Caoimhín's Content

Today we’re not going to be taking a look at the solstice. I have taken a look at the solstice in a few different ways over the past couple of pieces, so we’re going to look at something a little bit different today. We are going to take a look at an event that was suggested by a commenter. If there are any astronomical events, past, present or future, that you would like discussed here, all you need to do is let me know. Leave a comment here or on my YouTube channel and I will take a look.

This date was given to me in year, month, day format, which makes this nice and easy, as that is the default format in Stellarium. We’re taking a look at the planets Venus and Jupiter. We’re going to start with the sunset, hopefully Venus and Jupiter are above the horizon. At sunset we had Mercury, Saturn, Mars, so if we also have Venus and Jupiter, that’s a particularly full sky, a planet parade, as it were. We’ve covered a couple of planet parades in the past, and getting to sunrise we have Venus and Jupiter. They’re so close to the sunrise that I have a sneaking suspicion that this will not be visible in Ireland. It may be a conjunction, it may be an occultation, either way I have a feeling that it’s going to look better from elsewhere.

Moving forward a little bit in time, they appear to move apart. Moving back in time, they get closer together, which means this is likely going to happen under the horizon for us here in Ireland. Removing the ground and the atmosphere we can follow them regardless, so let’s see how close together they get. This is definitely going to be very close, if not a true occultation. It seems like an occultation, but of course, occultation wouldn’t be the correct term here. The term used by the commenter was transit, and normally transits are used for things moving in front of the Sun, but I would absolutely consider this to be a transit of Jupiter by Venus, because Venus is transiting in front of the planet. All of Jupiter is visible, Venus isn’t large enough to block it out entirely, even though Venus is much closer to us. In fact, let’s see the distance difference from this perspective. We’re looking at both of them very close to them being behind the Sun, we can tell by how full Venus looks. Venus is over an AU away from us because it’s almost on the far side of the Sun, just over 1.6 AU. Clicking on Jupiter, it’s also on the far side of the Sun from us, 6.2 AU. Not quite six times further, we’ll say three and a bit times, further from us than Venus, and yet Venus still looks tiny by comparison.

That’s a very good transit, but as I said, it’s happening under the horizon for us here in Ireland. It’s under the horizon to the west, pretty far under the horizon to the west. We’ll very quickly hop over to a different location on the planet. We want to move east, to where these would still be above the horizon at this time. We’re pretty far over, so we need to move to where the sunrise is just happening when it’s already, 9 o’clock UTC in January. It seems strange for the Sun to be under the horizon, given that the Sun is still above the horizon at the moment, even at 9 o’clock in the evening. As we move across the face of the Earth, the Sun and these planets get closer and closer to the eastern horizon at the same time UTC. We will need to go pretty close to the equator as well, just to get things in a position where the Sun will be far enough under the horizon for this to be visible. Or, for this to have been visible, because of course, we’re looking way back into the 1818 here, way back into the 1800s. In Stellarium, this means no light pollution by default. Of course, there was far less the light pollution in the 1800s than there is today. From somewhere around the Philippines, Venus and Jupiter were still transiting each other just as the Sun was rising.

Now, from that perspective, it looks like Venus is almost over Jupiter, Venus isn’t completely enclosed in the circle of Jupiter, but rather poking out the top. I believe that this is just down to parallax. We are so much closer to Venus than we are to Jupiter that it’s not too much of a surprise that that’s occurring. It’s way easier to get these kind of parallax effects with these closer objects that are in our solar system with us rather than with stars. Hopefully this will make it easier for us to see a difference if we change location. So let’s move back up on the planet a little bit closer to the latitude we’re at here in Ireland. They would still be under the horizon from Northern China at the same time due to the angle of the ecliptic. Moving back in time, closer to sunset, they’re still up and visible, with the glow of the Sun, in a dark sky. All skies were dark skies back then. They are close, but they go back under the horizon before the transit occurs. I must have deviated a little bit from the correct latitude, but as you can tell, I’m sure this would be, would have been, a tricky transit to catch. Removing the ground again, and yes, Venus is a little bit more wholly enclosed by Jupiter now that we’re looking at it from a little further north. That difference is down to parallax.

It’s definitely a tricky one to catch at its best, and not the only one that was suggested. The same commenter suggested another event involving Jupiter even further in the past. We’re going all the way back to the 1100s, the year 1170, so we’re very far in the past. Just to treat all of these events the same we’re going to return to our default location of Ireland and we’re going to bring back the atmosphere and the ground. We are yet again looking for Jupiter, but not Venus. Instead, we are looking for Jupiter and Mars. They are both up and next to each other during the night, so we don’t even have to look too hard to find them.

Again, this was described as a transit, and now that we’ve seen the transit of Venus and Jupiter I think I know what to expect. I am expecting Mars to completely go in front of Jupiter. Mars, of course, looks even smaller than Venus. As we move forward to get them closer together, they both go under the horizon for us here in Ireland, which is unfortunate. Again, we’ll remove the ground and atmosphere. Mars is smaller than Venus, but is is also closer to us here than Venus was for its transit. If we take a look at the distance we’re getting 4 AU away for Jupiter. That’s close, so it must be close to opposition. We’re getting just 0.83 au away Mars, so it is closer to us than Venus was, even though Mars on average is further from us than Venus. Mars here is closer to us than it is to the Sun, and for planets that are further from the Sun than us, that means they must be close to opposition, they must be on the same side of the Sun as we are. Allowing time to pass, they do line up, Mars, the red planet in front of Jupiter, the giant planet. As we move through time, we can see Jupiter rotating, with Mars almost aligning with the Great Red Spot. Not entirely, but the Great Red Spot is just coming into view just above Mars as the transit completes.

This is definitely a fantastic transit, but yet again not visible from here in Ireland. We’re going to do the exact same thing as last time. I’ve removed the atmosphere and the ground. We’re looking over in the northeast and they’re so close to opposition that this has got to be visible from a large portion of the world. We’ll get our location map up and we will move again in the same direction, eastward. We won’t have to move far, already we’re getting very close from around Moscow. They’re above the horizon in darkness and so close to opposition that we don’t need to worry about how close we are to the equator. They’re so far from the Sun in the sky that they’re going to be visible even when the ecliptic is being seen at quite a shallow angle. We will change latitude for a different reason in just a moment. From here, we’ve got Mars blocking out Jupiter. Let’s bring back the atmosphere in the ground, and it is indeed visible, of course through a telescope. They are so close together that to the naked eye it would appear almost like one solid object. You would have to look at this over the course of a couple of days to see Mars coming in and transiting Jupiter. Of course, through a telescope, the transit is only happening on the specific day, the transit itself will be pretty short lived.

Very similar to when we took a look at Venus, Mars is just above the bottom of Jupiter, only just fully backed by the disc of the giant planet. By changing our latitude we should be able to take advantage of parallax to change this view a little bit and make Mars appear to be in a slightly different position. As we move down on the Earth a little, the effect is already occurring as we come approach the southern hemisphere, Mars seems to be getting higher on Jupiter, with more of Jupiter visible beneath it. We’ll go all the way to Madagascar. It’s very tricky, and I don’t even know if this would be possible, these exact coordinates may be off the coast of Madagascar. However, we get Mars practically passing through the middle of Jupiter, practically level with that equatorial belt. This happens just as they come above the horizon, a bit before sunrise. As the Sun comes up, they will disappear from view fairly high in the sky. This would have been a fantastic place to see it. Way back in the year 1170, from roughly off the coast of Madagascar, you would have been able to see Mars emerging from the transit of Jupiter just as Mars and Jupiter rose.

There we go, two fantastic transits of Jupiter by other planets, Mars and Venus. Thank you very much to the commenter who made me aware of these events. If any of you reading this have events that you would like to see, past or future, just let me know and we will take a look. If you enjoyed this piece then please do like it. If you enjoy 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.