Title page of the Coelum Stellatum Christianum by Julius Schiller.
This
print, published in Richard Blome's "The Gentleman's Recreation" (1686)
shows the diverse ways in which cosmography can be applied
Celestial cartography, uranography, astrography or star cartography is the fringe of astronomy and branch of cartography concerned with mapping stars, galaxies, and other astronomical objects on the celestial sphere.
Measuring the position and light of charted objects requires a variety
of instruments and techniques. These techniques have developed from
angle measurements with quadrants and the unaided eye, through sextants combined with lenses for light magnification, up to current methods which include computer-automated space telescopes. Uranographers have historically produced planetary position tables, star tables, and star maps for use by both amateur and professional astronomers. More recently computerized star maps have been compiled, and automated positioning of telescopes is accomplished using databases of stars and other astronomical objects.
Etymology
The word "uranography" derived from the Greek "ουρανογραφια" (Koine Greekουρανος "sky, heaven" + γραφειν "to write") through the Latin"uranographia". In Renaissance times, Uranographia was used as the book title of various celestial atlases.
During the 19th century, "uranography" was defined as the "description
of the heavens". Elijah H. Burritt re-defined it as the "geography of
the heavens". The German word for uranography is "Uranographie", the French is "uranographie" and the Italian is "uranografia".
A determining fact source for drawing star charts is naturally a star
table. This is apparent when comparing the imaginative "star maps" of Poeticon Astronomicon – illustrations beside a narrative text from the antiquity – to the star maps of Johann Bayer, based on precise star-position measurements from the Rudolphine Tables by Tycho Brahe.
Important historical star tables
c:AD 150, Almagest – contains the last known star table from antiquity, prepared by Ptolemy, 1,028 stars.
15th century BC – The ceiling of the tomb TT71 for the Egyptian architect and minister Senenmut, who served Queen Hatshepsut, is adorned with a large and extensive star chart.
1092 – Xin Yi Xiang Fa Yao (新儀 象法要), by Su Song, a horological treatise which had the earliest existent star maps in printed form. Su Song's star maps also featured the corrected position of the pole star which had been deciphered due to the efforts of astronomical observations by Su's peer, the polymath scientist Shen Kuo.
1515 – First European printed star charts published in Nuremberg, Germany, engraved by Albrecht Dürer.
1693 – Firmamentum Sobiescanum sive Uranometria, by Johannes Hevelius, a star map updated with many new star positions based on Hevelius'es Prodromus astronomiae (1690) – 1564 stars.
Equirectangular
plot of declination vs right ascension of the modern constellations
with a dotted line denoting the ecliptic. Constellations are
colour-coded by family and year established.
Constellation families are collections of constellations sharing some defining characteristic, such as proximity on the celestial sphere,
common historical origin, or common mythological theme. In the Western
tradition, most of the northern constellations stem from Ptolemy's list in the Almagest
(which in turn has roots that go back to Mesopotamian astronomy), and
most of the far southern constellations were introduced by sailors and
astronomers who traveled to the south in the 16th to 18th centuries.
Separate traditions arose in India and China.
Menzel's families
Entirely northern:
Ursa Major
Primarily northern:
Perseus (except Cetus)
Straddling ecliptic:
Zodiac
Split between north and south:
Hercules
Entirely southern:
La Caille
Bayer
Orion
Primarily southern:
Heavenly Waters (except Delphinus & Equuleus)
Donald H. Menzel, director of the Harvard Observatory, gathered several traditional groups in his popular account, A Field Guide to the Stars and Planets (1975), and adjusted and regularized them so that his handful of groups covered all 88 of the modern constellations.
Of these families, one (Zodiac) straddles the ecliptic which
divides the sky into north and south; one (Hercules) has nearly equal
portions in the north and south; two are primarily in one hemisphere
(Heavenly Waters in the south and Perseus in the north); and four are
entirely in one hemisphere (La Caille, Bayer, and Orion in the south and
Ursa Major in the north).
The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving over the ecliptic (red), which is tilted on the equator (blue).
The Zodiac is a group of 12 constellations: Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, and Cancer.
Some version of these constellations are found in traditions around the
world, for this band around the celestial sphere includes the ecliptic, the apparent path of the sun through the year. These constellations therefore are all associated with zodiac signs. (The ecliptic also passes through the constellation Ophiuchus, which doesn't have an associated zodiac sign.)
Perseus Family
The Perseus Family includes several constellations associated with the Perseus myth: Cassiopeia, Cepheus, Andromeda, Perseus, Pegasus, and Cetus (representing the monster sent to devour Andromeda). Menzel also included a few neighboring constellations: Auriga, Lacerta, and Triangulum.
Except for Cetus, these constellations all lie north of the ecliptic.
The group reaches from near the north celestial pole to declination
−30°.
The Orion Family, on the opposite side of the sky from the Hercules Family, includes Orion, Canis Major, Canis Minor, Lepus, and Monoceros.
This group of constellations draws from Greek myth, representing the
hunter (Orion) and his two dogs (Canis Major and Canis Minor) chasing
the hare (Lepus). Menzel added the unicorn (Monoceros) for completeness.
Heavenly Waters
The Heavenly Waters draws from the Mesopotamian tradition associating the dim area between Sagittarius and Orion with the god Ea and the Waters of the Abyss.
Aquarius and Capricornus, derived from Mesopotamian constellations,
would have been natural members had they not already been assigned to
the Zodiac group. Instead, Menzel expanded the area and included several
disparate constellations, most associated with water in some form: Delphinus, Equuleus, Eridanus, Piscis Austrinus, Carina, Puppis, Vela, Pyxis, and Columba. Carina, Puppis, and Vela historically formed part of the former constellationArgo Navis, which in Greek tradition represented the ship of Jason.
Bayer Family
The Bayer Family collects several southern constellations first introduced by Petrus Plancius on several celestial globes in the late 16th century, based on astronomical observations by the Dutch explorers Pieter Dirkszoon Keyser and Frederick de Houtman. The constellations were named mostly for exotic animals reported in the travel journals of that period, and were copied in Johann Bayer's influential celestial atlas Uranometria in 1603. The group includes Hydrus, Dorado, Volans, Apus, Pavo, Grus, Phoenix, Tucana, Indus, Chamaeleon, and Musca.
Bayer labeled Musca as "Apis" (the Bee), but over time it was renamed.
(Bayer's twelfth new southern constellation, Triangulum Australe, was
placed by Menzel in the Hercules Family.) The Bayer Family circles the
south celestial pole, forming an irregular contiguous band. Because
these constellations are located in the far southern sky, their stars
were not visible to the ancient Greeks and Romans.
La Caille Family
The La Caille Family comprises 12 of the 13 constellations introduced by Nicolas-Louis de Lacaille in 1756 to represent scientific instruments, together with Mensa, which commemorates Table Mountain ("Mons Mensa") in South Africa, where he set up his telescope. The group includes Norma, Circinus, Telescopium, Microscopium, Sculptor, Fornax, Caelum, Horologium, Octans, Mensa, Reticulum, Pictor, and Antlia.
These dim constellations are scattered throughout the far southern sky,
and their stars were mostly not visible to the ancient Greeks and
Romans. (Menzel assigned Pyxis, the remaining Lacaille instrument, to
the Heavenly Waters group.)
Top: Baroque drawing of the constellation Orion from Johannes Hevelius'
Celestial catalogue, showing the stars as they would appear to an
observer looking down upon the imaginary celestial sphere from the
outside
Bottom: Contemporary map of Orion from the IAU and photography of the night sky
A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere, typically representing an animal, mythological person or creature, a god, or an inanimate object.
The origins of the earliest constellations likely go back to prehistory. People used them to relate stories of their beliefs, experiences, creation, or mythology. Different cultures and countries adopted their own constellations, some of which lasted into the early 20th century
before today's constellations were internationally recognized. The
recognition of constellations has changed significantly over time. Many
have changed in size or shape. Some became popular, only to drop into
obscurity. Others were limited to a single culture or nation.
The 48 traditional Western constellations are Greek. They are given in Aratus' work Phenomena and Ptolemy's Almagest, though their origin probably predates these works by several centuries. Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. Twelve ancient constellations belong to the zodiac (straddling the ecliptic, which the Sun, Moon, and planets all traverse). The origins of the zodiac remain historically uncertain; its astrological divisions became prominent c. 400 BC in Babylonian or Chaldean astronomy.
In 1922, the International Astronomical Union (IAU) formally accepted the modern list of 88 constellations, and in 1928 adopted official constellation boundaries that together cover the entire celestial sphere. Any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation name.
Other star patterns or groups called asterisms
are not constellations per se, but are used by observers to navigate
the night sky. Asterisms may be several stars within a constellation, or
they may share stars with more than one constellation. Examples of
asterisms include the Pleiades and Hyades within the constellation Taurus and the False Cross split between the southern constellations Carina and Vela, or Venus' Mirror in the constellation of Orion.
Terminology
The word "constellation" comes from the Late Latin term cōnstellātiō, which can be translated as "set of stars"; it came into use in English during the 14th century. The Ancient Greek word for constellation is ἄστρον.
These terms generally referred to a recognisable pattern of stars whose
appearance is associated with mythological characters or creatures,
earthbound animals, or objects. A more modern astronomical sense of the term "constellation" denotes one of the 88 IAU designated constellations recognized today.
Colloquial usage does not draw a sharp distinction between
"constellations" and smaller "asterisms" (pattern of stars), yet the
modern accepted astronomical constellations employ such a distinction.
E.g., the Pleiades and the Hyades
are both asterisms, and each lies within the boundaries of the
constellation of Taurus. Another example is the northern asterism
popularly known as the Big Dipper (US) or the Plough (UK), composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major. The southern False Cross asterism includes portions of the constellations Carina and Vela and the Summer Triangle is composed of the brightest stars in the constellations Lyra, Aquila and Cygnus.
A constellation (or star), viewed from a particular latitude on Earth, that never sets below the horizon is termed circumpolar. From the North Pole or South Pole, all constellations south or north of the celestial equator are circumpolar.
Depending on the definition, equatorial constellations may include
those that lie between declinations 45° north and 45° south, or those that pass through the declination range of the ecliptic or zodiac ranging between 23½° north, the celestial equator, and 23½° south.
Although stars in constellations appear near each other in the
sky, they usually lie at a variety of distances away from the Earth.
Since stars have their own independent motions, all constellations will
change slowly over time. After tens to hundreds of thousands of years,
familiar outlines will generally become unrecognizable. Astronomers can predict the past or future constellation outlines by measuring individual stars' common proper motions or cpm by accurate astrometry and their radial velocities by astronomical spectroscopy.
History of the early constellations
Lascaux Caves Southern France
It has been suggested that the 17,000 year old cave paintings in Lascaux
Southern France depict star constellations such as Taurus, Orion's Belt
and the Pleiades. However this view is not yet generally accepted
among scientists.
Mesopotamia
Inscribed stones and clay writing tablets from Mesopotamia
(in modern Iraq) dating to 3000 BC provide the earliest generally
accepted evidence for humankind's identification of constellations.[19]
It seems that the bulk of the Mesopotamian constellations were created
within a relatively short interval from around 1300 to 1000 BC.
Mesopotamian constellations appeared later in many of the classical
Greek constellations.
The oldest Babylonian catalogues of stars and constellations date back to the beginning of the Middle Bronze Age, most notably the Three Stars Each texts and the MUL.APIN, an expanded and revised version based on more accurate observation from around 1000 BC. However, the numerous Sumerian names in these catalogues suggest that they built on older, but otherwise unattested, Sumerian traditions of the Early Bronze Age.
The classical Zodiac is a revision of Neo-Babylonian
constellations from the 6th century BC. The Greeks adopted the
Babylonian constellations in the 4th century BC. Twenty Ptolemaic
constellations are from the Ancient Near East. Another ten have the same
stars but different names.
Biblical scholar E. W. Bullinger interpreted some of the creatures mentioned in the books of Ezekiel and Revelation as the middle signs of the four quarters of the Zodiac, with the Lion as Leo, the Bull as Taurus, the Man representing Aquarius, and the Eagle standing in for Scorpio. The biblical Book of Job also makes reference to a number of constellations, including עיש ‘Ayish "bier", כסיל chesil "fool" and כימה chimah "heap" (Job 9:9, 38:31-32), rendered as "Arcturus, Orion and Pleiades" by the KJV, but ‘Ayish "the bier" actually corresponding to Ursa Major. The term Mazzarothמַזָּרוֹת, translated as a garland of crowns, is a hapax legomenon in Job 38:32, and it might refer to the zodiacal constellations.
Classical antiquity
Ancient Egyptian star chart and decanal clock on the ceiling from the tomb of Senenmut
There is only limited information on ancient Greek constellations, with some fragmentary evidence being found in the Works and Days of the Greek poet Hesiod, who mentioned the "heavenly bodies". Greek astronomy essentially adopted the older Babylonian system in the Hellenistic era, first introduced to Greece by Eudoxus of Cnidus in the 4th century BC. The original work of Eudoxus is lost, but it survives as a versification by Aratus,
dating to the 3rd century BC. The most complete existing works dealing
with the mythical origins of the constellations are by the Hellenistic
writer termed pseudo-Eratosthenes and an early Roman writer styled pseudo-Hyginus. The basis of Western astronomy as taught during Late Antiquity and until the Early Modern period is the Almagest by Ptolemy, written in the 2nd century.
In the Ptolemaic Kingdom, native Egyptian tradition of anthropomorphic figures represented the planets, stars, and various constellations. Some of these were combined with Greek and Babylonian astronomical systems culminating in the Zodiac of Dendera;
it remains unclear when this occurred, but most were placed during the
Roman period between 2nd to 4th centuries AD. The oldest known depiction
of the zodiac showing all the now familiar constellations, along with
some original Egyptian constellations, decans, and planets. Ptolemy's Almagest remained the standard definition of constellations in the medieval period both in Europe and in Islamic astronomy.
Ancient China had a long tradition of observing celestial phenomena. Nonspecific Chinese star names, later categorized in the twenty-eight mansions, have been found on oracle bones from Anyang, dating back to the middle Shang dynasty. These constellations
are some of the most important observations of Chinese sky, attested
from the 5th century BC. Parallels to the earliest Babylonian (Sumerian)
star catalogues suggest that the ancient Chinese system did not arise
independently.
A well known map from the Song period is the Suzhou Astronomical Chart, which was prepared with carvings of stars on the planisphere
of the Chinese sky on a stone plate; it is done accurately based on
observations, and it shows the supernova of the year of 1054 in Taurus.
Influenced by European astronomy during the late Ming dynasty,
more stars were depicted on the charts but retaining the traditional
constellations; new stars observed were incorporated as supplementary
stars in old constellations in the southern sky which did not depict any
of the traditional stars recorded by ancient Chinese astronomers.
Further improvements were made during the later part of the Ming dynasty
by Xu Guangqi and Johann Adam Schall von Bell, the German Jesuit and was recorded in Chongzhen Lishu (Calendrical Treatise of Chongzhen period, 1628).
Traditional Chinese star maps incorporated 23 new constellations with
125 stars of the southern hemisphere of the sky based on the knowledge
of Western star charts; with this improvement, the Chinese Sky was
integrated with the World astronomy.
Early modern astronomy
Historically,
the origins of the constellations of the northern and southern skies
are distinctly different. Most northern constellations date to
antiquity, with names based mostly on Classical Greek legends. Evidence of these constellations has survived in the form of star charts, whose oldest representation appears on the statue known as the Farnese Atlas, based perhaps on the star catalogue of the Greek astronomer Hipparchus. Southern constellations are more modern inventions, sometimes as substitutes for ancient constellations (e.g. Argo Navis).
Some southern constellations had long names that were shortened to more
usable forms; e.g. Musca Australis became simply Musca.
Some of the early constellations were never universally adopted.
Stars were often grouped into constellations differently by different
observers, and the arbitrary constellation boundaries often led to
confusion as to which constellation a celestial object belonged. Before
astronomers delineated precise boundaries (starting in the 19th
century), constellations generally appeared as ill-defined regions of
the sky. Today they now follow officially accepted designated lines of Right Ascension and Declination based on those defined by Benjamin Gould in epoch 1875.0 in his star catalogue Uranometria Argentina.
The 1603 star atlas "Uranometria" of Johann Bayer
assigned stars to individual constellations and formalized the division
by assigning a series of Greek and Latin letters to the stars within
each constellation. These are known today as Bayer designations. Subsequent star atlases led to the development of today's accepted modern constellations.
Origin of the southern constellations
Sketch of the southern celestial sky by Portuguese astronomer João Faras (1 May 1500).
The southern sky, below about −65° declination,
was only partially catalogued by ancient Babylonians, Egyptian, Greeks,
Chinese, and Persian astronomers of the north. Knowledge that northern
and southern star patterns differed goes back to Classical writers, who
describe, for example, the African circumnavigation expedition commissioned by Egyptian Pharaoh Necho II in c. 600 BC and those of Hanno the Navigator in c. 500 BC. However, much of this history was lost with the Destruction of the Library of Alexandria.
The history of southern constellations is not straightforward.
Different groupings and different names were proposed by various
observers, some reflecting national traditions or designed to promote
various sponsors. Southern constellations were important from the 14th
to 16th centuries, when sailors used the stars for celestial navigation. Italian explorers who recorded new southern constellations include Andrea Corsali, Antonio Pigafetta, and Amerigo Vespucci.
Several modern proposals have not survived. The French astronomers Pierre Lemonnier and Joseph Lalande, for example, proposed constellations that were once popular but have since been dropped. The northern constellation Quadrans Muralis survived into the 19th century (when its name was attached to the Quadrantid meteor shower), but is now divided between Boötes and Draco.
88 modern constellations
A general list of 88 constellations was produced for the International Astronomical Union in 1922. It is roughly based on the traditional Greek constellations listed by Ptolemy in his Almagest in the 2nd century and Aratus' work Phenomena,
with early modern modifications and additions (most importantly
introducing constellations covering the parts of the southern sky
unknown to Ptolemy) by Petrus Plancius (1592, 1597/98 and 1613), Johannes Hevelius (1690) and Nicolas Louis de Lacaille (1763), who named fourteen constellations and renamed a fifteenth one. De Lacaille studied the stars of the southern hemisphere from 1750 until 1754 from Cape of Good Hope, when he was said to have observed more than 10,000 stars using a 0.5 inches (13 mm) refracting telescope.
In 1922, Henry Norris Russell produced a general list of 88 constellations and some useful abbreviations for them. However, these constellations did not have clear borders between them. In 1928, the International Astronomical Union (IAU) formally accepted 88 modern constellations, with contiguous boundaries along vertical and horizontal lines of right ascension and declination developed by Eugene Delporte that, together, cover the entire celestial sphere; this list was finally published in 1930. Where possible, these modern constellations usually share the names of their Graeco-Roman predecessors, such as Orion, Leo or Scorpius. The aim of this system is area-mapping, i.e. the division of the celestial sphere into contiguous fields. Out of the 88 modern constellations, 36 lie predominantly in the northern sky, and the other 52 predominantly in the southern.
Equirectangular plot of declination vs right ascension of stars brighter than apparent magnitude 5 on the Hipparcos Catalogue, coded by spectral type and apparent magnitude, relative to the modern constellations and the ecliptic.
The boundaries developed by Delporte used data that originated back to epochB1875.0, which was when Benjamin A. Gould
first made his proposal to designate boundaries for the celestial
sphere, a suggestion upon which Delporte would base his work. The
consequence of this early date is that because of the precession of the equinoxes, the borders on a modern star map, such as epoch J2000, are already somewhat skewed and no longer perfectly vertical or horizontal. This effect will increase over the years and centuries to come.
This picture of Brocchi's Cluster (the Coathanger), an asterism in the constellation Vulpecula, was taken through binoculars
In observational astronomy, an asterism is a popularly known pattern or group of stars that can be seen in the night sky. This colloquial definition makes it appear quite similar to a constellation, but they differ mostly in that a constellation is an officially recognized area
of the sky, while an asterism is a visually obvious collection of stars
and the lines used to mentally connect them; as such, asterisms do not
have officially determined boundaries and are therefore a more general
concept which may refer to any identified pattern of stars. This
distinction between terms remains somewhat inconsistent, varying among
published sources. An asterism may be understood as an informal group of
stars within the area of an official or defunct former constellation. Some include stars from more than one constellation.
Asterisms range from simple shapes of just few stars to more
complex collections of many bright stars. They are useful for people who
are familiarizing themselves with the night sky. For example, the
asterisms known as The Plough (Charles' Wain, the Big Dipper, etc.) comprises the seven brightest stars in the International Astronomical Union (IAU) recognised constellation Ursa Major. Another is the asterism of the Southern Cross, whose recognised constellation is Crux.
Background of asterisms and constellations
In many early civilizations, it was already common to associate groups of stars in connect-the-dotsstick-figure patterns; some of the earliest records are those of the Babylonians.
This process was essentially arbitrary, and different cultures have
identified different constellations, although a few of the more obvious
patterns tend to appear in the constellations of multiple cultures, such
as those of Orion and Scorpius. As anyone could arrange and name a grouping of stars there was no distinct difference between a constellation and an asterism. e.g. Pliny the Elder (23–79 AD) in his book Naturalis Historia refers and mentions 72 asterisms.
A general list containing 48 constellations likely began to develop with the astronomer Hipparchus
(c. 190 – c. 120 BC ), and was mostly accepted as standard in Europe
for 1,800 years. As constellations were considered to be composed only
of the stars that constituted the figure, it was always possible to use
any leftover stars to create and squeeze in a new grouping among the
established constellations.
Furthermore, exploration by Europeans to other parts of the globe
exposed them to stars unknown to them. Two astronomers particularly
known for greatly expanding the number of southern constellations were Johann Bayer (1572–1625) and Nicolas Louis de Lacaille
(1713–1762). Bayer had listed twelve figures made out of stars that
were too far south for Ptolemy to have seen; Lacaille created 14 new
groups, mostly for the area surrounding South Celestial Pole. Many of these proposed constellations have been formally accepted, but the rest have historically remained as asterisms.
In 1928, the International Astronomical Union (IAU) precisely divided the sky into 88 official constellations following geometric boundaries encompassing all of the stars within them. Any additional new selected groupings of stars or former constellations
are often considered as asterisms. However, depending on the particular
literature source, any technical distinctions between the terms
'constellation' and 'asterism' often remain somewhat ambiguous. e.g.
Both the open clustersThe Pleiades or Seven Sisters and The Hyades in Taurus are sometimes considered asterisms, but this depends on the source.
Large or bright asterisms
Component stars of asterisms are bright and mark out simple geometric shapes.
The Great Diamond consisting of Arcturus, Spica, Denebola, and Cor Caroli.
An East-West line from Arcturus to Denebola forms an equilateral
triangle with Cor Caroli to the North, and another with Spica to the
South. The Arcturus, Regulus, Spica triangle is sometimes given the name
Spring Triangle.[5] Together these two triangles form the Diamond. Formally, the stars of the Diamond are in the constellations Boötes, Virgo, Leo, and Canes Venatici.
The Summer Triangle of Deneb, Altair, and Vega — α Cygni, α Aquilae, and α Lyrae — is easily recognized in the northern hemisphere summer skies, as its three stars are all of the 1st magnitude. The stars of the Triangle are in the band of the Milky Way which marks the galactic equator, and are in the direction of the galactic center.
The Great Square of Pegasus is the quadrilateral formed by the stars Markab, Scheat, Algenib, and Alpheratz, representing the body of the winged horse. The asterism was recognized as the constellation ASH.IKU "The Field" on the MUL.APINcuneiform tablets from about 1100 to 700 BC.
One-third of the 1st-magnitude stars visible in the sky (seven of twenty-one) are in the so-called Winter Hexagon with Capella, Aldebaran, Rigel, Sirius, Procyon, and Pollux with 2nd-magnitude Castor, on the periphery, and Betelgeuse off-center.
Although somewhat flattened, and thus more elliptical than circular,
the figure is so large that it cannot be taken in all at once, thus
making the lack of true circularity less noticeable. (The projection in
the chart exaggerates the stretching.) Some prefer to regard it as a Heavenly 'G'.
A familiar asterism is the Big Dipper, Plough or Charles's Wain, which is composed of the seven brightest stars in Ursa Major. 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 Northern Cross in Cygnus. The upright runs from Deneb (α Cyg) in the Swan's tail to Albireo (β Cyg) in the beak. The transverse runs from ε Cygni in one wing to δ Cygni in the other.
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."
The Southern Cross is an asterism by name, but the whole area is now recognised as the constellation Crux. The main stars are Alpha, Beta, Gamma, Delta, and arguably also Epsilon Crucis. Earlier, Crux was deemed an asterism when Bayer created it in Uranometria (1603) from the stars in the hind legs of Centaurus, decreasing the size of Centaur. These same stars were probably identified by Pliny the Elder in his Naturalis Historia as the asterism 'Thronos Caesaris.'
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.
Although hardly an ancient notion, it is easy to see why the Ice Cream Cone is sometimes applied to Boötes. It is even better known as the Kite.
The stars of Cassiopeia form a W which is often used as a nickname.
Some asterisms may also be part of a constellation referring to the
traditional figuring of the whole outline. For example, there are:
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.
The four central stars in Hercules, Epsilon (ε Her), Zeta (ζ Her), Eta (η Her), and Pi (π Her), form the well-known Keystone.
The curve of stars at the front end of the Lion from Epsilon (ε Leo) to Regulus (α Leo), looking much like a mirror-image question mark, has long been known as the Sickle.
The bow and arrow of the Archer also make a well-formed Teapot. (There is even a bit of nebulosity near the "spout" to serve as steam).
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).
Dubhe and Merak (Alpha and Beta Ursae Majoris), the two stars at the end of the bowl of the Big Dipper are habitually called The Pointers:
a line from β to α and continued for a bit over 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 and thus helping to distinguish Crux from the False Cross.
Cross-border asterisms
Other asterisms that are formed from stars in more than one constellation.
There is another large asterism which, like the Diamond of Virgo, is composed of a pair of equilateral triangles. Sirius (α CMa), Procyon (α CMi), and Betelgeuse (α Ori) form one to the North (Winter Triangle) while Sirius, Naos (ζ Pup), and Phakt
(α Col) form another to the South. Unlike the Diamond, however, these
triangles meet, not base-to-base, but vertex-to-vertex, forming the Egyptian X.
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.
The Lozenge is a small diamond formed from three stars – Eltanin, Grumium, and Rastaban (Gamma, Xi, and Beta Draconis) – in the head of Draco and one – Iota Herculis – in the foot of Hercules.
The diamond-shaped False Cross is composed of the four stars Alspehina (δ Velorum) and Markeb (κ Velorum) and Avior (ε Carinae) and Aspidiske (ι Carinae). Although its component stars are not quite as bright as those of the Southern Cross, it is somewhat larger and better shaped than the Southern Cross, for which it sometimes mistaken, causing errors in astronavigation. Like the Southern Cross, three of its main four stars are whitish and one orange.
From latitudes above 40 degrees north especially, a prominent upper-case Y is formed by Arcturus (α Boötis), Seginus (γ Boötis) and Izar (ε Boötis), and Alpha Coronae Borealis
(Alphecca or Gemma). Alpha Coronae Borealis is far brighter than either
Delta or Beta Bootis, distorting the "kite" or "ice-cream cone" shape
of Bootes. 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 β and δ Bootis and the other stars in Corona
Borealis are not.
Telescopic asterisms
Asterisms range from the large and obvious to the small, and even telescopic.
