Caoimhín's Content

In this video, we take a look at the sky from the North Pole, at one of the most interesting times of the year to do so, the equinox. Specifically, this is the spring or vernal equinox, the March equinox in the Northern Hemisphere. After months of darkness, the Sun is finally starting to rise. On the other side of the planet, the opposite is happening. The March equinox is the autumnal equinox in the Southern Hemisphere, so after months of daylight, the Sun is finally starting to set. While here in Ireland the equinox is the most even day and night, both having equal length, and the least extreme position of the Sun during the day, neither the highest nor the lowest, the view looks different from the Poles. The equinoxes here are stretches of twilight, long dusks and dawns separating the even longer nights and days.

We will spend practically the whole video at 90 degrees North, exactly at the North Pole, which makes directions a little bit tricky. Normally we look for the Sun in the South at midday, but from the North Pole every direction is South. The Sun will still move westward from the East, at those times of the year where you can see the Sun, but without a sharp sunrise or sunset, where East and West really are from the North Pole is hard to define. Luckily, the Earth is divided up into lines of longitude, so we can still look for the Sun at a certain longitude. In the video, a grid is used to break up the sky into degrees, just like a circle or sphere. The grid being used here is the azimuthal grid, azimuth is how many degrees away from north you are and altitude is how high you are above the horizon. Really, the azimuth can measure how many degrees you have turned away from any fixed point, but usually it sets North at 0 degrees and South at 180 degrees. In the video, we look at the 180 degree line, as it should line up with the Prime Meridian in Greenwich in London. The last video discusses that topic in Irish, with English subtitles, if you would like to learn more.

Setting the time to 12 o’clock according to GMT or UTC, on the spring equinox, puts the Sun right on the horizon, pretty much in line with 180 degrees azimuth. As we push through the year day by day, the Sun rises pretty much directly up that line, until it peaks on midsummer. I say pretty much here, because the Sun does shift from side to side in it’s path over the year, a phenomenon known as analemma, another topic covered in the previous video. At midsummer, if we move through the days minute by minute or hour by hour, you can really see that the Earth is rotating, as the Sun transcribes a circle around the sky. Very slowly, the Sun is spiraling, from it’s highest peak on the summer solstices, it gets lower and lower as it moves toward the Winter Solstice. As we approach autumn the equinox, the Sun begins to set, but as it crosses the horizon, it continues to spiral around very gradually, meaning the brightest part of sunset also makes a circle, the whole way around the horizon. This continues for a few weeks, with the sky gradually darkening. Eventually the Sun sets, and the sky remains dark right through the Winter Solstice, through January, into February. By the end of February we start to see a little glow, but the planets, Venus and Jupiter at least, remain visible until almost mid March. Even when they disappear, the Sun doesn’t truly rise until we pass the spring equinox and the cycle begins again.

This night/day cycle spanning the entire year is all down to the tilt in the Earths axis. The Earth always points the same way, roughly towards the North Star (though this changes on very long timescales). For half the year this means pointing towards the Sun, with the North Star essentially above and behind the Sun, for the other half it means pointing away from the Sun, because we have orbited around to the same side of the Sun as the North Star. Of course, this means you can’t see the North Star from the North Pole for months at a time, because it’s day time! You can of course still find it, if you’re at the North Pole then it is right over you head.

At night, you might be able to tell that the North Star isn’t quite exactly overhead. By moving through time quickly, like a time-lapse, you’ll see that the North Star actually traces a very small circle in the sky. All of the other stars will circle the sky almost like the Sun, noticeably showing the rotation of the Earth, but the North Star is almost in line with the Earths axis, so it’s movement is a lot less noticeable. This also means that we don’t see many stars that are in line with the Earths equator, they’ll stay pretty much on the horizon, but the Earths equator doesn’t line up with the ecliptic. As the planets orbit the Sun, they do come into view at the poles, and thanks to the long nights they can stay visible for months as well.

Midwinter isn’t particularly noticeable. The Sun hasn’t risen for a few weeks by that point, and it won’t for a few more weeks to come. The stars and planets will continue their circle in the sky, but there is no day to have the shortest of, and the longest night is and has been happening. Midwinter for the North Pole is more like midnight, and so the Moon and the planets do reach their highest in the sky, but they are a good bit smaller than the Sun, and it is a relatively low high, compared with anywhere else besides . The summer solstice is of course in a similar position, but at least the the Sun is up to be in it’s highest position all year, though again, this is an oxymoronically low high.

The equinoxes however, those long stretches of dawn and dusk provide a much more noticeable change. In spring, once the first glow begins to show at the horizon, the sky gets brighter in a gradual continuous process. However gradual it may be, every few hours the sky is brighter, every day or so more stars have disappeared. The sky changes colour, shifting from black to midnight blue, into oranges and reds and eventually blue. Or from black to grey to white, the Arctic does have it’s fair share of blizzards after all, and clouds do still exists at the Poles. Luckily, this process does last a few weeks, so there’s a good chance you’ll see some of it, where as at other latitudes a stormy morning or evening can completely blot out the shifting colours of twilight. The lovely morning and evening time conjunctions we sometimes see also last for a lot longer, and this is before adding in the beauty of the Aurorae, the Aurora Borealis in this case or the Aurora Australis at the South Pole. Midwinter might be a favourite time of year for many astronomers thanks to the long nights, and midsummer is a festival in many areas around the world, but for the Poles, the equinoxes might be the best, even if they are a little more middling from other latitudes.

Travelling back to Ireland and coming back to the present, through the video with all of the different solstices and equinoxes we end up looking at 2025, and in January 2025 in the evening sky it looks like we will have 4 planets and the Moon in the sky together. Seeing as It cam up in the video I thought best to mention it here, even if it is a little off topic. You may know already that I am planning on adding extra Irish language videos this fortnight for Seachtain na Gaeilge, which is the Irish Week but it lasts for a fortnight. I usually put up one Irish video a week, always with subtitles and always with this companion article in English as well. So if you do prefer English you can read it here when you come back next time when an Irish video will be going up.