Astronomy: The Sun and the Constellations of the Zodiac

The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving along the ecliptic (red), which is tilted 23.44° with respect to the celestial equator (blue-white). The constellations of the Zodiac are in green. Image credit: Wikipedia.

Shalom, everyone! Genesis 1:14-16 gives the account of Day 4 of the Creation in which The Almighty divided the day from the night. He created two great lights, one with greater power than the other: The greater light, also known as the Sun, He created to rule the day; the lesser light, also known as the Moon, He created to rule the night. The Almighty also created the stars to be used in conjunction with the Sun and Moon to assess the seasons, days and years.

The solar calendar utilizes the positions of the Sun and the stars relative to the Earth’s rotation and annual orbit.  Each year on the solar calendar consisted of approximately 365 days. On the solar calendar, the first sighting of the Sun in each of the constellations visible to the naked eye during ancient times marked the beginning of a new month. There were 12 months in each year, and each month had either 29, 30 or 31 days. We will now explore the Sun and the constellations of the Zodiac.

The Sun

The Sun is at the center of our Solar System. It is made of hot plasma and is the most important physical source of energy for life on planet Earth. It is a stationary object that is orbited by a number of other objects including:

  • Eight known planets – four terrestrial planets (Mercury, Venus, Earth, and Mars), two gas planets (Jupiter and Saturn), two ice planets (Uranus and Neptune);
  • Five known dwarf planets  – Pluto, Ceres, Eris, Makemake, and Haumea;
  • Asteroids, comets, and other icy objects.

Our Solar System also has groups of stars called “constellations.” Like the Sun, the constellations are stationary but they appear to “move” in the night sky due to the Earth‘s rotation and annual orbit around the Sun. The Moon, the lesser light Elohim created to rule the night, orbits the Earth.

In astronomy, all objects in our Solar System form the “celestial sphere,” an imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie. Like planet Earth, this celestial sphere has assigned axes (north celestial pole and south celestial pole), and coordinates for measuring the positions of celestial objects in the sky (sun, planets, stars, constellations, etc). The circular “orbit” the Sun appears to follow on the celestial sphere over the course of one year is called the “ecliptic.” According to scientific research, one year of this solar orbit consists of 365.2425 days. The celestial sphere also has a celestial equator, an imaginary line on the same plane as the Earth‘s equator. Because the Earth‘s axis is tilted, the celestial equator is inclined at 23.44 degrees relative to the ecliptic plane.

The Sun and the Seasons: Equinoxes and Solstices

The Sun is key in the determination of the arrival of the four seasons, Spring, Summer, Fall, and Winter. Spring and Fall begin with the arrival of the Equinoxes. Summer and Winter begin with the arrival of the Solstices.

The Equinox is the time when the Sun crosses the plane of the Earth‘s equator, making night and day of approximately equal length all over the Earth. The Vernal (Spring) Equinox occurs about March 19, 20 or 21 in the Northern Hemisphere, and approximately September 22 in the Southern Hemisphere. The Autumn (Fall) Equinox occurs approximately September 22 in the Northern Hemisphere, and about March 19, 20 or 21 in the Southern Hemisphere.

The Solstice is the time when the Sun appears to reach its most northerly or southerly point in the sky at noon, and are marked by the longest and shortest days of the year. The Summer Solstice occurs annually around June 21 when the Sun is at its most northerly point from the Earth‘s equator and is the longest day of the year. The Winter Solstice occurs annually around December 21, when the Sun is at its most southerly point relative to the Earth‘s equator and is the shortest day of the year.

The Stars: The Constellations of the Zodiac

A visual representation of the Earth’s orbit in relation to the Sun and the constellations, and the calendar months. Image credit: Unknown

Constellations are groups of stars that form meaningful patterns in the celestial sphere. These patterns typically represent animals, mythical beings or creatures, or inanimate objects. The International Astronomical Union (IAU) confirms that there are 88 constellations covering the entire celestial sphere. In ancient times, only 48 constellations were known to astronomers.

About 8-degrees north and south of the ecliptic lies an area of the sky called the Zodiac, a circle of twelve 30-degree divisions of celestial longitude that are centered on the ecliptic. Within the Zodiac lie 13 constellations of stars that are visible to the naked eye from Earth. Though the International Astronomical Union (IAU) confirmed 13 constellations in the Zodiac in 1995, the ancient Mesopotamian and Egyptian astronomers referred to 12, and used the start date of the Sun‘s position in each of these constellations as the instance of a new month on the 365-day solar calendar.

Sidereal Solar Year and Constellations

Ancient Mesopotamian astronomers used the sidereal system to define a solar year. The sidereal system reckons the Earth‘s position in relation to the fixed positions of the stars in the celestial sphere. The dates when the Sun appeared nearest to a constellation were used to reckon a month. The ancient sidereal system originally divided the Zodiac into 12 constellations. The modern sidereal system divides the Zodiac into 13 constellations. The ancient Egyptian astronomers used the sidereal system up until the time of Ptolemy, who introduced the tropical system to define a solar year, based on the Earth‘s position relative to the Vernal Equinox in the Northern Hemisphere. The ancient pre-exilic Israelites used the ancient sidereal system to reckon time for their solar calendar, which began the year in the Fall with the Virgo constellation. The sidereal system is used today primarily by Eastern astronomers.

The following are the constellations of the Zodiac and their dates when the Sun “passes” through them according to the sidereal system. The names of these constellations are English translations. Naturally, each culture would have given these constellations names in their own language.

# Constellation Symbol Sidereal Dates # Days IAU Sidereal Dates # Days
1  Pisces Fishes  Mar 16 – Apr 14 30  Mar 12 – Apr 18 38
2  Aries Ram  Apr 15 – May 15 31  Apr 19 – May 13 25
3  Taurus Bull  May 16 – Jun 15 31  May 14 – Jun 19 37
4  Gemini Twins  Jun 16 – Jul 16 31  Jun 20 – Jul 20 31
5  Cancer Crab  Jul 17 – Aug 16 31  Jul 21 – Aug 9 20
6  Leo Lion  Aug 17 – Sep 16 31  Aug 10 – Sep 15 37
7  Virgo Maiden holding wheat stalks  Sep 17 – Oct 17 31  Sep 16 – Oct 30 45
8  Libra Scales/Weights  Oct 18 – Nov 16 30  Oct 31 – Nov 22 23
9  Scorpio Scorpion  Nov 17 – Dec 16 30  Nov 23 – Nov 29 7
10  Ophiuchus Snake  N/A  Nov 30 – Dec 17 18
11  Sagittarius Archer  Dec 17 – Jan 15 30  Dec 18 – Jan 18 32
12  Capricorn Goat-Fish  Jan 16 – Feb 14 30  Jan 19 – Feb 15 28
13  Aquarius Water-Bearer  Feb 15 – Mar 15 29  Feb 16 – Mar 11 24
 Total: 365  Total:  365

Tropical Solar Year and Constellations

The tropical system is used primarily by Western astronomers, although the use of the sidereal system among them is gaining traction. The tropical system divides the Zodiac into 12 constellations. The tropical system is based on the seasons of the Earth and does not reflect the true locations of sun and constellations relative to the Earth’s position. The following are the constellations of the Zodiac and their dates when the Sun “passes” through them according to tropical system. The names of these constellations are English translations. Naturally, each culture would have given these constellations names in their own language.

# Constellation Symbol Tropical Dates # Days
1  Aries  Ram  March 21 – April 20 31
2  Taurus  Bull  April 21 – May 21 31
3  Gemini  Twins  May 22 – June 21 31
4  Cancer  Crab  June 22 – July 22 31
5  Leo  Lion  July 23 – August 22 31
6  Virgo  Maiden holding wheat stalks  August 23 – September 22 31
7  Libra  Scales/Weights  September 23 – October 22 30
8  Scorpio  Scorpion  October 23 – November 21 30
9  Sagittarius  Archer  November 22 – December 21 30
10  Capricorn  Goat-Fish  December 22 – January 19 29
11  Aquarius  Water-Bearer  January 20 – February 19 31
12  Pisces  Fishes  February 20 – March 20 29
 Total Number of Days:  365

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