Sometimes comets are disappointing, generating great expectations, but they become timid and disintegrate, as happened to the ATLAS C/2024 S1. There are also those that positively surprise us and begin to strut near the Sun to leave us astonished with their beauty. This is the case of the new comet that begins to be visible near the horizon these coming afternoons.
ATLAS comets
The new visitor, ATLAS C/2024 G3, was discovered on April 5, 2024 by the ATLAS minor body search and tracking program (Asteroid Terrestrial-impact Last Alert System) based on images obtained with the 0.5 m reflecting telescope located in Río Hurtado, Chile. This detection system is so successful that we are already getting used to calling many of the new comets that grace the sky by its acronym.
At the time of discovery, comet 2024 G3 was a very faint object that was 655 million kilometers from our planet, almost half the distance that separates us from Saturn. On January 13 it passed through perihelion (its closest position to the Sun) just 14.5 million kilometers from the Sun, looking as bright as the planet Jupiter, although it is not easy to see it as it is very angularly close to our star. However, we can try to see or photograph it in the middle of the sunset.
Where does comet ATLAS 2024 G3 come from?
This comet approaches within 14 million kilometers of the Sun, so it is classified in a category known as skirt kites sunskirters. It comes from the call Oort clouda storehouse of icy bodies at the solar gravitational limit.
ATLAS C/2024 G3 moves in a slightly eccentric orbit whose aphelion (farthest distance from the Sun) is approximately 10,000 times the average Earth-Sun distance, known as the Astronomical Unit (au).
The comets stored in the Oort Cloud possibly formed between the outer edge of the main belt and the region dominated by the giant planets (Jupiter, Saturn, Uranus and Neptune). As a result of encounters with them, were gravitationally propelled toward this outer region of the solar system.
In the Oort Cloud, comets have literally remained ultra-frozen, at a temperature that ranges, depending on the distance from the Sun, between -173⁰ C and -233⁰ C. They can remain in these circumstances for billions of years. A close pass of another comet, or even a planetary body or a starcan propel them towards the Sun. This explains why dozens of new comets are discovered every year from that remote region.
How do we know that it has survived its close passage to the Sun?
As this is the first time that ATLAS C/2024 G3 has been observed, no one knew what its behavior would be. Until December, it shone little, but on January 2, 2025, specialist Terry Lovejoy reported that it had suffered an outburst and had increased its luminosity significantly. The next day it had already reached the brightness of the brightest stars. Since then the comet has continued to increase its luminosity and we can follow it despite its proximity to the Sun.
One of the big doubts we had was whether this comet would survive a passage so close to the Sun. It has succeeded, and with flying colors. That is, exceeding initial expectations in brilliance. This time, comet lovers have a passionate ally in the International Space Station (ISS). It’s about the astronaut Don Pettitwhich has surprised us with spectacular images of the ATLAS C/2024 G3 from the privileged height of the ISS.
How and when can we observe it?
Starting in the next few afternoons, the comet will separate angularly from the Sun and, although it will lose brightness, its visibility will improve.
To see it you have to look for a dark place with the western horizon completely free of obstacles and wait for the sun to set. Let’s enjoy the slow sunset to begin tracing the horizon in the area where we have seen the sun set. It is necessary to warn that no one should try to see it with optical means during the day at the risk of losing sight (never point an instrument at or near the Sun without adequate protection and expert advice).
Starting in the coming afternoons, the comet will separate angularly from the Sun and, although it will lose brightness, its visibility will improve.
Some specialists are now taking photographs in broad daylight, but they know the position of the comet well and block the dazzling action of the Sun with a wall or roof (which hides it). This way neither your eyesight nor the telescope is put at risk. However, it is not easy and reverses risks.
The best time to photograph it
The best afternoons to see or photograph it occur this week. The comet passes through the constellation of Capricorn. Every evening, if we look at the luminous pair of planets Saturn and Venus that are in the upper part of Aquarius, we can use binoculars, going down until we touch the southwest horizon, near which we will find the comet.
Next weekend, the comet will have moved about 15⁰ away from the Sun and will remain accessible for a few days in the first half hour of the night.
Astrophotographers can try applying a polarizing filter to avoid the dazzling halo of sunlight. The first few days there is very little margin but, particularly during the next weekend, the comet will have moved about 15 ⁰ away from the Sun and will remain accessible for a few days in the first half hour of the night. It will not be an easy goal, but it will be very rewarding and valuable for astrophotographers.
Nature sometimes serves us its surprises in small doses, given that a few days later, starting on the 21st, it will remain below the horizon at the same time that it will lose its luminosity as it falls into decline to only be visible, increasingly weaker, from the southern hemisphere.
Josep M. Trigo Rodríguez He is Principal Investigator of the Meteorites, Minor Bodies and Planetary Sciences Group, Institute of Space Sciences (ICE – CSIC).
This article was originally published in The Conversation. Read the original.
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