The “comet of the century” C/2023 A3 (Tsuchinshan-ATLAS) it is continuing to put on a show in the sunset sky after its close pass with the Earth on October 12, but its brightness is decreasing and the next few days will be the last days to be able to observe it in our skies. Even if the nickname “of the century” is journalistic and a bit excessive, it is still one of the comets most important and brightest of the decade. Currently, October 18, the comet is located between the constellations of the Serpent and that of Ophiuchushalfway between Venus and the star Arcturus. At sunset, around 6.20pm, the comet is heading west at ben 33° above the horizonwhich makes it observable for good three hours after sunset.
As it moves away from the Sun and our planet, however, the comet gradually fades, so this weekend and next week are probably the last good opportunities to try to spot the comet. AND hardly visible to the naked eyeunless you are in skies free of light pollution. Thanks to the lunar glow of October’s “supermoon”, we recommend using good binoculars to locate the comet and photograph it.
How long will the “comet of the century” be visible in the sky: days and times
Providing an exact value of the current apparent brightness of the comet is not immediate, since the databases that can be consulted online report values that are not homogeneous with each other: some provide only the value of the magnitude (the unit of measurement of brightness in astronomy) of the comet nucleus, others instead they give the magnitude of the entire comet, including the tail. Additionally, each site reports the brightness value in a specification in a certain wavelength range.
Using the database as a reference Minor Planet Ephemeris Service of theInternational Astronomical Unioncomet C/2023 A3 (Tsuchinshan-ATLAS) currently has a magnitude equal to 3.5which will rise to 4.1 Sunday 20 October (higher magnitudes mean lower luminosities according to astronomical convention). The comet will catch up magnitude 6conventionally defined as the threshold limit of naked eye vision in extremely dark skies, just the October 31ston the occasion of Halloween. As for times, at the moment observations of the comet are possible for about three hours after sunset, so approximately from 6.30pm to 9.30pm.
In any case, the comet will be there by the end of next week very difficult to spotrequiring a good deal of patience.
How to follow the position of comet C/2023 A3
Below you can observe the position of the comet in the sky in the next few days:
Over the course of the nights the comet it will move within the constellation of Ophiuchusgoing in conjunction with the star Beta Ophiuchi (the second brightest in the constellation) on October 28. Day after day, the comet will become higher and higher on the horizon as the Sun sets, passing by 33° current altitude at 45° on October 31st. Furthermore, thanks to the transition to solar time scheduled for the night between 26 and 27 October, the comet will be observable one hour earlier starting from Sunday 27 October, given that the Sun will set at approximately 5.15pm. It is possible to follow the path of the comet through dedicated apps such as Stellarium or online planetariums like TheSkyLive.
The spectacular bright tails of comet Tsuchinshan-ATLAS
From the dozens of wonderful photos of comet C/2023 A3 (Tsuchinshan-ATLAS) we can see how it has a tail covering at least 10-12° in heaven. From the photos it is visible both ion tail than dust tail: the first is formed by the volatile gases present in the coma which are ionized by the ultraviolet photons of the Sun and pushed in the direction of the solar wind (therefore opposite to the Sun), while the second is formed by small dust particles, which instead tend to follow the trajectory of the comet. Since the dust particles have greater inertia, the dust particles are expelled from the coma more slowly than the ions that make up the ion tail, so the two are very often not coincident and the dust tail tends to be more curved than the ion tail.
A particular feature of C/2023 A3 (Tsuchinshan-ATLAS) is its anti-tail. It is a further small tail that seems to emerge from the head of the comet, in the opposite direction to the main tails. This is a perspective effect due to the geometry of the Earth-comet system: the anti-tail is in fact the end of the tail itself which is curved and not straight, so when the comet moves in its orbit, part of the tail comes from the Earth seems to generate a forward anti-queue.
