User talk:Theindigowombat
Hi. I'm the user formerly known as
Test Page
I'm going to try an experiment here. As I mentioned on the Milky Way talk page recently, I happen to have a copy of a rewrite of the Milky Way article that was left on my system by an anonymous contributor when I was posting unsecurely through my IP address. I present it below to stimulate discussion and generate ideas. It should be noted that all sources and references cited were not checked out by me personally, but is strictly what was included in the text file left in my documents folder by an unknown editor. This version also does not include my final rewrite and updated sources for the central new statement about nomenclature that the recent debate has centered around. The only change I have made to the text file is to turn off the categories as requested in
- Hi, Theindigowombat. Just a thought - would it be possible to temporarily replace the new text below with the current contents of the article (you could revert it straight away), so that a diff could be performed between the two versions? It seems like most of the major changes are in the first couple of sections and at the end, but there might be other minor changes. Cosmo0 18:51, 12 October 2007 (UTC)
- Okay. I'll give that a try at some point today. The other major differences worthy of discussion are the usage of the formal nomenclature in the text of the article. The version currently up in the main namespace represents what I feel is the minimum acceptable concession to the formal nomenclature; the version below reflects my sense of the maximum acceptable concession. I feel the optimum is somewhere in between, but I feel much more discussion is warranted as to what level of concession to the formal nomenclature is appropriate for a Wikipedia article. Theindigowombat 19:51, 12 October 2007 (UTC)
- Done. If I made any technical errors in the process, please let me know. It looks like some things that I thought were changes were already in the article, but I had overlooked them somehow. Nonetheless, I hope this is useful. Theindigowombat 20:17, 12 October 2007 (UTC)
- Upon a careful review of the comparison between the two versions, I find that in many respects the current version is superior, but there is some additional content in the new version that seems worthy of inclusion in the article. Also, although in most respects re: spelling and grammar the current version is superior, the usage of the formal nomenclature in the below version is closer to what I would prefer (although not perfect). I could probably come up with a way to combine what I see as the best aspects of both, but I don't wish to do so unilaterally. Theindigowombat 03:50, 13 October 2007 (UTC)
Gross factual error on my part
When I found the below version as a text file in my documents folder, I had no memory of putting it there, and believed it could only have been deposited by a benign intruder. This was incorrect; I have investigated further and now realize that it was a version of the article that I had saved previously, in the midst of my editorial work, then forgotten about. I find it disturbing that I could have forgotten such a thing and that I prematurely accepted an unusual explanation for its presence on my system as fact. It seemed to me to be the most logical, sensible explanation for its presence on my system at the time, and that unsettles me, too. I apologize for any confusion or skepticism that may have been generated by my previous incorrect assumptions about the source of this version. Theindigowombat 06:18, 19 October 2007 (UTC)
Milky Way Galaxy (as written by anonymous contributor alternate version)
This is an article on our galaxy. For other uses see Milky Way (disambiguation)
The Milky Way Galaxy (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 which forms part of the Local Group. Although the Milky Way Galaxy is but one of billions of galaxies in the universe, the Galaxy has special significance to humanity as it is the home of the Solar System. Democritus (450 BC–370 BC) was the first known person to claim that the Milky Way Galaxy consists of distant stars.
The term "
The Milky Way appears brightest in the direction of
The main disk of the Milky Way Galaxy is about 80,000 to 100,000
The Milky Way's absolute magnitude, which cannot be measured directly, is assumed by astronomical convention to be −20.5, although other authors give an absolute magnitude of −21.3.
Age
The age of the Galaxy is currently estimated to be about 13.6
This estimate is based upon research performed in 2004 by a team of 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 Galaxy at 13.6 ± 0.8 billion years.
Composition and structure
The overall shape of the Milky Way Galaxy is believed to be a barred spiral. 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.[2] It was only in the 1980s that astronomers began to suspect that the Milky Way Galaxy is a barred spiral[3] 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.[4] This argues for a classification of type SBbc (loosely wound barred spiral). In 1970 Gérard de Vaucouleurs predicted that the Milky Way Galaxy was of type SAB(rs)bc, where the "rs" indicates a broken ring structure around the core region.[5]
As of 2006, the Milky Way Galaxy's mass is thought to be about 5.8×1011 M☉[6][7][8] 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.[8]
Galactic center
The galactic disk, which bulges outward at the galactic center, has a diameter of between 70,000 and 100,000 light-years.[9] 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.
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.[10]
The Milky Way Galaxy's bar is thought to be about 27,000 light-years long, running through the center of the Galaxy 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. The bar is surrounded by a ring called the "5-
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:
color | arm(s) |
---|---|
cyan | 3-kpc and Perseus Arm |
sky-blue | Cygnus Arm (Along with a newly discovered extension)
|
chlorine-green | Scutum Arm
|
pink | Sagittarius Arm
|
There are at least two smaller arms or spurs, including: | |
orange | Orion Arm (which contains the solar system and the Sun) |
Outside of the major spiral arms is the Outer Ring or Monoceros Ring, a ring of stars around the Milky Way Galaxy proposed by astronomers Brian Yanny and Heidi Jo Newberg, which consists of gas and stars torn from other galaxies billions of years ago.
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.
Halo
The galactic disk is surrounded by a
Recent discoveries have added dimension to the knowledge of the Galaxy's structure. With the discovery that the disc of the
On
Sun's location
The
The Apex of the Sun's Way, or the
It takes the
The Milky Way Galaxy's context in the universe
The Milky Way Galaxy is orbited by a number of
In January 2006, researchers reported that the heretofore unexplained warp in the disk of the Milky Way Galaxy 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. Previously, these two galaxies, at around 2% of the mass of the Milky Way Galaxy, were considered too small to influence our galaxy. However, by taking into account
Current measurements suggest the Andromeda Galaxy is approaching us at 100 to 140 kilometers per second (62 to 87 miles per second). The Milky Way Galaxy 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 Galaxy 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.[22]
Velocity
In the general sense, the absolute velocity of any object through space is not a meaningful question according to
Many astronomers believe the Milky Way Galaxy 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
Another reference frame is provided by the Cosmic microwave background (CMB). The Milky Way Galaxy is moving at around 552 km/s[23] with respect to this frame. This can be observed by satellites such as
Earth-based observations
The Milky Way appears brightest in the direction of the
Discovery of "our galaxy"
- See also:Galaxy-Observation history
The
The first attempt to describe the shape of the Milky Way Galaxy 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.
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.[26]
In 1917,
In 1920 the so-called 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.[28]
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 Galaxy.[29] In 1936 Hubble produced a classification system for galaxies that is used to this day, the Hubble sequence.[30]
Names and 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.
The term Milky Way first appeared in the English literature in a poem by Chaucer.
"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.[31]
In a large area from
There are many
According to Greek mythology, the Milky Way was formed by Hera, who spilled milk in the sky after discovering that Zeus had tricked her into feeding young Heracles. In another variant, Hermes snuck Heracles into Olympus to drink from the breasts of Hera who was asleep. Heracles bit Hera's nipple shooting her milk into the skies forming the Milky Way.
In Finnish mythology the Milky Way was called Linnunrata (pathway of the birds). The Finns observed the migratory birds used the galaxy as a guideline to travel south, where they believed Lintukoto (bird home) resided. Only later the scientists indeed confirmed the observation correct; the migratory birds use the Milky Way as a guide and dwell the winters in warm, southern lands. The Milky Way is even today called Linnunrata in the Finnish language.
In Swedish, the Milky Way is known as Vintergatan (winter street), for apparent reasons; it is most visible in the winter in Scandinavia.
Ancient Armenian mythology called the Milky Way the "Straw Thief's Way", relating to one of the gods stealing straw and attempting to flee across the heavens in a wooden chariot, spilling some of the straw along the way.
In Hindu mythology the Milky Way is called the s'is'umara cakra: the dolphin disc. Looking in the night sky one recognized the band of stars as the belly of a dolphin.
In Slovene, the Milky Way is called Rimska cesta, literally "The Roman Road" (or "The Road to Rome", alluding to the ancient pilgrim path). Sometimes, infrequently, it is also called Mlečna cesta, which is a literal translation of its Greek/Latin name. i.e. "Milky Way".
In Spanish, the Milky Way is sometimes called "Camino de Santiago", "The Road to Santiago <de Compostela>", alluding to the ancient pilgrim road to the town of Santiago de Compostela, in Spain.
References
- ^ 17 August 2004 - Press release, European Southern Observatory
- ^ Ortwin, Gerhard (2002). "Mass distribution in our Galaxy". Space Science Reviews. 100 (1/4): 129–138. Retrieved 2007-03-14.
- ^ Chen, W.; Gehrels, N.; Diehl, R.; Hartmann, D. (1996). "On the spiral arm interpretation of COMPTEL ^26^Al map features". Space Science Reviews. 120: 315–316. Retrieved 2007-03-14.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ McKee, Maggie (August 16, 2005). "Bar at Milky Way's heart revealed". New Scientist. Retrieved 2007-05-09.
- ^ López-Corredoira, M.; Cabrera-Lavers, A.; Mahoney, T. J.; Hammersley, P. L.; Garzón, F.; González-Fernández, C. (2007). "The Long Bar in the Milky Way: Corroboration of an Old Hypothesis". The Astronomical Journal. 133 (1): 154–161. Retrieved 2007-03-15.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Elert, Glenn (2006-07-13). "Mass of the Milky Way". The Physics Factbook. Hypertextbook. Retrieved 2007-05-09.
- ^ a b Battaglia, G.; Helmi, A.; Morrison, H.; Harding, P.; Olszewski, E. W.; Mateo, M.; Freeman, K. C.; Norris, J.; Shectman, S. A. (2005). "The radial velocity dispersion profile of the Galactic halo: Constraining the density profile of the dark halo of the Milky Way". Monthly Notices of the Royal Astronomical Society. 364: 433–442. Retrieved 2007-05-09.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) Cite error: The named reference "galmass" was defined multiple times with different content (see the help page). - ^ Grant. J.; Lin, B. (2000). "The Stars of the Milky Way". Fairfax Public Access Corporation. Retrieved 2007-05-09.
{{cite news}}
: CS1 maint: multiple names: authors list (link) - ^ Blandford, R.D. (1999). "Origin and evolution of massive black holes in galactic nuclei". Galaxy Dynamics, proceedings of a conference held at Rutgers University, 8–12 Aug 1998,ASP Conference Series vol. 182.
{{cite conference}}
: Cite has empty unknown parameter:|coauthors=
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suggested) (help) - ^ Staff (September 12, 2005). "Introduction: Galactic Ring Survey". Boston University. Retrieved 2007-05-10.
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(help) - ^ Imamura, Jim (August 10, 2006). "Mass of the Milky Way Galaxy". University of Oregon. Retrieved 2007-05-10.
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(help) - ^ Harris, William E. (February 2003). "Catalog of Parameters for Milky Way Globular Clusters: The Database" (text). SEDS. Retrieved 2007-05-10.
- ^ Ibata, R.; Chapman, S.; Ferguson, A. M. N.; Lewis, G.; Irwin, M.; Tanvir, N. (2005). "On the accretion origin of a vast extended stellar disk around the Andromeda galaxy". Astrophysical Journal. 634 (1): 287–313. Retrieved 2007-05-10.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ "Outer Disk Ring?". SolStation. Retrieved 2007-05-10.
- ^ Reid, Mark J. (1993). "The distance to the center of the Galaxy". Annual review of astronomy and astrophysics. 31: 345–372. Retrieved 2007-05-10.
- ^ Eisenhauer, F.; Schödel, R.; Genzel, R.; Ott, T.; Tecza, M.; Abuter, R.; Eckart, A.; Alexander, T. (2003). "A Geometric Determination of the Distance to the Galactic Center". The Astrophysical Journal. 597: L121–L124. Retrieved 2007-05-10.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Horrobin, M.; Eisenhauer, F.; Tecza, M.; Thatte, N.; Genzel, R.; Abuter, R.; Iserlohe, C.; Schreiber, J.; Schegerer, A.; Lutz, D.; Ott, T.; Schödel, R. (2004). "First results from SPIFFI. I: The Galactic Center" (PDF). Astronomische Nachrichten. 325: 120–123. Retrieved 2007-05-10.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Cite error: The named reference
eisenhaueretal2005
was invoked but never defined (see the help page). - ^ English, Jayanne (1991-07-24). "Exposing the Stuff Between the Stars". Hubble News Desk. Retrieved 2007-05-10.
{{cite news}}
: Unknown parameter|DUPLICATE_date=
ignored (help) - ^ Elert, Glenn (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". Hypertextbook. Retrieved 2007-05-10.
- ^ Wong, Janet (April 14, 2000). "Astrophysicist maps out our own galaxy's end". University of Toronto. Retrieved 2007-01-11.
- ^ Kogut, A.; Lineweaver, C.; Smoot, G. F.; Bennett, C. L.; Banday, A.; Boggess, N. W.; Cheng, E. S.; de Amici, G.; Fixsen, D. J.; Hinshaw, G.; Jackson, P. D.; Janssen, M.; Keegstra, P.; Loewenstein, K.; Lubin, P.; Mather, J. C.; Tenorio, L.; Weiss, R.; Wilkinson, D. T.; Wright, E. L. (1993). "Dipole Anisotropy in the COBE Differential Microwave Radiometers First-Year Sky Maps". Astrophysical Journal. 419: 1. Retrieved 2007-05-10.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ J. J. O'Connor, E. F. Robertson (November 2002). "Galileo Galilei". University of St Andrews. Retrieved 2007-01-08.
- ^ Evans, J. C. (November 24 1998). "Our Galaxy". George Mason University. Retrieved 2007-01-04.
{{cite web}}
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(help) - ^ Abbey, Lenny. "The Earl of Rosse and the Leviathan of Parsontown". The Compleat Amateur Astronomer. Retrieved 2007-01-04.
- ^ Heber D. Curtis (1988). "Novae in Spiral Nebulae and the Island Universe Theory". Publications of the Astronomical Society of the Pacific. 100: 6.
{{cite journal}}
: Check date values in:|year=
(help) - ^ Weaver, Harold F. "Robert Julius Trumpler". National Academy of Sciences. Retrieved 2007-01-05.
- ^ E. P. Hubble (1929). "A spiral nebula as a stellar system, Messier 31". Astrophysical JournalEngl. 69: 103–158.
{{cite journal}}
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(help) - ^ Sandage, Allan (1989). "Edwin Hubble, 1889–1953". The Journal of the Royal Astronomical Society of Canada. 83 (6). Retrieved 2007-01-08.
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(help) - ^ "Online Etymology Dictionary". Retrieved 2007-01-03.
- ^ Harutyunyan, Hayk (2003-08-29). "The Armenian name of the Milky Way". ArAS News. 6. Armenian Astronomical Society (ArAS). Retrieved 2007-01-05.
{{cite journal}}
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(help)
External links
- The Milky Way Galaxy, SEDS Messier pages
- MultiWavelength Milky Way NASA site with images and VRML models
- Composite image of the Milky Way
- Widefield Image of the Summer Milky Way
- The Milky Way Galaxy from An Atlas of the Universe
- Proposed Ring around the Milky Way
- Milky Way spiral gets an extra arm New Scientist.com
- Possible New Milky Way Spiral Arm Sky and Telescope .com
- The Milky Way spiral arms and a possible climate connection
- The 1920 Shapley - Curtis Debate on the size of the Milky Way
- Galactic center mosaic via sun-orbiting Spitzer infrared telescope
- Milky Way Plan Views
- Scientific American Magazine (January 2004 Issue) Our Growing, Breathing Galaxy
- Deriving The Shape Of The Galactic Stellar Disc (SkyNightly) Mar 17, 2006
- Digital Sky LLC, Digital Sky's Milky Way Panorama and other images
[[Category:Milky Way Galaxy| ]] [[Category:Milky Way Subgroup]] [[Category:Local Group]] [[Category:Galactic astronomy]] [[Category:Barred spiral galaxies]]
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I believe this Milky Way (Galaxy) article to be superior to the current one though the intro could be changed a little for pertinence. -Kain Nihil 04:42, 15 October 2007 (UTC)