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Today we’re going to very quickly go over the zodiacal constellations, the constellations that we see in the sky along the path of the ecliptic, which is where we see the planets, the Moon, and the Sun, roughly speaking at least.

We’ll start by taking a look at the planets at sunset in June. We have, of course, looked at these planets going through their wonderful conjunctions already. For example the conjunction between Venus and Jupiter that is coming up. Mercury is also coming to its greatest elongation, and then Mercury will change direction and move back in towards the Sun. We’ll very quickly take a closer look at that, we’re looking in the constellation Gemini. A little after sunset we’ll have the bright stars Pollux and Castor, the two twins of Gemini. Using Stellarium, we can bring up the lines that join the stars together to make the constellation. Mercury, Jupiter, and Venus are pretty much within Gemini, if we bring up the boundaries of the constellations then we can tell that Venus and Jupiter are close to the boundary with Cancer. Venus at least, is just about to move into Cancer. Jupiter moves into Cancer as well but more slowly, whereas Mercury turns around and moves back towards the Sun, remaining in Gemini.

This is part of Mercury’s retrograde motion. As we get later in June, Mercury will reach its farthest point from the Sun in our sky. Of course, Mercury is more or less making a circle around the Sun, it’s orbiting the Sun, it’s distance from the star isn’t really changing much. Mercury has come around the Sun and it’s about to go back around the Sun, continuing its orbit. Mercury doesn’t actually change direction, it just looks like it’s moving backwards from our position here on Earth. Venus is going to take a little bit longer to do the same thing. It is currently continuing to move away from the Sun, but eventually it reaches its greatest elongation and it starts falling back towards the Sun as well. That is really all that retrograde motion is, the planets apparent change in direction. Usually, when the planet is following the stars westward, behind the Sun, it is considered to be moving the normal way. However, the clear change in direction that the inner planets exhibit is usually called retrograde when they change, even if this isn’t wholly accurate. As we go through time, the planets are moving from constellation to constellation. Venus moves into Leo from cancer, but Jupiter stays in Cancer until it ends up going behind the Sun, the superior conjunction between Jupiter and the Sun. Then the Sun appears to move through Cancer and then into Leo as we move forward through time.

The Moon, of course, is doing the same thing, just quite a bit faster. A little bit later in June, the Moon will be near Mercury and Jupiter in Gemini, but quickly moving forward into Cancer and into Leo. It takes a couple of days for the Moon to get through Leo, it is a bigger constellation, and it will also take a few days for the Moon to get through Virgo, it is also a bigger constellation. Comparing this to Libra, for example, the Moon is there for just one day before it passes into Scorpius. These are the zodiacal constellations, the constellations that are on the ecliptic, where we see the planets, the Sun and the Moon. These are real constellations, and I’m sure you know most of their names. They are sometimes called the Signs of the Zodiac, they’re regularly written in the backs of the newspaper. Thanks to the motion of the Moon, as we move through time it is clear that these constellations are different sizes. The Sun also doesn’t exclusively pass through the famous 12. Moving forward until the Sun has left the boundaries of the constellation Scorpius, it moves through the constellation Ophiuchus. The Sun is in that constellation, the 13th sign of the zodiac, for several days before it moves into Sagittarius. Sagittarius is also a reasonably big constellation, so the Sun is there for quite a while. Capricornus is a bit smaller, so it’s not there for quite as long before it passes into Aquarius and eventually into Pisces. Pisces is a pretty big constellation, so it takes a while before the Sun passes into Aries, which is fairly small, then through Taurus, another larger constellation, and then back into Gemini a year later.

We are through to this time next year, in 2027. We’ll move back, and as we do, you might notice that the times that the Sun crosses these boundaries, it doesn’t line up with the months. For example, here we’re on the 19th of April as the Sun falls back into Pisces from Aries, we’re through to the 14th of March as the Moon falls back into Aquarius. We are moving backwards, but that is over a month, roughly a month and a quarter. Some of these constellations don’t last a full month, for example on the 16th day of February, the is just entering Sun Aquarius, and it’s out of it by the 18th day of January, just 29 days. That means it’s not a full month. The Moon will always be pretty much in one of these constellations, the same way the Sun will always be pretty much in one of these constellations. We’ll come back a little bit back closer today, which puts the Sun in Taurus.

The signs of the zodiac are abstractions, they’re terms for the zodiacal constellations that are sometimes a little bit easier to pronounce. For example, Scorpius is the constellation, the sign of the zodiac is usually called Scorpio. Another abstraction is that every one of those 12 zodiac signs is given a month. Not from the first to the end of the month, usually it’s around the 22nd day that one becomes another, but they all have an equal amount of time. As we have seen here, that isn’t true for the actual constellations in the sky, the actual pictures. Now, of course, these are the pictures that we use in the modern day, but they are also very old. We’re going to go back to the sky cultures of Stellarium and we’re going to take a look at the Greek constellations. We’re looking specifically for details based on the Almagest, an astronomy book written by Ptolemy in Egypt when it was a Roman territory, but he is believed to have been of Greek descent. There are a few options in Stellarium labeled as different kinds of Greek, and one that exclusively says the Almagest. This was one of the first records to discuss the constellations of the ecliptic in a familiar way, though they go back even further into the past.

Changing the sky culture changes the lines that are used to make the constellations, and it also changes the names of the planets. Venus is being called the goddess of love, Jupiter is being called the father of the gods, Mercury, the messenger of the gods. Of course, these would be names like Hermes, Zeus and Aphrodite if they were translated into Greek. We’re only getting a couple of actual pictures, so that’s not very useful for our purposes, but the lines still make the constellations easy to tell apart. As we move through the year, the Sun still moves through the same pictures. We’re still seeing Leo and Virgo, we’re still seeing Libra, albeit a little bit chopped up, but it’s still there. We’re still seeing Scorpius, then coming through to Ophiuchus. The Sun continues through to Sagittarius, into Capricornus and then Aquarius. With some of these drawings, the new lines actually come closer to looking like the picture there meant to be, Sagittarius and Virgo especially. Pisces, not so much, but we’re still going through the exact same constellations. Eventually, we are back to Taurus.

Those are the same constellations, they’ve been in the sky for hundreds of years, thousands of years depending on the picture. Some of the other Greek sky cultures, based on combinations of the Almagest with the work of later writers, show some more recognizable pictures. We can still see the Sun moving into Gemini and Cancer, but the years that were used in Ancient Greece and Rome, the dates they were very different. In ancient Greece and in ancient Rome, the way that the year was divided up was different. When these images were originally created, laid out across the sky, it was for years that weren’t broken into 12 months. They could have 13 moons or 12 depending on the year and culture. The way the calendar worked was very, very different.

We’ve gone all the way forward to 2028, so we’ll start coming back. If you download the software I use, Stellarium, you can use that to figure out where the Sun was on the day you were born and what picture it was actually in front of. Also on the Stellarium website is a web version that you can interact with without having to download anything. That same software shows all the planets and the moons, it will show you where the Moon was and the planets, what constellations they were in front of, on the day you were born, to the minute you were born. It may differ from what’s written in the back of the newspaper. It may differ from whatever any astrologer may have told you, it may be different from what astronomy says is true about the sky, which is why I wanted to be so clear about the differences. What retrograde motion actually is, where the Sun’s position actually is in the sky before I suggested to anyone to check it out, because if astrology is something that you’re interested in, it won’t agree with astronomy. They’re different things, so of course they’re going to look at these things in a slightly different way, but if you want to see where these stars actually are in the sky, then this is the way to do it.

Coming back to the way that we currently see the sky, we still use the same ideas based on the same constellations that have been used, particularly in this region of the sky, for thousands of years, but things have changed. Where the boundaries are between constellations has changed, how they’re drawn has changed, and how we measure the length of the year and the dates have changed. Of course, the dates, well, that’s the important thing. If you want to know exactly where the Sun was on a given date, the date, of course, matters.

I hope that you enjoyed this piece, I hope that you take a look at these constellations in some form of Stellarium yourself. You can also check out some of my past pieces on this topic on this website or on my YouTube channel. If you enjoy this kind of content, then please subscribe to my website or my YouTube channel and hopefully I’ll see you back here next time.