Caoimhín's Content

Today we are going to be looking at some conjunctions. A conjunction is when two planets, or a star and a planet, or the Moon and a planet, or the Moon and a star, anytime two interesting things get very close to each other in the sky. Some conjunctions are close conjunctions, when the two objects are practically on top of each other. The similar occultation is when the Moon or a planet blocks out a star or a planet from our view. Occultations and conjunctions, especially ones that involve the Moon, are often only visible from a certain part of the world. This is because of how quickly the Moon is moving as it orbits around us. This means that it can be very difficult to actually spot a conjunction or an occultation. There might be one visible on a given date, but not necessarily from your location. With Stellarium we get to journey to other parts of the world, so we can see the conjunctions or occultations no matter where they occur.

As an example, we’ll look at the Moon and Jupiter. On the 14th of February this year, the Moon is a crescent and quite close to Jupiter, just a little to it’s West. On the 15th, the very next night, the Moon is just on the other side of Jupiter to the East. Sometime between the Moon and Jupiter setting on the 14th, and when they come around to that position again the next night, the Moon has passed over Jupiter. From Ireland, we essentially miss the close conjunction between the Moon and Jupiter.

If we were to follow the Moon, chasing it into the west as it sets on the 14th, we’ll see the Moon come up to Jupiter. This would be very difficult here on Earth, but luckily with software like Stellarium we can hop around the Earth and look for the conjunction from other locations. We’re going to have to travel over the Atlantic ocean and over North America into the Pacific. In the video, I don’t vary the latitude, just the longitude, although changing latitude would have an effect as well.

Once we’ve moved as far as the Pacific Northwest Coast of America, around Vancouver and Seattle, we can see the Moon and Jupiter lining up just as they’re setting. Of course, looking at objects low to the horizon, especially from a populated area with light pollution, is far from ideal. The conjunction will look clearer, especially through a telescope, if you can see it when it is high to the South, or North if you are in the southern hemisphere. We can achieve this by pushing further West, out into the middle of the Pacific ocean. Just under the Bering Strait, around the Aleutian Islands, seems to be the perfect place to see this particular conjunction.

By the time they start setting from this new location they’ve begun to drift apart. If we keep pushing further West, back into Eurasia, we’ll see that they keep appearing further and further apart. We also need to keep pushing forward in time, to make sure that we see the night sky in each new location. This eventually brings us back around to Ireland, with Jupiter now on the other side of the Pleiades on the 15th. So this conjunction is happening, but it won’t be visible at it’s closest point for us here in Ireland

Luckily, we’re in a great position to see the Half Moon and the Pleiades next to each other there on the 16th of February. We will get to see that conjunction at its closest point from here in Ireland. This conjunction is a nice one, but if we get to see it from here, that means it will be missing from somewhere else. By the time the Sun has set on the Pacific Northwest Coast, on Seattle and Vancouver, the Moon has moved on to the other side of the Pleiades. Just like the Jupiter and Moon conjunction for us, the Moon is visible on either side of the Pleiades, hopping from one side to the other overnight. This behavior is true for any conjunction between the Moon and another object, the closest point is only ever visible from a certain set of locations. There are formulas and tables that can be used to predict when occultations and close conjunctions will occur or whether they’ll be visible from your location. Then again, software like Stellarium can be used to check as well.

Moving into early March, there is a close conjunction between Antares and the Moon. From here in Ireland, they certainly look close together as they rise ahead of the Sun, but they could be closer. Just a short hop across the Atlantic to Newfoundland puts them right on top of each other. Even a reasonably small change in location can make a huge difference to how a conjunction appears, and often where in the sky you will get to see it. The Half Moon, the Last Quarter Moon in this case, right next to the red star Antares is going to look good even if you only see a conjunction rather than a truly close conjunction.

I hope that some of you get a chance to see those conjunctions. The Moon and Jupiter will look good as they set over the Pacific and especially if you are in the Pacific itself. The Half Moon and the Pleiades will look especially nice from here in Ireland, while the other Half Moon early next month with Antares will look best if they are rising with the Sun over the Atlantic. Of course you can see a preview in the above video. Also, a quick reminder that there will be a Q&A video in celebration of my YouTube channel reaching 100 subscribers coming out next Tuesday, so feel free to ask questions here, on YouTube or on the Caoimhín’s Content Instagram page. I hope you come back next time to see some of those questions and answers.