Caoimhín's Content

Today we will be looking for a comet, a massive rock in space, the comet C/2025 F2 SWAN. You may have noticed that the attached video is in irish, and I did toy with the idea of calling SWAN, the Solar Wind ANisotropies instrument, “ealla”, the Irish word for swan. However, this is an acronym, SWAN the name of the instrument that saw this comet initially, so i won’t try to translate it.

We begin by looking at this comet on the 1st of May, the date of posting. The comet is still above the sunset in the northern hemisphere, but very difficult to see here. This comet is pretty interesting for a couple of reasons, but we’re going to push ahead to watch this comet going around the Sun. For us here on this side of the world, this comet is hard enough to see, and it was hard enough to see anyway, being small and faint. The comet is definitely over the horizon after the Sun sets, but with the atmosphere spreading the light there is a little sunlight in the sky. On the 1st but even more so on the 2nd of May, the comet is very close to the Seven Sisters, and therefore very close to the Sun while the Sun is setting as well. This makes it hard enough in the city, but out in the countryside you may see it like a little star. To the naked eye it’s a lot like a star, it would be hard to see any tail at the moment. If we pull back, it’s hard to see even in the countryside unassisted, however if you even have a binoculars, or a telescope you may spot it. If you have a telescope then that’s great, but a binoculars would be enough for this comet. If we zoom in we are able to see the tail, or would be able. We are not sure now if there will be a tail to see from this comet now that we’re intop May.

When this comet was first seen, it was seen by a satellite that was watching the Sun, SOHO, the Solar Orbiter and Heliosphere Observer. SWAN is an instrument on that satellite, and the job that that satellite has is looking at the Sun. Neither SOHO nor SWAN is watching out for comets like this one, but sometimes in the pictures that this instrument takes, you can see comets. However, once spotted, it is then up to people in here on Earth to confirm it. SWAN saw the comet first, but then astronomers had to look through telescopes from here on Earth and confirm that it was a comet rather than any other type of massive space rock, like a meteor or an interstellar visitor. It may also have been a mistake, sometimes there are mistakes in thes images, often due to “noise”. Noise, as it’s called, is sort of little lights that you see in a camera sometimes, the graininess of a camera looking at darkness is usually noise, and this can happen even in sensitive equipment. If we look ahead for this month, for the month of May, we will see the comet orbiting the Sun. It appears to go from the north side of the Sun, where it roughly is now, around to the south. If could look at the daytime sky with no atmosphere, we would see the comet sort of above the Sun, and to the east. As we go trough May, the comet is going to move down to the other side, and for that reason, we aren’t going to see it here on the north side of the planet. To look ahead, we will have to go south, to the southern hemisphere. Then we should be able to see the comet for a slightly longer span of time.

As an example, we’ll shift our view to South Africa. Even further ahead than the middle of May, the comet is very high over the sunset. However the comet isn’t as bright late in May. It is at least right next to Orion, and Orion is still visible if you are in the Southern Hemisphere. Pulling back at little earlier in the month again, the comet goes down in the direction of the Sun, but that is moving back in time, really the comet is pushing higher in the southern sky and further from the Sun. It will be very close to the bright star Aldebaran a little before mid May and almost, almost visible with your eye alone. It would still be hard due to the light of the sunset. Allowing it to set a little further, there is a tree in the way. This happens and normally I say that if you are in the city or similar, that’s the sort of view you’ll have, there’ll be buildings or trees in the way. If you are trying to see this comet, if you are doing your best to see the comet, you’ll be going somewhere without things like that in the way, like the coast or a higher vantage point.

Once the sky is dark, a 7th magnitude comet would be visible in a dark countryside sky. If we push ahead a further, it gets lower and the amount of atmosphere it has to shine through goes up. Therefore, how bright the comet is goes down. As with all comets, you have to see this comet when the comet is far enough from the Sun, high enough in the sky not to be drowned out by sunlight, but still close enough to the Sun for it to get enough sunlight be lit up. Very early in May it’s at its brightest up to 6th magnitude, but low in the sky that’s just 8th with the atmosphere. This is almost visible, almost visible with the naked eye, if you are on the right side of the planet, down in the southern hemisphere. There is a chance that you will be able to see that comet, but there is a problem. There is almost always a problem, and the problem with this comet is that there is a chance that this comet is after breaking down already. This happens with comets when they are very very close to the Sun. When the comet goes closer and closer to the Sun, it gets warmer and the ice inside the comet heats up. When you are out in the vacuum of space, when water ice warms up it goes straight from solid to gas. There is no liquid water in the vacuum of space. This steam is what creates the tail, the water ice and the various other ices. It is not only water that is frozen in comets, but frozen ammonia, methane and other molecules. These other things exist as solids, or ices, when the comet is far from the Sun, but when the comet comes in it heats up again and these ices melt.

This comet was expected to be periodic, a comet that will come back around again and again, which you can usually tell by the angle of its orbit. However, C/2025 F2 only a has C there rather than a P, like other periodic comets like 1/p Halley. This comet hasn’t already come back around, and now there is a good chance that the comet won’t come around again. If we go back again, to the month of April, and back to the right side of the planet, we may see why. Well, that is to say the side of the planet that I am comfortable with, no side of the planet is more correct than any other side of the planet, both sides of the planet are right. When the comet was coming in towards the Sun in April, the comet was getting brighter and brighter as it got closer. If we go back in time, the magnitude goes down 7th, if we push ahead again that number gets higher and higher, up to about 6th magnitude. Then the number starts to go down again as the comet moves further from the Sun. However, that process stopped before the comet’s closest approach.

Usually comets get brighter and brighter when the comet is getting closer to the Sun but this time, when astronomers were looking at the comet, the comet stopped getting brighter. Normally that tells us that the comet has broken, the comet is after breaking into smaller rocks. A small rock on its own isn’t going to reflect the same amount of light back in our direction, you need to have a big rock to reflect a lot of light from one point. That’s what makes the comet visible, when the comet is reflecting enough light from the Sun, we are able to see it as the comet is large enough. That’s one of the ways that people are able to find how big things are in space, how bright they are, especially with the various massive rocks like asteroids and meteors. If they are bigger, more sunlight will reflected back in our direction.

With the comets, usually if they stop getting brighter, they are after breaking apart, but from this side of the planet it will be very hard to find that out, due to the place that the comet is. It is very very close to the Sun from our side when the Sun is setting, the light of the Sun will still be in the sky with the comet, blocking it from view. It is up to the other side of the planet, it is up to the Southern Hemisphere, to look at this comet now and figure out if it is still in one piece or if it has broken up. This is one of the reasons that is is so important that astronomers in the Northern Hemisphere need to talk to the astronomers down in the Southern Hemisphere. Our planet is simply in the way, and for that reason the astronomers ,particularly down in South Africa and in Chile, those astronomers work with the European astronomers up on this side of the planet and astronomers in the United States as well, Both sides of the planet have to talk with each other because sometimes there are objects like this comet. We can’t see that object when it goes to the other side of the planet, in order to keep an eye on it, we have to use the telescopes on the other side of the planet. This is just one of the reasons due to that it is important that the astronomers here in Europe are talking with the astronomers down in the Southern Hemisphere, due to stuff like this. We have to rely on the astronomers down on the other side of the planet to look at this comet, we can’t use the telescopes in the north. We have satellites out in space that can keep an eye on things like this, but as I said the SWAN instrument for example was looking at the Sun. The job of that satellite is not to look for objects or comets going through space, that’s sort of our job here on Earth.

So that’s a little more about this comet. I am after putting up a video about that comet already in English, but we have a little bit of news, that comet is, we think, after breaking down. If you enjoyed this piece then make sure you push the button that says you like it. Also, if you enjoyed this piece then there is a good chance that you would enjoy the other pieces that I put out and if you subscribe to this website and my YouTube channel then there is a better chance that you will see the new articles as they come out. Most importantly, thank you very much for reading and I’m sure I’ll see you back here next time.