Which Constellations Can Be Seen Along The Ecliptic?

Starting in the constellation Aries, the Sun passes through 12 constellations as it moves along the ecliptic, which is the plane of its orbit around the galactic centre. However, while western astrologers recognize only 12 constellations, or signs in the zodiac, the Sun actually passes through 13 constellations, with Ophiuchus being the 13th.

We need not go into the reasons why astrologers do not count Ophiuchus as part of the zodiac; suffice to say that in astrology, the ecliptic is divided into twelve 30-degree segments, with a constellation assigned to each segment. See the image below for details on how the segments and constellations are arranged.

Image credit: USRA.edu
Image credit: USRA.edu

Starting at the First Point of Aries, also known as the Vernal Equinox (which is really in Pisces), the Sun passes through the constellation of the zodiac in this order: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, [Ophiuchus], Sagittarius, Capricorn, Aquarius and Pisces.

However, from an astronomical point of view, the division of the ecliptic does not agree with the dates (and number of days) the Sun actually spends in each constellation. See the table below for details of the differences between astrological and astronomical data.

Credit: Dionysia.org
Credit: Dionysia.org

An overview of the zodiac constellations

Astrology aside, let’s take a closer look at the constellations on the ecliptic, and in the order in which the Sun passes through them:

Aries: Quick Facts

  • Location: Northern hemisphere between latitudes +90° and -60°, taking up an area of 441 square degrees, making it the 39th biggest constellation.
  • Neighbouring constellations: Cetus, Perseus, Pisces, Taurus, and Triangulum.
  • Best seen: Autumn; during November, at about 9 PM local time.
  • Notable objects: Aries has no Messier objects, but it does contain several notable deep sky objects, such as the unbarred spiral galaxy NGC 772, and NGC 1156, an irregular dwarf galaxy.
  • Brightest star: Hamal – α Arietis (Alpha Arietis), a K-class variable orange giant whose apparent magnitude varies between 1.98 and 2.04. Hamal is located about 66 light years away.
  • Planets: 7 stars with 10 planets between them.
  • Meteor showers: May Arietids, Autumn Arietids, Delta Arietids, Epsilon Arietids, Daytime-Arietids, and Aries-Triangulids.

Taurus: Quick Facts

  • Location: Northern hemisphere between latitudes +90° and -65°, where it takes up 797 square degrees, making it the 17th biggest constellation.
  • Neighbouring constellations: Aries, Auriga, Cetus, Eridanus, Gemini, Orion and Perseus.
  • Best seen: Autumn; during December, at about 9 PM local time.
  • Notable objects: Taurus contains two famous Messier objects; M1, the Crab Nebula, and M45, the well known Pleiades star cluster.
  • Brightest star: Aldebaran – α Tauri (Alpha Tauri), a variable orange giant star that is at least 44.2 times as big and 425 times as bright as the Sun. Aldebaran is located about 65 light years away.
  • Planets: 10 stars with 12 planets between them.
  • Meteor showers: Taurids and the Beta Taurids. The Taurids peak in November, while the Beta Taurids peak in June and July.

Gemini: Quick Facts

  • Location: Northern hemisphere between latitudes +90° and -60°, where it takes up an area of 514 square degrees, making it the 39th biggest constellation.
  • Neighbouring constellations: Auriga, Cancer, Canis Minor, Lynx, Monoceros, Orion and Taurus.
  • Best seen: Winter; during January, at about 9 PM local time.
  • Notable objects: One Messier object, M35, a famous star cluster.
  • Brightest star: Pollux – β Geminorum (Beta Geminorum) is also the 17th brightest star in the entire sky, with an apparent visual magnitude of 1.14 from a distance of about 34 light years away. Pollux is a fully evolved class K0 III orange giant that is twice as massive, as nine times as big as the Sun.
  • Planets: 9 stars with one planet each.
  • Meteor showers: Geminids, and the Rho Geminids. The Geminids are almost always very bright, and peak around December 13-14.

Cancer: Quick Facts

  • Location: Northern hemisphere between latitudes +90° and -60°, where it takes up an area of 506 square degrees, making it the 31st biggest constellation.
  • Neighbouring constellations: Canis Minor, Gemini, Hydra, Leo, Leo Minor, and Lynx.
  • Best seen: Winter; during February, at about 9 PM local time.
  • Notable objects: two Messier objects, M44, the Beehive Cluster and M67, a large open star cluster.
  • Brightest star: Al Tarf – β Cancri (Beta Cancri) is a 3.5 magnitude binary system that consists of a K-class orange giant, and a dim, 14th magnitude companion located about 29 seconds of arc away. The system is located about 290 light years away from earth.
  • Planets: 8 stars with 12 planets between them.
  • Meteor showers: The Delta Cancrids is the only meteor shower associated with Cancer.

Leo: Quick Facts

  • Location: Northern hemisphere, between latitudes +90° and -65°, where it takes up an area of 947 square degrees, making it the 12th biggest constellation.
  • Neighbouring constellations: Cancer, Coma Berenices, Crater, Hydra, Leo Minor, Lynx, Sextans, Ursa Major, and Virgo.
  • Best seen: Winter; during March, at about 9 PM local time.
  • Notable objects: 5 Messier objects: M65, M66, M95, M96, and M104. All are visible with amateur equipment.
  • Brightest star: Regulus – α Leonis (Alpha Leonis) is a multiple star system that consists of two pairs of star that orbit another pair. The systems’ combined apparent visual magnitude of 1.35 also makes this system the 22nd brightest star in the entire sky. This system is located about 77 light years away.
  • Planets: 15 stars with 18 planets between them.  
  • Meteor showers: The Leonids is generally a very productive shower that peaks during the night of 17/18 November. A second shower associated with Leo, the January Leonids, is regarded as a minor shower that peaks in the first week of January.

Virgo: Quick Facts

  • Location: Southern hemisphere, between latitudes +80° and -80°, where it takes up an area of 1 294 square degrees, making it the 2nd biggest constellation, after Hydra.
  • Neighbouring constellations: Boötes, Coma Berenices, Corvus, Crater, Hydra, Leo, Libra and Serpens Caput.
  • Best seen: Spring; during April, at about 9 PM local time.
  • Notable objects: 11 Messier objects: Messier 49 (M49, NGC 4472), Messier 58 (M58, NGC 4579), Messier 59 (M59, NGC 4621), Messier 60 (M60, NGC 4649), Messier 61 (M61, NGC 4303), Messier 84 (M84, NGC 4374), Messier 86 (M86, NGC 4406), Messier 87 (M87, NGC 4486), Messier 89 (M89, NGC 4552), Messier 90 (M90, NGC 4569) and Messier 104 (M104, NGC 4594, Sombrero Galaxy). All are visible with amateur equipment.
  • Brightest star: Spica – α Virginis (Alpha Virginis) is a 1.04 magnitude binary star, and the 15th brightest star in the entire sky. What makes this system different from other binary stars is the fact that the component stars do not eclipse each other. Instead, they both rotate about a common centre of mass, but so closely that their mutual gravitational effect is distorting both stars, producing measurable variations in their respective luminosities.
  • Planets: 26 stars with 33 planets between them.    
  • Meteor showers: The Virginids, and the Mu Virginids. Both showers are included in the very complex Virginids Complex of meteor showers that stretches over several months.

Libra: Quick Facts

  • Location: Southern hemisphere, between latitudes +65° and -90°, where it takes up an area of 538 square degrees, making it the 29th biggest constellation.
  • Neighbouring constellations: Centaurus, Hydra, Lupus, Ophiuchus, Scorpius, Serpens Caput, and Virgo.
  • Best seen: Spring; during May, at about 9 PM local time.
  • Notable objects: Libra does not contain any Messier objects, or any other noteworthy objects. The only object of any interest is HD 140283, commonly known as Methuselah, which with an age of about 14 billion years, is the oldest known star in the observable universe.
  • Brightest star: Zubeneschamali – β Librae (Beta Librae) is a magnitude 2.61 blue-white dwarf located about 185 light years away. The star’s rotational velocity is around 250 km/sec at its equator, which is close to the speed at which it would break apart under its own centrifugal forces. This star is about 5 times as big, and at least 130 times as bright as the Sun.
  • Planets: 3 stars with 7 planets between them.
  • Meteor showers: May Librids.

Scorpio (Scorpius): Quick Facts

  • Location: Southern hemisphere, between latitudes +40° and -90°, where it takes up an area of 497 square degrees, making the 33rd biggest constellation.
  • Neighbouring constellations: Ara, Corona Australis, Libra, Lupus, Norma, Ophiuchus and Sagittarius.
  • Best seen: Spring; during June, at about 9 PM local time.
  • Notable objects: 4 Messier objects: Messier 4 (M4, NGC 6121), Messier 6 (M6, NGC 6405, Butterfly Cluster), Messier 7 (M7, NGC 6475, Ptolemy Cluster) and Messier 80 (NGC 6093).
  • Brightest star: Antares – α Scorpii (Alpha Scorpii) is a magnitude 0.96 red super giant, and the most evolved member of the Scorpius-Centaurus Association, the closest OB stellar association to the solar system. Antares is a spectacular star on all counts; it is about 15-18 times a massive as the Sun, and at least 10 000 times as bright, and 883 times as big as the Sun.
  • Planets: 27 stars with 34 planets between them.
  • Meteor showers: Alpha Scorpiids, and the Omega Scorpiids.

Ophiuchus: Quick Facts

  • Location: Southern hemisphere, between latitudes +80° and -80°, where it takes up an area of 948 square degrees, making it the 11th biggest constellation.
  • Neighbouring constellations: Aquila, Hercules, Libra, Sagittarius, Scorpius, and Serpens.
  • Best seen: Summer; during July, at about 9 PM local time.
  • Notable objects: 7 Messier objects: Messier 9 (M9, NGC 6333), Messier 10 (M10, NGC 6254), Messier 12 (M12, NGC 6218), Messier 14 (M14, NGC 6402), Messier 19 (M19, NGC 6273), Messier 62 (M62, NGC 6266) and Messier 107 (M107, NGC 6171). The constellation is also home to some famous nebulae, among which are the Twin Jet Nebula, Little Ghost Nebula, dark nebulae Barnard 68, Pipe Nebula, Snake Nebula, and the Dark Horse Nebula. All Messier objects in the constellation are visible with amateur equipment.
  • Brightest star: Rasalhague – α Ophiuchi (Alpha Ophiuchi) is a combined magnitude 2.07 binary system, in which the primary star is a class K5-7V white giant star that is about 2.4 times as massive as the Sun. The system has an orbital period of only 8.62 years.
  • Planets: 17 stars with 19 planets between them. 
  • Meteor showers: Ophiuchids, the Northern May Ophiuchids, the Southern May Ophiuchids and the Theta Ophiuchids.

Sagittarius: Quick Facts

  • Location: Southern hemisphere, between latitudes +55° and -90°, where it takes up an area of 867 square degrees, making it the 15th biggest constellation.
  • Neighbouring constellations: Aquila, Capricornus, Corona Australis, Indus, Microscopium, Ophiuchus, Scutum, Scorpius, Serpens Cauda and Telescopium.
  • Best seen: Summer; during July, at about 9 PM local time.
  • Notable objects: 15 Messier objects: Messier 8 (M8, NGC 6523, Lagoon Nebula), Messier 17 (M17, NGC 6618 Omega, Swan, Horseshoe or Lobster Nebula), Messier 18 (M18, NGC 6613), Messier 20 (M20, NGC 6514, Trifid Nebula), Messier 21 (M21, NGC 6531), Messier 22 (M22, NGC 6656, Sagittarius Cluster), Messier 23 (M23, NGC 6494), Messier 24 (M24, NGC 6603, Sagittarius Star Cloud), Messier 25 (M25, IC 4725), Messier 28 (M28, NGC 6626), Messier 54 (M54, NGC 6715), Messier 55 (M55, NGC 6809), Messier 69 (M69, NGC 6637), Messier 70 (M70, NGC 6681), and Messier 75 (M75, NGC 6864). The constellation also contains the rotational centre of the Milky Way galaxy. While all Messier objects in the constellation are visible with amateur equipment, the galactic centre is not.
  • Brightest star: Kaus Australis – ε Sagittarii (Epsilon Sagittarii) is a magnitude 1.79 binary system in which the primary star, Kaus Australis, is a class-B blue giant that is at least 375 times as bright as the Sun. The system is about 143 light years away.
  • Planets: 25 stars with 26 planets between them.    
  • Meteor showers: No meteor showers are associated with the constellation.

Capricorn (Capricornus): Quick Facts

  • Location: Southern hemisphere, between latitudes +60° and -90°, where it takes up an area of 414 square degrees, making the 40th biggest constellation.
  • Neighbouring constellations: Aquarius, Aquila, Microscopium, Piscis Austrinus, and Sagittarius.
  • Best seen: Summer; during August, at about 9 PM local time.
  • Notable objects: 1 Messier object; M30 (NGC 7099), a large globular cluster that is best seen from the southern hemisphere.
  • Brightest star: Deneb Algedi – δ Capricorni (Delta Capricorni) is a 2.85 magnitude four-star system that consists of two pairs of stars orbiting each other. The brightest star in the system, Delta Capricorni, is about 8.5 times as bright as the Sun. It is also very close to the ecliptic, meaning that it can be occulted by the Moon, and very rarely by the planets. The system is about 40 light years away.
  • Planets: 5 planets with 9 planets between them.      
  • Meteor showers: Alpha Capricornids, Chi Capricornids, Sigma Capricornids, t Tau Capricornids, and the Capricorniden-Sagittarids.

Aquarius: Quick Facts

  • Location: Southern hemisphere, between latitudes +65° and -90°, where it takes up an area of 980 square degrees, making it the 10th biggest constellation.
  • Neighbouring constellations: Aquila, Capricornus, Cetus, Delphinus, Equuleus, Pegasus, Pisces, Piscis Austrinus, and Sculptor.
  • Best seen: Summer; during September, at about 9 PM local time.
  • Notable objects: 3 Messier objects: M2 (NGC 7089), M72 (NGC 6981), and M73 (NGC 6994)
  • Brightest star: Sadalsuud – β Aquarii (Beta Aquarii) is a rare yellow super giant star with an apparent magnitude of 2.91, located about 610 light years away. It is also six times as massive and at least 2 200 times as bright as the Sun, which means that its luminosity makes it difficult to spot all of its suspected companion stars.
  • Planets: 14 stars with 19 planets between them.      
  • Meteor showers: March Aquariids, Eta Aquariids, Delta Aquariids, and Iota Aquariids, none of which is particularly spectacular.

Pisces: Quick Facts

  • Location: Northern hemisphere, between latitudes +90° and -65°, where it takes up an area of 889 square degrees, making it the 14th biggest constellation.
  • Neighbouring constellations: Andromeda, Aquarius, Aries, Cetus, Pegasus, and Triangulum.
  • Best seen: Autumn; during October, at about 9 PM local time.
  • Notable objects: 1 Messier object, M74, a spiral galaxy that is visible with amateur equipment.
  • Brightest star: Kullat Nunu – η Piscium (Eta Piscium), is a 3.26 magnitude yellow giant star that is 316 times brighter, 26 times bigger, and 3.5 – 4 times more massive than the Sun. The star is about 295 light years away, and has a very dim companion orbiting it at a distance of about one second of arc.
  • Planets: 39 stars with 41 planets between them.     

Meteor showers: The Piscids, which has been known to produce relatively large numbers of meteors at its maximum.

Where to locate Ophiuchus

The best time to observe Ophiuchus is during summer form the Northern Hemisphere or winter from the Southern Hemisphere.

From the Northern Hemisphere, the constellation can be seen high in the southern sky at nightfall and early evening during late July and early August. During Autumn evenings, it can be observed in the southwesterly skies.

Ophiuchus is joined in legend and in the sky to the constellation of the Serpent, which the name originates from two Greek words meaning serpent and holding.

If you have a very dark sky, you should be able to observe this constellation with a high quality telescope and see that actually looks similar what it’s supposed to be: a large man holding a snake!