At a time when we are watching for comet 2023 A3 Tsuchinshan-ATLAS, a new object, also discovered by the ATLAS program (Asteroid Terrestrial-impact Last Alert System), surprised us with its unexpected appearance. The new comet C/2024 S1 ATLAS, coming from the edge of the solar system, could be much brighter than the morning star, Venus. Additionally, it could be the second comet visible to the naked eye in just a month, a rather unusual event.
C/2024 S1 ATLAS enters the interior of the solar system and its orbit has a high inclination and eccentricity. Its orbits are also characterized by a close approach to the Sun, which includes the comet in the category of Kreutz sungrazers.
During this month, observing it from mid-latitudes will be a challenge due to the particular inclination of its orbit, which places it at a low altitude in the morning sky. In early November, it will once again be seen approaching the bright star Spica in Virgo.
Throughout history there have been very important comets of this type, whose transit through the inner solar system was as fleeting as it was extraordinary.
It can reach the brightness of a half-moon
Comet ATLAS is already accessible to amateur telescopes, but as it approaches the Sun angularly on its path, it can only be seen at dusk.
If the light behavior we observe continues, on October 28, when it reaches perihelion, just 1.23 million kilometers from the Sun, it could reach a magnitude of -8, similar to what we observe for the gibbous Moon (more than half full). . If this happens, it would occupy the second place in terms of brightness in the ranking of Kreutz grazing comets, now led by the famous great comet of 1965 C/1965 S1 (Ikeya-Seki), long awaited by astronomers. Unfortunately, comet ATLAS will then be very close to the Sun, even if by moving away from perihelion it could surprise us, just like Ikeya-Seki.
How to locate it
Currently, observing Comet 2024 S1 ATLAS is a challenge even for medium-sized telescopes. To locate it, this week you must discern the star Lambda in the constellation Hydra from a very high place, free from light pollution and with a clear horizon before dawn. With a telescope, by moving slightly towards the south, it can be observed as a nebulous star. The following sky map created by Gideon van Buitenen on his recommended page for Comet 2024 S1 details its trajectory across the sky.
It will still be visible after crossing perihelion, although low on the horizon. The first week of November, it could be seen at dawn under the constellation Virgo, under the star Spica. And it could even be seen during the day, which would be quite unusual.
Generally speaking, the comet will approach the Sun this month and, after crossing perihelion on October 28, it will be visible again from our latitudes from November 3. During the first half of November, it will remain accessible, although low on the horizon and moving away again towards the confines of the planetary system.
Its origin in the Oort cloud
This type of comet follows slightly hyperbolic orbits. Although one might think they come from the interstellar medium, we think they come from a large external repository called the Oort Cloud. Close encounters or even gravitational interaction with nearby stars could push them to encounter the Sun.
Dynamical models suggest that this enormous cloud of frozen bodies is the result of a large cataclysm. These would therefore be primitive bodies of the planetary system, of great cosmochemical interest, which would have formed in the outer region of the main asteroid belt and would have ended up being stored in the gravitational limit of the Sun.
Most are relatively fragile objects, called transitional objects because they are halfway between asteroids and comets, and made up of aggregates of ice, organic matter and tiny rocks.
At the beginning of evolution, the main belt was much more populated by objects and its mass increased so much that it forced the giant planets to move towards the interior of the planetary system. This had cataclysmic consequences and produced the gravitational dispersion of small icy bodies. Some ended up stored in the Oort Cloud, others escaped into interstellar space, and still others crashed into planets.
The late bombardment of the Earth
Most of the objects contained in the Oort cloud were pushed mainly by Jupiter and Saturn to the limits of the solar gravitational field. This was the time when rocky planets, such as the Earth-Moon double system, had just consolidated and were undergoing what is known as the Great Late Bombardment. This explains why new comets are discovered every year in this peripheral region, located between about 2,000 and 200,000 times the average Earth-Sun distance (called an astronomical unit and equivalent to about 150 million kilometers).
The consequences of this cataclysm persist. Then, the distribution and distances between the current planets were established. The process hammered the Earth and Moon, as revealed by the dating of many of the lunar rocks brought back by astronauts on NASA’s Apollo missions. Furthermore, our impacts with bodies several tens of kilometers in diameter have produced most of the large impact craters that we see on the Moon, dug by these bodies of low inclination which, instead of being projected towards the outside, dispersed inwards and fell until they met. the inner planets.
Scientific fascination
Astronomers continue to be fascinated by the lessons left by comets. One of my greatest professional adventures was participating in NASA’s Stardust, the first mission to bring back samples from a body other than the Moon and obtain clues about its composition. Following them closely and bringing samples are the best ways to continue learning from these bodies that bring us bottled messages from the same origin and composition of our planetary system.
Hopefully a day will come soon when humans will stop their countless fratricidal wars and devote a small portion of these resources to continuing to explore our environment to understand what these frozen and wandering worlds have to tell us.
Josep M. Trigo Rodríguez is a principal investigator of the Meteorites, Minor Bodies and Planetary Sciences group of the Space Sciences Institute (ICE – CSIC).
This article was originally published on The Conversation. Read the original.
