astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

, the Great Rift (sometimes called the Dark Rift or less commonly the Dark River) is a dark band caused by

interstellar cloud An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium, the matter and radiation that exists in t ...

s of

cosmic dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

that significantly obscure ( extinguish) the

center Center or centre may refer to: Mathematics *Center (geometry), the middle of an object * Center (algebra), used in various contexts ** Center (group theory) ** Center (ring theory) * Graph center, the set of all vertices of minimum eccentricity ...

and most radial sectors of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

galaxy A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

's perspective. In dark, clear

night skies ''Night Skies'' is an unproduced science fiction horror film that was in development in the late 1970s. Steven Spielberg conceived the idea after ''Close Encounters of the Third Kind''. Instead, material developed at the time was used in ''Polt ...

, the rift appears as clear as the bright

bulge __NOTOC__ Bulge may refer to: Astronomy and geography *Bulge (astronomy), a tightly packed group of stars at the center of a spiral galaxy *Equatorial bulge, a bulge around the equator of a planet due to rotation * Tharsis bulge, vast volcanic pl ...

of stars around the Galactic Center does to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

. The rift is largely between the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

(which is close to the inner edge of the

Orion Arm The Orion Arm is a minor spiral arm of the Milky Way Galaxy that is across and approximately in length, containing the Solar System, including Earth. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion ...

) and the next arm, inward, the

Sagittarius Arm Sagittarius ( ) may refer to: *Sagittarius (constellation) *Sagittarius (astrology), a sign of the Zodiac Ships *'' SuperStar Sagittarius'', a cruise ship * USS ''Sagittarius'' (AKN-2), a World War II US Navy cargo ship Music *Sagittarius (ba ...

. The clouds are an obstruction to millions of the galaxy's stars detected at visible wavelengths, which compose a bright hazy band appearing 30° wide and arching through the night sky. The clouds within our radial sector of the galaxy span about from Earth. The clouds are estimated to contain about 1 million

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es of

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

and dust.

Properties

To the

, the Great Rift appears as a dark lane that divides the bright band of the

vertically. The Great Rift covers one third of the Milky Way, and is flanked by strips of numerous stars, such as the ''Cygnus Star Cloud''. West of the ''Cepheus Clouds'', the ''Funnel cloud''/''Le Gentil 3'' and the bordering

North America Nebula The North America Nebula (NGC 7000 or Caldwell 20) is an emission nebula in the constellation Cygnus, close to Deneb (the tail of the swan and its brightest star). The shape of the nebula resembles that of the continent of North America, complet ...

, the Great Rift starts with the

Northern Coalsack Cygnus is a northern constellation on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent as ...

at the constellation of Cygnus, where it is known as the

Cygnus Rift In astronomy, the Great Rift (sometimes called the Dark Rift or less commonly the Dark River) is a dark band caused by interstellar clouds of cosmic dust that significantly obscure ( extinguish) the center and most radial sectors of the Milky ...

. The Great Rift stretches from there over the Serpens-Aquila Rift; to

Ophiuchus Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constella ...

, where it broadens out; to Sagittarius, where it obscures the

Galactic Center The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact rad ...

; essentially ending at

Centaurus Centaurus is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one o ...

Milkyway360-hemispheres-32k m14-g1 Clouds

One of the regions obscured by the Great Rift is the Cygnus OB2 association, a

cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Asteroid cluster, a small asteroid family * Cluster II (spacecraft), a European Space Agency mission to study t ...

of young stars and one of the largest regions of star formation within 2 kiloparsecs. Similar dark rifts can be seen in many edge-on galaxies, such as

NGC 891 NGC 891 (also known as Caldwell 23, the Silver Sliver Galaxy, and the Outer Limits Galaxy) is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, ...

in Andromeda and

NGC 4565 NGC 4565 (also known as the Needle Galaxy or Caldwell 38) is an edge-on spiral galaxy about 30 to 50 million light-years away in the constellation Coma Berenices. It lies close to the North Galactic Pole and has a visual magnitude of approximatel ...

(the Needle Galaxy) in

Coma Berenices Coma Berenices is an ancient asterism in the northern sky, which has been defined as one of the 88 modern constellations. It is in the direction of the fourth galactic quadrant, between Leo and Boötes, and it is visible in both hemisphere ...

Human observation

left, Layout of some Great Rift "constellations" as represented by the Inca Dark zones obscuring the night-sky lighting mass of the bulk of the Milky Way in a dry atmosphere (or at long exposures) were recognized by many ancient civilizations in which a seasonally or regularly dry climate is a frequent feature. In South America, the

Inca The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...

gave some patterns of darkness and stars names much as normal stellar constellations were, including a series of animals like

llama The llama (; ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the Pre-Columbian era. Llamas are social animals and live with othe ...

s, a

fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...

toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scientif ...

, and others, thought to be drinking from the "great river" (the Milky Way) and seen in silhouette. The classical Greeks sometimes described the Great Rift as being the path of devastation left by Phaeton, who tried to guide the chariot of

Helios In ancient Greek religion and Greek mythology, mythology, Helios (; grc, , , Sun; Homeric Greek: ) is the deity, god and personification of the Sun (Solar deity). His name is also Latinized as Helius, and he is often given the epithets Hyper ...

(the Sun god) across the sky before losing control, wreaking havoc, and finally being struck down by a lightning bolt of Zeus. Modern astronomy first began to notice the rift in the 18th century, but struggled to explain it until

E. E. Barnard Edward Emerson Barnard (December 16, 1857 – February 6, 1923) was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of the high proper mo ...

and

Max Wolf Maximilian Franz Joseph Cornelius Wolf (21 June 1863 – 3 October 1932) was a German astronomer and a pioneer in the field of astrophotography. He was the chairman of astronomy at the University of Heidelberg and director of the Heidelberg-K� ...

in the early 20th century, who produced the currently accepted explanation after careful photographic study. Regioni_celesti_scelte_-_Osc_A

Of this, Barnard said:

Properties

Human observation

See also

References

Further reading