The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is an immense galaxy filament. It is one of the largest known superstructures in the

observable universe The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these ob ...

. This structure was discovered c. 1989 by a team of

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

s led by Margaret J. Geller and John Huchra while analyzing data gathered by the second

CfA Redshift Survey The Center for Astrophysics (CfA) Redshift Survey was the first attempt to map the large-scale structure of the universe. The first survey began in 1977 with the objective of calculating the velocities of the brighter galaxies in the nearby unive ...

of the Center for Astrophysics Harvard & Smithsonian (CfA).

Characteristics

The term "Great" has been added to distinguish it as an even larger type compared to standard galaxy walls. Great walls are so rare that only five or possibly six (if the disputed

Hercules–Corona Borealis Great Wall The Hercules–Corona Borealis Great Wall or simply the Great Wall is the largest known structure in the observable universe, measuring approximately 10 billion light-years in length (the observable universe is about 93 billion light-years in di ...

is counted) of them have been discovered to date. The CfA2 Great Wall has the maximum dimensions of either 500 million or 750 million light years depending on the figure and the reference used. It is 200 million light years in width and about 16 million light years in thickness. Its nearest point is about 300 million light years from Earth, while its farthest point is 550 million light years away. It consists of three massive galaxy superclusters:

Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the ...

Coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

, and Leo. The CfA2 Great Wall includes the

Coma Filament The Coma Filament is a galaxy filament. The filament contains the Coma Supercluster of galaxies and forms a part of the CfA2 Great Wall. See also * Abell catalogue * Large-scale structure of the universe * Supercluster A supercluster is a large ...

Components

It was discovered in 1989 by

Margaret Geller Margaret J. Geller (born December 8, 1947) is an American astrophysicist at the Center for Astrophysics Harvard & Smithsonian. Her work has included pioneering maps of the nearby universe, studies of the relationship between galaxies and their ...

and

John Huchra John Peter Huchra ( ; December 23, 1948 – October 8, 2010) was an American astronomer and professor. He was the Vice Provost for Research Policy at Harvard University and a Professor of Astronomy at the Center for Astrophysics Harvard & Smi ...

based on

redshift survey In astronomy, a redshift survey is a survey of a section of the sky to measure the redshift of astronomical objects: usually galaxies, but sometimes other objects such as galaxy clusters or quasars. Using Hubble's law, the redshift can be used ...

data from the

. It is not known how much farther the wall extends due to the light absorption in the plane 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 ...

in which Earth is located. The gas and dust from the Milky Way (known as the

Zone of Avoidance The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), is the area of the sky that is obscured by the Milky Way. The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard ...

) obscure the view of astronomers and have so far made it impossible to determine if the wall ends or continues on further than they can currently observe. In the

standard model The Standard Model of particle physics is the theory describing three of the four known fundamental forces ( electromagnetic, weak and strong interactions - excluding gravity) in the universe and classifying all known elementary particles. It ...

of the evolution of the universe, such structures as the Great Wall form along and follow web-like strings of

dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ...

. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts

baryon In particle physics, a baryon is a type of composite subatomic particle which contains an odd number of valence quarks (at least 3). Baryons belong to the hadron family of particles; hadrons are composed of quarks. Baryons are also classifie ...

ic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.

References

External links

Map of CfA2 Great Wall

The CfA Redshift Survey
{{DEFAULTSORT:Cfa2 Great Wall Astronomical objects discovered in 1989 Galaxy filaments Large-scale structure of the cosmos