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Today we are going to be taking a look at some partial occultations and conjunctions involving the Jovian satellites. This is something we have taken a look at in a previous piece, for occurences early in September. There were some conjunctions and occultations in involving Jupiter’s moons, early in the morning and from various locations, and here are a few more.

We’ll start nice and early in the morning, at about 6:45 am so not too early, and we have Jupiter reasonably high above the sunrise. This is from here in Ireland. We will zoom in and take a closer look just in case any of Jupiter’s moons are overlapping each other or close to overlapping each other from here. Taking a closer look reveals the Jovian system, the Jupiter system. On the morning of the 19th we are not seeing the Great Red Spot, but we are seeing Ganymede, Io, Callisto and Europa. These are Jupiter’s four biggest moons, they’re often known as the Galilean moons. Jupiter has many more moons, and if we take a closer look we may see some, in this case Metis and Thebe. As we move around, other moons will no doubt move around, coming into and out of view. We’re going to move back in time to bring Jupiter lower in the sky, keeping an eye on its magnitude and the air masses we’re seeing it through. We do have a while until the air masses increase up to about17 or so, that will tell us that Jupiter is very low in the sky.

Just as Jupiter is rising up from under the horizon, we’re getting up to about 25 air masses. This must be very close to the horizon, but still above low bushes and walls. Moving through time, some of the moons are visible moving around, for example Amalthea. Unfortunately it doesn’t look like any of the moons are blocking each other out, except maybe Amalthea and Callisto. Zooming in on that pair take a closer look, they’re not quite overlapping but it is a very close conjunction. Amalthea isn’t one of the Galilean moons, it’s much smaller and much more difficult to see. It is the Galilean moons and particularly that we’re going to be concentrating on. Just like the recent piece, we are going to particular locations where we know these things are going to overlap.

These locations have been suggested by a commenter, so thank you to them. We’re headed to St. Pierre, of St. Pierre and Miquelon, off the coast of Eastern Africa. It’s out in the Indian Ocean, St. Pierre and Miquelon are a group of islands close to Madagascar. We’re still on the 19th, but we’re after moving so far across the world that we’re back into daytime. We are still looking at sunrise in the east, but because we are now on the other side of the equator, we are seeing Jupiter to the north of the east rather than seeing it to the south. Mars is also is still up, Mars will be there in the early morning in September for quite a while. We are zooming in on Jupiter and it looks like Callisto is just in front of Jupiter. We’ll move through time a little but it looks like all we can catch is Callisto occulting, or transiting, Jupiter. If we move forward Callisto moves off the face of Jupiter, but not quite all the way. Callisto stays in front of Jupiter really the whole time that it is up and not too bright.

Of course not what I expected, the past few suggestions from this commenter, the other suggestions on this list, showed the moons moving in front of each other. I am surprised that this one didn’t and it does seem unfortunate that they are not occulting, or at least not while they’re visible to the naked eye. If we get rid of the atmosphere and move through a little bit of time, then we might get an occultation of Europa and Callisto. We do, but it is happening during the day while the Sun is up. Although Callisto moving in front of Europa is a great occultation, it would be a great occultation to see, but as we can see, it’s happening during the day. For people in St. Pierre and Miquelon, it looks like you’re going to have a very similar view of Jupiter in the morning as we will here in Ireland. A good view, but it doesn’t look like an occultation will be visible, even though one is occurring, just at the wrong time. At other times, in other pieces, I would mess around with the location and figure out exactly where this would be visible, but this time we have a number of other locations and dates to check out.

Next we are going for Islamabad in Pakistan. We will bring the Sun back under the horizon, bringing Jupiter back into the sky and we’re going to move forward to almost the end of the month, to the 28th. We will zoom in on Jupiter once again and hopefully this occultation will happen while the sky is still reasonably dark, it looks like it will. Callisto and Europa are very close together. We’ll move back in time just a little and this is happening after everything has rise, Europa and Callisto line up. Europa is completely in front of Callisto. This is an occultation, this is one object going in front of another, but it isn’t really one blocking out another completely. This is really Europa transiting in front of Callisto without blocking it out entirely. This gives us a great idea of their relative sizes, Europa has to be smaller than Callisto. For us to see this perspective Europa has to be closer to us than Callisto, and if Callisto still looks bigger, well, Callisto must actually be bigger. This is visible on the morning of the 28th, at just 3:26. I would say start looking at about 3:20 or so just to make sure you give yourself plenty of time to see Europa transiting in front of Callisto. Even by the time it’s done, at just about 3:30, the sky is still reasonably dark. This is very early in the morning, and as we get towards the end of the month, especially for locations a little closer to the equator, Jupiter is going to be up and visible at much earlier times.

That’s not all. We do have a couple of other locations and a couple of other conjunctions or occultations to take a look at. All of the locations that have been provided by the commenter are capital cities, so we are going to French Guiana, to Cayenne, the capital of that country. We are also moving back a couple of days to the 25th. We arrive just after sunset, Saturn is just after rising, so we will have to move pretty far forward to get Jupiter into the sky. We’ll come back a little bit because this occultation, conjunction, whatever it turns out to be, we do want to see it while the sky is dark, hopefully dark enough to point a telescope. Zooming in to take a closer look, and immediately it is clear that Io and Ganymede are close together. Taking a closer look to check how close they get, we’ll move through a little bit of time. Without overlapping, they set. Perhaps if there was no trees and buildings in the way, we would be able to catch something, so we will get rid of the ground and we will try and get these objects closer together. They get very close, but they don’t appear to transit past each other. Io is closer to Jupiter than Ganymede, and in this case it seems to approach Ganymede before dropping away again. Io orbits Jupiter faster than Ganymede, so this is similar to seeing Mercury reach almost as far from the sunrise as Venus, before seeing it drop away again. That would take days to be observable, but these moons are moving much quicker.

Asd we follow the moons, they appear to jump as they cross where our horizon would be. That is the extra distortion of the atmosphere making things look a little bit strange as they reach a certain point. They look a little bit squished because of the atmosphere and the extinction by air masses goes up to incredible heights. It gets into hundreds of air masses, but of course this would happen almost exactly on the horizon, an incredibly difficult view to achieve. However, that view puts Ganymede and Io very close together, though not quite crossing over each other. The other moons, Callisto and Europa, are pretty far apart. Moving forward both Io and Ganymede get occulted by Jupiter, but that would be after they set in the evening. It looks like this is another location where there are close conjunctions of these moons, but not necessarily occultations. However, with most telescopes, this would look like an occultation or a conjunction. It Would look like Io and Ganymede are blended together, even though on closer inspection we can see that there is a little bit of separation. What you see will depend on your telescope.

We are going to travel to yet another location, another capital city, Manila in the Philippines, way over in the Pacific. We’re also going to move forward again to the 30th. If anybody reading this knows of things happening in the sky, wants to hear about certain things from certain locations, just let me know the dates, the locations, and we can take a look. Zooming in again, we have Europa and Ganymede next to each other, let’s see if they actually occult while things are visible. They do, Europa gets completely blocked out by Ganymede. Just coming up to 3:50 in the morning it is still definitely dark enough for all of this to be visible. We’ll move through a little bit more time just to see what else you would get to see looking at the Jovian system. As things got brighter Europa and Ganymede will visibly separate, this would be just as they’re rising.

That definitely brings us through to the end of the occultations and conjunctions of the Jovian satellites that I am aware of, but these things happen all of the time. Some of them are only visible from certain locations on Earth, but these things are always happening. Jupiter has so many moons, they’re always moving around and blocking each other out. I hope that you enjoyed hearing about how they would look from different views here. You can also check out the recent piece talking about the other occultations and conjunctions of the Jovian satellites that happened earlier in September. 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.