Eridanus is a
constellationIn modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
. It is represented as a
riverA river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
; its name is the
Ancient GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
name for the
Po RiverThe Po |Ligurian]]: Bodincus or Bodencus) is a river that flows either or – considering the length of the Maira, a right bank tributary – eastward across northern Italy, from a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face...
. It was one of the 48 constellations listed by the 2nd century astronomer
PtolemyClaudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
, and it remains one of the 88 modern constellations. It is the
sixth largest of the modern constellations.
Stars
At its southern end is the
first magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
starA star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
AchernarAchernar , sometimes spelled Achenar, is the brightest star in the constellation Eridanus and the ninth-brightest star in the night sky. Of the top ten apparent brightest stars —Sirius, Canopus, Alpha Centauri, Arcturus, Vega, Capella, Rigel, Procyon, Achernar and Betelgeuse—Achernar is the hottest...
(α Eri). Achernar is a very peculiar star because it is one of the flattest stars known. Observations indicate that its radius is about 50% larger at the equator than at the poles. This distortion occurs because the star is spinning extremely rapidly.
Another well-known star in Eridanus is
Epsilon EridaniEpsilon Eridani is a star in the southern constellation Eridanus, along a declination 9.46° south of the celestial equator. This allows the star to be viewed from most of the Earth's surface. At a distance of 10.5 light years , it has an apparent magnitude of 3.73...
, which has been popular in
science fictionScience fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
because it is relatively close and
sunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
-like (see
Epsilon Eridani in fictionThe fifth brightest star in the constellation Eridanus. As a Sun-like star relatively close to the Solar System, Epsilon Eridani regularly appears in science fiction....
). It is now suspected to have at least one
extrasolar planetAn extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
, which is thought to be a gas giant, like
JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
.
Supervoid
The Eridanus Supervoid is the largest supervoid (an area of the
universeThe Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...
devoid of galaxies) discovered . At a diameter of about one billion light years it is much larger than any other known void and represents a challenge for current theories of the origins of the universe to explain. It was discovered by linking a "cold spot" in the cosmic microwave background to an absence of
radio galaxiesRadio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths, with luminosities up to 1039 W between 10 MHz and 100 GHz. The radio emission is due to the synchrotron process...
in data of the US
National Radio Astronomy ObservatoryThe National Radio Astronomy Observatory is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy...
's
Very Large ArrayThe Very Large Array is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles west of Socorro, New Mexico, USA...
Sky Survey. There is some speculation that the void may be due to
quantum entanglementQuantum entanglement occurs when electrons, molecules even as large as "buckyballs", photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description , which is...
between our universe and
anotherThe multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...
.
Deep sky objects
Eridanus contains the galaxies
NGC 1234NGC 1234 is barred spiral galaxy in the constellation Eridanus, discovered by Francis Preserved Leavenworth in 1886.Its apparent magnitude is 14.2-External links:*...
and
NGC 1300NGC 1300 is a barred spiral galaxy about 61 million light-years away in the constellation Eridanus. The galaxy is about 110,000 light-years across; just slightly larger than our own galaxy, the Milky Way. It may be part of the Eridanus Cluster...
, a grand design barred spiral galaxy.
Visualizations
The name Eridanus refers to the
Po RiverThe Po |Ligurian]]: Bodincus or Bodencus) is a river that flows either or – considering the length of the Maira, a right bank tributary – eastward across northern Italy, from a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face...
, the main river of northern
ItalyItaly , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. Its association with a river comes from the way its stars trace a tortuous path. In some star maps, Eridanus is depicted as a river flowing from the waters poured by
AquariusAquarius is a constellation of the zodiac, situated between Capricornus and Pisces. Its name is Latin for "water-bearer" or "cup-bearer", and its symbol is , a representation of water....
. In such maps, Aquarius is visualized as facing Eridanus, requiring a different perspective and a redesign of how the stars of Aquarius connect, so the water pours onto the same side as Eridanus.
History and mythology
According to one theory, the Greek constellation takes its name from the Babylonian constellation known as the Star of Eridu (MUL.NUN.KI).
EriduEridu is an ancient Sumerian city in what is now Tell Abu Shahrain, Dhi Qar Governorate, Iraq. Eridu was considered the earliest city in southern Mesopotamia, and is one of the oldest cities in the world...
was an ancient city in the extreme south of Babylonia; situated in the marshy regions it was held sacred to the god Enki-Ea who ruled the cosmic domain of the Abyss - a mythical conception of the fresh-water reservoir below the Earth's surface.
Eridanus is connected to the myth of
PhaëtonIn Greek mythology, Phaëton or Phaethon was the son of Helios and the Oceanid Clymene. Alternate, less common genealogies make him a son of Clymenus by Merope, of Helios and Rhode or of Helios and Prote....
, who took over the reins of his father
HeliosHelios was the personification of the Sun in Greek mythology. Homer often calls him simply Titan or Hyperion, while Hesiod and the Homeric Hymn separate him as a son of the Titans Hyperion and Theia or Euryphaessa and brother of the goddesses Selene, the moon, and Eos, the dawn...
' sky chariot (i.e., the Sun), but didn't have the strength to control it and so veered wildly in different directions, scorching both earth and heaven. Zeus intervened by striking Phaëton dead with a thunderbolt and casting him to earth. The constellation was supposed to be the path Phaëton drove along; in later times, it was considered a path of souls. Since
Eridanos was also a Greek name for the Po (Latin
Padus), in which the burning body of Phaëton is said by Ovid to have extinguished, the mythic geography of the celestial and earthly Eridanus is complex.
Equivalents
The stars that correspond to Eridanus are also depicted as a river in Indian astronomy. Eridanus is called
Srotaswini in
SanskritSanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...
,
srótas meaning the course of a river or stream. Specifically, it is depicted as the Ganges on the head of Dakshinamoorthy, a
HinduHindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...
incarnation of
SivaSiva may refer to:*Shiva, a major Hindu God*Živa , a Slavic goddess*A pro-apoptotic signaling protein*1170 Siva, asteroid named after the god*Siva , name of several rural localities in Russia...
. Dakshinamoorthy himself is represented by the constellation
Orion- Astronomy :* Orion * Orion Nebula, a nebula in the Orion Constellation* Orion Arm, a spiral arm of the Milky Way galaxy* Project Orion, a 1980 NASA astrometry study of a system of methods of detecting extrasolar planets using astronomical interferometry- Places :United States* Orion, California*...
.
The stars that correspond to Eridanus cannot be fully seen from China. In hinese astronomy, the northern part is located within the White Tiger of the West (西方白虎,
Xī Fāng Bái Hǔ). The unseen southern part was classified among the Southern Asterisms (近南極星區,
Jìnnánjíxīngōu) by
Xu GuangqiXu Guangqi , was a Chinese scholar-bureaucrat, agricultural scientist, astronomer, and mathematician in the Ming Dynasty. Xu was a colleague and collaborator of the Italian Jesuits Matteo Ricci and Sabatino de Ursis and they translated several classic Western texts into Chinese, including part of...
, based on knowledge of western star charts.
In popular culture
In some maps of the
Star TrekStar Trek is an American science fiction entertainment franchise created by Gene Roddenberry. The core of Star Trek is its six television series: The Original Series, The Animated Series, The Next Generation, Deep Space Nine, Voyager, and Enterprise...
universe the planet
VulcanVulcans, or sometimes Vulcanians, are an extraterrestrial humanoid species in the Star Trek universe who evolved on the planet Vulcan, and are noted for their attempt to live by reason and logic with no interference from emotion. They were the first extraterrestrial species in the Star Trek...
is shown to be located at
40 Eridani A.
The character Eridan Ampora's name in Andrew Hussie's comic
MS Paint AdventuresMS Paint Adventures is a collection of webcomics written and illustrated by Andrew Hussie. Because of the frequency with which the site is updated, MS Paint Adventures is estimated to be the longest web comic on the Internet with over 6000 pages total among its four series.These comics are written...
Homestuck was based off of the name Eridanus his associated Zodiac sign in Aquarius.
Namesakes
USS Eridanus (AK-92)USS Eridanus was an Crater-class cargo ship commissioned by the U.S. Navy for service in World War II, named after the constellation Eridanus. She was responsible for delivering goods and equipment to locations in the war zone....
was a
United States NavyThe United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
Crater class cargo shipCrater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....
named after the constellation.
External links