|
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Amazing Andromeda Galaxy
| Title |
Amazing Andromeda Galaxy |
| Description |
The many "personalities" of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope. The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's "fiery" nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively "cool" side, which includes embryonic stars hidden in their dusty cocoons. Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars. Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them. Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist. Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across. This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red). |
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Andromeda Makes a Splash
| Title |
Andromeda Makes a Splash |
| Description |
This infrared composite image from NASA's Spitzer Space Telescope shows the Andromeda galaxy, a neighbor to our Milky Way galaxy. The main image (top) highlights the contrast between the galaxy's choppy waves of dust (red) and smooth sea of older stars (blue). The panels below the main image show the galaxy's older stars (left) and dust (right) separately. Spiral galaxies tend to form new stars in their dusty, clumpy arms, while their cores are populated by older stars. The Spitzer view also shows Andromeda's dust lanes twisting all the way into the center of the galaxy, a region that is crammed full of stars. In visible-light pictures, this central region tends to be dominated by starlight. Astronomers used these new images to measure the total infrared brightness of Andromeda. Because the amount of infrared light given off by stars depends on their masses, the brightness measurements provided a novel method for "weighing" the Andromeda galaxy. According to this method, the mass of the stars in Andromeda is about110 billion times that of the sun, which is in agreement with past calculations. This means the galaxy contains about one trillion stars (because most stars are actually less massive than the sun). For comparison, the Milky Way is estimated to hold about 400 billion stars. A small, companion galaxy called NGC 205 is visible above Andromeda. Another companion galaxy called M32 can also been seen below the galaxy. The Andromeda galaxy, also known affectionately by astronomers as Messier 31, is located 2.5 million light-years away in the constellation Andromeda. It is the closest major galaxy to the Milky Way, making it the ideal specimen for carefully examining the nature of galaxies. On a clear, dark night, the galaxy can be spotted with the naked eye as a fuzzy blob. Andromeda's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, the Milky Way is about 100,000 light-years across. When viewed from Earth, Andromeda occupies a portion of the sky equivalent to seven full moons. Because this galaxy is so large, the infrared images had to be stitched together out of about 3,000 separate Spitzer exposures. The light detected by Spitzer's infrared array camera at 3.6 and 4.5 microns is sensitive mostly to starlight and is shown in blue and green, respectively. The 8-micron light shows warm dust and is shown in red. The contribution from starlight has been subtracted from the 8-micron image to better highlight the dust structures. |
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Andromeda Makes a Splash
| Title |
Andromeda Makes a Splash |
| Description |
This infrared composite image from NASA's Spitzer Space Telescope shows the Andromeda galaxy, a neighbor to our Milky Way galaxy. The main image (top) highlights the contrast between the galaxy's choppy waves of dust (red) and smooth sea of older stars (blue). The panels below the main image show the galaxy's older stars (left) and dust (right) separately. Spiral galaxies tend to form new stars in their dusty, clumpy arms, while their cores are populated by older stars. The Spitzer view also shows Andromeda's dust lanes twisting all the way into the center of the galaxy, a region that is crammed full of stars. In visible-light pictures, this central region tends to be dominated by starlight. Astronomers used these new images to measure the total infrared brightness of Andromeda. Because the amount of infrared light given off by stars depends on their masses, the brightness measurements provided a novel method for "weighing" the Andromeda galaxy. According to this method, the mass of the stars in Andromeda is about110 billion times that of the sun, which is in agreement with past calculations. This means the galaxy contains about one trillion stars (because most stars are actually less massive than the sun). For comparison, the Milky Way is estimated to hold about 400 billion stars. A small, companion galaxy called NGC 205 is visible above Andromeda. Another companion galaxy called M32 can also been seen below the galaxy. The Andromeda galaxy, also known affectionately by astronomers as Messier 31, is located 2.5 million light-years away in the constellation Andromeda. It is the closest major galaxy to the Milky Way, making it the ideal specimen for carefully examining the nature of galaxies. On a clear, dark night, the galaxy can be spotted with the naked eye as a fuzzy blob. Andromeda's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, the Milky Way is about 100,000 light-years across. When viewed from Earth, Andromeda occupies a portion of the sky equivalent to seven full moons. Because this galaxy is so large, the infrared images had to be stitched together out of about 3,000 separate Spitzer exposures. The light detected by Spitzer's infrared array camera at 3.6 and 4.5 microns is sensitive mostly to starlight and is shown in blue and green, respectively. The 8-micron light shows warm dust and is shown in red. The contribution from starlight has been subtracted from the 8-micron image to better highlight the dust structures. |
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Andromeda Makes a Splash
| Title |
Andromeda Makes a Splash |
| Description |
This infrared composite image from NASA's Spitzer Space Telescope shows the Andromeda galaxy, a neighbor to our Milky Way galaxy. The main image (top) highlights the contrast between the galaxy's choppy waves of dust (red) and smooth sea of older stars (blue). The panels below the main image show the galaxy's older stars (left) and dust (right) separately. Spiral galaxies tend to form new stars in their dusty, clumpy arms, while their cores are populated by older stars. The Spitzer view also shows Andromeda's dust lanes twisting all the way into the center of the galaxy, a region that is crammed full of stars. In visible-light pictures, this central region tends to be dominated by starlight. Astronomers used these new images to measure the total infrared brightness of Andromeda. Because the amount of infrared light given off by stars depends on their masses, the brightness measurements provided a novel method for "weighing" the Andromeda galaxy. According to this method, the mass of the stars in Andromeda is about110 billion times that of the sun, which is in agreement with past calculations. This means the galaxy contains about one trillion stars (because most stars are actually less massive than the sun). For comparison, the Milky Way is estimated to hold about 400 billion stars. A small, companion galaxy called NGC 205 is visible above Andromeda. Another companion galaxy called M32 can also been seen below the galaxy. The Andromeda galaxy, also known affectionately by astronomers as Messier 31, is located 2.5 million light-years away in the constellation Andromeda. It is the closest major galaxy to the Milky Way, making it the ideal specimen for carefully examining the nature of galaxies. On a clear, dark night, the galaxy can be spotted with the naked eye as a fuzzy blob. Andromeda's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, the Milky Way is about 100,000 light-years across. When viewed from Earth, Andromeda occupies a portion of the sky equivalent to seven full moons. Because this galaxy is so large, the infrared images had to be stitched together out of about 3,000 separate Spitzer exposures. The light detected by Spitzer's infrared array camera at 3.6 and 4.5 microns is sensitive mostly to starlight and is shown in blue and green, respectively. The 8-micron light shows warm dust and is shown in red. The contribution from starlight has been subtracted from the 8-micron image to better highlight the dust structures. |
|
Andromeda Makes a Splash
| Title |
Andromeda Makes a Splash |
| Description |
This infrared composite image from NASA's Spitzer Space Telescope shows the Andromeda galaxy, a neighbor to our Milky Way galaxy. The main image (top) highlights the contrast between the galaxy's choppy waves of dust (red) and smooth sea of older stars (blue). The panels below the main image show the galaxy's older stars (left) and dust (right) separately. Spiral galaxies tend to form new stars in their dusty, clumpy arms, while their cores are populated by older stars. The Spitzer view also shows Andromeda's dust lanes twisting all the way into the center of the galaxy, a region that is crammed full of stars. In visible-light pictures, this central region tends to be dominated by starlight. Astronomers used these new images to measure the total infrared brightness of Andromeda. Because the amount of infrared light given off by stars depends on their masses, the brightness measurements provided a novel method for "weighing" the Andromeda galaxy. According to this method, the mass of the stars in Andromeda is about110 billion times that of the sun, which is in agreement with past calculations. This means the galaxy contains about one trillion stars (because most stars are actually less massive than the sun). For comparison, the Milky Way is estimated to hold about 400 billion stars. A small, companion galaxy called NGC 205 is visible above Andromeda. Another companion galaxy called M32 can also been seen below the galaxy. The Andromeda galaxy, also known affectionately by astronomers as Messier 31, is located 2.5 million light-years away in the constellation Andromeda. It is the closest major galaxy to the Milky Way, making it the ideal specimen for carefully examining the nature of galaxies. On a clear, dark night, the galaxy can be spotted with the naked eye as a fuzzy blob. Andromeda's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, the Milky Way is about 100,000 light-years across. When viewed from Earth, Andromeda occupies a portion of the sky equivalent to seven full moons. Because this galaxy is so large, the infrared images had to be stitched together out of about 3,000 separate Spitzer exposures. The light detected by Spitzer's infrared array camera at 3.6 and 4.5 microns is sensitive mostly to starlight and is shown in blue and green, respectively. The 8-micron light shows warm dust and is shown in red. The contribution from starlight has been subtracted from the 8-micron image to better highlight the dust structures. |
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Chandra X-ray & Spitzer Infr
…
| Name |
Chandra X-ray & Spitzer Infrared Image of Andromeda Galaxy (M31) |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
|
Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
|
Hubble Discovers Black Holes
…
| Title |
Hubble Discovers Black Holes in Unexpected Places |
| General Information |
What is a Space Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a Space Science Update (SSU), broadcast on NASA television. The SSU includes a question and answer session with members of the media. Back to top [ #top ] |
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Hubble Space Telescope Finds
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| Title |
Hubble Space Telescope Finds a Double Nucleus in the Andromeda Galaxy |
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Hubble Space Telescope Image
…
| Name of Image |
Hubble Space Telescope Image of NGC 4676, "The Mice |
| Date of Image |
2002-04-07 |
| Full Description |
The Advanced Camera for Surveys (ACS), the newest camera on the Hubble Space Telescope, has captured a spectacular pair of galaxies. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed "The Mice" because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy. In the galaxy at left, the bright blue patch is resolved into a vigorous cascade of clusters and associations of young, hot blue stars, whose formation has been triggered by the tidal forces of the gravitational interaction. The clumps of young stars in the long, straight tidal tail (upper right) are separated by fainter regions of material. These dim regions suggest that the clumps of stars have formed from the gravitational collapse of the gas and dust that once occupied those areas. Some of the clumps have luminous masses comparable to dwarf galaxies that orbit the halo of our own Milky Way Galaxy. Computer simulations by astronomers show that we are seeing two near identical spiral galaxies approximately 160 million years after their closest encounter. The simulations also show that the pair will eventually merge, forming a large, nearly spherical galaxy (known as an elliptical galaxy). The Mice presage what may happen to our own Milky Way several billion years from now when it collides with our nearest large neighbor, the Andromeda Galaxy (M31). This picture is assembled from three sets of images taken on April 7, 2002, in blue, orange, and near-infrared filters. Credit: NASA, H. Fort (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA. |
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Galaxy Dwingeloo 1 Emerges
| Title |
Galaxy Dwingeloo 1 Emerges |
| Explanation |
Sometimes you can't see the forest for the trees. But if you look closely at the center of the above photograph, you will see a whole spiral galaxy behind the field of stars. Named Dwingeloo 1, this nearby galaxy was only discovered recently (1994) because much of its light was obscured by dust, gas and bright stars of our own Milky Way Galaxy. In fact, all the individually discernible stars in the above photograph are in our Galaxy. Dwingeloo 1 turned out to be a large galaxy located only five times as distant as the closest major galaxy - M31. |
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Andromeda Island Universe
| Title |
Andromeda Island Universe |
| Explanation |
How far can you see? The most distant object easily visible to the unaided eye is M31 [ http://www.seds.org/messier/xtra/history/m-m31_42.html ], the great Andromeda Galaxy [ http://www.seds.org/messier/m/m031.html ] some two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda [ http://www.astronomical.org/constellations/and.html ]. But a bright yellow nucleus, dark winding dustlanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital [ http://www.geocities.com/CapeCanaveral/Hall/6432/ homepage.html ] mosaic of the nearby island universe. While even casual skygazers [ http://badastronomy.com/bitesize/galaxies.html ] are now inspired by the knowledge that there are many [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ] distant galaxies like M31, astronomers seriously debated [ http://adsbit.harvard.edu/cgi-bin/ nph-iarticle_query?1995PASP%2E%2E107%2E1133T ] this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate20.html ] debate [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] of 1920, which was later resolved by observations [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] of M31 in favor of Andromeda, island universe [ http://www.astr.ua.edu/goodies/data_resources/galaxies.text ]. |
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M31: The Andromeda Galaxy
| Title |
M31: The Andromeda Galaxy |
| Explanation |
Andromeda is the nearest major galaxy [ http://www.seds.org/messier/galaxy.html] to our own Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. Our Galaxy is thought to look much like Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap020518.html ]. Together these two galaxies dominate the Local Group [ http://www.seds.org/messier/more/local.html ] of galaxies. The diffuse light from Andromeda [ http://www.seds.org/messier/m/m031.html ] is caused by the hundreds of billions of stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] that compose it. The several distinct stars that surround Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap010917.html ]'s image are actually stars in our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000518.html ] that are well in front of the background object. Andromeda [ http://www.noao.edu/image_gallery/html/im0424.html ] is frequently referred to as M31 since it is the 31st object [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ] on Messier [ http://www.seds.org/messier/xtra/history/biograph.html ]'s list of diffuse sky objects. M31 [ http://antwrp.gsfc.nasa.gov/apod/ap020412.html ] is so distant it takes about two million years for light to reach us from there. Although visible without aid, the above image [ http://www.robgendlerastropics.com/M31Page.html ] of M31 is a digital mosaic of 20 frames taken with a small telescope. Much about M31 remains unknown [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1995ApJ...444..157A ], including how the center acquired two nuclei [ http://antwrp.gsfc.nasa.gov/apod/ap961011.html ]. |
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Dwarf Elliptical Galaxy NGC
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| Title |
Dwarf Elliptical Galaxy NGC 205 in the Local Group |
| Explanation |
Our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] is not alone. It is part of a gathering of about 25 galaxies known as the Local Group [ http://www.seds.org/messier/more/local.html ]. Members include the Great Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991114.html ] (M31), M32 [ http://antwrp.gsfc.nasa.gov/apod/ap991103.html ], M33 [ http://antwrp.gsfc.nasa.gov/apod/ap980721.html ], the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000222.html ], the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000430.html ], Dwingeloo 1 [ http://antwrp.gsfc.nasa.gov/apod/ap000109.html ], several small irregular galaxies [ http://www.seds.org/messier/irre.html ], and many dwarf elliptical [ http://nedwww.ipac.caltech.edu/level5/Ferguson/frames.html ] and dwarf spheroidal galaxies [ http://www.astro.uu.se/~ns/review.html ]. Pictured [ http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw061299.html ] on the lower left is one of the many dwarf ellipticals [ http://www.astro.psu.edu/users/pdurrell/dE.html ]: NGC 205 [ http://www.seds.org/messier/m/m110.html ]. Like M32 [ http://www.seds.org/messier/m/m032.html ], NGC 205 [ http://nedwww.ipac.caltech.edu/level5/Hodge/Hodge5_5.html ] is a companion to the large M31, and can sometimes be seen to the south of M31 [ http://www.seds.org/messier/m/m031.html ]'s center in photographs. The above image [ http://www.cfht.hawaii.edu/Science/Astros/Imageofweek/ciw061299.html ] shows NGC 205 to be unusual [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...499..209W ] for an elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/elliptical_galaxies.html ] in that it contains at least two dust clouds [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] (at 1 and 4 o'clock - they are visible but hard to spot) and signs of recent star formation [ http://antwrp.gsfc.nasa.gov/apod/stellar_nurseries.html ]. This galaxy is sometimes known as M110, although it was actually not part of Messier [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ]'s original catalog [ http://antwrp.gsfc.nasa.gov/apod/messier.html ]. |
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Bright Spiral Galaxy M81 fro
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| Title |
Bright Spiral Galaxy M81 from Hubble |
| Explanation |
The Hubble Space Telescope has resolved individual stars in a spectacular new image of nearby spiral galaxy M81. The feat is similar to Edwin Hubble [ http://en.wikipedia.org/wiki/Edwin_Hubble ]'s historic images with the Mt. Wilson 100-inch Hooker Telescope [ http://en.wikipedia.org/wiki/Mount_Wilson_Observatory#100_inch_.282.5_m.29_Hooker_telescope ] in the 1920s that resolved stars [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] in neighboring galaxy M31 [ http://antwrp.gsfc.nasa.gov/apod/ap061126.html ]. Edwin Hubble [ http://antwrp.gsfc.nasa.gov/apod/ap960217.html ] was able to use individual Cepheid variable stars [ http://antwrp.gsfc.nasa.gov/apod/ap960110.html ] to show that M31 was not nearby swirling gas but rather an entire galaxy [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate20.html ] like our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ]. This above image [ http://www.cfa.harvard.edu/press/2007/pr200716_images.html ] in visible light [ http://science.hq.nasa.gov/kids/imagers/ems/visible.html ] taken by the Hubble Space Telescope [ http://www.stsci.edu/hst/HST_overview/ ] is being used in conjunction with images [ http://antwrp.gsfc.nasa.gov/apod/ap070515.html ] being taken in ultraviolet [ http://science.hq.nasa.gov/kids/imagers/ems/uv.html ] by Galex [ http://en.wikipedia.org/wiki/GALEX ], infrared by Spitzer [ http://en.wikipedia.org/wiki/Spitzer_Space_Telescope ], and X-rays [ http://science.hq.nasa.gov/kids/imagers/ems/xrays.html ] with Chandra [ http://en.wikipedia.org/wiki/Chandra_X-ray_Observatory ] to study how stars have formed and died over the history M81. Light takes about 12 million years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] to reach us from M81. M81 [ http://seds.org/messier/m/m081.html ] is visible with binoculars toward the constellation of the Great Bear (Ursa Major [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=83 ]). |
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Southwest Andromeda
| Title |
Southwest Andromeda |
| Explanation |
This new image composite [ http://www.subaru.naoj.org/Latestnews/200109/M31/index.html ] of the southwest region of M31 [ http://antwrp.gsfc.nasa.gov/apod/ap991114.html ] from the Subaru Telescope [ http://www.subaru.naoj.org/Introduction/outline.html ] shows many stars, nebulae, and star clusters never before resolved. An older population of stars near Andromeda's center [ http://antwrp.gsfc.nasa.gov/apod/ap961011.html ] causes the yellow hue visible on the upper right. Young blue stars stand out in the spiral arms [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] on the lower left. Red emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], blue open clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars, and sweeping lanes of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] punctuate the swirling giant. Andromeda [ http://www.seds.org/messier/m/m031.html ], at about 2.5 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant, and our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] are the largest galaxies [ http://www.seds.org/messier/galaxy.html ] in the Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. Understanding M31 [ http://antwrp.gsfc.nasa.gov/apod/ap000908.html ] helps astronomers to understand our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000130.html ], since the two are so similar. |
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Elements of Nearby Spiral M3
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| Title |
Elements of Nearby Spiral M33 |
| Explanation |
Spiral galaxy [ http://www.seds.org/messier/spir.html ] M33 is a mid-sized member of our Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap980721.html ] is also called the Triangulum Galaxy [ http://www.seds.org/messier/m/m033.html ] for the constellation [ http://www.astronomical.org/constellations/tri.html ] in which it resides. About four times smaller (in radius) than our Milky Way Galaxy [ http://www.star.le.ac.uk/edu/mway/ ] and the Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991114.html ] (M31), it is much larger than the many of the local dwarf spheroidal [ http://antwrp.gsfc.nasa.gov/apod/ap991003.html ] galaxies. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960708.html ]'s proximity to M31 [ http://antwrp.gsfc.nasa.gov/apod/ap010917.html ] causes it to be thought by some to be a satellite galaxy of this more massive galaxy. M33 [ http://sirtf.caltech.edu/Education/Messier/m33.html ]'s proximity to our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] causes it to appear more than twice the angular size of the Full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ], and be visible with a good pair of binoculars. The above high-resolution image [ http://www.lowell.edu/users/massey/lgsurvey.html ] highlights light emitted by hydrogen [ http://periodic.lanl.gov/elements/1.html ] in red and oxygen [ http://periodic.lanl.gov/elements/8.html ] in blue. It was taken to help separate stars from emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], and therefore help study [ http://www.aas.org/publications/baas/v32n4/aas197/743.htm ] how galaxies form stars. |
|
Andromeda Island Universe
| Title |
Andromeda Island Universe |
| Explanation |
The most distant object easily visible to the unaided eye is M31 [ http://www.seds.org/messier/xtra/history/m-m31_42.html ], the great Andromeda Galaxy [ http://www.seds.org/messier/m/m031.html ] some two and a half million light-years away. But without a telescope, even this immense spiral galaxy - spanning over [ http://antwrp.gsfc.nasa.gov/apod/ap061228.html ] 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda [ http://www.hawastsoc.org/deepsky/and/index.html ]. In contrast, a bright yellow nucleus, dark winding dust lanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital mosaic [ http://astrophoto.com/M31.htm ]. While even casual skygazers [ http://badastronomy.com/bitesize/galaxies.html ] are now inspired by the knowledge that there are many [ http://antwrp.gsfc.nasa.gov/apod/ap070208.html ] distant galaxies like M31, astronomers seriously debated [ http://adsbit.harvard.edu/cgi-bin/ nph-iarticle_query?1995PASP%2E%2E107%2E1133T ] this fundamental concept less than 90 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate20.html ] debate [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] of 1920, which was later resolved by observations [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] of M31 in favor of Andromeda, island universe [ http://www.astr.ua.edu/goodies/data_resources/galaxies.text ]. |
|
Galaxy Dwingeloo 1 Emerges
| Title |
Galaxy Dwingeloo 1 Emerges |
| Explanation |
If you look closely at the center of the above photograph, you will see a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950912.html ] behind the field of stars. Named Dwingeloo 1 [ http://planxty.stsci.edu:1024:/dogs/dogsrgb2cap.html ], this nearby galaxy was only discovered recently (1994) [ http://planxty.stsci.edu:1024:/dogs/dogs.html ] because much of its light was obscured by dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ], gas and bright stars of our own Milky Way galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ]. In fact, all the individually discernible stars in the above photograph are in our Galaxy. Dwingeloo 1 turned out to be a large galaxy located only five times as distant as the closest major galaxy - M31 [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ]. |
|
Andromeda Island Universe
| Title |
Andromeda Island Universe |
| Explanation |
How far can you see? The most distant object easily visible to the unaided eye is M31 [ http://www.seds.org/messier/xtra/history/m-m31_42.html ], the great Andromeda Galaxy [ http://www.seds.org/messier/m/m031.html ] some two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda [ http://www.astronomical.org/constellations/and.html ]. But a bright yellow nucleus, dark winding dust lanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital [ http://www.robgendlerastropics.com/index.html ] mosaic of the nearby island universe. While even casual skygazers [ http://badastronomy.com/bitesize/galaxies.html ] are now inspired by the knowledge that there are many [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ] distant galaxies like M31, astronomers seriously debated [ http://adsbit.harvard.edu/cgi-bin/ nph-iarticle_query?1995PASP%2E%2E107%2E1133T ] this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate20.html ] debate [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] of 1920, which was later resolved by observations [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] of M31 in favor of Andromeda, island universe [ http://www.astr.ua.edu/goodies/data_resources/galaxies.text ]. |
|
The X-ray Sources of M31
| Title |
The X-ray Sources of M31 |
| Explanation |
Just like our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ], the nearest major galaxy M31 [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ] has many star systems spewing high energy radiation [ http://www.astro.washington.edu/strobel/lightnotes/lightnotes.html ]. High energy X-radiation [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] is visible to certain satellites in Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ] orbit such as ROSAT [ http://heasarc.gsfc.nasa.gov/Images/pretty_pictures_rosat.html ] - which took the above picture. The X-ray sources in M31 occur in globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap951019.html ], the spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap950912.html ], and near the galaxy's center. Probably most of these sources are accretion disk binary star systems [ http://antwrp.gsfc.nasa.gov/apod/ap951226.html ]. M31 has more X-ray sources near its center than our Galaxy, and the reason for this is currently unknown. |
|
Local Group Galaxy NGC 205
| Title |
Local Group Galaxy NGC 205 |
| Explanation |
The Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ] is not alone. It is part of a gathering of about 25 galaxies known as the Local Group [ http://www.csc.fi/jpr/galaxy/lbang.html ]. Members include the Great Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ] (M31), M32 [ http://antwrp.gsfc.nasa.gov/apod/ap960106.html ], M33 [ http://seds.lpl.arizona.edu/messier/m/m033.html ], the Large Magellanic Clouds [ http://antwrp.gsfc.nasa.gov/apod/ap950918.html ], the Small Magellanic Clouds [ http://antwrp.gsfc.nasa.gov/apod/ap950919.html ], Dwingeloo 1 [ http://antwrp.gsfc.nasa.gov/apod/ap951017.html ], several small irregular galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap950728.html ], and many dwarf elliptical galaxies [ http://www.physics.mcmaster.ca/Grads/PRD2.html ]. Pictured is one of the many dwarf ellipticals: NGC 205. Like M32, NGC 205 is a companion to the large M31, and can sometimes be seen to the south of M31 [ http://seds.lpl.arizona.edu/messier/m/m031.html ]'s center in photographs. The above image [ http://crux.astr.ua.edu/gifimages/m110r.html ] shows this galaxy to be unusual for an elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950913.html ] in that it contains at least two dust clouds [ http://antwrp.gsfc.nasa.gov/apod/ap951107.html ] (at 7 and 11 o'clock - they are visible but hard to spot) and signs of recent star formation. This galaxy is sometimes known as M110, although it was actually not part of Messier [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#messier ]'s original catalog. |
|
Dwarf Elliptical Galaxy M32
| Title |
Dwarf Elliptical Galaxy M32 |
| Explanation |
Being the largest galaxy around can sometimes make you popular. Pictured is M31's companion galaxy M32 [ http://crux.astr.ua.edu/gifimages/m32.html ]. M31 [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ], the Andromeda galaxy, is the largest galaxy in our Local Group [ http://www.csc.fi/jpr/galaxy/lbang.html ] of galaxies - even our tremendous Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ] is smaller. Little M32 is visible in most pictures of M31 - it is the small circular spot north of M31's center. M32 is a dwarf elliptical galaxy [ http://www.physics.mcmaster.ca/Grads/PRD2.html ]. Elliptical galaxies [ http://sousun1.phys.soton.ac.uk/PH308/galaxies/ellipticals.html ] have little or no measurable gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ] or dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] - they are composed completely of stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] and typically appear more red than spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap951218.html ]. Elliptical galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap950913.html ] do not have disks - they generally have oblong shapes and therefore show elliptical profiles on the sky. |
|
Island Universe, Cosmic Sand
| Title |
Island Universe, Cosmic Sand |
| Explanation |
On August 13, while counting Perseid meteors [ http://comets.amsmeteors.org/meteors/showers/ perseids.html ] under dark [ http://www.darksky.org/ida/darksky/ index.html ], early morning Arizona skies, Rick Scott set out to photograph [ http://members.cox.net/rmscott/ gallery_space_sky02.html ] their fleeting but fiery trails. The equipment he used included a telephoto lens and fast color film. After 21 pictures he'd caught only two meteors, but luckily this was one of them. Tracking the sky, his ten minute long exposure shows a field of many stars in our own Milky Way galaxy [ http://www.seds.org/messier/ more/mw.html ], most too faint to be seen by the unaided eye. Flashing [ http://antwrp.gsfc.nasa.gov/apod/ap990219.html ] from lower left to upper right, the bright meteor would have been an easy eyeful though, as friction with Earth's atmosphere vaporized [ http://antwrp.gsfc.nasa.gov/apod/ap020816.html ] the hurtling grain of cosmic sand [ http://antwrp.gsfc.nasa.gov/apod/ap001117.html ], a piece of dust from Comet Swift-Tuttle [ http://comets.amsmeteors.org/comets/pcomets/ 109p.html ]. Just above and left of center, well beyond the stars of the Milky Way, lies the island universe [ http://antwrp.gsfc.nasa.gov/apod/ap020518.html ] known as M31 or the Andromeda galaxy. The visible meteor trail begins about 100 kilometers above Earth's surface, one of the closest celestial objects seen in the sky. In contrast, Andromeda [ http://www.seds.org/messier/m/ m031.html ], about 2 million light-years away, is the most distant object easily visible to the naked-eye. |
|
A Giant Globular Cluster in
…
| Title |
A Giant Globular Cluster in M31 |
| Explanation |
G1, pictured above, is the brightest known globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap960221.html ] in the whole Local Group [ http://antwrp.gsfc.nasa.gov/apod/ap960108.html ] of galaxies. Also called Mayall II, it orbits the center of the largest nearby galaxy: M31 [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ]. G1 contains over 300,000 stars and is almost as old as the entire universe [ http://antwrp.gsfc.nasa.gov/apod/ap960216.html ]. In fact, observations of this globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap951120.html ] show stars as old as the oldest of the roughly 250 known globular clusters [ http://antwrp.gsfc.nasa.gov/apod/lib/globular_clusters.html ] in our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960213.html ]. This image [ http://www.stsci.edu/pubinfo/PR/96/11/A.html ] was taken with the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap951116.html ] in July of 1994. It shows, for the first time, the same fine detail in a distant globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap950913.html ] as can be discerned from a ground-based telescope of a globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap950726.html ] in our own Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ]. |
|
Nearby Dwarf Galaxy Leo I
| Title |
Nearby Dwarf Galaxy Leo I |
| Explanation |
Leo I is a dwarf spheroidal galaxy [ http://www.astro.uu.se/~ns/review.html ] in the Local Group [ http://antwrp.gsfc.nasa.gov/apod/lib/local_group.html ] of galaxies dominated by our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960213.html ] and M31 [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ]. Leo I is thought to be the most distant of the eleven known small satellite galaxies [ http://www.astro.uu.se/~ns/mwsat.html ] orbiting our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950908.html ]. Besides the LMC [ http://antwrp.gsfc.nasa.gov/apod/ap950918.html ] and the SMC [ http://antwrp.gsfc.nasa.gov/apod/ap950919.html ], all Milky Way satellite galaxies are small, dim, dwarf spheroidals [ http://www.astro.uu.se/~ns/dsph.html ], including the closest galaxy - the Sagittarius Dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap960204.html ]. Leo I is most distant than most of them, thought to be about 250 kpc away. Analysis of stars in Leo I show it contains many stars only about 3 billion years old - much younger than in most galaxies. |
|
Nearby Spiral M33
| Title |
Nearby Spiral M33 |
| Explanation |
Spiral galaxy [ http://www.seds.org/messier/spir.html ] M33 is a mid-sized member of our Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap980721.html ] is also called the Triangulum Galaxy [ http://www.seds.org/messier/m/m033.html ] for the constellation [ http://www.astronomical.org/constellations/tri.html ] in which it resides. About four times smaller (in radius) than our Milky Way Galaxy [ http://www.star.le.ac.uk/edu/mway/ ] and the Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap021021.html ] (M31), it is much larger than the many of the local dwarf spheroidal [ http://antwrp.gsfc.nasa.gov/apod/ap991003.html ] galaxies. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960708.html ]'s proximity to M31 [ http://antwrp.gsfc.nasa.gov/apod/ap010917.html ] causes it to be thought by some to be a satellite galaxy of this more massive galaxy. M33 [ http://sirtf.caltech.edu/Education/Messier/m33.html ]'s proximity to our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] causes it to appear more than twice the angular size of the Full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ], and be visible with a good pair of binoculars. The above high-resolution image [ http://www.noao.edu/image_gallery/html/im0775.html ] from the 0.90-m telescope [ http://www.noao.edu/0.9m/manual.html ] at Kitt Peak National Observatory [ http://www.noao.edu/kpno/ ] is a four-color composite. |
|
M33: The Triangulum Galaxy
| Title |
M33: The Triangulum Galaxy |
| Explanation |
The spiral galaxy [ http://www.astro.rug.nl/~jansen/www/articles/spectrum/spectrum.html ] M33 [ http://ftp.seds.org/messier/m/m033.html] is a mid-sized member of our Local Group of galaxies [ http://antwrp.gsfc.nasa.gov/apod/lib/local_group.html ]. M33 is also called the Triangulum Galaxy for the constellation [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Triangulum.html ] in which it resides. About four times smaller (in radius) than our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960213.html ] and the Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap950724.html ] (M31), it is much larger than the many of the local dwarf spheroidal galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap960519.html ]. M33's proximity to M31 causes it to be thought by some to be a satellite galaxy of this more massive galaxy. M33's proximity to our Milky Way galaxy causes it to appear more than twice the angular size of the full moon [ http://antwrp.gsfc.nasa.gov/apod/ap950821.html ], and visible with a good pair of binoculars [ http://jersey.uoregon.edu/~bdany/optics.html ]. In the above picture [ http://fondue.gsfc.nasa.gov/UIT/Astro1/Astro1_pictures.html ], visible light is shown in red and ultraviolet light superposed in blue [ http://antwrp.gsfc.nasa.gov/apod/ap960409.html ]. Stars in M33 are the most distant ever to be studied spectroscopically [ http://www.aas.org/ApJ/v455n2/5526/sc0.html ]. |
|
The Aquarius Dwarf
| Title |
The Aquarius Dwarf |
| Explanation |
Our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] is not alone. It is part of a gathering of about 50 galaxies known as the Local Group [ http://www.seds.org/messier/more/local.html ]. Members include the Great Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap021021.html ] (M31), M32 [ http://antwrp.gsfc.nasa.gov/apod/ap991103.html ], M33 [ http://antwrp.gsfc.nasa.gov/apod/ap021202.html ], the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ], the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000430.html ], Dwingeloo 1 [ http://antwrp.gsfc.nasa.gov/apod/ap000109.html ], several small irregular galaxies [ http://www.seds.org/messier/irre.html ], and many dwarf elliptical [ http://nedwww.ipac.caltech.edu/level5/Ferguson/frames.html ] and dwarf spheroidal galaxies [ http://www.astro.uu.se/~ns/review.html ]. Pictured above is the Aquarius Dwarf [ http://www.seds.org/~spider/spider/LG/aqr_dw.html ], a faint dwarf irregular galaxy over 3 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away. An earlier [ http://antwrp.gsfc.nasa.gov/apod/ap970329.html ] APOD [ http://antwrp.gsfc.nasa.gov/apod/ap960204.html ] erroneously identified [ http://www.solstation.com/x-objects/sag-deg.htm ] the above image as the Sagittarius Dwarf [ http://www.seds.org/messier/more/sagdeg.html ]. |
|
Island Universe, Cosmic Sand
| Title |
Island Universe, Cosmic Sand |
| Explanation |
On August 13, 2002, while counting Perseid meteors [ http://science.nasa.gov/headlines/y2003/ 17jul_perseids2003.htm ] under dark [ http://www.darksky.org/ida/darksky/ index.html ], early morning Arizona skies, Rick Scott set out to photograph [ http://members.cox.net/rmscott/ gallery_space_sky02.html ] their fleeting but fiery trails. The equipment he used included a telephoto lens and fast color film. After 21 pictures he'd caught only two meteors, but luckily this was one of them. Tracking the sky, his ten minute long exposure shows a field of many stars in our own Milky Way galaxy [ http://www.seds.org/messier/ more/mw.html ], most too faint to be seen by the unaided eye. Flashing [ http://antwrp.gsfc.nasa.gov/apod/ap990219.html ] from lower left to upper right, the bright meteor would have been an easy eyeful though, as friction with Earth's atmosphere vaporized [ http://antwrp.gsfc.nasa.gov/apod/ap020816.html ] the hurtling grain of cosmic sand [ http://antwrp.gsfc.nasa.gov/apod/ap001117.html ], a piece of dust from Comet Swift-Tuttle [ http://comets.amsmeteors.org/comets/pcomets/ 109p.html ]. Just above and left of center, well beyond the stars of the Milky Way, lies the island universe [ http://antwrp.gsfc.nasa.gov/apod/ap020518.html ] known as M31 or the Andromeda galaxy. The visible meteor trail begins about 100 kilometers above Earth's surface, one of the closest celestial objects seen in the sky. In contrast, Andromeda [ http://www.seds.org/messier/m/ m031.html ], about 2 million light-years away, is the most distant object easily visible to the naked-eye. |
|
The Northern Milky Way
| Title |
The Northern Milky Way |
| Explanation |
Many of the stars in our home Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] appear together as a dim band on the sky that passes nearly over the Earth's north [ http://antwrp.gsfc.nasa.gov/apod/ap020818.html ] and south poles. Pictured above [ http://www.astropix.com/HTML/SHOWCASE/NMW.HTM ] is the part of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] that passes closest over the north pole [ http://antwrp.gsfc.nasa.gov/apod/ap000715.html ]. Placing your cursor [ http://www.hyperdictionary.com/dictionary/cursor] over the image will bring up the names of several constellations [ http://www.adlerplanetarium.org/history/exhibits/constellations/timeline.html ] and bright stars [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ]. The diffuse white Galaxy glow is created by billions of stars, while red patches are large emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], usually marking areas where bright stars have recently formed. In the north, all of the lights visible at night and all lights that created this image were emitted within the past few thousand years from within the Milky Way Galaxy -- except one. On the upper right is a small faint patch designated M31, the Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap021021.html ]. M31 is a spiral galaxy [ http://www.seds.org/messier/spir.html ] similar to our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] but so distant it emits the oldest light distinguishable by the unaided eye -- light that takes over two million years to reach us. |
|
The Andromeda Galaxy from GA
…
| Title |
The Andromeda Galaxy from GALEX |
| Explanation |
Why does the Andromeda Galaxy have a giant ring? Viewed in ultraviolet light [ http://imagers.gsfc.nasa.gov/ems/uv.html ], the closest major galaxy to our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] looks more like a ring galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap020909.html ] than a spiral [ http://antwrp.gsfc.nasa.gov/apod/ap030911.html ]. The ring is highlighted beautifully in this newly released image mosaic of Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap021021.html ] (M31) taken by the GALaxy Evolution Explorer [ http://www.galex.caltech.edu/ABOUT/about.html ] (GALEX), a satellite launched into Earth orbit in April. In the above image [ http://www.galex.caltech.edu/popups/gallery-M31.html ], ultraviolet colors have been digitally shifted to the visual. Young blue stars [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1964ApJS....9...65V ] dominate the image, indicating the star forming ring [ http://antwrp.gsfc.nasa.gov/apod/ap010612.html ] as well as other star forming regions even further from the galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap000121.html ]. The origin of the huge 150,000-light year [ http://chandra.harvard.edu/photo/cosmic_distance.html ] ring is unknown but likely related to gravitational interactions [ http://antwrp.gsfc.nasa.gov/apod/ap020506.html ] with small satellite galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap021202.html ] that orbit near the galactic giant. M31 [ http://www.seds.org/messier/m/m031.html ] lies about three million light-years distant and is bright enough to be seen without binoculars toward the constellation [ http://en2.wikipedia.org/wiki/Constellations ] of Andromeda [ http://www.astronomical.org/constellations/and.html ]. |
|
M31: The Andromeda Galaxy
| Title |
M31: The Andromeda Galaxy |
| Explanation |
Andromeda is the nearest major galaxy to our own Milky Way Galaxy. Our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ] on Messier's [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#messier ] list of diffuse sky objects. M31 is so distant it takes about 2 million years for light to reach us from there. Much about M31 remains unknown, including why the center contains two nuclei. |
|
M31: The Andromeda Galaxy
| Title |
M31: The Andromeda Galaxy |
| Explanation |
Andromeda is the nearest major galaxy [ http://www.seds.org/messier/galaxy.html ] to our own Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. Our Galaxy is thought to look much like Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap020518.html ]. Together these two galaxies dominate the Local Group [ http://www.seds.org/messier/more/local.html ] of galaxies. The diffuse light from Andromeda [ http://www.seds.org/messier/m/m031.html ] is caused by the hundreds of billions of stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] that compose it. The several distinct stars that surround Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap010917.html ]'s image are actually stars in our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000518.html ] that are well in front of the background object. Andromeda [ http://www.noao.edu/image_gallery/html/im0424.html ] is frequently referred to as M31 since it is the 31st object [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ] on Messier [ http://www.seds.org/messier/xtra/history/biograph.html ]'s list of diffuse sky objects. M31 [ http://antwrp.gsfc.nasa.gov/apod/ap020412.html ] is so distant it takes about two million years for light to reach us from there. Although visible without aid, the above image [ http://www.robgendlerastropics.com/M31Page.html ] of M31 is a digital mosaic of 20 frames taken with a small telescope. Much about M31 remains unknown [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1995ApJ...444..157A ], including how the center acquired two nuclei [ http://antwrp.gsfc.nasa.gov/apod/ap961011.html ]. |
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Nearby Spiral M33
| Title |
Nearby Spiral M33 |
| Explanation |
M33 is a prominent nearby spiral galaxy. Nicknamed the Triangulum [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Triangulum.html ], M33 [ http://ftp.seds.org/messier/m/m033.html ] is one of the larger members of the Local Group of Galaxies [ http://ftp.seds.org/messier/more/local.html ]. Two massive spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap970726.html ] dominate the Local Group: M31 [ http://antwrp.gsfc.nasa.gov/apod/ap971101.html ] and our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ]. M33 is the only other spiral galaxy known in the Local Group. At 3 million light-years, M33 is the second closest spiral galaxy. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960708.html ] is thought by some to be a satellite galaxy to massive M31 [ http://ftp.seds.org/messier/m/m031.html ]. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap960816.html ] is close enough to appear twice the angular size of the full moon [ http://antwrp.gsfc.nasa.gov/apod/ap980107.html ], when viewed with binoculars. Globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap970214.html ] in M33's halo appear unusual [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=J97-05618&db_key=AST&high=34f6e1de7f02701 ] and might be much younger than globular clusters in our Galaxy's halo [ http://antwrp.gsfc.nasa.gov/apod/ap971105.html ]. |
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Galaxy Dwingeloo 1 Emerges
| Title |
Galaxy Dwingeloo 1 Emerges |
| Explanation |
Sometimes you can't see the forest for the trees. But if you look closely at the center of the above photograph, you will see a whole spiral galaxy behind the field of stars. Named Dwingeloo 1, this nearby galaxy was only discovered recently (1994) because much of its light was obscured by dust, gas and bright stars of our own Milky Way Galaxy. In fact, all the individually discernible stars in the above photograph are in our Galaxy. Dwingeloo 1 turned out to be a large galaxy located only five times as distant as the closest major galaxy - M31. |
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Andromeda's Core
| Title |
Andromeda's Core |
| Explanation |
The center of the Andromeda galaxy is beautiful but strange. Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap040718.html ], indexed as M31, is so close to our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] that it gives a unique perspective into galaxy composition by allowing us to see into its core. Billions of stars swarm around a center that has two nuclei [ http://antwrp.gsfc.nasa.gov/apod/ap961011.html ] and likely houses a supermassive black hole [ http://antwrp.gsfc.nasa.gov/apod/ap040908.html ] over 5 million times the mass of our Sun [ http://www.nineplanets.org/sol.html ]. M31 is about two million light years away and visible with the unaided eye towards the constellation [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=1 ] of Andromeda, the princess [ http://www.windows.ucar.edu/tour/link=/the_universe/Constellations/andromeda.html ]. Pictured above [ http://www.robgendlerastropics.com/Andromedacore.html ], dark knots [ http://en.wikipedia.org/wiki/Knots ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] are seen superposed on the inner 10,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] of M31's core. The brighter stars are foreground stars located in our Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. |
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Nearby Spiral M33
| Title |
Nearby Spiral M33 |
| Explanation |
Spiral galaxy [ http://www.seds.org/messier/spir.html ] M33 is a mid-sized member of our Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. M33 [ http://antwrp.gsfc.nasa.gov/apod/ap030924.html ] is also called the Triangulum Galaxy [ http://www.seds.org/messier/m/m033.html ] for the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] in which it resides. About four times smaller (in radius) than our Milky Way Galaxy [ http://www.star.le.ac.uk/edu/mway/ ] and the Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap040718.html ] (M31), it is much larger than the many of the local dwarf spheroidal [ http://antwrp.gsfc.nasa.gov/apod/ap991003.html ] galaxies. M33 [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?m33 ]'s proximity to M31 [ http://antwrp.gsfc.nasa.gov/apod/ap010917.html ] causes it to be thought by some to be a satellite galaxy of this more massive galaxy. M33 [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/multiwavelength_astronomy/multiwavelength_museum/m33.html ]'s proximity to our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ] causes it to appear more than twice the angular size of the Full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap040829.html ], and be visible with a good pair of binoculars. |
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A Giant Globular Cluster in
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| Title |
A Giant Globular Cluster in M31 |
| Explanation |
This cluster of stars, known as G1, is the brightest globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap960221.html ] in the whole Local Group [ http://www.seds.org/messier/more/local.html ] of galaxies. Also called Mayall II, it orbits the center of the largest nearby galaxy: M31 [ http://antwrp.gsfc.nasa.gov/apod/ap971101.html ]. G1 contains over 300,000 stars and is almost as old as the entire universe [ http://www.sciam.com/specialissues/0398cosmos/0398peebles.html ]. In fact, observations of this globular star cluster show it to be as old as the oldest of the roughly 250 known globular clusters [ http://www.seds.org/messier/glob.html ] in our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap960213.html ]. Two bright foreground stars appear in this image of G1 [ http://www.stsci.edu/pubinfo/PR/96/11/A.html ] taken with the orbiting Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap951116.html ] in July of 1994. It shows detail in the distant cluster comparable to ground-based telescopic views of globular star clusters in our own Galaxy [ http://www.limber.org/globs.html ]. |
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The Colliding Galaxies of NG
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| Title |
The Colliding Galaxies of NGC 520 |
| Explanation |
Is this one galaxy or two? The jumble of stars, gas, and dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] that is NGC 520 is now thought to incorporate the remains of two separate galaxies. A combination of observations and simulations indicate the NGC 520 [ http://www.kopernik.org/images/archive/n520.htm ] is actually the collision of two disk galaxies. Interesting features of NGC 520 include an unfamiliar looking tail of stars [ http://antwrp.gsfc.nasa.gov/apod/ap040515.html ] at the image bottom and a perhaps more familiar looking band of dust [ http://antwrp.gsfc.nasa.gov/apod/ap031008.html ] running diagonally across the image center. A similar looking collision might be expected were our disk Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] to collide [ http://www.cita.utoronto.ca/~dubinski/merger/bigmerger.html ] with our large galactic neighbor Andromeda [ http://antwrp.gsfc.nasa.gov/apod/ap040718.html ] (M31). The collision that defines NGC 520 [ http://www.cv.nrao.edu/~jhibbard/n520/n520.html ] started about 300 million years ago and continues today. Although the speeds of stars are fast, the distances are so vast that the interacting pair will surely not change its shape noticeably during our lifetimes. NGC 520 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005MNRAS.359..455R ], at visual magnitude [ http://en.wikipedia.org/wiki/Apparent_magnitude ] 12, has been noted to be one of the brightest interacting galaxies on the sky, after interacting pairs of galaxies known as the Antennae [ http://antwrp.gsfc.nasa.gov/apod/ap971022.html ]. NGC 520 was imaged above [ http://www.gemini.edu/index.php?option=content&task=view&id=150&Itemid=0&limit=1&limitstart=1 ] in spectacular fashion by the Gemini Observatory [ http://antwrp.gsfc.nasa.gov/apod/ap030909.html ] in Hawaii [ http://en.wikipedia.org/wiki/Hawaii ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. Also known as Arp [ http://www.haltonarp.com/ ] 157, NGC 520 lies about 100 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant, spans about 100 thousand light years, and can be seen with a small telescope toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of the Fish (Pisces [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=66 ]). |
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The Andromeda Galaxy in Infr
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| Title |
The Andromeda Galaxy in Infrared |
| Explanation |
What is the Andromeda galaxy really like? To find out, astronomers looked at our largest galactic neighbor [ http://www.seds.org/messier/m/m031.html ] in a different light: infrared [ http://en.wikipedia.org/wiki/Infrared ]. Astronomers [ http://www.aas.org/education/publications/careerbrochure.html ] trained the orbiting Spitzer Space Telescope [ http://ssc.spitzer.caltech.edu/geninfo/ ] at the Messier [ http://antwrp.gsfc.nasa.gov/apod/ap000311.html ] monster (M31) for over 18 hours, creating a mosaic that incorporated 11,000 separate exposures. The result, pictured above [ http://www.spitzer.caltech.edu/Media/releases/ssc2005-20/release.shtml ], shows M31 in greater infrared detail than ever before. Infrared light in this 24-micron color band is particularly sensitive to dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] heated up by stars. Visible above are previously undiscovered features [ http://uanews.org/cgi-bin/WebObjects/UANews.woa/1/wa/SRStoryDetails?ArticleID=11798 ] including intricate structure in the spiral arms, a spiral arc near the center, an off center ring of star formation, and an unusual hole in the galaxy's disk. In contrast, the Andromeda galaxy appears much smoother in visible light [ http://antwrp.gsfc.nasa.gov/apod/ap040718.html ] and even ultraviolet light [ http://antwrp.gsfc.nasa.gov/apod/ap031222.html ]. Analyses and comparison of this image to other images will likely yield clues not only to the violent past of M31 [ http://antwrp.gsfc.nasa.gov/apod/ap041227.html ] but to our own Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ] as well. |
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Andromeda Island Universe
| Title |
Andromeda Island Universe |
| Explanation |
The most distant object easily visible to the unaided eye is M31 [ http://www.seds.org/messier/xtra/history/m-m31_42.html ], the great Andromeda Galaxy [ http://www.seds.org/messier/m/m031.html ] some two million light-years away. But without a telescope, even this immense spiral galaxy - spanning over 200,000 light years - appears as a faint, nebulous cloud in the constellation Andromeda [ http://www.hawastsoc.org/deepsky/and/index.html ]. In contrast, a bright yellow nucleus, dark winding dust lanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital mosaic [ http://www.robgendlerastropics.com/M31NMmosaic.html ] with a cumulative exposure of over 90 hours. While even casual skygazers [ http://badastronomy.com/bitesize/galaxies.html ] are now inspired by the knowledge that there are many [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ] distant galaxies like M31, astronomers seriously debated [ http://adsbit.harvard.edu/cgi-bin/ nph-iarticle_query?1995PASP%2E%2E107%2E1133T ] this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/ debate20.html ] debate [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] of 1920, which was later resolved by observations [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] of M31 in favor of Andromeda, island universe [ http://www.astr.ua.edu/goodies/data_resources/galaxies.text ]. |
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