The ‘comet of the century’ approaches closest point to Earth

Comet C/2023 A3 has been on a long journey through space. This celestial body, composed of dust and ice, has been traveling from the far reaches of our cosmic neighborhood, the solar system. Dubbed the ‘comet of the century’ by astronomers and amateurs, it was first detected by telescopes at the Tsuchinshan Observatory in China and by the ATLAS project (Asteroid Terrestrial-impact Last Alert System) in 2023.

It is now approaching its closest point to Earth. The star successfully passed close to the Sun without disintegrating at the end of September, a phenomenon known as perihelion. From October 12, its bright, long tail, whose length is equivalent to the diameter of 42 moons, should be visible in the northern hemisphere.

Also known as the Tsuchinshan-ATLAS comet, it will become one of the most outstanding astronomical spectacles of recent times due to the stunning intensity of its brightness. This is measured by stellar magnitude, a scale that determines the brightness of a space object. Javier Licandro, an astronomer at the Canaries Astrophysics Institute (IAC), explains that right now the comet “is much brighter than Mercury,” which is located 77 million kilometers from Earth.

On October 12, the comet will be 70 million kilometers from Earth, or about half the distance between our planet and the Sun. “It is very likely that the comet will be more active now than when it was visible in the southern hemisphere,” Licandro predicts. C/2023 A3 could surpass the stellar magnitude of comet NEOWISE, which in 2020 reached magnitude 0.5.

It is estimated that the Tsuchinshan-ATLAS comet would have last passed around the Sun 80,000 years ago, when the Neanderthals would have been around to observe it. This explains why it bears the letter C in its name, since it is a non-periodic comet, i.e., with an open trajectory estimated in thousands of years. Tsuchinshan-ATLAS comes from the Oort cloud, at the limits of the gravitational field of the solar system; its place of origin is a huge storehouse of stellar objects which also produced Halley’s comet.

Other impressive comet events in recent years have been the Hale-Bopp and Hyakutake, almost three decades ago, which are indelibly etched on the memory of scientists and astronomy lovers. “Hale-Bopp came to have negative brightness and with the telescopes at the Teide Observatory we could see it during the day, despite the brightness of the daytime sky and the Sun,” says Licandro.

Where to see the comet?

According to Josep Trigo, an astronomer at the Institute of Space Sciences-CSIC, the comet will be perfectly visible from most countries, particularly those located in the northern hemisphere. “Given a horizon free of obstacles and away from the big cities, we might see it on the evening of the October 11, but from the 12th or 13th we will have more margin,” says Trigo. Sunset, at around 8 p.m., will be the best time to look to the west. “Every day the comet will be a little higher after sunset,” he says.

No special eye protection is needed to look at the comet and Licandro recommends using binoculars with a magnification of 7×50 or 12×50. Rural areas with little light pollution are ideal to appreciate this phenomenon. The faint glint of its tail will be visible at sunset. And so, this celestial wanderer will continue its trajectory until, in a few hundred thousand years, it will pass by again or change its course due to the influence of another planet.

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