Caoimhín's Content

Today, as promised, we are going to take a look at a couple of comets. We’re beginning on the 3rd of April, which is just a little before Comet 2026 A1 MAPS reaches perihelion. MAPS is the name of the observation program, really the initials of the astronomers involved, that discovered this comet. This comet was, of course, discovered right at the beginning of 2026, we can tell by the A1, meaning the first comet discovered in the first half of January. This comet is coming up to its perihelion, and its perihelion is going to place the comet between us and the Sun. On the 4th of April, the comet will loop around the Sun, bringing it from behind to in front of it relative to us. By moving through a little bit of time, the comet completes its perihelion and returns roughly in the direction it came. At perihelion, this comet is going to be very close to the Sun, just 0.019 of an AU from the Sun. Its distance from the Earth is just under an AU, and that is part of what indicates that it is between us and the Sun. As the comet goes from behind the Sun to in front of the Sun, it is briefly visible to the side as it comes around. It will be in front of the Sun after this little maneuver, but it is also incredibly bright just as it comes around the side.

While next to the Sun, almost in front of the Sun, it will be at a magnitude of -7. Just as it’s coming around the Sun, that is when it would be at its most illuminated, technically it’s best possible view, but only achievable with no atmosphere in the way. Even a day either side of the perihelion, its magnitude has dropped down to just 5, so it’s gotten much fainter. Close to perihelion, it’s still not that far from the Sun, so that is going to put it in a more difficult position to see. Comets don’t make their own light, they can only reflect the light of the Sun, so as they get further from the Sun they get harder to see. While they are close to the Sun, its light usually blocks them from view. As the comet moves away from the Sun and into a more visible position where it won’t be blocked out by the Sun’s glow, that will cause its brightness, its magnitude, to go down. That puts that comet in a very difficult position for us to see here in Ireland. When it’s close to the Sun, it will be incredibly bright, but invisible from anywhere. This comet should be visible as it moves away while the Sun is setting from lower latitudes, very similar to the conjunctions of the planets that I mentioned in the last piece.

We’ll quickly jump down closer to the equator to check. We’ve gone back to the day that it is closest to the Sun so we’ll move it out from the Sun just a little bit by moving ahead a couple of days. Then we’ll get the Sun under the horizon and turn the atmosphere back on to see if it remains visible. It does not, it’s still not quite dark enough. This comet is going to be very difficult to see, by the time it’s far enough from the Sun to be out in darkness, it’s going to be quite faint. By almost the middle of April, it’s down to almost magnitude 13, and it might as well be magnitude 13 thanks to the air masses we have to look through, it’s still very low in the sky. This comet is going to be a very difficult one to see, but it is going to be very bright just as it comes next to the Sun. For satellites that are observing the Sun, it going to be in view and it will be imaged by those satellites. Even though the satellites that are looking at the Sun, their mission really is to study the Sun, they do still image and sometimes discover comets. These comets that go very close to the Sun, they get caught in the satellites field of view, even if they’re not the target of observation.

That comet isn’t the only comet that’s going to be making its closest approach to the Sun in April. C/2025 R3 PANSTARRS is a comet that doesn’t seem to be known by Stellarium, but that’s okay, we can add it in. This comet was discovered later in 2025. R3 that tells us the half month was the first half of September, and that it was the third comet discovered in that half month. We can user the Solar System editor plugin in Stellarium to add comets like this that it doesn’t already track. If you look through the archived posts, there is a piece on this website that goes into more detail about adding comets using Stellarium’s solar system editor plugin. We will import this comet using it’s orbital elements, which we’ll find by searching for it online through Stellarium. We need to make sure that we spell everything correctly because it needs to be correct for this system to find it. Once found, we just select and import it.

PANSTARRS or The Panoramic Survey Telescope and Rapid Response System is the name of the telescope system that was used by humans to discover this comet. This comet is going to be making its closest approach to the Sun later in the month, coming up on the 24th by the looks of it. To get the best view we will bring ourselves back to daytime, we’ll get rid of the atmosphere again and we’ll take a closer look. This comet isn’t as bright at perihelion, and it’s also non-periodic. At perihelion it passes between us and the Sun, it must as it’s closer to us than 1 AU, which is the distance between us and the Sun. It’s actually a little bit further from the Sun than it is to us, almost half an AU away. This comet isn’t going to look as bright, it’s not getting lit up as much by the Sun, but its brightness should be a little bit higher when it’s between us and the Sun. The comet should brighten up a little bit because of light bouncing around its surface and getting diffused by the ice that it has around it, diffused by its coma, in a phenomenon called forward scattering. It does seem a little brighter, around magnitude 7 at perihelion, so it’s not going to be a particularly bright comet. However, it stays a little bit brighter while it gets further from the Sun. Hopefully this is a comet that we may have a slightly better chance of seeing, but again, because of the angle at which we are seeing things at the moment it will be hard to do from Ireland.

C/2025 R3 looks to be south of the Sun from our perspective during its perihelion, it doesn’t transit the Sun. It’s also inclined to the ecliptic, and that’s going to make it even more difficult to see. As it gets further away from the Sun, it will almost seem to follow the horizon, which means it will stay setting with the Sun. This is different to the planets, which seem to climb up the ecliptic. This is a comet that looks like it will be best seen from the Southern hemisphere as well, so that’s where we will go to take a look at it. Despite the fact that it’s not going to be visible really from the northern hemisphere, C/2025 R3 PANSTARRS is going to be a little bit brighter when it’s further from the Sun than the Comet C/2026 A1 MAPS, which we’re also not going to have a particularly good view of from here in the northern hemisphere. It looks like both of these comets are going to be primarily southern hemisphere comets. Looking at the comet around sunset from the southern hemisphere, we’re a few days after perihelion to move it a little away from the Sun so that it’s not too close. It should be much more visible than C/2026 A1, and we want to see if it is above the horizon while it’s still a reasonable magnitude and the sky isn’t too bright. With the atmosphere back on, it looks like the sky’s a little too bright. Thankfully, we can move more days ahead with the comet still being 8th magnitude. Even reduced to 9 because of how close it is to the horizon, it should be visible with a telescope or a good pair of binoculars.

That is Comet C/2025 R3 PANSTARRS stars and Comet C/2026 A1 MAPS. Those are the main comets that are going to be getting close to the Sun in April, but they’re not the only comets that we’re going to be able to to see in April. Of course, there are various comets out there and many of them are visible when they’re quite far from the Sun if you have a powerful enough telescope, they’re still technically out there even if under most normal conditions it would be quite hard to see them. However, there is another comet that is going through the sky around this time. Surprisingly, it does look like, yet again, it’s not known by Stellarium, so we will add it in. This is surprising because it is a better known comet than the other recently discovered ones, it is a known periodical comet, 88P/Howell. The Comet R3 PANSTARRS is a non periodical comet, so it is going to get thrown out of the solar system. Once it passes around the Sun, it’s going to get slingshot out of the solar system entirely.

Comet 88P/Howell has a 5 and a half year period, but it’s available to Stellarium with its 2026 data, so that means its path should be accurate for this year. It is currently at 14th magnitude and it is moving across the morning sky pretty slowly. We’re after traveling pretty far into the future to catch C/2025 R3, so we’ll come back to April. It is closer to the Sun in April, and it’s also at an angle that would make it very difficult to see for us here in Ireland. It will move out away from the Sun pretty slowly, and it is also not too close to us or the Sun. It’s almost twice as far from us as we are from the Sun, having hit perihelion in March. It is reasonably far from the Sun in the morning, but not at a particularly good angle for us to see here in Ireland. It’s another comet that’s going to be better seen from closer to the equator.

So those are three comets, none of which are particularly easy to see or observable from here in Ireland, at least not until we get pretty far into the future when these comets will be above the horizon when the sky is dark enough for us to take a look at them, and of course by then they’ll also be quite faint having traveled quite far from the Sun. Those comets, 88P/Howell, a periodic comet, C/2025 R3 PANSTARRS which is a non-periodic comet, it’s going to leave our solar system and not come back, and C/2026 A1 MAPS which I do believe is a periodic comet, it just hasn’t come around more than once. It’s only just discovered, we haven’t seen it go through its period. All of those comets are better seen from the equator but at least we all know they’re out there. Even if you don’t get a chance to see them in the real sky, I hope you enjoyed this description of them here. If you did enjoy this piece then please do like it. If you like this kind of content then please subscribe to this website and my YouTube channel. Thank you very much for reading and hopefully I’ll see you back here next time.