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Encyclopedia > Milky Way
For other uses, see Milky Way (disambiguation).
Milky Way Galaxy

Infrared image of the core of the Milky Way galaxy
Observation data
Type SBbc (barred spiral galaxy)
Diameter 100,000 light years
Thickness 12,000 light years (gas)[1]
1,000 light years (stars)
Number of stars 200 to 400 billion
Oldest star 13.2 billion years
Mass 5.8×1011 M☉
Sun's distance to galactic center 26,000 ± 1400 light-years
Sun's galactic rotation period 220 million years (negative rotation)
Spiral pattern rotation period 50 million years[2]
Bar pattern rotation period 15 to 18 million years[2]
Speed relative to the universe 590 km/s[3]
See also: Galaxy, List of galaxies
This box: view • talk • edit
The Milky Way as seen from Death Valley, 2007. This is a panoramic picture.
The Milky Way as seen from Death Valley, 2007. This is a panoramic picture.

The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias) sometimes referred to simply as "the Galaxy"), is a barred spiral galaxy that is part of the Local Group of galaxies. Although the Milky Way is one of billions of galaxies in the observable universe,[4] the Galaxy has special significance to humanity as it is the home galaxy of the planet Earth. The plane of the Milky Way galaxy is visible from Earth as a band of light in the night sky, and it is the appearance of this band of light which has inspired the name for our galaxy. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia Kuklos (meaning milky way)) traditionally refers to the a hazy band of white light across the celestial sphere, formed by stars within the disc of its namesake galaxy (the plane of the Milky... Image File history File links Metadata Size of this preview: 800 × 577 pixelsFull resolution (3501 × 2525 pixel, file size: 9. ... Astronomers classify galaxies based on their overall shape (elliptical, spiral or barred spiral) and further by the specific properties of the individual galaxy (for example degree of ellipse, number of spirals or definition of bar). ... NGC 1300, viewed nearly face-on. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... For the series of books, see Galactic Center Saga. ... Sol redirects here. ... Density Wave Theory or the Lin-Shu Density Wave Theory is a theory proposed by C.C. Lin and Frank Shu in the mid-1960s to explain spiral arm structure of certain galaxies. ... NGC 1300, viewed nearly face-on. ... For other uses, see Galaxy (disambiguation). ... List of galaxies: Abell 1835 IR1916 AM 0644-741 Andromeda Galaxy (M31/NGC 224) Andromeda I Andromeda II Andromeda III Aquarius Dwarf Barnards Galaxy (NGC 6822) Black Eye Galaxy (M64/NGC 4826) Bodes Galaxy (M81/NGC 3031) Canis Major Dwarf Galaxy Carina Dwarf Centaurus A Galaxy Draco Dwarf Fornax... Image File history File links Size of this preview: 800 × 258 pixelsFull resolution (4000 × 1290 pixel, file size: 1. ... Image File history File links Size of this preview: 800 × 258 pixelsFull resolution (4000 × 1290 pixel, file size: 1. ... For other uses, see Death Valley (disambiguation). ... This article is about the artistic term Panorama. ... For other uses, see Latins and Latin (disambiguation). ... For other uses, see Galaxy (disambiguation). ... NGC 1300, viewed nearly face-on. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... See universe for a general discussion of the universe. ... This article is about Earth as a planet. ...


Some sources hold that, strictly speaking, the term Milky Way should refer exclusively to the observation of the band of light, while the full name Milky Way Galaxy, or alternatively the Galaxy should be used to describe our galaxy as an astrophysical whole.[5][6][7] It is unclear how widespread the usage of this convention is, however, and the term Milky Way is routinely used in either context. Context is a notion used in the language sciences (linguistics, sociolinguistics, discourse analysis, pragmatics, semiotics, etc. ...

Contents

View from Earth

Visible from Earth as a hazy band of white light that is seen in the night sky, arching across the entire celestial sphere, the visual phenomenon of the Milky Way (as seen in the night sky) originates from stars and other material which lies within the galactic plane. This article is about Earth as a planet. ... This article is about the color. ... For other uses, see Light (disambiguation). ... Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ... The celestial sphere is divided by the celestial equator. ... For other uses, see Phenomena (disambiguation). ... This article is about the time of day. ... For other uses, see Sky (disambiguation). ... This article is about the astronomical object. ...


The Milky Way looks brightest in the direction of the constellation of Sagittarius, toward the galactic center. Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic relative to the galactic plane. The fact that the Milky Way divides the night sky into two roughly equal hemispheres indicates that our Solar System lies close to the galactic plane. The Milky Way has a relatively low surface brightness, making it difficult to see from any urban or suburban location suffering from light pollution. This article is about the star grouping. ... For other uses, see Sagittarius. ... For the series of books, see Galactic Center Saga. ... The celestial equator is a great circle on the imaginary celestial sphere, which could be constructed by inflating the Earths equator until it intersects with said sphere. ... Cassiopeia (pronounced , colloquially ) is a northern constellation which Greek mythology considered to represent the vain queen Cassiopeia who boasted about her unrivaled beauty. ... CRUX is a lightweight, i686-optimized Linux distribution targeted at experienced Linux users. ... World map showing the equator in red In tourist areas, the equator is often marked on the sides of roads The equator marked as it crosses Ilhéu das Rolas, in São Tomé and Príncipe. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... The celestial sphere is divided by the celestial equator. ... The galactic plane is the plane in which the majority of a flattened galaxys mass lies. ... Surface brightness is a concept used in astronomy when describing extended astronomical objects such as galaxies and nebulae. ... Cities with at least a million inhabitants in 2006 An urban area is an area with an increased density of human-created structures in comparison to the areas surrounding it. ... Illustration of the backyards of a surburban neighbourhood Suburbs are inhabited districts located either on the outer rim of a city or outside the official limits of a city (the term varies from country to country), or the outer elements of a conurbation. ... This time exposure photo of New York City shows sky glow, one form of light pollution. ...

360-degree photographic panorama of the galaxy.
360-degree photographic panorama of the galaxy.

Image File history File linksMetadata Milkyway_pan1. ... Image File history File linksMetadata Milkyway_pan1. ...

Size

The stellar disk of the Milky Way galaxy is approximately 100,000 light years in diameter, and is believed to be, on average, about 1,000 light years thick.[8] It is estimated to contain at least 200 billion stars[9] and possibly up to 400 billion stars,[10] the exact figure depending on the number of very low-mass stars, which is highly uncertain. Extending beyond the stellar disk is a much thicker disk of gas. Recent observations indicate that the gaseous disk of the Milky Way has a thickness of around 12,000 light years - twice the previously accepted value.[11] As a guide to the relative physical scale of the Milky Way, if it were reduced to 130 km (80 mi) in diameter, the Solar System would be a mere 2 mm (0.08 inches) in width. The concept of scale is applicable if a system is represented proportionally by another system. ...


The Galactic Halo extends outward, but is limited in size by the orbits of the two Milky Way satellites, the Large and the Small Magellanic Clouds, whose perigalacticon is at ~180,000 light-years.[12] The galactic halo is a region of space surrounding spiral galaxies, including our galaxy, the Milky Way. ... The two Magellanic Clouds are irregular dwarf galaxies that may be orbiting our Milky Way galaxy[1], and thus are members of our Local Group of galaxies. ... A diagram of Keplerian orbital elements. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ...


Age

A green and red Perseid meteor is striking the sky just below the Milky Way in August 2007.
A green and red Perseid meteor is striking the sky just below the Milky Way in August 2007.
Main article: Galaxy formation and evolution

It is extremely difficult to define the age at which the Milky Way formed, but the age of the oldest star in the Galaxy yet discovered is estimated to be about 13.2 billion years, nearly as old as the Universe itself. Image File history File links Size of this preview: 662 × 600 pixelsFull resolution (777 × 704 pixel, file size: 509 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 662 × 600 pixelsFull resolution (777 × 704 pixel, file size: 509 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The Perseids (pûrsÄ“-Ä­dz, or [pʰɝsijɪdz] in IPA) are a prolific meteor shower[1] associated with the comet Swift-Tuttle. ... In astrophysics, the questions of galaxy formation and evolution are: How, from a homogeneous universe, did we obtain the very heterogeneous one we live in? How did galaxies form? How do galaxies change over time? A spectacular head-on collision between two galaxies is seen in this NASA Hubble Space... HE 1523-0901 is the designation given to a red giant star located in the Milky Way galaxy. ... This box:      This article is about scientific estimates of the age of the universe. ...


This estimate is based on research done in 2004 by astronomers Luca Pasquini, Piercarlo Bonifacio, Sofia Randich, Daniele Galli, and Raffaele G. Gratton. The team used the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure, for the first time, the beryllium content of two stars in globular cluster NGC 6397. This allowed them to deduce the elapsed time between the rise of the first generation of stars in the entire Galaxy and the first generation of stars in the cluster, at 200 million to 300 million years. By including the estimated age of the stars in the globular cluster (13.4 ± 0.8 billion years), they estimated the age of the oldest stars in the Milky Way at 13.6 ± 0.8 billion years. (See also nucleocosmochronology.) Based upon this emerging science, the Galactic thin disk is estimated to have been formed between 6.5 and 10.1 billion years ago[13]. One of the four telescopes that make up the VLT, named Kueyen. ... Measurement is the estimation of the magnitude of some attribute of an object, such as its length or weight, relative to a unit of measurement. ... General Name, symbol, number beryllium, Be, 4 Chemical series alkaline earth metals Group, period, block 2, 2, s Appearance white-gray metallic Standard atomic weight 9. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ... Globular Cluster NGC 6397 (also known as NGC 6397) is a globular cluster in the Ara constellation. ... Nucleocosmochronology is the study of the evolution of the Universe with respect to the four fundamental processes of Nucleosynthesis. ...


Composition and structure

NGC 7331 is often referred to as "the Milky Way's twin." This is what observers from another galaxy might see when looking at our own. IC 342 is another galaxy that may resemble the Milky Way.

Observations by the Spitzer Space Telescope in 2005 backed up previously collected evidence that suggested the Milky Way is a barred spiral galaxy. It consists of a bar-shaped core region surrounded by a disk of gas, dust and stars. Within the disk region are several arm structures that spiral outward in a logarithmic spiral shape. The mass distribution within the Galaxy closely resembles the Sbc Hubble classification, which is a spiral galaxy with relatively loosely-wound arms.[14] It was only in the 1980s that astronomers began to suspect that the Milky Way is a barred spiral[15] rather than an ordinary spiral, which observations in 2005 with the Spitzer Space Telescope have since confirmed, showing that the Galaxy's central bar is larger than previously suspected.[16] This argues for a classification of type SBbc (loosely wound barred spiral). In 1970 Gérard de Vaucouleurs predicted that the Milky Way was of type SAB(rs)bc, where the "rs" indicates a broken ring structure around the core region.[17] Image File history File links NASA/JPL-Caltech/M. Regan (STScI), and the SINGS Team File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links NASA/JPL-Caltech/M. Regan (STScI), and the SINGS Team File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... NGC 7331 is a spiral galaxy about 40 million light-years away in the constellation Pegasus. ... The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility [SIRTF]) is an infrared space observatory, the fourth and final of NASAs Great Observatories. ... NGC 1300, viewed nearly face-on. ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... A logarithmic spiral, equiangular spiral or growth spiral is a special kind of spiral curve which often appears in nature. ... Astronomers classify galaxies based on their overall shape (elliptical, spiral or barred spiral) and further by the specific properties of the individual galaxy (for example degree of ellipse, number of spirals or definition of bar). ... An example of a spiral galaxy, the Pinwheel Galaxy (also known as Messier 101 or NGC 5457) A spiral galaxy is a galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae”[1] and, as... The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility [SIRTF]) is an infrared space observatory, the fourth and final of NASAs Great Observatories. ... Gérard Henri de Vaucouleurs (April 25, 1918–October 7, 1995) was a French-American astronomer. ...


As of 2006, the Milky Way's mass is thought to be about 5.8×1011 M☉[18][19][20] comprising 200 to 400 billion stars. Its integrated absolute visual magnitude has been estimated to be −20.9. Most of the mass of the Galaxy is thought to be dark matter, forming a dark matter halo of an estimated 600–3000 billion solar masses (M☉) which is spread out relatively evenly.[20] For other uses, see Mass (disambiguation). ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... For other uses, see Dark matter (disambiguation). ... Beyond the visible, inner portion of the galactic halo lies a much larger region, known as the dark matter halo which contains large amounts of dark matter. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ...


Galactic center

Main article: Galactic Center
The galactic center in the direction of Sagittarius. The primary stars of Sagittarius are indicated in red.
The galactic center in the direction of Sagittarius. The primary stars of Sagittarius are indicated in red.

The galactic disc, which bulges outward at the galactic center, has a diameter of between 70,000 and 100,000 light-years.[21] The distance from the Sun to the galactic center is now estimated at 26,000 ± 1400 light-years, while older estimates could put the Sun as far as 35,000 light-years from the central bulge. For the series of books, see Galactic Center Saga. ... Image File history File links Download high-resolution version (1531x1021, 546 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Milky Way User:Moondigger ... Image File history File links Download high-resolution version (1531x1021, 546 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Milky Way User:Moondigger ... For other uses, see Sagittarius. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ... Sol redirects here. ...


The galactic center harbors a compact object of very large mass (named Sagittarius A*), strongly suspected to be a supermassive black hole. Most galaxies are believed to have a supermassive black hole at their center.[22] Sagittarius A* (pronounced A-star) is a bright and very compact source of radio emission at the center of the Milky Way Galaxy, part of a larger astronomical feature at that location (Sagittarius A). ... Top: artists conception of a supermassive black hole tearing apart a star. ...


The Galaxy's bar is thought to be about 27,000 light-years long, running through its center at a 44 ± 10 degree angle to the line between the Sun and the center of the Galaxy. It is composed primarily of red stars, believed to be ancient (see red dwarf, red giant). The bar is surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Galaxy, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of our own galaxy.[23] This article is about the British sitcom. ... According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... This article is about the unit of length. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ...


Spiral arms

Each spiral arm describes a logarithmic spiral (as do the arms of all spiral galaxies) with a pitch of approximately 12 degrees. There are believed to be four major spiral arms which all start at the Galaxy's center. These are named as follows, according to the image at left: A logarithmic spiral, equiangular spiral or growth spiral is a special kind of spiral curve which often appears in nature. ...

Observed and extrapolated structure of the spiral arms
Observed and extrapolated structure of the spiral arms
color arm(s)
cyan 3-kpc and Perseus Arm
purple Norma and Cygnus Arm (Along with a newly discovered extension)
green Scutum-Crux Arm
pink Carina and Sagittarius Arm
There are at least two smaller arms or spurs, including:
orange Orion Arm (which contains our own Solar System and Sun)

Outside of the major spiral arms is the Outer Ring or Monoceros Ring, a ring of stars around the Milky Way proposed by astronomers Brian Yanny and Heidi Jo Newberg, which consists of gas and stars torn from other galaxies billions of years ago. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... The Perseus Arm (labeled +I) is a spiral arm of the Milky Way galaxy with a radius of 10. ... The Norma Arm or 3-kpc Arm is an inner spiral arm at the center of the Milky Way galaxy. ... Diagram of the Milky Ways spiral arms. ... The Scutum-Crux Arm or Centaurus Arm is a spiral arm of the Milky Way galaxy. ... The Sagittarius Arm or Sagittarius-Carina Arm (labeled -I) is one of two major spiral arms of the Milky Way galaxy, along with the Cygnus Arm. ... Observed structure of the Milky Ways spiral arms The Orion Arm or Local Arm (labeled 0) is a minor, spiral arm of the Milky Way galaxy. ... Sol redirects here. ... Monoceros Ring is a proposed ring of stars around the Milky Way which consists of a stellar stream torn from the Canis Major Dwarf Galaxy as it merges with the Milky Way over the course of billions of years. ... Monoceros Ring is a proposed ring of stars around the Milky Way which consists of stars torn from the Canis Major Dwarf Galaxy as it merges with the Milky Way over the course of billions of years. ...


As is typical for many galaxies, the distribution of mass in the Milky Way Galaxy is such that the orbital speed of most stars in the Galaxy does not depend strongly on its distance from the center. Away from the central bulge or outer rim, the typical stellar velocity is between 210 and 240 km/s.[24] Hence the orbital period of the typical star is directly proportional only to the length of the path traveled. This is unlike in the Solar System where different orbits are also expected to have significantly different velocities associated with them, and is one of the major pieces of evidence for the existence of dark matter. Another interesting aspect is the so-called "wind-up problem" of the spiral arms. If one believes that the inner parts of the arms rotate faster than the outer part, then the Galaxy will wind up so much that the spiral structure will be thinned out. But this is not what is observed in spiral galaxies; instead, astronomers propose that the spiral arms form as a result of a matter-density wave emanating from the galactic center. This can be likened to a moving traffic jam on a highway — the cars are all moving, but there is always a region of slow-moving cars. Thus this results in several spiral arms where there are a lot of stars and gas. This model also agrees with enhanced star formation in or near spiral arms; the compressional waves increase the density of molecular Hydrogen and protostars form as a result.
The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... For other uses, see Dark matter (disambiguation). ...


Halo

The galactic disk is surrounded by a spheroid halo of old stars and globular clusters, of which 90% lie within 100,000 light-years,[25] suggesting a stellar halo diameter of 200,000 light-years. However, a few globular clusters have been found farther, such as PAL 4 and AM1 at more than 200,000 light-years away from the galactic center. While the disk contains gas and dust obscuring the view in some wavelengths, the spheroid component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent areas of high density), but not in the halo. Open clusters also occur primarily in the disk. Spiral galaxies have a typical structure related to their history. ... The Globular Cluster M80 in the constellation Scorpius is located about 28,000 light years from the Sun and contains hundreds of thousands of stars. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... Galactic cluster redirects here. ...


Recent discoveries have added dimension to the knowledge of the Milky Way's structure. With the discovery that the disc of the Andromeda Galaxy (M31) extends much further than previously thought,[26] the possibility of the disk of the Galaxy extending further is apparent, and this is supported by evidence of the newly discovered Outer Arm extension of the Cygnus Arm.[27] With the discovery of the Sagittarius Dwarf Elliptical Galaxy came the discovery of a ribbon of galactic debris as the polar orbit of Sagittarius and its interaction with the Milky Way tears it apart. Similarly, with the discovery of the Canis Major Dwarf Galaxy, it was found that a ring of galactic debris from its interaction with the Milky Way encircles the galactic disk. The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... Diagram of the Milky Ways spiral arms. ... The Sagittarius Dwarf Elliptical Galaxy (Sag DEG) is a satellite galaxy of the Milky Way Galaxy. ... The Canis Major Dwarf galaxy is located in the same part of the sky as the constellation of Canis Major. ...


On January 9, 2006, Mario Juric and others of Princeton University announced that the Sloan Digital Sky Survey of the northern sky found a huge and diffuse structure (spread out across an area around 5,000 times the size of a full moon) within the Milky Way that does not seem to fit within current models. The collection of stars rises close to perpendicular to the plane of the spiral arms of the Galaxy. The proposed likely interpretation is that a dwarf galaxy is merging with the Milky Way. This galaxy is tentatively named the Virgo Stellar Stream and is found in the direction of Virgo about 30,000 light-years away. is the 9th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... The title given to this article is incorrect due to technical limitations. ... Princeton University is a private coeducational research university located in Princeton, New Jersey. ... SDSS Logo The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2. ... A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Ways 200-400 billion stars. ... The Virgo Stellar Stream (or Virgo Overdensity) is the proposed name for a stream of stars in the constellation of Virgo which was discovered in 2005. ... Virgo (pronounced , Latin: , symbol , ) is a constellation of the zodiac. ...


Sun's location

The Sun (and therefore the Earth and Solar System) may be found close to the inner rim of the Galaxy's Orion Arm, in the Local Fluff or the Gould Belt, at a hypothesized distance of 7.62±0.32 kpc from the Galactic Center.[28][29][30][31] The distance between the local arm and the next arm out, the Perseus Arm, is about 6,500 light-years.[32] The Sun, and thus the Solar System, is found in what scientists call the galactic habitable zone. Sol redirects here. ... This article is about Earth as a planet. ... This article is about the Solar System. ... Observed structure of the Milky Ways spiral arms The Orion Arm or Local Arm (labeled 0) is a minor, spiral arm of the Milky Way galaxy. ... The Local Fluff is a relatively dense cloud of interstellar gas which formed where the Local Bubble and the Loop I Bubble met. ... There are very few or no other articles that link to this one. ... This article is about the unit of length. ... For the series of books, see Galactic Center Saga. ... The Perseus Arm (labeled +I) is a spiral arm of the Milky Way galaxy with a radius of 10. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ...


The Apex of the Sun's Way, or the solar apex, is the direction that the Sun travels through space in the Milky Way. The general direction of the Sun's galactic motion is towards the star Vega near the constellation of Hercules, at an angle of roughly 60 sky degrees to the direction of the Galactic Center. The Sun's orbit around the Galaxy is expected to be roughly elliptical with the addition of perturbations due to the galactic spiral arms and non-uniform mass distributions. In addition the Sun oscillates up and down relative to the galactic plane approximately 2.7 times per orbit. This is very similar to how a simple harmonic oscillator works with no drag force (dampening) term. The solar apex, or the Apex of the Suns Way, refers to the direction that the Sun travels through space. ... For other uses, see Vega (disambiguation). ... Hercules (IPA: ) is the fifth largest of the 88 modern constellations. ... For the series of books, see Galactic Center Saga. ... A harmonic oscillator is either a mechanical system in which there exists a returning force F directly proportional to the displacement x, i. ...


It takes the Solar System about 225–250 million years to complete one orbit of the galaxy (a galactic year),[33] so it is thought to have completed 20–25 orbits during the lifetime of the Sun and 1/1250th of a revolution since the origin of humans. The orbital speed of the Solar System about the center of the Galaxy is approximately 220 km/s. At this speed, it takes around 1400 years for the Solar System to travel a distance of 1 light-year, or 8 days to travel 1 AU.[34] // Galactic time NGC 4414, a typical spiral galaxy alike our Milky Way Galactic time, not to confuse with siderial time, is the time that is described by our spin relative to the center of the galaxy. ... For the history of humans on Earth, see History of the world. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... The astronomical unit (AU or au or a. ...


Environment

Main articles: Local group and Andromeda-Milky Way collision

The Milky Way and the Andromeda Galaxy are a binary system of giant spiral galaxies. Together with their companion galaxies they form the Local Group, a group of some 50 closely bound galaxies. The Local Group is part of the Virgo Supercluster. A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... It has been suggested that this article or section be merged into Milky Way. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... A binary system is an astronomy term referring to two objects in space, usually stars, which are so close that their gravitational forces attract one another into a mutual orbit. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... The Virgo Supercluster The Virgo Supercluster or Local Supercluster is the galactic supercluster that contains the Local Group, the latter which, in its turn, contains the Milky Way and Andromeda galaxies. ...


The Milky Way is orbited by two smaller galaxies and a number of dwarf galaxies in the Local Group. The largest of these is the Large Magellanic Cloud with a diameter of 20,000 light-years. It has a close companion, the Small Magellanic Cloud. The Magellanic Stream is a peculiar streamer of neutral hydrogen gas connecting these two small galaxies. The stream is thought to have been dragged from the Magellanic Clouds in tidal interactions with the Galaxy. Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf. The smallest Milky Way dwarf galaxies are only 500 light-years in diameter. These include Carina Dwarf, Draco Dwarf, and Leo II Dwarf. There may still be undetected dwarf galaxies, which are dynamically bound to the Milky Way. Observations through the zone of avoidance are frequently detecting new distant and nearby galaxies. Some galaxies consisting mostly of gas and dust may also have evaded detection so far. A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Ways 200-400 billion stars. ... The Large Magellanic Cloud (LMC) is a nearby satellite galaxy of our own galaxy, the Milky Way. ... The Small Magellanic Cloud (SMC) is a dwarf galaxy[1] in orbit around the Milky Way Galaxy. ... // Introduction Hierarchical Clustering tells us that galaxies are built up over time from collisions of smaller galaxies. ... This article is about the chemistry of hydrogen. ... The Canis Major Dwarf Galaxy located in the same part of the sky as the constellation of Canis Major. ... The Sagittarius Dwarf Elliptical Galaxy (Sag DEG) is a satellite galaxy of the Milky Way Galaxy. ... The Ursa Minor Dwarf dwarf galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. ... for SDIG, see Sculptor Dwarf Irregular Galaxy The Sculptor Dwarf Galaxy (also called E351-G30, PGC 3589, A0058, Sculptor Dwarf Spheroidal Galaxy) is a dwarf spheroidal galaxy in the Local Group that is a satellite of the Milky Way in the direction of the constellation of Sculptor. ... Sextans Dwarf on November 3, 1998 The Sextans Dwarf is a dwarf galaxy that was discovered in 1990 by Mike Irwin, M.T. Bridgeland, P.S. Bunclark and R.G. McMahon as the 8th satellite of the Milky Way [1], and is named fittingly, as it is part of Sextans... The Fornax Dwarf is a dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. ... Leo 1, courtesy of NOAO The Leo I Dwarf Galaxy (or simply Leo I) is a dwarf spheroidal galaxy in the Local Group. ... The Carina Dwarf is a dwarf galaxy in the Carina constellation. ... The Draco Dwarf galaxy was discovered by Albert G. Wilson of Lowell Observatory in 1954. ... Leo II (or Leo B) is an dwarf spheroidal galaxy of the Local Group, in the constellation of Leo. ... The Zone of Avoidance is the area of the night sky that is obscured by our own galaxy, the Milky Way. ...


In January 2006, researchers reported that the heretofore unexplained warp in the disk of the Milky Way has now been mapped and found to be a ripple or vibration set up by the Large and Small Magellanic Clouds as they circle the Galaxy, causing vibrations at certain frequencies when they pass through its edges.[35] Previously, these two galaxies, at around 2% of the mass of the Milky Way, were considered too small to influence the Milky Way. However, by taking into account dark matter, the movement of these two galaxies creates a wake that influences the larger Milky Way. Taking dark matter into account results in an approximately twentyfold increase in mass for the Galaxy. This calculation is according to a computer model made by Martin Weinberg of the University of Massachusetts, Amherst. In this model, the dark matter is spreading out from the galactic disc with the known gas layer. As a result, the model predicts that the gravitational effect of the Magellanic Clouds is amplified as they pass through the Galaxy. For other uses, see Dark matter (disambiguation). ... The center of the UMass Amherst campus. ...


Current measurements suggest the Andromeda Galaxy is approaching us at 100 to 140 kilometers per second. The Milky Way may collide with it in 3 to 4 billion years, depending on the importance of unknown lateral components to the galaxies' relative motion. If they collide, it is thought that the Sun and the other stars in the Milky Way will probably not collide with the stars of the Andromeda Galaxy, but that the two galaxies will merge to form a single elliptical galaxy over the course of about a billion years.[36] The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... The giant elliptical galaxy ESO 325-G004. ...


Velocity

In the general sense, the absolute velocity of any object through space is not a meaningful question according to Einstein's Special Theory of Relativity, which declares that there is no "preferred" inertial frame of reference in space with which to compare the Galaxy's motion. (Motion must always be specified with respect to another object.) “Einstein” redirects here. ... Special relativity (SR) or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. ... An inertial frame of reference, or inertial reference frame, is one in which Newtons first and second laws of motion are valid. ...


Many astronomers believe the Milky Way is moving at approximately 600 km per second relative to the observed locations of other nearby galaxies. Most recent estimates range from 130 km/s to 1,000 km/s. If the Galaxy is moving at 600 km/s, Earth travels 51.84 million km per day, or more than 18.9 billion km per year, about 4.5 times its closest distance from Pluto. The Galaxy is thought to be moving towards the constellation Hydra, and may someday become a close-knit member of the Virgo cluster of galaxies. For other uses, see Pluto (disambiguation). ... Hydra (IPA: ) is the largest of the 88 modern constellations, and was also one of the 48 constellations listed by Ptolemy. ... A sky field near some of the brighter galaxies in the Virgo cluster. ...


Another reference frame is provided by the Cosmic microwave background (CMB). The Milky Way is moving at around 552 km/s[37] with respect to the photons of the CMB. This can be observed by satellites such as COBE and WMAP as a dipole contribution to the CMB, as photons in equilibrium at the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction. WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ... The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was the first satellite built dedicated to cosmology. ... Artist depiction of the WMAP satellite at the L2 point The Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA satellite whose mission is to survey the sky to measure the temperature of the radiant heat left over from the Big Bang. ... A source of waves moving to the left. ... This article is about the physical phenomenon. ...


History

Etymology and beliefs

Jacopo Tintoretto's "The Origin of the Milky Way"
Jacopo Tintoretto's "The Origin of the Milky Way"
Main articles: List of names for the Milky Way and Milky Way (mythology)

There are many creation myths around the world which explain the origin of the Milky Way and give it its name. The English phrase is a translation from Greek Γαλαξίας, Galaxias, which is derived from the word for milk (γάλα, gala). This is also the origin of the word galaxy. In Greek myth, the Milky Way was caused by milk spilt by Hera when suckled by Heracles. Image File history File links Size of this preview: 665 × 600 pixelsFull resolution (2024 × 1825 pixel, file size: 309 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 665 × 600 pixelsFull resolution (2024 × 1825 pixel, file size: 309 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Tintoretto (real name Jacopo Comin; September 29, 1518 - May 31, 1594) was one of the greatest painters of the Venetian school and probably the last great painter of the Italian Renaissance. ... This is a list of the names for the Milky Way in various languages. ... “Great Sky River” redirects here. ... A creation myth is a supernatural mytho-religious story or explanation that describes the beginnings of humanity, earth, life, and the universe (cosmogony),[1] usually as a deliberate act of creation by a supreme being. ... The English language is a West Germanic language that originates in England. ... For other uses, see Galaxy (disambiguation). ... The bust of Zeus found at Otricoli (Sala Rotonda, Museo Pio-Clementino, Vatican) Greek mythology is the body of stories belonging to the Ancient Greeks concerning their gods and heroes, the nature of the world and the origins and significance of their own cult and ritual practices. ... For other uses, see Hera (disambiguation). ... Alcides redirects here. ...


The term Milky Way first appeared in English literature in a poem by Chaucer. The term English literature refers to literature written in the English language, including literature composed in English by writers not necessarily from England; Joseph Conrad was Polish, Robert Burns was Scottish, James Joyce was Irish, Dylan Thomas was Welsh, Edgar Allan Poe was American, Salman Rushdie is Indian, V.S... Chaucer redirects here. ...

"See yonder, lo, the Galaxyë
 Which men clepeth the Milky Wey,
 For hit is whyt."

—Geoffrey Chaucer, Geoffrey Chaucer The House of Fame, c. 1380.[38]

In a large area from Central Asia to Africa, the name for the Milky Way is related to the word for straw. It has been claimed that this was spread by Arabs who in turn borrowed the word from Armenian.[39] In several Uralic, Turkic languages, Fenno-Ugric languages and in the Baltic languages the Milky Way is called the "Birds' Path". The Chinese name "Silver River" (銀河) is used throughout East Asia, including Korea. In Japanese, "Silver River" (銀河 ginga) means galaxies in general and the Milky Way is called the "Silver River System" (銀河系 gingakei) or the "River of Heaven" (天の川 ama no kawa). In Swedish, it is called Vintergatan, or "Winter Street", because the stars in the belt were used to predict time of the approaching winter. The House of Fame is a poem by Geoffrey Chaucer, it is one of his early works, probably written between 1379 and 1380. ... Map of Central Asia showing three sets of possible boundaries for the region Central Asia located as a region of the world Central Asia is a vast landlocked region of Asia. ... A world map showing the continent of Africa Africa is the worlds second-largest and second most-populous continent, after Asia. ... Bales of straw bundles of rice straw Pile of straw bales, sheltered under a tarpaulin Straw is an agricultural byproduct, the dry stalk of a cereal plant, after the nutrient grain or seed has been removed. ... For other uses, see Arab (disambiguation). ... Geographical distribution of Samoyedic, Finnic, Ugric and Yukaghir languages  Yukaghir  Samoyedic  Ugric  Finnic The Uralic languages (pronounced: ) form a language family of about 30 languages spoken by approximately 20 million people. ... The Turkic languages constitute a language family of some thirty languages, spoken across a vast area from Eastern Europe and the Mediterranean to Siberia and Western China, and are traditionally considered to be part of the proposed Altaic language family. ... Approximate geographical distribution of areas where indigenous Finno-Ugric languages are spoken. ... The Baltic languages are a group of related languages belonging to the Indo-European language family and spoken mainly in areas extending east and southeast of the Baltic Sea in Northern Europe. ... East Asia Geographic East Asia. ... This article is about the Korean civilization. ...


Discovery

See also:Galaxy-Observation history
The shape of the Milky Way as deduced from star counts by William Herschel in 1785; the Solar System was assumed near center.
The shape of the Milky Way as deduced from star counts by William Herschel in 1785; the Solar System was assumed near center.

The Greek philosopher Democritus (450–370 BC) was the first known person to propose that the Milky Way might consist of distant stars. Actual proof of this came in 1610 when Galileo Galilei used a telescope to study the Milky Way and discovered that it was composed of a huge number of faint stars.[40] In a treatise in 1755, Immanuel Kant, drawing on earlier work by Thomas Wright, speculated (correctly) that the Milky Way might be a rotating body of a huge number of stars, held together by gravitational forces akin to the Solar System but on much larger scales. The resulting disk of stars would be seen as a band on the sky from our perspective inside the disk. Kant also conjectured that some of the nebulae visible in the night sky might be separate "galaxies" themselves, similar to our own.[41] For other uses, see Galaxy (disambiguation). ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Greek philosophy focused on the role of reason and inquiry. ... ‎ Democritus (Greek: ) was a pre-Socratic Greek materialist philosopher (born at Abdera in Thrace ca. ... Galileo redirects here. ... Eight Inch refracting telescope. ... Kant redirects here. ... See also : Thomas Wright (disambiguation) Categories: Stub | 1711 births | 1786 deaths | British astronomers ... Gravity redirects here. ... The Triangulum Emission Nebula NGC 604 The Pillars of Creation from the Eagle Nebula For other uses, see Nebula (disambiguation). ...


The first attempt to describe the shape of the Milky Way and the position of the Sun within it was carried out by William Herschel in 1785 by carefully counting the number of stars in different regions of the sky. He produced a diagram of the shape of the Galaxy with the Solar System close to the center. Sol redirects here. ... For other persons named William Herschel, see William Herschel (disambiguation). ...

Photograph of the "Great Andromeda Nebula" from 1899, later identified as the Andromeda Galaxy
Photograph of the "Great Andromeda Nebula" from 1899, later identified as the Andromeda Galaxy

In 1845, Lord Rosse constructed a new telescope and was able to distinguish between elliptical and spiral-shaped nebulae. He also managed to make out individual point sources in some of these nebulae, lending credence to Kant's earlier conjecture.[42] Image File history File links Pic_iroberts1. ... Image File history File links Pic_iroberts1. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... Lord Rosse William Parsons, 3rd Earl of Rosse KP (June 17, 1800 – October 31, 1867) was born in Monkstown, County Cork and was an Irish astronomer. ...


In 1917, Heber Curtis had observed the nova S Andromedae within the "Great Andromeda Nebula" (Messier object M31). Searching the photographic record, he found 11 more novae. Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred within our galaxy. As a result he was able to come up with a distance estimate of 150,000 parsecs. He became a proponent of the "island universes" hypothesis, which held that the spiral nebulae were actually independent galaxies.[43] In 1920 the Great Debate took place between Harlow Shapley and Heber Curtis, concerning the nature of the Milky Way, spiral nebulae, and the dimensions of the universe. To support his claim that the Great Andromeda Nebula was an external galaxy, Curtis noted the appearance of dark lanes resembling the dust clouds in the Milky Way, as well as the significant Doppler shift.[44] Heber Doust Curtis (June 27, 1872 – January 9, 1942) was an American astronomer. ... S Andromedae (also SN 1885A) was a supernova in the Andromeda Galaxy, the only one seen in that galaxy so far by astronomers, and the first ever noted outside the Milky Way. ... Andromeda (IPA: ) is a constellation named for the princess Andromeda (which is Greek for Ruler over men), a character in Greek mythology. ... The Messier objects are a set of astronomical objects catalogued by Charles Messier in his catalogue of Nebulae and Star Clusters first published in 1774. ... The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Great Andromeda Nebula) is a spiral galaxy approximately 2. ... Artists conception of a white dwarf star accreting hydrogen from a larger companion A nova (pl. ... In science, magnitude refers to the numerical size of something: see orders of magnitude. ... The Andromeda Galaxy in ultraviolet In astronomy, The Great Debate was an influential debate between the astronomers Harlow Shapley and Heber Curtis which concerned the nature of spiral nebulae and the size of the universe. ... Harlow Shapley in his earlier years. ... A source of waves moving to the left. ...


The matter was conclusively settled by Edwin Hubble in the early 1920s using a new telescope. He was able to resolve the outer parts of some spiral nebulae as collections of individual stars and identified some Cepheid variables, thus allowing him to estimate the distance to the nebulae: they were far too distant to be part of the Milky Way.[45] In 1936 Hubble produced a classification system for galaxies that is used to this day, the Hubble sequence.[46] Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. ... Cepheid in the Spiral Galaxy M100 A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute luminosity. ... It has been suggested that this article or section be merged with Galaxy classification. ...


Further reading

  • Thorsten Dambeck in Sky and Telescope, "Gaia's Mission to the Milky Way", March 2008, p. 36 - 39

See also

  • Smith's Cloud

References

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2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 51st day of the year in the Gregorian calendar. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 51st day of the year in the Gregorian calendar. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 332nd day of the year (333rd in leap years) in the Gregorian calendar. ... is the 9th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... 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Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 129th day of the year (130th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 129th day of the year (130th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 129th day of the year (130th in leap years) in the Gregorian calendar. ... is the 255th day of the year (256th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... is the 222nd day of the year (223rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 224th day of the year (225th in leap years) in the Gregorian calendar. ... Year 1991 (MCMXCI) was a common year starting on Tuesday (link will display the 1991 Gregorian calendar). ... is the 205th day of the year (206th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... The University of Cambridge is the second-oldest university in the English-speaking world, with one of the most selective sets of entry requirements in the United Kingdom. ... Sather tower (the Campanile) looking out over the San Francisco Bay and Mount Tamalpais. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 9th day of the year in the Gregorian calendar. ... For information on Wikipedia press releases, see Wikipedia:Press releases. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... is the 104th day of the year (105th in leap years) in the Gregorian calendar. ... Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 11th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 3rd day of the year in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... is the 241st day of the year (242nd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 5th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 8th day of the year in the Gregorian calendar. ... is the 328th day of the year (329th in leap years) in the Gregorian calendar. ... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 4th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 4th day of the year in the Gregorian calendar. ... Heber Doust Curtis (June 27, 1872 – January 9, 1942) was an American astronomer. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 5th day of the year in the Gregorian calendar. ... Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 8th day of the year in the Gregorian calendar. ...

External links

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v • d • e
The Milky Way
Location Universe · Virgo Supercluster · Local Group
The Milky Way Galaxy
Galactic core Center of the Milky Way
Spiral arms Sagittarius-Carina · Scutum-Crux · Norma-Cygnus · Perseus · Orion
Satellite galaxies
Dwarves Boötes · Canes Venatici · Canis Major · Carina · Draco · Fornax · Leo I · Leo II · Phoenix · Sagittarius Elliptical · Sculptor · Sextans Spheroidal · Ursa Major · Ursa Minor
Other Large Magellanic Cloud · Magellanic Stream · Monoceros Ring · Small Magellanic Cloud · Virgo Stream · Willman 1
v • d • e
Earth's location in space
Earth · Solar System · Local Interstellar Cloud · Local Bubble · Orion Arm · Milky Way · Local Group · Virgo Supercluster · Observable universe · Universe

Image File history File links Commons-logo. ... VRML (Virtual Reality Modeling Language, pronounced vermal or by its initials, originally known as the Virtual Reality Markup Language) is a standard file format for representing 3-dimensional (3D) interactive vector graphics, designed particularly with the World Wide Web in mind. ... is the 76th day of the year (77th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... For other uses, see Universe (disambiguation). ... The Virgo Supercluster The Virgo Supercluster or Local Supercluster is the galactic supercluster that contains the Local Group, the latter which, in its turn, contains the Milky Way and Andromeda galaxies. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... Image File history File links Download high resolution version (1350x1350, 954 KB)Barred Spiral Milky Way Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA From http://apod. ... For the series of books, see Galactic Center Saga. ... The Sagittarius Arm or Sagittarius-Carina Arm (labeled -I) is one of two major spiral arms of the Milky Way galaxy, along with the Cygnus Arm. ... The Scutum-Crux Arm or Centaurus Arm is a spiral arm of the Milky Way galaxy. ... Diagram of the Milky Ways spiral arms. ... The Perseus Arm (labeled +I) is a spiral arm of the Milky Way galaxy with a radius of 10. ... Observed structure of the Milky Ways spiral arms The Orion Arm or Local Arm (labeled 0) is a minor, spiral arm of the Milky Way galaxy. ... Category: ... A dwarf galaxy is a small galaxy composed of up to several billion stars, a small number compared to our own Milky Ways 200-400 billion stars. ... The Boötes Dwarf Galaxy (Boo dSph) is the faintest galaxy yet discovered, as of 2006, with a total luminosity of 100,000 Suns, and an absolute magnitude of -5. ... The Canes Venatici Dwarf Galaxy (CVn dSph) is the most distant satellite galaxy of the Milky Way as of 2006. ... The Canis Major Dwarf Galaxy located in the same part of the sky as the constellation of Canis Major. ... The Carina Dwarf is a dwarf galaxy in the Carina constellation. ... The Draco Dwarf galaxy was discovered by Albert G. Wilson of Lowell Observatory in 1954. ... The Fornax Dwarf is a dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. ... Leo I is a dwarf spheroidal galaxy in the constellation Leo. ... Leo II (or Leo B) is an dwarf spheroidal galaxy of the Local Group, in the constellation of Leo. ... The Phoenix Dwarf Galaxy is a dwarf galaxy and an irregular galaxy that was discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster. ... The Sagittarius Dwarf Elliptical Galaxy (Sag DEG) is a satellite galaxy of the Milky Way Galaxy. ... The Sculptor Dwarf Galaxy (also called the Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. ... It has been suggested that this article or section be merged with Sextans A. (Discuss) The Sextans Dwarf Spheroidal is a dwarf spheroidal galaxy that was discovered in 1990 by Mike Irwin, M.T. Bridgeland, P.S. Bunclark and R.G. McMahon as the 8th satellite of the Milky Way... Ursa Major Dwarf is a dwarf spheroidal galaxy orbiting the Milky Way galaxy. ... The Ursa Minor Dwarf dwarf galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. ... The Large Magellanic Cloud (LMC) is a nearby satellite galaxy of our own galaxy, the Milky Way. ... // Introduction Hierarchical Clustering tells us that galaxies are built up over time from collisions of smaller galaxies. ... Monoceros Ring is a proposed ring of stars around the Milky Way which consists of stars torn from the Canis Major Dwarf Galaxy as it merges with the Milky Way over the course of billions of years. ... The Small Magellanic Cloud (SMC) is a dwarf galaxy[1] in orbit around the Milky Way Galaxy. ... The Virgo Stellar Stream (or Virgo Overdensity) is the proposed name for a stream of stars in the constellation of Virgo which was discovered in 2005. ... Willman 1 or SDSS J1049+5103[2] is an extreme globular cluster or ultra low-mass dwarf galaxy discovered by a team lead by Beth Willman of New York University, using Sloan Digital Sky Survey data. ... This article is about Earth as a planet. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... This article is about Earth as a planet. ... This article is about the Solar System. ... The Local Interstellar Cloud is the interstellar cloud that our solar system is currently moving through. ... The Local Bubble is a cavity in the local interstellar medium (ISM) at least 300 light years across containing a neutral hydrogen density that is approximately one tenth of that of the average ISM in the Milky Way (approximately 0. ... Observed structure of the Milky Ways spiral arms The Orion Arm or Local Arm (labeled 0) is a minor, spiral arm of the Milky Way galaxy. ... A member of the Local Group of galaxies, irregular galaxy Sextans A is 4. ... The Virgo Supercluster The Virgo Supercluster or Local Supercluster is the galactic supercluster that contains the Local Group, the latter which, in its turn, contains the Milky Way and Andromeda galaxies. ... See universe for a general discussion of the universe. ... For other uses, see Universe (disambiguation). ...


  Results from FactBites:
 
SPACE.com -- The New Tourist's Guide to the Milky Way (1743 words)
Were an intergalactic traveler to approach the Milky Way edge-on, the first thing she would notice is a luminous halo made up of gas and stars enveloping the galaxy.
According to one hypothesis, the strange warp in the Milky Way's hydrogen disk is caused by the movement of two dwarf galaxies-the Large and Small Magellanic Clouds- and their interactions with dark matter as they orbit our galaxy.
The Milky Way is believed to contain four major spiral arms, all of which start at the galaxy's center, plus a number of smaller arms.
Milky Way - Wikipedia, the free encyclopedia (2654 words)
Relative to the celestial equator, the Milky Way passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic relative to the galactic plane.
With the discovery of the Sagittarius Dwarf Elliptical Galaxy came the discovery of a ribbon of galactic debris as the polar orbit of Sagittarius and its interaction with the Milky Way tears it apart.
The Milky Way is thought to be moving in the direction of the constellation Hydra, and may someday become a close-knit member of the Virgo cluster of galaxies.
  More results at FactBites »


 

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