Blackdragon666
Well-known member
If you are a regular stargazer, you may have noticed that there are times in the year a certain star or constellation is not visible in the sky throughout the whole night. This is due to what is known as the rising and setting of the star. Not to be confused with the east to west daily rise and set of the sun, stars and other heavenly bodies, this type of rising and setting is known as “heliacal rising”.
To understand the concept, we need to go back to the Celestial Sphere. The Sun moves through the ecliptic slowly as observed from the earth. It moves approximately 1 degree every day as seen from the earth. It finishes a cycle every year, returning to the starting point (there are 360 degrees in a circular path, which is approximately the number of days in a year, 365). Imagine the Sun being positioned at the Vernal Equinox at the beginning of Spring in March.
During daytime, you’ll be on the side of the earth facing the Sun and at night, you’ll be facing the opposite side. Therefore, constellations that are near the Sun are impossible for you to see as the time you are facing them happens to also be daytime and the light from the Sun outshines nearby celestial bodies in the sky. The next image shows the constellations on the celestial sphere to better illustrate it.
For instance, we know that the constellation of Pisces has been on the Vernal Equinox for the past two millennia (Age of Pisces). This means that on Spring Equinoxes, you couldn’t see the constellation of Pisces for quite some time.
It is important to note that the Earth spins in the same direction the Sun is moving along the ecliptic. We know the Sun enters the constellations in the order of Aries, Taurus, Gemini and so on. Likewise, the earth rotates such that as you’re observing from the earth, you should see the constellation of Aries, then Taurus and so on.
Going back to the illustration and with the above in mind, visualize the Sun directly on the constellation of Pisces, assuming it is around Spring Equinox. When the Sun rises in the east during sunrise, it rises together with Pisces. This is known as the “cosmical rising” of a constellation or star, that is when it rises together with the Sun due to being in conjunction with each other. They also set together. During this time, the Sun’s light is blocking the stars in the constellation of Pisces and other nearby ones and so they are not visible.
However, as time passes, the Sun slowly moves past the stars and the constellations it was directly blocking from view with its light. Remember, the Earth is spinning in the same direction as the Sun is moving along the ecliptic. As the Sun moves farther from a star, the star will rise earlier in the sky before the Sun. Day after day, as the Sun moves along the ecliptic, the star rises an increasing amount of time earlier than the Sun. However, the light from the Sun still blinds the star from view due to being close in the sky so there is a period after the cosmical rising where the star isn’t seen.
However, there comes a point when the star is far enough for its light to be visible in the sky. The star is still quite close to the Sun. If you’re observing the eastern horizon, the star should appear visible for the first time above the eastern horizon when this happens. This lasts a few minutes, after which the Sun will rise and then all stars in the sky will be blinded by the Sun’s light. The first time a star or constellation is visible in the night sky, usually a few minutes before sunrise, is known as its “heliacal rising” and usually happens approximately the same time every year.
As the days go by, the Sun moves farther and farther from the star or constellation. Remember the earth spins in the same direction the Sun is moving. So the constellation or star in question will rise on the eastern horizon first before the Sun rises in the morning. Due to the increasing distance between the star and the Sun, the star will rise in the sky earlier in the night each passing day and therefore be visible for a longer time in the night sky before sunrise.
Note the difference between the daily rise and set of the star and its heliacal rising. Heliacal rising is when it is first visible in the night sky after the Sun is a considerable distance away from the star such that its light is visible. Heliacal rising happens a short while before sunrise. On the previous day before a star’s heliacal rising, the star was too near to the Sun for is light to be seen.
We can use this image again to illustrate the process better.
During March, around the time of Spring Equinox, the constellations near the Spring Equinox point rise together with the Sun (cosmical rising). These constellations are not visible in the sky as the time when we are facing them happens also be the same time we are directly facing the Sun. The Sun outshines them at the time we are supposed to be seeing them.
As the days go by and the Sun moves slowly past the Spring Equinox, these constellations rise earlier and earlier than the Sun each passing day. When the Sun’s light is unable to block these constellations from view, their stars begin to be visible in the night sky (heliacal rising), usually some minutes before sunrise as the distance between the constellations and the Sun is still quite small.
The Sun keeps moving farther from these constellations, making them rise earlier in the night and therefore they are visible for longer durations in the night sky. Consider when the Sun reaches and passes the point marked “June” (which is the Summer Solstice), moving towards “September” (the Fall Equinox). As the Sun moves closer to the Fall Equinox, the constellations around the Vernal (Spring) Equinox will be visible almost throughout the entire night. The Sun is now opposite these constellations and the time in the night they rise in the eastern horizon has moved from just before sunrise all the way to moments after sunset. This is because shortly after the Sun sets in the west, these constellations are in the far opposite so they are rising in the eastern horizon and therefore being visible for almost the whole night. The rising of a star or constellation in the eastern horizon at sunset is called its “acronycal rising” (also spelt ‘acronical’).
Eventually, the constellations are no longer visible at sunrise as when the Sun is rising; they have already set in the western horizon. Remember from the moment of heliacal rising and onwards, the star or constellation would be visible in the night sky and after sunrise the light from the rising sun would overwhelm it together with other celestial bodies. Even though the star would rise earlier night after night, it would be visible in the sky just before being outshined by the rising Sun. However, after the star is past the point where it is opposing the Sun, it will have already set in the western hemisphere before the Sun rises. Specifically, acronycal rising refers to the last time the star is seen rising in the eastern hemisphere and happens shortly after the Sun has set. The next day after this, the star will still rise but it is rising when daylight is too bright for it to be seen. So we don’t see it rising. We will only see it in the night sky after the Sun has set, but we will not see it rising in the eastern horizon.
The Sun is now past the Fall Equinox and is slowly moving back toward the Vernal Equinox. At this point, the Sun is rising before the constellation or star. The constellation then rises during daytime so we miss seeing it rise as the Sun is outshining it. It only gets visible in the sky after the Sun sets. We only get to see it setting in the western horizon during the course of the night.
Let’s go back to the point where the Sun is approaching the Fall Equinox. Shortly before the Sun crossed the Fall Equinox, we saw the constellations near the Vernal Equinox rise shortly after sunset. Remember, they are pretty much on opposite sides of the celestial sphere so as one is setting (the Sun), the other is rising. The acronycal rising is the last time we see the constellation rising shortly after the Sun has set. The following day, the Sun is pretty much past the opposite point from the constellation and so when the constellation is rising, the Sun is still visible in the sky so we no longer see it rising above the eastern horizon. However, it gets visible in the sky after sunset and remains up in the sky, setting at some point before sunrise.
As the Sun is still pretty much opposite the constellation, it still gets a lot of visibility throughout the night after the Sun has set. Day after day, as the Sun is now approaching the constellation, the distance between them gets smaller. In this case remember we are looking at the constellations near the Vernal Equinox. As the Sun approaches the Vernal Equinox, these constellations rise earlier and earlier in the day. This is due to the shortening distance between the two and so the constellation’s rising time gets closer to that of the Sun. Consequently, the time we get to see the constellation in the sky after the Sun has set gets shorter and shorter. At this point, the closer the star or the constellation is to the Sun, the faster it will set in the western horizon after the Sun has set.
Now consider a time when the Sun is too close to the Spring Equinox. The constellations rise in the sky shortly after the Sun rises. Immediately after sunset, the constellation is visible for a short while in the night sky before setting. As the days go by, the Sun is too near the constellations such that even after it sets, the constellations are no longer visible in the evening sky. The last time we observe a constellation or star setting shortly after the Sun has set is known as its “heliacal setting”.
Eventually, the Sun gets into conjunction with the constellations again and they rise and set at the same time, in what is known as the “cosmical rise” or “cosmical set” of the star or constellation. The next event is the heliacal rise when the Sun has moved to a point where the star or constellation is visible shortly before sunrise, starting the cycle again.
To go over the process again, the Sun starts from being in conjunction with a star and so they rise and set at the same time (cosmical rise and set). The Sun then moves to a point where the distance is enough for the star’s light to first be visible in the sky, shortly before being outshined by the rising sun (heliacal rise). As the Sun moves farther from the star, it rises an increasing amount of time before the Sun, giving it more exposure in the pre-dawn night sky. As the Sun approaches an opposition with the star, the star has maximum exposure in the night sky and rises closer to sunset. Eventually, the star rises for the last time just before sunset (acronycal rise).
After the Sun has passed the opposition point, the star is now rising while the Sun is still in the sky. At first, this happens just shortly before sunset. The star still has much exposure during the night. We no longer get to see the star rising as the Sun outshines this moment, but we instead see the star setting at some point in the night. As the Sun starts to move closer to the star, the time it rises in the daytime sky gets closer to that of the rising Sun and also the period at night it remains visible in the sky before setting gets shorter.
The Sun eventually gets too close such that even though the star sets after the Sun, we no longer see it in the sky. The last time we see the star briefly after sunset before we see it setting in the western horizon is known as its heliacal setting. The star then disappears from visibility for some period of time. The Sun then gets to a point where it is rising and setting at the same time with the star as they are now in conjunction with each other, before the next heliacal rise.
It is important to note that the above doesn’t apply to all stars. Depending on where you are on earth, some stars never rise or set. If you are nearer the North Pole, the stars in the north polar regions will never set below the horizon. A star like Polaris will always be above the horizon. This is because the earth’s axis is tilted and when you move closer to the poles, you will always be exposed to certain stars. Likewise, when nearer the North Pole, stars and constellations in the South will never be visible in your night sky. This is because you are constantly facing away from them, never being exposed to them. A constellation like the Southern Cross (a constellation located around the south pole on the celestial sphere) is never visible in the sky for people living in places like Greenland.
So we can divide the stars into three categories depending on your location (latitude above or below the equator): rise and set stars (stars that undergo heliacal rising and setting), circumpolar stars (always above the horizon and visible throughout the year) and stars that never rise.
Something to note about heliacal rising is that it is a visual occurrence, in that it is based on us first seeing a star above the eastern horizon. Things like weather and atmospheric pollution can affect it. This is why the dates for the rising of stars can vary.
Heliacal rising was very important to the ancients. In particular, the heliacal rising of Sirius, the brightest star in the night sky, was highly regarded by many cultures, notably the ancient Egyptians. The heliacal rising of Sirius heralded the Egyptian new year and it also coincided with the annual flooding of the Nile. [1] Sirius was extremely important to the ancients and was revered all over the ancient world. Its significance was that it represented the third eye (from High Priest Hoodedcobra).
The rising of various stars and constellations was used in the construction of calendars and also marked the beginning of important seasons for various groups of ancient peoples such as the sailing season, agricultural season and so on. For instance, the heliacal rising of the Pleiades marked the start of the sailing season for the ancient Greeks. [2]
The Babylonians had extensive star catalogues that recorded detailed information about various constellations. The MUL.APIN is a Babylonian star catalogue that dates from at least 1000 BC. It lists several constellations (including the zodiac constellations) and their corresponding heliacal rise and set dates. [3] The Babylonians were excellent at Astrology and had a huge hand in the Astrological system we use today.
Lastly, it is important to note that heliacal rising is not really used when it comes to modern Astrology and reading horoscopes. However, it is an important part of Astronomy/Astrology to know. In the ancient world, Astronomy and Astrology were pretty much the same thing and the priests who kept track of the movement of heavenly bodies were also the ones who interpreted the spiritual significance of what was observed. There are also some concepts that require one to understand heliacal rising before they can be understood properly, such as decans (these are divisions of the zodiac wheel into parts that are 10 degrees wide, or a third of a sign). This will all be covered in the next lessons.
Sources
1. Wikipedia page on heliacal rising, https://en.wikipedia.org/wiki/Heliacal_rising
2. ibid.
3. Wikipedia page on MUL.APIN, https://en.wikipedia.org/wiki/MUL.APIN
To understand the concept, we need to go back to the Celestial Sphere. The Sun moves through the ecliptic slowly as observed from the earth. It moves approximately 1 degree every day as seen from the earth. It finishes a cycle every year, returning to the starting point (there are 360 degrees in a circular path, which is approximately the number of days in a year, 365). Imagine the Sun being positioned at the Vernal Equinox at the beginning of Spring in March.
During daytime, you’ll be on the side of the earth facing the Sun and at night, you’ll be facing the opposite side. Therefore, constellations that are near the Sun are impossible for you to see as the time you are facing them happens to also be daytime and the light from the Sun outshines nearby celestial bodies in the sky. The next image shows the constellations on the celestial sphere to better illustrate it.
For instance, we know that the constellation of Pisces has been on the Vernal Equinox for the past two millennia (Age of Pisces). This means that on Spring Equinoxes, you couldn’t see the constellation of Pisces for quite some time.
It is important to note that the Earth spins in the same direction the Sun is moving along the ecliptic. We know the Sun enters the constellations in the order of Aries, Taurus, Gemini and so on. Likewise, the earth rotates such that as you’re observing from the earth, you should see the constellation of Aries, then Taurus and so on.
Going back to the illustration and with the above in mind, visualize the Sun directly on the constellation of Pisces, assuming it is around Spring Equinox. When the Sun rises in the east during sunrise, it rises together with Pisces. This is known as the “cosmical rising” of a constellation or star, that is when it rises together with the Sun due to being in conjunction with each other. They also set together. During this time, the Sun’s light is blocking the stars in the constellation of Pisces and other nearby ones and so they are not visible.
However, as time passes, the Sun slowly moves past the stars and the constellations it was directly blocking from view with its light. Remember, the Earth is spinning in the same direction as the Sun is moving along the ecliptic. As the Sun moves farther from a star, the star will rise earlier in the sky before the Sun. Day after day, as the Sun moves along the ecliptic, the star rises an increasing amount of time earlier than the Sun. However, the light from the Sun still blinds the star from view due to being close in the sky so there is a period after the cosmical rising where the star isn’t seen.
However, there comes a point when the star is far enough for its light to be visible in the sky. The star is still quite close to the Sun. If you’re observing the eastern horizon, the star should appear visible for the first time above the eastern horizon when this happens. This lasts a few minutes, after which the Sun will rise and then all stars in the sky will be blinded by the Sun’s light. The first time a star or constellation is visible in the night sky, usually a few minutes before sunrise, is known as its “heliacal rising” and usually happens approximately the same time every year.
As the days go by, the Sun moves farther and farther from the star or constellation. Remember the earth spins in the same direction the Sun is moving. So the constellation or star in question will rise on the eastern horizon first before the Sun rises in the morning. Due to the increasing distance between the star and the Sun, the star will rise in the sky earlier in the night each passing day and therefore be visible for a longer time in the night sky before sunrise.
Note the difference between the daily rise and set of the star and its heliacal rising. Heliacal rising is when it is first visible in the night sky after the Sun is a considerable distance away from the star such that its light is visible. Heliacal rising happens a short while before sunrise. On the previous day before a star’s heliacal rising, the star was too near to the Sun for is light to be seen.
We can use this image again to illustrate the process better.
During March, around the time of Spring Equinox, the constellations near the Spring Equinox point rise together with the Sun (cosmical rising). These constellations are not visible in the sky as the time when we are facing them happens also be the same time we are directly facing the Sun. The Sun outshines them at the time we are supposed to be seeing them.
As the days go by and the Sun moves slowly past the Spring Equinox, these constellations rise earlier and earlier than the Sun each passing day. When the Sun’s light is unable to block these constellations from view, their stars begin to be visible in the night sky (heliacal rising), usually some minutes before sunrise as the distance between the constellations and the Sun is still quite small.
The Sun keeps moving farther from these constellations, making them rise earlier in the night and therefore they are visible for longer durations in the night sky. Consider when the Sun reaches and passes the point marked “June” (which is the Summer Solstice), moving towards “September” (the Fall Equinox). As the Sun moves closer to the Fall Equinox, the constellations around the Vernal (Spring) Equinox will be visible almost throughout the entire night. The Sun is now opposite these constellations and the time in the night they rise in the eastern horizon has moved from just before sunrise all the way to moments after sunset. This is because shortly after the Sun sets in the west, these constellations are in the far opposite so they are rising in the eastern horizon and therefore being visible for almost the whole night. The rising of a star or constellation in the eastern horizon at sunset is called its “acronycal rising” (also spelt ‘acronical’).
Eventually, the constellations are no longer visible at sunrise as when the Sun is rising; they have already set in the western horizon. Remember from the moment of heliacal rising and onwards, the star or constellation would be visible in the night sky and after sunrise the light from the rising sun would overwhelm it together with other celestial bodies. Even though the star would rise earlier night after night, it would be visible in the sky just before being outshined by the rising Sun. However, after the star is past the point where it is opposing the Sun, it will have already set in the western hemisphere before the Sun rises. Specifically, acronycal rising refers to the last time the star is seen rising in the eastern hemisphere and happens shortly after the Sun has set. The next day after this, the star will still rise but it is rising when daylight is too bright for it to be seen. So we don’t see it rising. We will only see it in the night sky after the Sun has set, but we will not see it rising in the eastern horizon.
The Sun is now past the Fall Equinox and is slowly moving back toward the Vernal Equinox. At this point, the Sun is rising before the constellation or star. The constellation then rises during daytime so we miss seeing it rise as the Sun is outshining it. It only gets visible in the sky after the Sun sets. We only get to see it setting in the western horizon during the course of the night.
Let’s go back to the point where the Sun is approaching the Fall Equinox. Shortly before the Sun crossed the Fall Equinox, we saw the constellations near the Vernal Equinox rise shortly after sunset. Remember, they are pretty much on opposite sides of the celestial sphere so as one is setting (the Sun), the other is rising. The acronycal rising is the last time we see the constellation rising shortly after the Sun has set. The following day, the Sun is pretty much past the opposite point from the constellation and so when the constellation is rising, the Sun is still visible in the sky so we no longer see it rising above the eastern horizon. However, it gets visible in the sky after sunset and remains up in the sky, setting at some point before sunrise.
As the Sun is still pretty much opposite the constellation, it still gets a lot of visibility throughout the night after the Sun has set. Day after day, as the Sun is now approaching the constellation, the distance between them gets smaller. In this case remember we are looking at the constellations near the Vernal Equinox. As the Sun approaches the Vernal Equinox, these constellations rise earlier and earlier in the day. This is due to the shortening distance between the two and so the constellation’s rising time gets closer to that of the Sun. Consequently, the time we get to see the constellation in the sky after the Sun has set gets shorter and shorter. At this point, the closer the star or the constellation is to the Sun, the faster it will set in the western horizon after the Sun has set.
Now consider a time when the Sun is too close to the Spring Equinox. The constellations rise in the sky shortly after the Sun rises. Immediately after sunset, the constellation is visible for a short while in the night sky before setting. As the days go by, the Sun is too near the constellations such that even after it sets, the constellations are no longer visible in the evening sky. The last time we observe a constellation or star setting shortly after the Sun has set is known as its “heliacal setting”.
Eventually, the Sun gets into conjunction with the constellations again and they rise and set at the same time, in what is known as the “cosmical rise” or “cosmical set” of the star or constellation. The next event is the heliacal rise when the Sun has moved to a point where the star or constellation is visible shortly before sunrise, starting the cycle again.
To go over the process again, the Sun starts from being in conjunction with a star and so they rise and set at the same time (cosmical rise and set). The Sun then moves to a point where the distance is enough for the star’s light to first be visible in the sky, shortly before being outshined by the rising sun (heliacal rise). As the Sun moves farther from the star, it rises an increasing amount of time before the Sun, giving it more exposure in the pre-dawn night sky. As the Sun approaches an opposition with the star, the star has maximum exposure in the night sky and rises closer to sunset. Eventually, the star rises for the last time just before sunset (acronycal rise).
After the Sun has passed the opposition point, the star is now rising while the Sun is still in the sky. At first, this happens just shortly before sunset. The star still has much exposure during the night. We no longer get to see the star rising as the Sun outshines this moment, but we instead see the star setting at some point in the night. As the Sun starts to move closer to the star, the time it rises in the daytime sky gets closer to that of the rising Sun and also the period at night it remains visible in the sky before setting gets shorter.
The Sun eventually gets too close such that even though the star sets after the Sun, we no longer see it in the sky. The last time we see the star briefly after sunset before we see it setting in the western horizon is known as its heliacal setting. The star then disappears from visibility for some period of time. The Sun then gets to a point where it is rising and setting at the same time with the star as they are now in conjunction with each other, before the next heliacal rise.
It is important to note that the above doesn’t apply to all stars. Depending on where you are on earth, some stars never rise or set. If you are nearer the North Pole, the stars in the north polar regions will never set below the horizon. A star like Polaris will always be above the horizon. This is because the earth’s axis is tilted and when you move closer to the poles, you will always be exposed to certain stars. Likewise, when nearer the North Pole, stars and constellations in the South will never be visible in your night sky. This is because you are constantly facing away from them, never being exposed to them. A constellation like the Southern Cross (a constellation located around the south pole on the celestial sphere) is never visible in the sky for people living in places like Greenland.
So we can divide the stars into three categories depending on your location (latitude above or below the equator): rise and set stars (stars that undergo heliacal rising and setting), circumpolar stars (always above the horizon and visible throughout the year) and stars that never rise.
Something to note about heliacal rising is that it is a visual occurrence, in that it is based on us first seeing a star above the eastern horizon. Things like weather and atmospheric pollution can affect it. This is why the dates for the rising of stars can vary.
Heliacal rising was very important to the ancients. In particular, the heliacal rising of Sirius, the brightest star in the night sky, was highly regarded by many cultures, notably the ancient Egyptians. The heliacal rising of Sirius heralded the Egyptian new year and it also coincided with the annual flooding of the Nile. [1] Sirius was extremely important to the ancients and was revered all over the ancient world. Its significance was that it represented the third eye (from High Priest Hoodedcobra).
The rising of various stars and constellations was used in the construction of calendars and also marked the beginning of important seasons for various groups of ancient peoples such as the sailing season, agricultural season and so on. For instance, the heliacal rising of the Pleiades marked the start of the sailing season for the ancient Greeks. [2]
The Babylonians had extensive star catalogues that recorded detailed information about various constellations. The MUL.APIN is a Babylonian star catalogue that dates from at least 1000 BC. It lists several constellations (including the zodiac constellations) and their corresponding heliacal rise and set dates. [3] The Babylonians were excellent at Astrology and had a huge hand in the Astrological system we use today.
Lastly, it is important to note that heliacal rising is not really used when it comes to modern Astrology and reading horoscopes. However, it is an important part of Astronomy/Astrology to know. In the ancient world, Astronomy and Astrology were pretty much the same thing and the priests who kept track of the movement of heavenly bodies were also the ones who interpreted the spiritual significance of what was observed. There are also some concepts that require one to understand heliacal rising before they can be understood properly, such as decans (these are divisions of the zodiac wheel into parts that are 10 degrees wide, or a third of a sign). This will all be covered in the next lessons.
Sources
1. Wikipedia page on heliacal rising, https://en.wikipedia.org/wiki/Heliacal_rising
2. ibid.
3. Wikipedia page on MUL.APIN, https://en.wikipedia.org/wiki/MUL.APIN
Always interesting, thank you!
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