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Topic: Spiral galaxy


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  Spiral galaxy - Wikipedia, the free encyclopedia
Spiral Galaxy M74 presents a face-on view of its spiral arms.
Spiral galaxies are so named due to the bright arms of star formation within the disk that extend—roughly logarithmically—from the bulge.
The disks of spiral galaxies tend to be surrounded by large spheroid halos of Population II stars, many of which are concentrated in globular clusters that orbit the galactic center.
en.wikipedia.org /wiki/Spiral_galaxy   (483 words)

  
 Barred spiral galaxy - Wikipedia, the free encyclopedia
A barred spiral galaxy is a spiral galaxy with a band of bright stars emerging from the center and running across the middle of the galaxy.
Spiral arms appear to emerge from the ends of the "bar" in these galaxies, whereas they appear to emerge directly from the core in ordinary spiral galaxies.
When observing a distant spiral galaxy with a rotational axis perpendicular to the line of site, or one that appears "edge-on" to the observer, the shape of the bulge can be easily observed, and therefore quickly classified as either a barred spiral or a regular spiral.
en.wikipedia.org /wiki/Barred_spiral_galaxy   (698 words)

  
 Spiral Galaxies
Galaxies come in a variety of shapes, with the shapes depending in a way not yet completely understood on the evolution of the galaxies.
The image shown adjacent left is of the spiral galaxy ESO 269-57, which is in the southern constellation Centaurus (Ref).
Spiral galaxies are rich in gas and dust, which is often visible as lanes of dust when viewed from the "top" or "bottom", and as layers of dust when viewed from the side.
csep10.phys.utk.edu /astr162/lect/galaxies/spiral.html   (544 words)

  
 World Almanac for Kids
In contrast, spiral galaxies are flattened disk systems containing not only some old stars but also large populations of young stars, much gas and dust, and molecular clouds that are the birthplace of stars.
In viewing a galaxy with a telescope, inferring its distance is impossible, for it may be a gigantic galaxy at a large distance or a smaller one closer to earth.
Galaxies are generally not isolated in space but are often members of small or moderate-size groups, which in turn form large clusters of galaxies.
www.worldalmanacforkids.com /explore/space/galaxy.html   (1441 words)

  
 Sea and Sky's Cosmic Wonders: Galaxies
Galaxies are defined as large groupings of stars, dust, and gas held together by gravity.
Spiral galaxies are represented by the letter S and are divided into four subgroups.
Barred spiral galaxies are represented by the letters SB and are arranges into three subgroups according to the openness of the arms.
www.seasky.org /cosmic/sky7a07.html   (1136 words)

  
 Spiral (and other Disk) Galaxies
spiral galaxies often have an ellipsoidally formed "bulge" which may be very luminous (as in case of the Sombrero galaxy M104) or rather inconspicuous; some spirals seem to lack this component at all.
Spiral galaxies, "normal" and barred, with conspicuous bulges (especially near their center) are classified "Sa" or "SBa", those which have prominent bulges and pronounced arms are clssified "Sb" or "SBb", and those which are dominated by the arms are "Sc" or "SBc".
Spiral galaxies in Messier's catalog: M31, M33, M51, M58, M61, M63, M64, M65, M66, M74, M77, M81, M83, M88, M90, M91, M94, M95, M96, M98, M99, M100, M101, M104, M106, M108, M109.
www.seds.org /messier/spir.html   (727 words)

  
 spiral galaxy concept from the Astronomy knowledge base   (Site not responding. Last check: 2007-11-07)
barred spiral (3 kinds, 9 facts) - (in Hubble's (1936) classification, SB: in Morgan's classification, B) A spiral galaxy whose nucleus is in the shape of a bar, at the ends of which the spiral arms start.
It is a normal spiral galaxy of class Sb, with a diameter now reckoned to be probably less than 100,000 light-years, and a strong but obscure energy source at the center (emitting infrared radiation).
Sa spiral (4 facts) (early-type spiral) - Spiral galaxy with arms tightly wound around the nucleus., In Hubble's classification, a spiral with a large nuclear bulge and closely coiled arms.
www.site.uottawa.ca:4321 /astronomy/spiralgalaxy.html   (456 words)

  
 Galaxies
Galaxies are large systems of stars and interstellar matter, typically containing several million to some trillion stars, of masses between several million and several trillion times that of our Sun, of an extension of a few thousands to several 100,000s light years, typically separated by millions of light years distance.
The most massive galaxies are giants which are a million times more massive than the lightest: Their mass range is from at most some million times that of our Sun in case of the smallest dwarfs, to several trillion solar masses in case of giants like M87 or M77.
Our Milky Way Galaxy, a spiral galaxy, is among the massive and big galaxies with at least 250 billion solar masses (there are hints that the total mass may even be as large as 750 billion to 1 trillion times that of the Sun) and a disk diameter of 100,000 light years.
www.seds.org /messier/galaxy.html   (1771 words)

  
 [No title]
Several classifications for galaxies were proposed early in their study; Hubble's classification system has proven remarkably robust, correlating well with physically interesting measurements such as stellar content, gas content, and environment despite being designed only to describe the appearance of the galaxy as seen on photographs with blue-sensitive emulsions.
Elliptical galaxies were denoted by the letter E and a number describing the galaxy's apparent shape - 0 for a completely round form, 5 for one twice as long as wide, and 7 for the apparently flattest genuine ellipticals.
Spirals are subdivided into a sequence jointly defined by the winding and prominence of the spiral arms, and the relative importance of the central bulge.
www.astr.ua.edu /goodies/data_resources/galaxies.text   (3930 words)

  
 Spiral Galaxies
Spiral galaxies are complex objects and have several components: a disk, a bulge, and a halo.
Spirals are subdivided based on the appearance of the arms and the central region.
There are not many of spirals in a cluster usually, but they are more common than ellipticals in the regions between clusters.
www.windows.ucar.edu /cgi-bin/tour.cgi?link=/the_universe/Spirals.html   (244 words)

  
 Multiwavelength Messier 33 - Spiral Galaxy(Type Sc)
Messier 33 is a small spiral galaxy within the Local Group of Galaxies, which also includes our own Milky Way Galaxy and its sister galaxy the Andromeda Galaxy (Messier 31).
Spiral galaxies typically contain large amounts of dust and gas (in atomic and molecular form), the essential ingredients for future star formation.
This effect is dramatically illustrated in the southern spiral arm tracing an arc from the galaxy center to the 4 o'clock position.
coolcosmos.ipac.caltech.edu /cosmic_classroom/multiwavelength_astronomy/multiwavelength_museum/m33.html   (897 words)

  
 2MASS Atlas Image Gallery
Imaging this galaxy in the near-IR allows us to look deeper through the extinction caused by the dust and also better map the light and mass distribution of the galaxy, since the light from spiral galaxies in the near-IR is dominated by lower-mass stars, which comprise most of a galaxy's visible mass.
It is this galaxy for which water megamasers detected in the radio orbiting very near the galaxy's center indicate the presence of a supermassive fl hole and allow an accurate kinematical measurement of the fl hole's mass.
This galaxy has been host to six historical supernovae, four of which are thought to arise from young, massive stellar progenitors, both near the nucleus and in the spiral arms, further evidence for the vigorous galactic star formation.
www.ipac.caltech.edu /2mass/gallery/images_galaxies.html   (5729 words)

  
 BBC News | SCI/TECH | Spiral galaxy winds up astronomers
The beautiful but strange galaxy NGC 4622 is confounding astronomers as it appears to break all the rules about how galaxies should rotate.
All so-called spiral galaxies seem to rotate in such a way that the spiral arms are winding up, even though their galactic arms do not become crowded together because stars move in and out of them all the time.
But the galaxy called NGC 4622 appears to be rotating in the opposite direction to that expected throwing astronomers into confusion.
news.bbc.co.uk /hi/english/sci/tech/newsid_1813000/1813648.stm   (334 words)

  
 Galaxies   (Site not responding. Last check: 2007-11-07)
For some reason Elliptical galaxies formed all their stars a long time ago, using up all their gas, so that new stars are no longer forming, there is virtually no young stellar population nor gas nor dust.
Spirals, on the other hand, have retained much of their gas and are continuing to form stars.
It has become apparent that collisions, both between galaxies themselves and between the fragments that conglomerated together to build galaxies, are important in the formation/evolution of galaxies.
cassfos02.ucsd.edu /public/tutorial/Galaxies.html   (1087 words)

  
 M-77, Spiral Galaxy
Spiral galaxy M-77 is one of the most unusual objects in Messier's catalog.
In 1943 Seyfert described this class as spiral galaxies with nuclei that showed emission lines in addition to the normal continuous spectrum.
M77 is the largest member of a small group of galaxies, which includes spiral galaxies NGCs 1055 and 1073, as well as five small irregular galaxies.
www.kopernik.org /images/archive/m77.htm   (428 words)

  
 Spiral Galaxies - Zoom Astronomy
Spiral galaxies are galaxies with a central, dense area and spiraling arms (which are often sites of star formation).
The Milky Way and the Andromeda Galaxy (M31) are two of a multitude of known spiral galaxies.
The Andromeda Galaxy (also known as M31 and NGC 224) is the closest major galaxy.
www.enchantedlearning.com /subjects/astronomy/stars/galaxy/spiral.shtml   (460 words)

  
 Andromeda Galaxy
The faint outer parts of a spiral galaxy are more susceptible to warping because they are less strongly bound by the gravitational and other forces that keep disk stars in a plane and are also more susceptible to the influence of neighboring galaxies.
Satellite galaxy M32 may be interacting to distort the disk structure of Andromeda itself, whose spiral arms of neutral hydrogen are displaced from those consisted of stars by around 4,000 light-years and so cannot be continuously followed in the area closest to its smaller neighbor.
One hypothesis is that such satellite galaxies are tiny left-overs from the break-up of a more massive galaxy which has since been swallowed by their host but still move within the orbital plane of their predecessor, as galactic mergers are believed to be a main mechanism of galactic growth.
www.solstation.com /x-objects/andromeda.htm   (2098 words)

  
 Catalog Page for PIA04224   (Site not responding. Last check: 2007-11-07)
The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise.
Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise.
NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions.
photojournal.jpl.nasa.gov /catalog/PIA04224   (381 words)

  
 M-31, Spiral Galaxy
The Great Andromeda Galaxy is the brightest and nearest of all the spiral galaxies.
Simon Marius, a contemporary of Galileo, was the first to examine it through the telescope on Dec. 15th, 1612 and described it in the preface to his Mundus Jovialis as, 'like the flame of a candle seen through horn'....
The spiral arms are mostly colored blue and most of the gas, dust, and blue stars are at the junction of the spiral arms and the nucleus.
www.kopernik.org /images/archive/m31.htm   (577 words)

  
 Spirals and Ellipses   (Site not responding. Last check: 2007-11-07)
like our own galaxy, fall into several classes depending on their shape and the relative size of the bulge: ordinary spirals are labelled either Sa-d,m while those which have developed a bar in the interior region of the spiral arms are SBa-d,m.
Spiral galaxies are characterized by the presence of gas in the disk which means star formation remains active at the present time, hence the younger population of stars.
Spirals are usually found in the low density galactic field where their delicate shape can avoid disruption by tidal forces from neighbouring galaxies.
www.damtp.cam.ac.uk /user/gr/public/gal_class.html   (221 words)

  
 BBC News | SCI/TECH | Spiral galaxy stays young at heart
Astonomers observing the spiral galaxy have realised it has a much smaller central bulge of older stars than was expected.
According to current theory, spiral galaxies begin as a giant rotating mass of gas and dust, which starts out in a roughly spherical shape before the edges flatten into a disk.
The original spherical shape remains in the form of a "halo" surrounding the galaxy and, to a lesser extent, in the central bulge.
news.bbc.co.uk /hi/english/sci/tech/newsid_1369000/1369458.stm   (484 words)

  
 New Scientist Breaking News - Spiral galaxy spins the wrong way
A galaxy in the constellation Centaurus is puzzling astronomers by spinning in the wrong direction.
In almost all spiral galaxies, the spiral arms trail behind as the galaxy rotates.
They then used earlier measurements of the speeds of gas on different sides of the galaxy to show that it is spinning clockwise, with leading spiral arms.
www.newscientist.com /article.ns?id=dn1902   (370 words)

  
 SPACE.com -- Milky Way’s Central Structure Seen with Fresh Clarity
The bar is embedded in the center of the galaxy's spiral arms and cuts across the heart of it all where a supermassive fl hole resides.
Churchwell's team also found that the bar is oriented at about a 45-degree angle relative to the main plane of the galaxy, in which the Sun and the other spiral-arm stars orbit.
Bars are fairly common in large spiral galaxies, but some do not have them.
www.space.com /scienceastronomy/050816_milky_way.html   (558 words)

  
 CBC News: Spiral galaxy spinning backwards, astronomers find   (Site not responding. Last check: 2007-11-07)
Astronomers using the Hubble Space Telescope captured the image of galaxy NGC 4622, and said its strange behaviour could be the result of a collision with another, smaller galaxy.
Most spiral galaxies spin so that their arms are trailing behind.
The image of the galaxy was taken with the Wide Field Planetary Camera on the Hubble and shows the galaxy is tilted so that it's nearly face-on to the Earth, giving us an excellent view of its arms of stars and gas.
www.cbc.ca /stories/2002/02/12/galaxy020212   (452 words)

  
 SDSC Blue Horizon Simulations
Long streams of stars thrown off in beautiful open spiral patterns are characteristic of these collisions and are known as tidal tails and bridges because of their origin in the strong mutual gravitational tides of the two interacting galaxies.
Galaxy interactions are not that common an event in the local neighbourhood (maybe one in a hundred galaxies) but the rates of merging and interaction is much larger at early times in the universe.
Galaxy merging is fundamental to building up structure in the universe and explains many of the peculiar features of young galaxies seen by the Hubble Space Telescope.
www.cita.utoronto.ca /~dubinski/tflops   (1196 words)

  
 University of Alabama News
Remarkable Hubble Space Telescope images of the disk of a distant spiral galaxy will be presented by astronomers from The University of Alabama and Bevill State Community College on Jan. 8 at the American Astronomical Society meeting in Washington, D.C. Tarsh Freeman, professor at Bevill State Community College, and Drs.
“The galaxy was presented in the text as a superb example of a spiral galaxy, with two bright spiral arms that open outward in a clockwise direction.
It has long been believed that most spiral arms seen in galaxies are trailing, meaning they wind outward opposite the direction of rotation of the disk material, something like what one sees while stirring cream into a cup of coffee.
uanews.ua.edu /jan02/galaxy010802.htm   (863 words)

  
 Multiwavelength Messier 81 - Spiral Galaxy (Type Sb)
Messier 81 is a magnificent spiral galaxy located in the northern constellation of Ursa Major (which also includes The Big Dipper), and is easily visible through binoculars or a small telescope.
Moreover, the thin HI gas in a spiral galaxy often extends well beyond the visible-light edge of the disk and arms.
The brighter of the two, directly south of the galaxy center, corresponds with a cataloged x-ray source that could be a distant quasar.
coolcosmos.ipac.caltech.edu /cosmic_classroom/multiwavelength_astronomy/multiwavelength_museum/m81.html   (923 words)

  
 New Scientist Breaking News - 'Perfect' spiral galaxy may harbour dark secret
A picture-perfect spiral galaxy may harbour two colossal fl holes instead of the usual one, new observations suggest.
Most galaxies are thought to contain a single large fl hole with a mass proportional to that of its galaxy.
Those masses, along with a previous observation of an arc of star formation near the galaxy's centre, led the team to consider the possibility that the nuclei are supermassive fl holes.
www.newscientist.com /article.ns?id=dn7405   (603 words)

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