Galactic quadrant

A galactic quadrant, or quadrant of the Galaxy, is one of four circular sectors in the division of the Milky Way Galaxy.

Galactic longitude
Longitudinal lines of the galactic coordinate system.

Quadrants in the galactic coordinate system

In actual astronomical practice, the delineation of the galactic quadrants is based upon the galactic coordinate system, which places the Sun as the pole of the mapping system. The Sun is used instead of the Galactic Center for practical reasons since all astronomical observations (by humans) to date have been based on Earth or within the solar system.


Quadrants are described using ordinals—for example, "1st galactic quadrant"[1] "second galactic quadrant,"[2] or "third quadrant of the Galaxy."[3] Viewing from the north galactic pole with 0 degrees (°) as the ray that runs starting from the Sun and through the galactic center, the quadrants are as follows (where l is galactic longitude):

  • 1st galactic quadrant – 0° ≤ l ≤ 90°[4]
  • 2nd galactic quadrant – 90° ≤ l ≤ 180°[2]
  • 3rd galactic quadrant – 180° ≤ l ≤ 270°[3]
  • 4th galactic quadrant – 270° ≤ l ≤ 360°[1]

Constellations grouped by galactic quadrants

Galactic quadrants
Constellations grouped in galactic quadrants (N/S, 1-4)
Quad Constellations (Zodiacal constellations in bold)
NGQ1 7 (Lyra, Hercules, Serpens, Corona Borealis, Ophiuchus, Cygnus, Boötes)
NGQ2 8 (Cepheus, Draco, Ursa Minor, Canes Venatici, Ursa Major, Lynx, Camelopardalis, Auriga)
NGQ3 9 (Gemini, Cancer, Leo, Canis Minor, Sextans, Monoceros, Pyxis, Leo Minor)
NGQ4 12 (Virgo, Libra, Scorpius, Coma Berenices, Corvus, Crater, Lupus, Centaurus, Norma, Crux, Antlia, Vela)
SGQ1 11 (Sagittarius, Capricornus, Aquarius, Equuleus, Delphinus, Sagitta, Aquila, Vulpecula, Microscopium, Scutum, Piscis Austrinus)
SGQ2 10 (Pisces, Aries, Taurus, Andromeda, Cassiopeia, Cetus, Perseus, Triangulum, Lacerta, Hydra, Pegasus)
SGQ3 9 (Orion, Eridanus, Caelum, Lepus, Pictor, Columba, Canis Major, Puppis, Fornax)
SGQ4 22 (Circinus, Musca, Telescopium, Triangulum Australe, Apus, Chamaeleon, Corona Australis, Pavo, Indus, Grus, Octans, Sculptor, Phoenix, Reticulum, Dorado, Mensa Tucana, Volans, Carina, Ara, Hydrus, Horologium)

Visibility of each quadrant

Orientation of the galactic, ecliptic and equatorial coordinate systems, projected on the celestial sphere.

Due to the orientation of the Earth with respect to the rest of the Galaxy, the 2nd galactic quadrant is primarily only visible from the northern hemisphere while the 4th galactic quadrant is mostly only visible from the southern hemisphere. Thus, it is usually more practical for amateur stargazers to use the celestial quadrants. Nonetheless, cooperating or international astronomical organizations are not so bound by the Earth's horizon.

Based on a view from Earth, one may look towards major constellations for a rough sense of where the borders of the quadrants are:[5] (Note: by drawing a line through the following, one can also approximate the galactic equator.)

  • For 0°, look towards the Sagittarius constellation. (The galactic center)
  • For 90°, look towards the Cygnus constellation.
  • For 180°, look towards the Auriga constellation. (The galactic anticenter)
  • For 270°, look towards the Vela constellation.

Traditional fourfold divisions of the skies

A long tradition of dividing the visible skies into four precedes the modern definitions of four galactic quadrants. Ancient Mesopotamian formulae spoke of "the four corners of the universe" and of "the heaven's four corners",[6] and the Biblical Book of Jeremiah echoes this phraseology: "And upon Elam will I bring the four winds from the four quarters of heaven" (Jeremiah, 49:36). Astrology too uses quadrant systems to divide up its stars of interest. And the astronomy of the location of constellations sees each of the Northern and Southern celestial hemispheres divided into four quadrants.

In fiction

Star Trek

"Galactic quadrants" within Star Trek are based around a meridian that runs from the center of the Galaxy through Earth's solar system,[7] which is not unlike the system used by astronomers. However, rather than have the perpendicular axis run through the Sun, as is done in astronomy, the Star Trek version runs the axis through the galactic center. In that sense, the Star Trek quadrant system is less geocentric as a cartographical system than the standard. Also, rather than use ordinals, Star Trek designates them by the Greek letters Alpha, Beta, Gamma, and Delta.

The Canadian Galactic Plane Survey (CGPS) created a radio map of the Galaxy based on Star Trek's quadrants, joking that "the CGPS is primarily concerned with Cardassia, while the SGPS (Southern Galactic Plane Survey) focuses on Romulans."[8]

See also


  1. ^ a b Thomas L. Wilson, Kristen Rohlfs, Susanne Hüttemeister Tools of radio astronomy
  2. ^ a b Kiss, Cs; Moór, A; Tóth, L. V (2004). "Far-infrared loops in the 2nd Galactic Quadrant". Astronomy & Astrophysics. 418: 131–141. arXiv:astro-ph/0401303. Bibcode:2004A&A...418..131K. doi:10.1051/0004-6361:20034530.
  3. ^ a b M. Lampton et al. An All-Sky Catalog of Faint Extreme Ultraviolet Sources The Astrophysical Journal Supplement Series . 1997
  4. ^ THE BEGINNINGS OF RADIO ASTRONOMY IN THE NETHERLANDS. Journal of Astronomical History and Heritage. 2006
  5. ^ "Galactic Coordinates". Retrieved 2010-08-17.
  6. ^ Michalowski, Piotr (2010), "masters of the Four Corners of the Heavens: Vies of the Universe in Early Mesopotamian Writings", in Raaflaub, Kurt A.; Talbert, Richard J. A., Geography and Ethnography: Perceptions of the World in Pre-Modern Societies, The ancient world: comparative histories, 3, John Wiley and Sons, pp. 147–168 [153], ISBN 978-1-4051-9146-3
  7. ^ Okuda, Michael; Okuda, Denise; Mirek, Debbie (1999). The Star Trek Encyclopedia. Pocket Books. ISBN 978-0-671-53609-1.
  8. ^ "Plan Views of the Milky Way Galaxy". The Canadian Galactic Plane Survey. Retrieved 2010-08-19.

External links

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 located in the fourth galactic quadrant, between Leo and Boötes, and is visible in both hemispheres. Its name means "Berenice's Hair" in Latin and refers to Queen Berenice II of Egypt, who sacrificed her long hair as a votive offering. It was introduced to Western astronomy during the third century BC by Conon of Samos and was further corroborated as a constellation by Gerardus Mercator and Tycho Brahe. Coma Berenices is the only modern constellation named for a historic person.

The constellation's major stars are Alpha Comae Berenices, Beta Comae Berenices and Gamma Comae Berenices. They form a 45-degree triangle, from which Berenice's imaginary tresses, formed by the Coma Star Cluster, hang. The constellation's brightest star is Beta Comae Berenices, a 4.2-magnitude main sequence star similar to the Sun. Coma Berenices contains the North Galactic Pole and one of the richest known galaxy clusters, the Coma Cluster, part of the Coma Supercluster. Galaxy Malin 1, in the constellation, is the first-known giant low-surface-brightness galaxy. Supernova SN 2005ap discovered in Coma Berenices is the second-brightest known, and SN 1940B was the first observed example of a type II supernova. The star FK Comae Berenices is the prototype of an eponymous class of variable stars. The constellation is the radiant of one meteor shower, Coma Berenicids, which has one of the fastest meteor speeds, up to 65 kilometres per second (40 mi/s).

Coma Filament

Coma Filament is a galaxy filament. The filament contains the Coma Supercluster of galaxies and forms a part of the CfA2 Great Wall.

Far 3 kpc Arm

The Far 3 kpc Arm was discovered in 2008 by astronomer Tom Dame (Harvard-Smithsonian CfA), while preparing a talk on the Galaxy's spiral arms for a meeting of the 212th American Astronomical Society. It is one of Milky Way's spiral arms and it is located in the first galactic quadrant at a distance of 3 kpc (about 10,000 ly) from the galactic center. Along with the Near 3 kpc Arm whose existence is known since the mid-1950s, the counterpart inner arms establish our Galaxy's simple symmetry.Tom Dame and collaborator Patrick Thaddeus analyzed data obtained using a 1.2-meter-diameter millimeter-wave telescope located at Cerro Tololo Inter-American Observatory (CTIO) in Chile. They detected the presence of the spiral arm in a CO survey and later confirmed their discovery using 21-centimeter radio measurements of atomic hydrogen collected by colleagues in Australia.

How William Shatner Changed the World

How William Shatner Changed the World (or How Techies Changed the World with William Shatner in Europe, Asia, and Australia) is a 2005 two-hour television documentary, commissioned by Discovery Channel Canada and co-produced for History Channel in the United States and Channel Five in the United Kingdom. Hosted and narrated by William Shatner, known for his portrayal of Captain James T. Kirk, and based on his book, I'm Working on That, the show focuses on technological advancements and people in the real world that were inspired by the Star Trek phenomenon.

IAU designated constellations

In contemporary astronomy, 88 constellations are recognized by the International Astronomical Union (IAU). Each constellation is a region of the sky, bordered by arcs of right ascension and declination. Together they cover the entire celestial sphere and were adopted officially by the International Astronomical Union in 1922.The ancient Sumerians, and later the Greeks (as recorded by Ptolemy), established most of the northern constellations in international use today. The constellations along the ecliptic are called the zodiac. When explorers mapped the stars of the southern skies, European astronomers proposed new constellations for that region, as well as ones to fill gaps between the traditional constellations. Not all of these proposals caught on, but in 1922, the International Astronomical Union adopted the modern list of 88 constellations. After this, Eugène Joseph Delporte drew up boundaries for each constellation so that every point in the sky belonged to one constellation.

List of Star Trek regions of space

Several films and episodes of the science fiction franchise Star Trek are set in distinct regions of space. Some of these fictional locations exhibit anomalous physical properties; others are defined as sensitive buffer zones under various fictional political accords.

This list describes some of the more significant settings for Star Trek films or story arcs over multiple television episodes.

Milky Way

The Milky Way is the galaxy that contains our Solar System. The name describes 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. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλαξίας κύκλος (galaxías kýklos, "milky circle"). From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies.

The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars and more than 100 billion planets. The Solar System is located at a radius of 26,490 (± 100) light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust. The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, assumed to be a supermassive black hole of 4.100 (± 0.034) million solar masses.

Stars and gases at a wide range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much (about 90%) of the mass of the Milky Way is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This conjectural mass has been termed "dark matter". The rotational period is about 240 million years at the radius of the Sun. The Milky Way as a whole is moving at a velocity of approximately 600 km per second with respect to extragalactic frames of reference. The oldest stars in the Milky Way are nearly as old as the Universe itself and thus probably formed shortly after the Dark Ages of the Big Bang.The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster.

Near 3 kpc Arm

The Near 3 kpc Arm (also called Expanding 3 kpc Arm or simply 3 kpc Arm) was discovered in the 1950s by astronomer van Woerden and collaborators through 21-centimeter radio measurements of HI (atomic hydrogen). It was found to be expanding away from the center of the Milky Way at more than 50 km/s. This spiral arm contains about 10 million solar masses of gas, mostly hydrogen atoms and molecules.It is located in the fourth galactic quadrant at a distance of about 5.2 kpc from the Sun and 3.3 kpc from the galactic center. The last attempt to search for star forming regions in the Near 3 kpc Arm (in 1980) showed little star formation occurring in the numerous molecular clouds of this arm.Along with the Far 3 kpc Arm discovered in 2008, these inner arms establish our Galaxy's simple symmetry.

Orion Arm

The Orion Arm is a minor spiral arm of the Milky Way some 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length, containing the Solar System, including the Earth. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion Bridge, and formerly, the Local Spur and Orion Spur.

The arm is named for the Orion constellation, which is one of the most prominent constellations of Northern Hemisphere winter (Southern Hemisphere summer). Some of the brightest stars and most famous celestial objects of the constellation (e.g. Betelgeuse, Rigel, the three stars of Orion's Belt, the Orion Nebula) are within it as shown on the interactive map below.

The arm is between the Carina–Sagittarius Arm (the local portions of which are toward the Galactic Center) and the Perseus Arm (the local portion of which is the main outer-most arm and one of two major arms of the galaxy).

Long thought to be a minor structure, namely a "spur" between the two arms mentioned, evidence was presented in mid 2013 that the Orion Arm might be a branch of the Perseus Arm, or possibly an independent arm segment.Within the arm, the Solar System is close to its inner rim, in a relative cavity in the arm's Interstellar Medium known as the Local Bubble, about halfway along the arm's length, approximately 8,000 parsecs (26,000 light-years) from the Galactic Center.


SQ1 may refer to:

Space Quest I, a 1986 video game

SQ1, a galactic quadrant in the Milky Way

SQ1, a mixtape by Lil Wayne

SQ1, a Singapore Airlines flight that flies from Hong Kong to Singapore in the morning, and from San Francisco at night.


SQ2 may refer to:

Backcountry Super Cubs Mackey SQ2, an American amateur-built aircraft design

SQ2, a galactic quadrant in the Milky Way

SQ2, mixtape by Lil Wayne


SQ3 may refer to:

SQ3, a galactic quadrant in the Milky Way

SQ3, mixtape by Lil Wayne


SQ4 may refer to:

SQ4, a galactic quadrant in the Milky Way

SQ4, a mixtape by Lil Wayne

Space Quest IV, an adventure game by Sierra Entertainment

Trek Nation

Trek Nation is a 2011 documentary film directed by Scott Colthorp examining the positive impact that Star Trek and creator Gene Roddenberry may have had on people's lives as seen through the eyes of his son, Eugene "Rod" Roddenberry, Jr.. It includes interviews with castmembers and crew from all five Star Trek incarnations as well as with various fans and celebrities who were markedly influenced by the show while growing up. Rod Roddenberry also visits Skywalker Ranch to learn about the influence Star Trek had on George Lucas. The film premiered on November 30, 2011 on Science.

Ursa Major Filament

Ursa Major Filament is a galaxy filament. The filament is connected to the CfA Homunculus, a portion of the filament forms a portion of the "leg" of the Homunculus.

Vulcan salute

The Vulcan salutation is a hand gesture popularized by the 1960s television series Star Trek. It consists of a raised hand with the palm forward and the thumb extended, while the fingers are parted between the middle and ring finger.

X-factor (astrophysics)

The X-factor in astrophysics, often labeled XCO, is an empirically determined proportionality constant which converts carbon monoxide (CO) emission line brightness to molecular hydrogen (H2) mass.

Galactic core
Spiral arms
Satellite galaxies
Active nuclei
Energetic galaxies
Low activity
See also

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