Asterism (astronomy)

Other asterisms consist partially of multiple first-magnitude stars.

• The
  False Cross
  .

All other first-magnitude stars are the only such stars in their asterisms or constellations, with Canopus in the Argo Navis asterism south of Sirius, visually east of the Carina Nebula and near the Large Magellanic Cloud (both being first-magnitude deep-sky objects), Achernar in the Eridanus constellation east of Canopus, Fomalhaut in the Southern Fish constellation east of Achernar and Antares in the Scorpius constellation visually near the Galactic Center.

Constellation-based asterisms

• The Big Dipper, also known as The Plough or Charles's Wain, is composed of the seven brightest stars in Ursa Major.^[5] These stars delineate the Bear's hindquarters and exaggerated tail, or alternatively, the "handle" forming the upper outline of the bear's head and neck. With its longer tail, Ursa Minor hardly appears bearlike at all, and is widely known by its pseudonym, the Little Dipper.
• The
  δ Cygni
  in the other.
• The Southern Cross is an asterism by name, but the whole area is now recognised as the constellation
  Naturalis Historia as the asterism 'Thronos Caesaris.'^[3]
• The Fish Hook is the traditional Hawaiian name for Scorpius. The image will be even more obvious if the chart's lines from Antares (α Sco) to Beta Scorpii (β Sco) and Pi Scorpii (π Sco) are replaced with a line from Beta through Delta Scorpii (δ Sco) to Pi forming a large capped "J." Adding vertical lines to connect the limbs at the left and right in the main diagram of Hercules will complete the figure of the Butterfly.^[8]
• Boötes is sometimes known as the Ice Cream Cone.^[9] It is also known as the Kite.^[10]
• The stars of Cassiopeia form a W which is often used as a nickname.^[11]
• The Great Square of
  Alpheratz, representing the body of the winged horse.^[12] The asterism was recognized as the constellation ASH.IKU "The Field" on the MUL.APIN cuneiform tablets from about 1100 to 700 BC.^[13]
  Alpheratz is now only considered a part of the constellation Andromeda whereas formerly the star was a part of both constellations.
• The Bowl of Virgo is formed by the stars Beta, Gamma, Delta, Epsilon and Eta Virginis. Together with Spica, they form a Y shape.

• The Three Leaps of the Gazelle consists of three pairs of stars in Ursa Major aligned in a row spanning about 30 degrees. In Arabic lore, the star pairs are pictured as the hoof prints of a gazelle startled from a pond by Leo the lion. (The "pond" is pictured as the Coma Star Cluster.) The first pair of stars are Xi and Nu, second pair Upsilon and Lambda, third pair Kappa and Iota Ursa Majoris. The pairs also mark three of the bear's paws.

Some asterisms refer to portions of traditional constellation figures. These include:

• The Water Jar or Urn of Aquarius is a Y-shaped figure centered upon Zeta Aquarii and includes Gamma, Eta and Pi. It pours water in a stream of more than 20 stars terminating with the star Fomalhaut.
• The Crab Breast of Cancer is a quadrilateral formed by the four stars Gamma, Delta, Eta and Theta Cancri which make up the carapace (inner shell) of the Crab. Contained within is the Beehive Cluster (Messier 44) which includes Epsilon Cancri.
• The Snake Head is the westernmost portion of Hydra consisting of the stars Delta, Epsilon, Zeta, Eta, Rho and Sigma Hydrae.
• Orion's Belt consists of the three bright stars Zeta (Alnitak), Epsilon (Alnilam) and Delta Orionis (Mintaka) which form the belt of Orion.
• The Bull's Face of Taurus is a V-shaped figure formed by prominent members of the Hyades cluster, including stars Gamma, Delta¹, Delta², Delta³, Epsilon, Theta Tauri, as well as the bright star Alpha Tauri (Aldebaran) which forms the red eye of the Bull.

Other particular asterisms

Other asterisms are also composed of stars from one constellation, but do not refer to the traditional figures.

• Four stars (
  Diamond Cross.^[14]
• The Saucepan or Pot, being the same stars as the Belt and Sword of Orion. The end of the handle is at
  ι Orionis, with the far rim at η Orionis.^{[citation needed}
  ]
• The four central stars in Hercules, Epsilon (ε Her), Zeta (ζ Her), Eta (η Her), and Pi (π Her), form the Keystone.^[4]
• The curve of stars at the front end of the Lion from
  Regulus (α Leo), looking much like a mirror-image question mark, has long been known as the Sickle.^[5]
• The brighter stars of Sagittarius form the Teapot.^[15] (The Large Sagittarius Star Cloud appears to be steam emerging from the "spout".)
• Northeast of the Teapot asterism lies the fainter Teaspoon, consisting of the stars ξ¹, ξ², ο, π, ρ¹ and ρ² Sagitarii.^[16]
• Four bright stars in Delphinus (Sualocin or α Delphini, Rotanev or β Delphini, γ Delphini and δ Delphini) form Job's Coffin.^[5]
• The
  Terebellum is a small quadrilateral of four faint stars (Omega, 59, 60, 62) in Sagittarius' hindquarters.^[17]
• Just south of Pegasus, the western fish of Pisces is home to the Circlet formed from Gamma (γ Piscium), Kappa (κ Piscium), Lambda (λ Piscium), TX Piscium, Iota (ι Piscium), and Theta (θ Piscium).^[4][5]
• Merak (Alpha and Beta Ursae Majoris), the two stars at the end of the bowl of the Big Dipper are often called the Pointers:^[18] a line from β to α and continued for about five times the distance between them arrives at the North Celestial Pole and the star Polaris
  (α UMi/Alpha Ursae Minoris), the North Star.
• Rigil Kentaurus (α Centauri) and Hadar (β Centauri) are the Southern Pointers leading to the Southern Cross^[19] and thus helping to distinguish Crux from the False Cross.

Asterisms across multiple constellations

Other asterisms that are formed from stars in more than one constellation.

• The Egyptian X is a large asterism which, like the Diamond of Virgo, is composed of a pair of equilateral triangles.
  Phakt (α Col) form another to the South. Unlike the Diamond, however, these triangles meet, not base-to-base, but vertex-to-vertex. The name derives from both the shape and, because the stars straddle the Celestial Equator, it is more easily seen from south of the Mediterranean than in Europe.^{[citation needed}
  ]
• The Lozenge is a small diamond formed from three stars –
  Rastaban (Gamma, Xi, and Beta Draconis) – in the head of Draco and one – Iota Herculis – in the foot of Hercules.^{[citation needed}
  ]
• The diamond-shaped False Cross is composed of the four stars
  astronavigation. Like the Southern Cross, three of its main four stars are whitish and one orange.^[20]
• From latitudes above
  Izar (ε Boötis), and Alphecca (α Coronae Borealis). Alphecca is far brighter than either Delta or Beta Boötis, diminishing the "kite" or "ice-cream cone" shape of Boötes. From the United Kingdom in particular, where there is serious light pollution in many areas and also twilight all night for much of the time these constellations appear, this "Y" is often visible while the other stars of Boötes and Corona Borealis are not.^{[citation needed}
  ]
• The Lightning Bolt, aligned north to south, consists of the stars Epsilon Pegasi, Alpha Aquarii, Beta Aquarii and Delta Capricorni. Easily visible to naked eyes even in light polluted skies, the asterism is useful for orienting among three constellations.^[21]
• The Serpent Bowl is a large curved asterism spanning 3.5 hours of right ascension, from mid-northern latitudes best seen in July and August evenings. From west to east, it includes the stars Delta, Alpha and Epsilon Serpentis, Delta, Epsilon, Upsilon, Zeta and Eta Ophiuchi, Xi Serpentis, Nu and Tau Ophiuchi, Eta and Theta Serpentis.
• The Eagle Tail Corona is a flattened curved figure in the tail of
  Messier 11
  is also aligned with the curve.

Telescopic asterisms

Asterisms range from the large and obvious to the small, and even telescopic.

• The 37 or LE of NGC 2169, in Orion.^[22]
• The Engagement Ring in Ursa Minor has the north star Polaris as the diamond, at one end of a ring of much fainter stars about one degree across.^[23]
• The Broken Engagement Ring in Ursa Major at 10:51 / +56°10' (preceding β Ursae Majoris, Merak).^[24]
• The Christmas Tree shape of the
  Monoceros. It is made up of about approximately 40 stars.^[25][26]
• The Coathanger, in Vulpecula, also known as Brocchi's Cluster (see image at top).^[27]
• Kemble's Cascade, a chain of stars that ends in open cluster NGC 1502, in Camelopardalis.^[27]
• Napoleon's Hat (Picot 1), in
  Bootes (south of α Bootis, Arcturus).^{[citation needed}
  ]
• The Ring of the Nibelungen (Ferrero 27) in Draco, named after the 1857 German epic drama, at 15:57 / +62°32' (near galaxy NGC 6015).^[28][29]
• The V-shaped Messier 73 in Aquarius, determined to be an asterism in 2002.^[30]

See also

• Australian Aboriginal astronomy
• Chinese constellation
• Nakshatra

References