Caoimhín's Content

Constellations and asterisms are a favourite topic of mine, so you can expect more vidoes on this subject in the future. As a few asterisms and constellations have come up in previous videos already, those are the ones we’re going to look at,

Thankfully the Summer Triangle is still visible for at least some of the night, as it is one of the easiest asterisms to spot, and a big one. From the bright Vega, across to Deneb and down to Altair, a huge triangle takes up a large portion of the southern sky in early October, it’s high above the south as early as 9 o’clock. Each of the three stars named are part of three different constellations.

The unofficial Summer Triangle has the official constellations of Cygnus the Swan, Aquila the Eagle and Lyra the Lyre making up its three corners, with two more whole constellations inside the triangle, Sagitta the Arrow and Vulpecula the Little Fox. We go through how the lines between the stars look before revealing the pictures, very often the lines are a pretty crude facsimile of the intended object.

Sagitta the Arrow and Sagittarius the Bowman have something in common, “sagitta”, the Latin for arrow. Sagittarius being an archer is more important than being half-man half-horse. There is a centaur called Centaurus in the sky as well, but for Sagittarius wielding a bow and arrow is the important part. People on horses (or part horse in this case) wielding bows had a big impact on the Ancient Greek empire, from Seleucids to Sassanids, Achaemenids and Parthians. The Parthians give their name to the Parthenian Shot, firing a bow backwards while your horse runs away after a charge.

it is a lot easier to see the stars under a dark sky, and that can have implications for the constellations. In the city some stars will be missing, making some shapes harder to make out. On the other hand, if there are thousands instead of hundreds of stars visible, it can be hard to spot the important ones for the constellation lines. It is worth remembering that the Ancient Greeks, who created most of the constellations we see in the Northern Hemisphere, the Romans, who gave us the Latin names we use today, even the explorers of the 17th and 18th century who influenced the constellations we use in the Southern Hemisphere, none of them had to deal with the levels of light pollution that we have today. A dark sky free of light pollution really is the intended condition for imagining these pictures in the sky.

Turning into the North, The Plough or Big Dipper is probably the most famous asterism. It is wholly part of the constellation Ursa Major the Big Bear, but it is not the whole constellation. From the Plough, legs and a head extend out to form the full picture. With the pictures up, you might see that the bear’s tail is a bit too long. This is true for the Little Bear, Ursa Minor, as well. We will eventually talk about the story behind these constellations, the story of Calisto and Archos.

We also take a quick look at Cassiopeia the Queen and Pegasus the Flying Horse. Pegasus in particular practically connects to the constellation of Andromeda, but a boundary needs to be drawn somewhere. All constellations have an official area around them, fitting together like a jigsaw puzzle to divide up the entire sky. We take a quick look at these boundaries, but we will return to talk about their usage in another video.

As this video was posted in Space Week, I think it’s appropriate to encourage to try to get to a dark sky to see these things. Officially in Ireland, Cahersiveen in County Kerry and Ballycroy in County Mayo are both host to Dark Skies, a Dark Sky Reserve and Park respectively. If you can get out to a sky free of light pollution, you can imagine the constellations as the Ancient Greeks saw them, as they were originally imagined.