(ORDO NEWS) — A comet that has visited the inner solar system for the first time in 80,000 years could outshine the “green comet” of 2023 in brightness.
The last time the Earth saw the very bright Comet McNaught was in 2007, but only when observed in the Southern Hemisphere did it appear brightest.
Comet Tsuchinshan-ATLAS may never become as bright, but if it does, the whole world will see it.
A comet that will make its closest approach to Earth in September 2024 is already causing a stir among amateur astronomers.
Comets are unpredictable beasts, and many have proven disappointing, but C/2023 A3 (Tsuchinshan-ATLAS) has many of the characteristics needed for the best possible visibility for at least a decade.
Comets visit the inner solar system quite often, but few of them can be seen with the naked eye.
Most of them are either regular visitors who slowly lost material on previous approaches to the Sun and lost their former brightness. Others never get close enough to Earth to be seen with the naked eye.
The orbit of Tsuchinshan-ATLAS is so long that it is still debated whether it visited the inner solar system 80,000 years ago or never visited.
With the upcoming approach, it will be at a distance of 58 million kilometers, or just under 0.39 AU. (distance from the Earth to the Sun) from the Earth.
The comet’s brightness estimate also has a lot of uncertainty. It is not a giant object like the Bernardinelli-Bernstein megacomet.
However, we can already see signs of a tail as low-melting ices sublime into gas, even though it is much farther from the Sun than Jupiter.
By the time Tsuchinshan-ATLAS is inside the orbit of Venus, gases will begin to drain from it, carrying dust with it and forming a tail that will probably stretch far across the sky.
How long and bright the tail will be depends largely on the exact composition of the rocks and ice that make up the Tsuchinshan-ATLAS, and whether it sticks together or breaks apart under the scorching rays of the Sun.
Comet modeller Gideon van Buytenen notes on his website, “The ability of comets to either disappoint or pleasantly surprise us is one of the many things that makes them so interesting.”
Van Buitenen predicts a zero peak for now (the figure is updated every six hours based on new observations).
This would make it brighter than all but the four brightest stars, and about forty times brighter than C/2022 E3.
However, this figure does not take into account the possibility of forward scattering, which, if it occurs, could cause Tsuchinshan-ATLAS to reflect almost as much light back to Earth as Venus.
Moreover, it will still be close to the celestial equator.
Tsuchinshan-ATLAS is currently within a degree of the celestial equator, making it visible from virtually any part of the Earth.
Unfortunately, at magnitude 18, it is beyond the reach of most amateur telescopes. Even with binoculars, it will only be visible in July or August 2024, but then it should quickly increase its brightness.
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