This story in the original appeared in WIRED in Spanish and translated from Spanish.
C/2023 A3, also known as Tsuchinshan–ATLAS and considered the “comet of the century,” will appear in all its splendor in our skies in September and October 2024. Due to its characteristics, astronomers believe that it will be very bright, similar to Halley’s comet in 1986 or NEOWISE in 2020.
Comets like C/2023 A3 are balls of icy gas, rock, and dust that orbit the sun. They are often amazing because of two physical phenomena that occur during their journey.
The first is the tail, which extends from the comet’s nucleus as it approaches the star it orbits. Solar radiation from the star—in our case the sun—vaporizes some of the comet’s icy material, spewing gas and dust away from the nucleus that then reflects the star’s light. As a comet approaches its star, its tail grows larger due to increased solar radiation.
The second phenomena is the coma of the comet. This is an envelope of sublimated ice that forms a kind of atmosphere around the nucleus as it approaches its star, again due to solar radiation. It also enhances the brightness of the comet.
What is the Best Day to See the Comet?
C/2023 A3 will shine in the northern hemisphere sky from September 27 and will remain visible until the last week of October. During this time, the comet will reach its minimum distance from the sun, before beginning its journey back into the solar system.
According to the specialist blog Cometography, the day when C/2023 A3 will shine brightest will be on October 2. The comet’s tail will be long and impressive at this point due to its proximity to the sun.
What Time Will the Comet Be Seen?
Because of its proximity to the sun, the comet will be similar to Mercury and Venus: It will be visible near the horizon, in the path of the sun, and before sunrise. The appropriate window to admire it is between 5 am and 7 am from September 27 onwards. The timing and position will be similar throughout the northern hemisphere.
As October progresses, the comet will raise its position relative to the horizon and at the same time lose its brightness. Because Tsuchinshan–ATLAS is a long-orbiting body and originates from the Oort cloud, beyond the edge of the solar system, it will not reappear in our sky for tens of thousands of years.
