Caoimhín's Content

Today we are going back in time to take a look at a conjunction. We aren’t going too far back, some of you may know that we have gone back into prehistory to take a look at things before. We’re only going back to 1988 this time and we’re going to be looking for a conjunction between Uranus and Mars. We may have been able to see it from here in Ireland, and there was also a conjunction between Saturn and Mars at the time. Taking a closer look, Uranus right next to Mars and there is some nice nebulosity behind them as well.

Uranus and Mars are quite close together, but not overlapping. We’ll get rid of the atmosphere and the ground, which shows the Trifid Nebula behind and above the conjunction, one of my favorites. We’ll move through time to see if we can get them any closer together or if this is the closest. It does look like they are getting very close, in fact it looks almost like an occultation of Uranus by Mars, but not quite. Mars is a little higher in the sky than Uranus. Mars is so close to being in front of Uranus that some of Uranus’s moons are visible behind Mars, so that might give you an idea of how big the Uranian system is, the moons can orbit pretty far from the planet. There are several moons orbiting Uranus, we’re up to 29. Mars’s two moons, Deimos and Phobos, are just barely visible. If we move through time a little bit, again, we can see them moving, and Mars does occult Oberon, one of Uranus’s moons, so that is interesting. I am quite surprised by how good they look, but of course, this is with the atmosphere turned off, so that will improve things.

If we pull back, we’ll see where this is occurring in the sky, if it’s visible from Ireland, and it’s not. In fact, it looks like it will be on the exact opposite side of the planet where this would look best, and by the opposite side, I don’t mean down south, but rather on the eastern hemisphere rather than the western hemisphere. The conjunction appears to be under our northern horizon. We will try to go around to pretty much the opposite side of the world, and we’ll also come down a little bit closer to the equator. We’ll aim roughly for Japan. All of the relevant planets are up above the horizon while the Sun is under the horizon. It is twilight rather than true darkness, it’s quite close to sunrise, but it is still dark enough for Mars and Uranus to be seen. Taking a closer look again, the moons look much more faint with the atmosphere. That also affects the reduction by air masses as well. Mars is at roughly magnitude 1, quite bright, definitely visible to the naked eye. Uranus is just about 6th magnitude, so much fainter, but still just about on the edge of being visible to the naked eye. Just about visible if you were in a countryside sky, that is. Also, we’re looking at the sky quite close to sunrise, so that would of course block out Uranus. There is also some light pollution being used here. 1988 was certainly recent enough for some places to have light pollution, though not as bad and not as much as we have it today.

Mars and Uranus are very close together in our sky, and because Mars is so much closer to us than Uranus is, by changing our position on the Earth, we should be able to change where they are appearing in the sky.This is similar to trying to find the best place to see the eclipse, there is going to be a certain place where this looks a little bit better. I think moving closer to the equator should help, but it looks like they’re only getting further apart rather than coming up to a perfect alignment. Mars is clearly moving much faster than Uranus, it just kind of zooms past, but I think we may have to travel quite far in order to get these things to line up better, if they can line up better at all. With the atmosphere removed, it’s visible that Oberon is now more passing directly behind Mars, not just passing over kind of the top of Mars, so it has gotten a little bit closer to a perfect occultation. We’ll move further south, and now Oberon is practically under Mars rather than at the top. Moving further north does bring Mars under Oberon, a little closer to Uranus, but unfortunately not quite enough to cause an occultation. However, that does show that where we see Oberon relative to Mars varies due to the effect of parallax.

While we’re quite high on the planet in the north, Mars appears to be under Oberon, if we go too high up, it goes under the ground, thanks to the angle of the ecliptic. While it’s visible, Mars is kind of under Oberon, but if we move back down south, Mars kind of comes up, covering Oberon. If we keep going down into the southern hemisphere, Oberon starts to come out the bottom of Mars, the south pole of Mars. That is parallax having an effect, that apparent motion that we’re seeing isn’t the real motion of the planets or the moon, it’s all down to us changing our position on the Earth and how that influences our view of the planets. It does look like the further north we get closer to Mars being over Uranus, but I think we will run out of planet before Mars gets close enough to Uranus to have any sort of occultation. Indeed, it does, that does seem to be the case, but this is a very interesting, very, close conjunction, and it is a multiple conjunction, with Uranus, Mars, and Saturn quite nearby as well.

I’ll turn the atmosphere back on and we’ll take a closer look at Saturn while we’re here. I think something else was labeled as we were zooming in and out, presumably just one of Saturn’s hundreds of moons, compared to only 29 around Uranus. Saturn has close to 300 moons. Jupiter has just over 100 moons. These larger planets do have many more moons than we do, Neptune also has quite a large number of moons. Looking at this conjunction was suggested to me by a commenter, and if there are any similar astronomical events that you would like to see in the past or in the future, you can leave them in a comment and I will go and take a look. Back to the view from Ireland, when Mars and Uranus are actually above the horizon they’re going to be moved further out of alignment, near each other, but not close enough for mars to be over Uranus’s moons.However, but it does look like this close conjunction was visible from everywhere. Mars and Uranus were still fairly close together when they came up for us here in Ireland, just not quite as close as they were in, for example, Japan.

If we take a look with binoculars, we can just about see Mars and Uranus, as well as Saturn, in one field of view. Without Stellarium’s planetary labels, it would be tough to recognize Uranus at this level of magnification. Going down to smaller binoculars it gets even harder. A very large set of binoculars does give quite a good view. With a fairly small telescope, a Meade ETX90, Uranus is clearly visible, you might even be able to see that little bit of a tealy blue color that Uranus has. We’ll need to zoom in quite a lot more using quite a large telescope to see more, a Meade LX200,16-inch aperture telescope, plus a 14 millimeter PLOSSL eyepiece which is going to increase the magnification a little as well. With this level of magnification, Uranus’s Moons are visible when the sky is dark. We’ll get rid of everything that’s in the way and very quickly hop back to Japan. We’ll move through time a little bit here and Mars goes zooming past because Mars is orbiting the Sun so much faster than Uranus. With a very big telescope, Mars was visible passing just under Oberon.

With no atmosphere, Mars, its moons, Uranus and its moons are visible. With the atmosphere on, the glow of the Sun blocks out the moons. Unfortunately, just because it’s so close to daytime when this occurs and because of the position of these planets in the sky, they’re going to be quite close to the Sun in the sky. It would be very difficult to find a location where this is visible in darkness, and if this was visible in darkness, these planets would be much closer to the horizon and that’s going to make them a little bit tougher to see as well but I hope you enjoyed this look into the past at this long gone conjunction.

As I mentioned, if there is anything that you would like to see on this channel, all you have to do is leave a comment mentioning the event and the date and I will go and take a look. 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.