The memories of the famous comet C/2023 A3 (Tsuchinshan – ATLAS), which we admired in October, are still fresh, and an even more spectacular comet, C/2024 G3 (ATLAS), is already approaching the Sun. What does it look like? When will it reach its peak brightness? Will we be able to see it, and what can we expect from it? Please read about this and much more in our materials.
A new comet tail
The promising comet was discovered on April 5, 2024, using a half-meter telescope of the ATLAS robotic system – the Asteroid Terrestrial-Impact Last Alert System, designed primarily to monitor potentially dangerous asteroids. It was moving through the southern constellation of the Apus and was an inconspicuous, slightly blurry speck of +19 magnitude, which means it was almost 160 thousand times fainter than what the human eye can see in the sky.
The first calculations of the orbit showed that the comet is periodic, but the period reaches 160 thousand years. Therefore, if the calculations are correct, our distant ancestors still lived in Africa when the “tailed guest” last visited the central part of the Solar System.
Since this comet was the third to be confirmed in the first half of April and a long-period comet at that, it was given the permanent designation C/2024 G3 and inherited the ATLAS designation from the discoverers.
Almost immediately it became clear that in the winter of 2024/2025, the comet would become very bright, almost as bright as Venus is now. However, the calculations of the specific peak brilliance fluctuated. The optimistic forecasts are primarily due to the comet’s close passage around the Sun: On January 13, it will pass perihelion at a distance of only 0.0935 AU, which means it will be 4 times closer to the hot luminary than Mercury is on average. C/2024 G3 (ATLAS) is classified as a near-solar comet because 14 million kilometers from the Sun is close to the depth of dirty ice.
Will the comet survive the hot “kiss” of our central star? Or will it melt in its hot embrace? We have already seen this happen with last year’s comet C/2023 S1, which at first promised to be bright, then showed several flashes, and completely evaporated before perihelion. If the comet is indeed periodic, it has already passed this test (i.e., it is dynamically old), and this increases the chances of survival.
Sudden flash
Over the past few months, observations of the main character of our story have been quite a challenge. First of all, the comet’s orbit is located in such a way that most of the time it can be observed only in the southern hemisphere. But even there, observations faced difficulties: the apparent position of the “tail” was too close to the Sun! This circumstance caused C/2024 G3 to be much less popular than its “predecessor” C/2023 A3 (Tsuchinshan – ATLAS), whose images flooded the Internet in the fall. Nevertheless, the available data showed a gradual planned increase in brightness. By the beginning of January, the comet’s brightness was already ~4.9m, which exactly matched the forecasts. Its calm behavior confirmed the hypothesis that the comet was dynamically old.
The accumulated observations allowed scientists to update the orbit parameters. Now it turned out that the comet is moving in an open, almost parabolic trajectory, so it most likely came to us from the Oort Cloud and is approaching the Sun for the first time.
On January 2, before sunrise, the famous comet discoverer and observer Terry Lovejoy noticed that C/2024 G3 suddenly increased its brightness several times. Unexpectedly for himself, Terry was able to find the comet in a fairly bright sky with small binoculars. The comet clearly showed its first outburst. Such events usually indicate nucleus fragmentation.
Lovejoy’s conclusions were confirmed by other observers on the same day. On January 3, Gus Ballan (Argentina) was even able to see the comet with the naked eye! It could be expected that after the outbreak the comet would dim somewhat, but over the next few days it did not diminish in luster but continued to increase. Now, the maximum brightness predicted for January 13 has reached an incredible -6m, which is much brighter than Venus! This means that, theoretically, it will be possible to observe it even in the daytime sky near perihelion. However, there is one “but” here…
Observations in the Northern Hemisphere
The trajectory of C/2024 G3 (ATLAS) is oriented in such a way that the comet will be in the northern sky during its perihelion, and it is at this time that it should become extremely bright. The period during which its brilliance peaks is very narrow – it lasts just a day. Although a couple of days before and after the peak, the comet will still be bright.
The only difficulty we face here is its extremely close proximity to the Sun. During perihelion, the comet will be only 5° from daylight and will rise just 20 minutes before it. If the fragmentation of the nucleus does not continue (and so far no other outbursts have been observed), the comet may even become a daytime object. But to capture it, it is necessary to take certain precautions. In particular, you need to reliably hide from the Sun behind a building.
Despite the extreme conditions, there are still chances to see a comet. You will need a clear horizon. Between January 10 and January 12, you can try to catch the comet in the southeast, just before the Sun appears from behind the horizon. On January 13-15, it is worth hunting for it right after the daytime star disappears – here you will need an open southwest.
And there is another opportunity to track the movement of the “tailed traveler”. On the evening of January 11, it should appear in the field of view of the SOHO space solar telescope and will move there for at least 4 days.
