually has a rather unfavorable trajectory. According to Weingrill, it actually reached its closest point to Earth at the beginning of October – but at that time it only fell into our field of vision in broad daylight. It could only have been seen, if at all, with astronomical equipment.

The head of the Urania Planetarium Potsdam is optimistic

Conditions are also not ideal on Saturday and Sunday. The best viewing time is directly after sunset in a westerly direction. But you have to go out into the open field because the comet is near the horizon. Behind this it will soon disappear again due to the rotation of the earth. At around 30 degrees high in the sky, Tsuchinshan Atlas could actually be seen much better at the end of November.

Unfortunately, it is now so far away from Earth that it can no longer be discovered without very good telescopes. However, the director of the Potsdam Urania Planetarium, Simon Plate, is quite optimistic that individual observations with the naked eye will be possible even after October 13th. “Comets are notoriously unpredictable,” he says. Perhaps Tsuchinshan Atlas will shine so brightly again at a later date that it can be seen higher in the sky at a later date.

What does C/2023 A3 look like?

Unfortunately, the comet doesn’t look quite like the photos already circulating showing its beautiful long tail. Photographers can set long exposure times and post-process the images to reveal the best of the comet. To the naked eye, the comet looks more like “white lint in the sky,” says Weingrill. Nevertheless, it is worth looking at.

“The tail should be very clearly visible,” says Weingrill. This is impressive and clear with this comet. “The tail will point away from the sun,” says Weingrill. Given the visibility conditions this time, this means that it is more perpendicular to the horizon.

Comet is easy to distinguish from Mercury

Its tail and overall rather blurry appearance also make it distinguishable from Mercury, which – if the weather is good – is likely to appear nearby as a clear, shining point. The blurriness is what makes the comet different from Mercury, which appears nearby. Telescope owners are even better off. You can probably see the classic comet shape much more clearly.

What is a comet?

“It’s actually kind of a dirty snowball,” Weingrill says. Comets are a mixture of rock forms and ice. Like many other small celestial bodies, they fly around the sun in an elliptical orbit. Normally they don’t glow, but once they pass through Mars’ orbit, they are close enough to the sun to be heated and vaporize water and gases.

These, mixed with small particles, make up its tail, which shines in the light of the sun. Comets lose some of their mass and are therefore temporary objects. “There was also a fear with Tsuchinshan Atlas that it would break up at the moment when it was closest to the sun,” says Weingrill. But he “survived” that moment on September 27th.

Even now it is threatened by large solar flares, which even gave Brandenburg the northern lights. “But I think that it will survive that too.” At some point, after many rotations, the entire ice mass will be lost and then it will break up into individual chunks. Like the Perseids, we can perceive them as shooting stars in August when the Earth crosses their orbit.

Where does Tsuchinshan Atlas actually come from?

The origin of comets and other solid celestial bodies lies in the so-called Kuiper Belt. This ring-shaped extensive area begins far out in space directly behind the orbit of Neptune. We don’t yet know exactly how far the Kuiper Belt extends, says Weingrill.

Tens of thousands of objects have already been identified in this area. “It is assumed that the attraction of Jupiter causes these objects to have their orbits disturbed,” says Weingrill. Then their orbit around the sun takes on an elliptical orbit – and some of these objects, such as the Tsuchinshan Atlas or the famous Halley’s Comet, are also directed close to the Earth.

Observation system is intended to warn of dangers to Earth

Weingrill can imagine that Tsuchinshan Atlas flew past the Earth in earlier epochs, but was not perceived as a comet at the time due to a lack of instruments. “You can’t even say how many times he’s been there,” said Weingrill. The fact that it was noticed at the beginning of 2023 is only thanks to modern technology.

Atlas is an automated observation system that scans the sky for objects to warn us of potentially dangerously close asteroids – rather than to point out aesthetically interesting features. The observatory on Purple Mountain near Nanjing is connected to this system. C/2023 A3 ran in front of the telescope on January 9th last year – and that’s the only reason we’re now following its flyby of Earth for the first time.

MAZ