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Andromeda of Milky Way Galaxy and Andromeda Galaxy
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Dwarf Galaxies Swimming in T
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| Title |
Dwarf Galaxies Swimming in Tidal Tails |
| Description |
This false-color infrared image from NASA's Spitzer Space Telescope shows little "dwarf galaxies" forming in the "tails" of two larger galaxies that are colliding together. The big galaxies are at the center of the picture, while the dwarfs can be seen as red dots in the red streamers, or tidal tails. The two blue dots above the big galaxies are stars in the foreground. Galaxy mergers are common occurrences in the universe, for example, our own Milky Way galaxy will eventually smash into the nearby Andromeda galaxy. When two galaxies meet, they tend to rip each other apart, leaving a trail, called a tidal tail, of gas and dust in their wake. It is out of this galactic debris that new dwarf galaxies are born. The new Spitzer picture demonstrates that these particular dwarfs are actively forming stars. The red color indicates the presence of dust produced in star-forming regions, including organic molecules called polycyclic aromatic hydrocarbons, or PAHs. PAHs are also found on Earth, in car exhaust and on burnt toast, among other places. Here, the PAHs are being heated up by the young stars, and, as a result, shine in infrared light. This image was taken by the infrared array camera on Spitzer. It is a 4-color composite of infrared light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). Starlight has been subtracted from the orange and red channels in order to enhance the dust, or PAH, features. |
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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. |
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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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Chandra X-ray & Spitzer Infr
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| Name |
Chandra X-ray & Spitzer Infrared Image of Andromeda Galaxy (M31) |
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Hubble Sees Early Building B
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| Title |
Hubble Sees Early Building Blocks of Today's Galaxies |
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Hubble Astronomer Creates Sp
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| Title |
Hubble Astronomer Creates Spectacular Galaxy Collision Visualization for the National Air and Space Museum |
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Hubble Discovers Black Holes
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| 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
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| 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
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| 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
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| 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
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| 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
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| 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
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| 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
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| 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
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| 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
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| 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 Astronomer Creates Sp
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| Title |
Hubble Astronomer Creates Spectacular Galaxy Collision Visualization for the National Air and Space Museum |
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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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Astronomers Discover Nearby
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| Title |
Astronomers Discover Nearby Spiral Galaxy Hidden Behind the Milky Way |
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Hubble Space Telescope Image
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| 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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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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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. |
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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 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 ]. |
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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 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 ]. |
|
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. |
|
Nearby Spiral Galaxy NGC 494
…
| Title |
Nearby Spiral Galaxy NGC 4945 |
| Explanation |
For such a close galaxy, NGC 4945 is easy to miss. NGC 4945 [ http://www.ast.cam.ac.uk/AAO/images/captions/aat101.html ] is a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980525.html ] in the Centaurus Group of galaxies, located only six times farther away than the prominent Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991114.html ]. The thin disk galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] is oriented nearly edge-on, however, and shrouded in dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]. Therefore galaxy-gazers searching the southern constellation of Centaurus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Centaurus.html ] need a telescope to see it. The above picture [ http://www.eso.org/outreach/press-rel/pr-1999/phot-18-99.html ] was taken with a large telescope [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/ ] testing a new wide-angle, high-resolution CCD camera [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/WFI/ ]. Most of the spots scattered about the frame [ http://www.eso.org/outreach/epr/posters/ ] are foreground stars in our own Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ], but some spots are globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] orbiting the distant galaxy. NGC 4945 [ http://astro.ph.unimelb.edu.au/central/images/mbrown/ngc4945.html ] is thought to be quite similar to our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ]. X-ray [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] observations reveal, however, that NGC 4945 has an unusual, energetic, Seyfert [ http://antwrp.gsfc.nasa.gov/apod/ap010701.html ] 2 nucleus that might house a large black hole [ http://antwrp.gsfc.nasa.gov/apod/ap960911.html ]. |
|
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. |
|
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 ]. |
|
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 ]. |
|
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. |
|
Nearby Spiral Galaxy NGC 494
…
| Title |
Nearby Spiral Galaxy NGC 4945 |
| Explanation |
For such a close galaxy, NGC 4945 is easy to miss. NGC 4945 [ http://www.aao.gov.au/local/www/dfm/aat101.html ] is a spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980525.html ] in the Centaurus Group of galaxies, located only six times farther away than the prominent Andromeda Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971101.html ]. The thin disk galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap981220.html ] is oriented nearly edge-on, however, and shrouded in dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ]. Therefore galaxy-gazers searching the southern constellation of Centaurus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Centaurus.html ] need a telescope to see it. The above picture [ http://www.eso.org/outreach/press-rel/pr-1999/phot-18-99.html ] was taken with a large telescope [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/E2p2M.html ] testing a new wide-angle, high-resolution CCD camera [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/WFI/WFI.html ]. Most of the spots scattered about the frame are foreground stars in our own Galaxy, but some spots are globular clusters [ http://antwrp.gsfc.nasa.gov/apod/ap980719.html ] orbiting the distant galaxy. NGC 4945 [ http://astro.ph.unimelb.edu.au/central/images/mbrown/ngc4945.html ] is thought to be quite similar to our own Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ]. X-ray [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] observations reveal, however, that NGC 4945 has an unusual, energetic, Seyfert [ http://antwrp.gsfc.nasa.gov/apod/ap981023.html ] 2 nucleus that might house a large black hole [ http://antwrp.gsfc.nasa.gov/apod/ap960911.html ]. |
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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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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/ap960626.html ] list of diffuse sky objects. M31 is so distant it takes about two million years for light to reach us from there. Much about M31 remains unknown, including why the center contains two nuclei. |
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Galaxy NGC 55
PIA04923
GALEX Telescope
| Title |
Galaxy NGC 55 |
| Original Caption Released with Image |
This image of the nearby edge-on spiral galaxy NGC 55 was taken by Galaxy Evolution Explorer on September 14, 2003, during 2 orbits. This galaxy lies 5.4 million light years from our Milky Way galaxy and is a member of the "local group" of galaxies that also includes the Andromeda galaxy (M31), the Magellanic clouds, and 40 other galaxies. The spiral disk of NGC 55 is inclined to our line of sight by approximately 80 degrees and so this galaxy looks cigar-shaped. This picture is a combination of Galaxy Evolution Explorer images taken with the far ultraviolet (colored blue) and near ultraviolet detectors, (colored red). The bright blue regions in this image are areas of active star formation detected in the ultraviolet by Galaxy Evolution Explorer. The red stars in this image are foreground stars in our own Milky Way galaxy. |
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