https://nordan.daynal.org/w/index.php?title=Galaxy&feed=atom&action=historyGalaxy - Revision history2024-03-29T00:57:42ZRevision history for this page on the wikiMediaWiki 1.35.0https://nordan.daynal.org/w/index.php?title=Galaxy&diff=130538&oldid=prevMywikis: Text replacement - "http://" to "https://"2020-12-13T03:54:30Z<p>Text replacement - "http://" to "https://"</p>
<table class="diff diff-contentalign-left diff-editfont-monospace" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 03:54, 13 December 2020</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l3" >Line 3:</td>
<td colspan="2" class="diff-lineno">Line 3:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The [[word]] '''galaxy''' derives from the [[Greek]] term for our own galaxy, galaxias (γαλαξίας), or kyklos galaktikos, meaning "milky [[circle]]" for its appearance in the sky. In Greek [[mythology]], Zeus places his son born by a [[mortal]] woman, the infant Heracles, on Hera's breast while she is asleep so that the baby will drink her divine milk and will thus become [[immortal]]. Hera wakes up while breastfeeding and then realizes she is nursing an unknown baby: she pushes the baby away and a jet of her milk sprays the night sky, producing the faint band of light known as the [[Milky Way]].</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The [[word]] '''galaxy''' derives from the [[Greek]] term for our own galaxy, galaxias (γαλαξίας), or kyklos galaktikos, meaning "milky [[circle]]" for its appearance in the sky. In Greek [[mythology]], Zeus places his son born by a [[mortal]] woman, the infant Heracles, on Hera's breast while she is asleep so that the baby will drink her divine milk and will thus become [[immortal]]. Hera wakes up while breastfeeding and then realizes she is nursing an unknown baby: she pushes the baby away and a jet of her milk sprays the night sky, producing the faint band of light known as the [[Milky Way]].</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>In the astronomical [[literature]], the capitalized word 'Galaxy' is used to refer to our galaxy, the [[Milky Way]], to distinguish it from the billions of other galaxies. The term Milky Way first appeared in the [[English]] [[language]] in a [[poem]] by [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Geoffrey_Chaucer Chaucer].</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>In the astronomical [[literature]], the capitalized word 'Galaxy' is used to refer to our galaxy, the [[Milky Way]], to distinguish it from the billions of other galaxies. The term Milky Way first appeared in the [[English]] [[language]] in a [[poem]] by [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Geoffrey_Chaucer Chaucer].</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:: "See yonder, lo, the Galaxyë</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:: "See yonder, lo, the Galaxyë</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:: Which men clepeth the Milky Wey,</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:: Which men clepeth the Milky Wey,</div></td></tr>
<tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l9" >Line 9:</td>
<td colspan="2" class="diff-lineno">Line 9:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:::—Geoffrey Chaucer. The House of Fame, c. 1380.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>:::—Geoffrey Chaucer. The House of Fame, c. 1380.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>When [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/William_Herschel William Herschel] constructed his catalog of deep sky objects, he used the name [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Spiral_nebula spiral nebula] for certain objects such as M31. These would later be recognized as immense conglomerations of [[stars]], when the true distance to these objects began to be appreciated, and they would be termed island universes. However, the [[word]] [[Universe]] was understood to mean the entirety of [[existence]], so this expression fell into disuse and the objects instead became known as galaxies.</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>When [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/William_Herschel William Herschel] constructed his catalog of deep sky objects, he used the name [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Spiral_nebula spiral nebula] for certain objects such as M31. These would later be recognized as immense conglomerations of [[stars]], when the true distance to these objects began to be appreciated, and they would be termed island universes. However, the [[word]] [[Universe]] was understood to mean the entirety of [[existence]], so this expression fell into disuse and the objects instead became known as galaxies.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Description==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Description==</div></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Dark_matter dark matter]. The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Dark_matter dark matter]. The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy], which has an ellipse-shaped light profile. [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy], which has an ellipse-shaped light profile. [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>There are probably more than 100 billion (10¹¹) galaxies in the [<del class="diffchange diffchange-inline">http</del>://en.wikipedia.org/wiki/Observable_universe observable universe].[7] Most galaxies are 1,000 to 100,000[4] parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs). Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>There are probably more than 100 billion (10¹¹) galaxies in the [<ins class="diffchange diffchange-inline">https</ins>://en.wikipedia.org/wiki/Observable_universe observable universe].[7] Most galaxies are 1,000 to 100,000[4] parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs). Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.[10]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.[10]</div></td></tr>
</table>Mywikishttps://nordan.daynal.org/w/index.php?title=Galaxy&diff=52200&oldid=prevRdavis at 21:18, 4 March 20102010-03-04T21:18:02Z<p></p>
<table class="diff diff-contentalign-left diff-editfont-monospace" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 21:18, 4 March 2010</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg]][[File:Milky_way_galaxy.jpg|right|frame]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg]][[File:Milky_way_galaxy.jpg|right|frame]]</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">==Etymology==</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The [[word]] '''galaxy''' derives from the [[Greek]] term for our own galaxy, galaxias (γαλαξίας), or kyklos galaktikos, meaning "milky [[circle]]" for its appearance in the sky. In Greek [[mythology]], Zeus places his son born by a [[mortal]] woman, the infant Heracles, on Hera's breast while she is asleep so that the baby will drink her divine milk and will thus become [[immortal]]. Hera wakes up while breastfeeding and then realizes she is nursing an unknown baby: she pushes the baby away and a jet of her milk sprays the night sky, producing the faint band of light known as the [[Milky Way]].</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">In the astronomical [[literature]], the capitalized word 'Galaxy' is used to refer to our galaxy, the [[Milky Way]], to distinguish it from the billions of other galaxies. The term Milky Way first appeared in the [[English]] [[language]] in a [[poem]] by [http://en.wikipedia.org/wiki/Geoffrey_Chaucer Chaucer].</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">:: "See yonder, lo, the Galaxyë</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">:: Which men clepeth the Milky Wey,</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">::For hit is whyt."</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">:::—Geoffrey Chaucer. The House of Fame, c. 1380.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">When [http://en.wikipedia.org/wiki/William_Herschel William Herschel] constructed his catalog of deep sky objects, he used the name [http://en.wikipedia.org/wiki/Spiral_nebula spiral nebula] for certain objects such as M31. These would later be recognized as immense conglomerations of [[stars]], when the true distance to these objects began to be appreciated, and they would be termed island universes. However, the [[word]] [[Universe]] was understood to mean the entirety of [[existence]], so this expression fell into disuse and the objects instead became known as galaxies.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">==Description==</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter]. The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter]. The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
</table>Rdavishttps://nordan.daynal.org/w/index.php?title=Galaxy&diff=52198&oldid=prevRdavis at 21:12, 4 March 20102010-03-04T21:12:37Z<p></p>
<table class="diff diff-contentalign-left diff-editfont-monospace" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 21:12, 4 March 2010</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg]][[File:Milky_way_galaxy.jpg|right|frame]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg]][[File:Milky_way_galaxy.jpg|right|frame]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter].<del class="diffchange diffchange-inline">[1][2] </del>The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million<del class="diffchange diffchange-inline">[3] </del>(107) stars up to giants with one trillion<del class="diffchange diffchange-inline">[4] </del>(10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravity|gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter]. The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [http://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy],<del class="diffchange diffchange-inline">[5] </del>which has an ellipse-shaped light profile. [http://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [http://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [http://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [http://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].[<del class="diffchange diffchange-inline">6</del>]</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [http://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy], which has an ellipse-shaped light profile. [http://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [http://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [http://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [http://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins class="diffchange diffchange-inline">There are probably more than 100 billion (10¹¹) galaxies in the </ins>[<ins class="diffchange diffchange-inline">http://en.wikipedia.org/wiki/Observable_universe observable universe].[7] Most galaxies are 1,000 to 100,000[4</ins>] <ins class="diffchange diffchange-inline">parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs). Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">There are probably more than 100 billion (10¹¹) galaxies in the [http://en.wikipedia.org/wiki/Observable_universe observable universe].[7] Most galaxies are 1,000 to 100,000[4] parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs).[8] Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.[9]</del></div></td><td colspan="2"> </td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.[10]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.[10]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td></tr>
</table>Rdavishttps://nordan.daynal.org/w/index.php?title=Galaxy&diff=38921&oldid=prevRdavis at 06:23, 26 October 20092009-10-26T06:23:28Z<p></p>
<table class="diff diff-contentalign-left diff-editfont-monospace" data-mw="interface">
<col class="diff-marker" />
<col class="diff-content" />
<col class="diff-marker" />
<col class="diff-content" />
<tr class="diff-title" lang="en">
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 06:23, 26 October 2009</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1" >Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg]]</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[File:lighterstill.jpg<ins class="diffchange diffchange-inline">]][[File:Milky_way_galaxy.jpg|right|frame</ins>]]</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'>−</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter].[1][2] The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million[3] (107) stars up to giants with one trillion[4] (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''galaxy''' is a massive, [[<ins class="diffchange diffchange-inline">gravity|</ins>gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter].[1][2] The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million[3] (107) stars up to giants with one trillion[4] (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [http://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy],[5] which has an ellipse-shaped light profile. [http://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [http://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [http://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [http://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].[6]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [http://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy],[5] which has an ellipse-shaped light profile. [http://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [http://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [http://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [http://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].[6]</div></td></tr>
</table>Rdavishttps://nordan.daynal.org/w/index.php?title=Galaxy&diff=38919&oldid=prevRdavis: Created page with 'File:lighterstill.jpg A '''galaxy''' is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, ...'2009-10-26T06:21:09Z<p>Created page with '<a href="/wiki/File:Lighterstill.jpg" title="File:Lighterstill.jpg">File:lighterstill.jpg</a> A '''galaxy''' is a massive, <a href="/wiki/Gravitational" class="mw-redirect" title="Gravitational">gravitationally</a> bound <a href="/wiki/System" class="mw-redirect" title="System">system</a> that consists of stars and stellar remnants, an interstellar medium of gas and dust, ...'</p>
<p><b>New page</b></p><div>[[File:lighterstill.jpg]]<br />
<br />
A '''galaxy''' is a massive, [[gravitational]]ly bound [[system]] that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed [http://en.wikipedia.org/wiki/Dark_matter dark matter].[1][2] The name is from the Greek root galaxias [γαλαξίας], meaning "milky," a reference to the [http://en.wikipedia.org/wiki/Milky_Way Milky Way] galaxy. Typical galaxies range from dwarfs with as few as ten million[3] (107) stars up to giants with one trillion[4] (10¹²) stars, all orbiting the galaxy's center of [[mass]]. Galaxies can also contain many multiple star systems, star clusters, and various interstellar clouds. The [[Sun]] is one of the stars in the Milky Way galaxy; the Solar System includes the Earth and all the other objects that orbit the Sun.<br />
<br />
Historically, galaxies have been categorized according to their apparent shape (usually referred to as their visual [[morphology]]). A common form is the [http://en.wikipedia.org/wiki/Elliptical_galaxy elliptical galaxy],[5] which has an ellipse-shaped light profile. [http://en.wikipedia.org/wiki/Spiral_galaxy Spiral galaxies] are disk-shaped assemblages with dusty, curving arms. Galaxies with irregular or unusual shapes are known as [http://en.wikipedia.org/wiki/Peculiar_galaxy peculiar galaxies], and typically result from disruption by the gravitational pull of neighboring galaxies. Such interactions between nearby galaxies, which may ultimately result in galaxies merging, may induce episodes of significantly increased star formation, producing what is called a [http://en.wikipedia.org/wiki/Starburst_galaxy starburst galaxy]. Small galaxies that lack a coherent [[structure]] could also be referred to as [http://en.wikipedia.org/wiki/Irregular_galaxy irregular galaxies].[6]<br />
<br />
There are probably more than 100 billion (10¹¹) galaxies in the [http://en.wikipedia.org/wiki/Observable_universe observable universe].[7] Most galaxies are 1,000 to 100,000[4] parsecs in diameter and are usually separated by distances on the order of millions of parsecs (or megaparsecs).[8] Intergalactic space (the space between galaxies) is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations called clusters, which, in turn, can form larger groups called superclusters. These larger structures are generally arranged into sheets and filaments, which surround immense voids in the universe.[9]<br />
Although it is not yet well understood, dark matter appears to account for around 90% of the mass of most galaxies. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. They are proposed to be the primary cause of active galactic nuclei found at the core of some galaxies. The Milky Way galaxy appears to harbor at least one such object within its nucleus.[10]<br />
==References==<br />
# Sparke, L. S.; Gallagher III, J. S. (2000). Galaxies in the Universe: An Introduction. Cambridge: Cambridge University Press. ISBN 0-521-59704-4.<br />
# Hupp, E.; Roy, S.; Watzke, M. (2006-08-12). "NASA Finds Direct Proof of Dark Matter". NASA. Retrieved 2007-04-17.<br />
# "Unveiling the Secret of a Virgo Dwarf Galaxy". ESO. 2000-05-03. Retrieved 2007-01-03.<br />
# "Hubble's Largest Galaxy Portrait Offers a New High-Definition View". NASA. 2006-02-28. Retrieved 2007-01-03.<br />
# Hoover, Aaron (2003-06-16). "UF Astronomers: Universe Slightly Simpler Than Expected". Hubble News Desk. Retrieved 2007-02-05.<br />
# Jarrett, T.H.. "Near-Infrared Galaxy Morphology Atlas". California Institute of Technology. Retrieved 2007-01-09.<br />
# Mackie, Glen (2002-02-01). "To see the Universe in a Grain of Taranaki Sand". Swinburne University. Retrieved 2006-12-20.<br />
# Gilman, D.. "The Galaxies: Islands of Stars". NASA WMAP. Retrieved 2006-08-10.<br />
^ "Galaxy Clusters and Large-Scale Structure". University of Cambridge. Retrieved 2007-01-15.<br />
# Finley, D.; Aguilar, D. (2005-11-02). "Astronomers Get Closest Look Yet At Milky Way's Mysterious Core". National Radio Astronomy Observatory. Retrieved 2006-08-10.<br />
# Koneãn˘, Lubomír. "Emblematics, Agriculture, and Mythography in The Origin of the Milky Way" (PDF). Academy of Sciences of the Czech Republic. Retrieved 2007-01-05.<br />
# "Online Etymology Dictionary". Retrieved 2007-01-03.<br />
<br />
[[Category: Astronomy]]</div>Rdavis