Caoimhín's Content

Today we are going to talk about the equinox. The date of posting, the 20th, is the equinox, so we are coming through the equinox right now. This is the vernal equinox or the spring equinox for the northern hemisphere and the autumnal equinox or the autumn equinox for the Southern Hemisphere. It could be the fall equinox if that’s what you call autumn the season, the southern hemisphere is in the the season of fall or the season of autumn. We are going to talk a little bit about the equinox but before we do I’m going to go back in time.

We’re going to take a look back to the 1st of March. A commenter on one of the previous YouTube videos was kind enough to warn me of this before it happened, but because it isn’t something that is visible from the Earth, it’s not something any of us could actually seen happening didn’t prioritise going to take a look at it. Also, I was concentrating on the Irish language videos for Seachtain na Gaeilge, but we are going to take a look at it now. We’re going to head to Mercury for the 1st of March. Looking at the sky from mercury is one of the nice things about software like Stellarium. Furthermore, not only does it give us the opportunity to look forward into the future and see what’s coming up, it does also give us the opportunity, for at least somethings, to look at the past. There are historical astronomical events such as the transits of Mercury and Venus, that you can see through Stellarium by going back in time as it were and seeing what those things looked like. Of course there are some other historical events that would not be visible through Stellarium, certain things like very powerful aurorae that happened in the past or very powerful meteor storms. We can simulate the very powerful meteor storms, but Stellarium doesn’t generate the radiant that they came from or show how many fire balls were produced.

From Mercury we are supposed to be looking back at the Earth. Moving through time is a little more complicated on Mercury. Minutes and seconds work the same on Mercury, but days are different and so is moving by a fraction of the day, you end up moving for days and days instead. Rather than moving through time, we can change location to change our view of the sky. We’re aiming for a position that is in night time without the Sun after coming up but with Earth visible. I didn’t take a look at this particular astronomical event before starting to record the attached video because I wanted to enjoy the surprise of whatever it is that I was looking for. Of course, without the details I wasn’t completely sure what exactly I was looking for. At first, it looked like there was going to be some sort of occultation of the Earth by Venus. However, although they get very close there it ended up being just a close conjunction. It was not an occultation, but there was a close conjunction of the Earth and Venus visible from Mercury visible on the 1stc of March.

I alos took a closer look at the Earth, just in case it was something to do with the Earth -Moon system. The Moon moved in front of the Earth, though of course it didn’t block out the Earth. This provided a fantastic view of the dark side of the Moon fully illuminated. That is a particularly interesting thing to see, even just Stellarium’s version, which isn’t a perfect map. The dark side of the Moon is visible from Mercury illuminated because we are closer to the Sun on Mercury than the Moon or the Earth. Interesting things like occultations, conjunctions, eclipses happen across the whole solar system and some are only visible from certain locations. You could, hypothetically, see the Earth occult Mars from Mercury, and of course that’s not something we’d ever see from the Earth because we’re on the Earth. There are a bunch of things that you can see from other locations in the Solar system. You can even observe eclipses from the outside, something I went over in a previous piece.

We’re going to head back to the Earth, and back to Ireland as well. As I mentioned we are at the equinox. Taking a look at the sky at 5:30 in the morning from the city, and we can see a little bit of a glow. The sunrise will really come closer to 6 o’clock, but at 5:30 there is a little bit of light visible, not too much, we’ve still got plenty of the stars visible in the sky. As this is the vernal equinox we’re sort of, in terms of day length at least, in the middle of spring now. The shorter days and longer nights are all behind us, the longer days and shorter nights are all in front of us. Sticking with 5:30 and heading forward in time, the sky gets brighter. By exactly a month later it’s completely bright at 5:30. At least here in the city, nothing is visible. Except maybe Venus, but really nothing is visible at this time just a in the future. That’s the difference that a month can make, especially when you’re as far up on the planet as Ireland. These differences, the difference between the short days in the winter and the longer days in the summer, it’s a considerably bigger difference if you’re very close to the North Pole or very close to the South Pole.

If we go back a month instead, if we go all the way back to the 20th of February, if it wasn’t for the Moon it would be completely dark. The example doesn’t work as well for that date, so we’ll get the Moon out of the way by moving to the very ends of the months. On the 1st of March we’re looking at what really is a night-time sky from the city, it’s about as dark is it can get at 5:30 at the beginning of the month. If we come all the way through to the end of the month it gets significantly brighter across the sky and by the 31st, there’s only a couple of stars visible. We’re definitely leaving night time there at 5:30 by the end of March. If we continue through into April, everything disappears, and the Sun is practically risen at the very same time. The days are about to change length, we’re about to get much longer days and much shorter night and that’s going to change our times of sunset and sunrise. Altogether, it’s going to affect when we see things in the sky.

Moving around to evening time, by the end of April at just 8 o’clock there’s nothing visible, it’s still completely bright. It is essentially still daytime at 8 o’clock in April. If we come back to the very end of March, still coming up, still at 8 o’clock and it is essentially night-time. Almost, there’s still a little bit of the glow of the Sun, over at the western horizon, but is pretty dark there at 8 o’clock. If we come back just a little bit further, one more month, and it’s definitely night time at 8 o’clock. With no trace of the glow of the Sun, the faint outer arm of the Milky Way would be visible if it wasn’t the city sky.

That is the difference across just a couple of months. Going from the month before the equinox when it’s completely dark at 8 o’clock, through to the month of the equinox when we’ve got that little bit of sunlight glow, and all the way through to the end of next month, when it’s daytime. All without changing the time, all at 8 o’clock. We’re now moving through that change, we’re going through the equinox and we’re going to see the length of the day really change now as we move back into summer time. That will also be the best time to take a look at the Milky Way, so we have that to look forward as well.

I hope you enjoyed this piece, even the brief detour to Mercury to look at some things from there and this view of the stretch in the evenings. This is a preview of the lengthening day that we will have as we move past the equinox. I hope you enjoyed this reading this, if you did please do like it, and if you like this kind of content you can subscribe to my website and my YouTube channel. Thank you for reading and hopefully I’ll see you back here next time.