Caoimhín's Content

Continuing my series taking a closer look at the planets, we are now onto Uranus. In previous pieces I have covered mercury, Venus, Mars, Jupiter and Saturn, so you can take a look back to see those if you’d like. The Earth, of course may fall a little outside the realm of astronomy, and for observational astronomy it isn’t very relevant, just look down and you’ll see it. I could never exhaustively describe any planet in videos as short as the ones I make, so of course some details get skipped. I was a little surprised when reviewing the video that I had apparently failed to mention that Uranus is rolling around the Sun on it’s side, but that does leave me something for the next video about Uranus.

Uranus is the first planet we will be looking at that isn’t visible to the naked eye. Uranus may be on the edge of visibility to the naked eye under perfect conditions, but the other planets are easy to see even from most cities. Speaking of these other planets, several are visible at the moment. Early in the morning we can see Jupiter, Mars and Saturn. Saturn is already visible in the late evening, and the other planets currently visible in the morning will end up visible earlier in the night as we move later in the year. These planets all sit on the same line in our sky, the ecliptic. Every planet follows the ecliptic, reasonably closely at least, so Uranus has to be somewhere along this line. Unfortunately, this line does go the whole way around the Earth and the far side of the Sun, meaning that a given planet won’t necessarily be visible at a given time, even if it is normally visible to the naked eye. For example, even though Mercury and Venus both are on that line in the sky, roughly, we’re not able to see them at the moment because they’re too close to the Sun. Right now, this isn’t the problem with Uranus. Uranus is up in the sky in the morning with the other planets, you just can’t see it with the naked eye in the city due to light pollution.

Going to a dark countryside sky will remove the issue of light pollution, making everything easier to see. Uranus however is a best on the edge of visibility. I’ve never seen Uranus with just my own eyes, but it is out there just next to Mars. Over the past few days, Mars has appeared to move past Uranus, from East to West just underneath it. The motion of Mars past Uranus is the same as it’s apparent motion past the stars. Uranus will seem to be following the motion of the stars in the sky, which is to say that the changes in its apparent position in the sky over short time periods is actually caused by the Earths motion around the Sun. This can also be seen with other distant, slow orbiting planets, like Saturn and Jupiter, but to an even greater extent with Uranus. On the other hand, planets like Mars, Venus and Mercury, they very often visibly move differently to the stars, even over the course of just a few days. We can see that at the moment with Mars, over the course of a few nights, at the same time each night, it will appear that Mars is holding its position above the East, while everything else moves behind it. This is because Mars is orbiting the Sun reasonably quickly, and at the moment it’s moving away from us. The Earth is moving faster than Mars, but we still have to catch up before we can move past it and see it moving in a more expected way. Uranus however is orbiting so slowly, it’s significantly harder to notice.

At the moment, Uranus is in the East above sunrise, quite close to the Pleiades. Uranus is hard to spot, but the Pleiades at the moment work as a landmark, they are much easier to see and Uranus will be nearby a little below them. Travelling forward a year to the same time and date, the stars will all be back to the same positions, and Uranus will still be very close to the Pleiades. Saturn, which also orbits quite slowly, won’t seem to have moved much compared to the stars either. Planets with shorter years however will be in drastically different positions. Jupiter next July will be much lower and closer to the Sun. Mars won’t be visible in the East at sunrise, but Venus will be in its stead. Our orbit is not in sync with the orbits of these planets, so their positions are going to shift from year to year. They are still predictable, but not as easily as the stars. Moving forward year by year, Jupiter and the inner planets will flit from place to place, where as Saturn and Uranus will appear to drift across the sky, much like the inner planets do over the course of days or weeks. Uranus takes a much longer time to orbit the Sun than Saturn, so it takes longer for it to noticeably move.

You do have to watch closely for years and years to notice Uranus moving, and that’s if you can spot it at all. Especially looking at the sky with the glow of sunrise coming up, faint objects like Uranus will disappear quicker than the brighter objects. However, it is marked as being roughly magnitude 5.63 on average. Technically, its mean apparent magnitude is 5.63, and I will not be getting into the mathematics of that here. At the moment, especially if you are early enough to avoid the glow of sunrise, Uranus will be quite low in the sky, making it appear fainter due to the atmosphere, a tiny bit fainter than 6th magnitude. I cannot deny that 6th magnitude is definitely visible to the naked eye somewhere an example I give in the video is a rather faint star in Aries. Due to the fact that I don’t speak Latin, I called it “63 Ariei” instead of the correct “63 Arietis”, which is a mistake on the order of saying “gooses” instead of “geese”. I went with the Flamsteed designation rather than the Bayer designation of Tau 2 Arietis, and I have discussed these designations in my piece “Undiscovering the Planet Vulcan”. This star is absolutely visible to the naked eye at about magnitude 5.3. At 6 point something, I don’t think I could reliably spot Uranus without Stellarium highlighting it for me. It is very difficult, so I don’t tell people that they can rely on their naked eye to find Uranus. Another hint that it is tricky to spot unaided is that it wasn’t document by the Ancient Greeks and Ancient Romans. They had already discovered planets like Jupiter and Saturn, and understood that way were different from the stars. Those planets are very bright, but not all planets are brighter than the stars. One of the main clues to their true nature is the way they move through the sky. For example, Saturn is pretty much 1st magnitude, while the star Capella which is up at the same time, is very nearly 0th magnitude. Jupiter and Venus are the two brightest things we see in the sky besides the Sun and the Moon, but Mars, Saturn, and even Mercury are not as bright, there are stars brighter than them. The inner, rocky planets distinctly move over a short period of time, and Mars has a distinct colour as well. Uranus will also move, but this is really only noticeable over the course of several years or even decades. Then again, it also takes quite a while for Saturn to noticeably move across the sky, though not as long as Uranus it is much longer than Jupiter. The Ancient Greeks and Ancient Romans were able to correctly distinguish even Saturn without a telescope, but they never noticed Uranus.

Taking a closer look at Uranus is easier, as even medium sized telescopes can reveal its bluish colour, as long as you have some idea where to look. To make the viewing conditions a bit better in the video, I got rid of the atmosphere. Uranus is much closer to us than Neptune, making it a much more viable target through a telescope or a binoculars. On the 15th and 16th of July, Mars and Uranus were at their closest in the sky, though they are still pretty close together for the next couple of days. With Uranus and Mars practically right on top of each other, a big enough field of view will let you take a closer look at both of them, though a larger field of view often goes along with lower magnification. Zooming in, you will begin to see some of Uranus’s colour before seeing any detail on the surface of Mars. Some Martian surface details can be visible with pretty small telescopes, just 150mm or 6-inches aperture. If you can see some detail on the surface of Mars, you will almost certainly see Uranus’s slightly bluish colour. With a larger telescope you may even see it’s moons, as they are reasonably large, bright, and far out from the planet. They are not as visible as the moons of the gas giants, but do look similar under the right magnification. Uranus is always really far away from us, and it isn’t at its closest to us right now either. When Uranus is directly behind the Earth it will be at its highest position above the South at roughly midnight, rather than being low to the East at sunrise. Uranus is 19 and a half-ish, AU from the Sun, so, you know, about 19 times further from the Sun than we are because we are one AU from the Sun and it’s distance from us then is about 20 AU, and that’s because it’s still almost on the far side of the Sun so it’s the distance from the Sun to Uranus plus the distance from the Sun to the Earth, when we are on the same side of the sky as Uranus, this number will be closer to 18, because, well, we’ll be on the same side, it will be the distance from Uranus to the Sun minus the distance to the Earth, and we get a chance to move forward an look at that in the near future,

taking a look at Uranus here, Stellarium is able to show us this very faint ring, but that ring is incredibly difficult to detect and wasn’t discovered until comparatively recently, we can also see Uranus’s kind of pale tealy colour here, recent images of indicated that Uranus is actually a closer colour to Neptune or that Neptune is a closer colour to Uranus, they’re kind of bluish, and that bluish colour comes from things like methane and ammonia in their atmosphere, as I mentioned in my Ice Giants vs Gas Giants video the composition of Neptune and Uranus are just little different from Jupiter and Saturn, because you’re just so recently, it was the first planet where there was any argument about what to name it, Uranus didn’t have an ANcient Greek or Latin name when we discovered it, or when WIlliam Herschel discoverd it, William Herschel was the discoverer of Uranus, so Herschel’s Planet was put forward as a potential name, Herschel instead proposed George’s Planet or the Georgian Planet after King George, who was the king of England at the time, eventually Uranus or Ouranos was suggested because Ouranos, the Titan of the Sky, was the father of Kronos or Saturn, who was the father of Jupiter or Zeus, so because we already had a kind of a father-son thing, astronomers thought it would be fitting to have a grandfather, a grandfather-father kind of thing going on, so in order of the generations, you’ve got Ares or Mars followed by Jupiter or Zeus followed by Saturn or Kronos, followed by Uranus or Ouranos, the difference between the Greek and Latin there is a little bit more slight than the differences with Jupiter and Zeus and Saturn and Kronos for example, so this was discovered much later and when its moons were discovered, they where not originally given names from Greek and Roman mythology,

because Uranus was the Titan of the Sky, it was considered a good idea to name these moons after fairies, airy creatures, spirits of the air, sylphs, these kinds of things, so they got named after characters from A Midsummer’s Night Dream by Shakespeare and The Rape of Lock by Alexander Pope, even though they do sound appropriate, names like Miranda and Ariel, Puck, Umbriel Ophelia, these are all great names and they do hark back in many cases, names like Titania, they do to hark back to Greek and Roman stories or Greek and Latin stories I suppose, but in reality these names come from works of English fiction, so that’s been maintained, there are only three named after characters from The Rape of Lock, Belinda being one of them, Ariel I believe being another, although Ariel or Ariel, is also one of Shakespeare’s plays, there’s also a Margaret out here somewhere, it doesn’t seem to be showing up, but Margaret from Much Ado About Nothing wrong Shakespeare’s plays, that’s another name behind one of the moons of Uranus,

so, Uranus, very distant, very difficult to observe, really I don’t think it’s possible to see Uranus with the naked eye, but not everyone is going to believe that, some people are going to be certain that they can see Uranus, and I have to admit that there is a chance that their eyesight is just, flat out, better than mine, that is definitely a possibility, I do not have the best eyes, so we’re going to move forward to the middle of the night or, that was towards daytime, we need to back to around 1:30 in the morning if we’re looking for it here in Ireland, and then we’ve got to go forward, I think we’re after coming out of summertime by now, so I can actually pull us back closer to midnight, about 00:30, and speed it forward a little bit so it’s actually half past, Stellarium can be a little bit sensitive with the time sometimes, somewhere around here, and there is Uranus right above the South and there we go, 18 and a bit AU instead of 20 and a bit AU, so Uranus has now made its way all the way back around to there, and even better from this position we would be able to see it changing where it is in the sky, if I bring back the atmosphere, Uranus is just that very very faint dot, very very easy to mistake for a star, it won’t twinkle, but honestly without a telescope or a binoculars even that might not help you too much,

so I hope you enjoyed this quick look at Uranus and how difficult it is to see and why it’s so difficult to recognise compared to the other planets, if you enjoyed this video I will have a similar video about Neptune in the near future as well as previous videos covering the other planets in a similar way so if you subscribe to my YouTube channel you’re more likely to see this video about Neptune that will be coming up, and you can also take a look back through my videos to see a little bit about these planets, you can also visit my website caoimhinscontent.ie to read a little bit about them, I hope you enjoyed this show and I hope you come back next time.