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Open Cluster NGC 290: A Stel
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| Title |
Open Cluster NGC 290: A Stellar Jewel Box |
| Explanation |
Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster [ http://en.wikipedia.org/wiki/Open_cluster ] NGC 290 glitter in a beautiful display [ http://antwrp.gsfc.nasa.gov/apod/ap010618.html ] of brightness and color. The photogenic cluster, pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/17/image/a ], was captured recently by the orbiting Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap021124.html ]. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] of stars. NGC 290 lies about 200,000 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant in a neighboring galaxy called the Small Cloud of Magellan [ http://antwrp.gsfc.nasa.gov/apod/ap050617.html ] (SMC). The open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ] contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve [ http://en.wikipedia.org/wiki/Stellar_evolution ], since all the open cluster's stars were born at about the same time. |
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NGC 253: Dusty Island Univer
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| Title |
NGC 253: Dusty Island Universe |
| Explanation |
Shiny NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ], sometimes called the Silver Dollar Galaxy, is one of the brightest spiral galaxies visible - and also one of the dustiest. First swept up [ http://antwrp.gsfc.nasa.gov/apod/ap991016.html ] in 1783 by mathematician and astronomer Caroline Herschel [ http://www.scottlan.edu/LRIDDLE/WOMEN/ herschel.htm ], the dusty island universe lies a mere 10 million light-years away in the southern constellation [ http://www.astronomy.org.nz/aas/Journal/Oct2004/ GreatGalaxyGrab.asp ] Sculptor. About 70 thousand light-years across, NGC 253 is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/ sclgr.html ], the nearest to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/ local.html ]. In addition to its spiral dust lanes, striking tendrils of dust seem to be rising [ http://antwrp.gsfc.nasa.gov/apod/ap060414.html ] from the galactic disk in this gorgeous view [ http://ccd.cosmotography.com/images/small_ngc253.html ]. The high dust content accompanies frantic star formation, giving [ http://www.arxiv.org/abs/astro-ph/0509430 ] NGC 253 the designation of a starburst galaxy. NGC 253 is also known to be a strong source of high-energy [ http://antwrp.gsfc.nasa.gov/apod/ap010607.html ] x-rays and gamma rays, likely due to massive black holes near the galaxy's center. |
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Spiral Galaxy NGC 3310 in Ul
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| Title |
Spiral Galaxy NGC 3310 in Ultraviolet |
| Explanation |
Why is NGC 3310 bursting with young stars? The brightest of these new stars are so hot that they light up this spiral galaxy not only in blue light, but in light so blue humans can't see it: ultraviolet [ http://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ]. The Hubble Space Telescope [ http://www.stsci.edu/hst/ ] took the above photograph [ http://oposite.stsci.edu/pubinfo/PR/2001/04/index.html ] in different bands of ultraviolet light. Speculation holds that NGC 3310 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996ApJ...473L..21S ] collided with one of its own dwarf companion galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap991003.html ] only about 50 million years previously. This merger sent density waves [ http://fuse.pha.jhu.edu/~danforth/spiral/ ] rippling around the spiral disk, causing many gas clouds to condense into star forming regions. Imaging nearby galaxies in ultraviolet light [ http://oposite.stsci.edu/pubinfo/PR/2001/04/fastfacts.html ] allows astronomers to better understand the images of distant highly redshift [ http://www.astro.virginia.edu/~jh8h/glossary/redshift.htm ]ed galaxies in visible light, and so to understand why many of these distant galaxies appear relatively fragmented [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ]. The unusually smooth NGC 3310 [ http://oposite.stsci.edu/pubinfo/PR/2001/04/content/prc0104.txt ] spans over 20 thousand light years [ http://www.howstuffworks.com/question94.htm ] and lies about 50 million light years away towards the constellation of Ursa Major [ http://www.astronomical.org/constellations/uma.html ]. |
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NGC 5139: Omega Centauri
| Title |
NGC 5139: Omega Centauri |
| Explanation |
Centaurus [ http://hawastsoc.org/deepsky/cen/index.html ] is one of the most striking constellations in the southern sky. The Milky Way flows through this celestial expanse [ http://www.astro.wisc.edu/~dolan/constellations/extra/ Centaurus.html ] whose wonders also include the closest star system to the Sun, Alpha Centauri [ http://antwrp.gsfc.nasa.gov/apod/ap030323.html ], and the largest globular star cluster in our galaxy, Omega Centauri [ http://seds.org/messier/xtra/ngc/n5139.html ] (aka NGC 5139). This sharp [ http://www.martinpughastrophotography.id.au/Star_Clusters/ NGC5139.htm ] telescopic view of Omega Centauri shows off the central regions of the cluster of about 10 million stars. Omega Cen itself is about 15,000 light-years away and 150 light-years in diameter - the largest of 150 or so known globular [ http://seds.lpl.arizona.edu/messier/xtra/supp/mw_gc.html ] star clusters that roam the halo of our galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ]. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits [ http://arxiv.org/abs/astro-ph/0402144 ] the presence of different stellar populations with a spread of ages and chemical abundances. In [ http://antwrp.gsfc.nasa.gov/apod/ap031213.html ] fact, Omega Cen may be the remnant core of a small galaxy merging [ http://arxiv.org/abs/astro-ph/0402144 ] with the Milky Way. |
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In the Center of Reflection
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| Title |
In the Center of Reflection Nebula NGC 1333 |
| Explanation |
The dust is so thick in the center of NGC 1333 that you can hardly see the stars forming. Conversely, the very dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds that hide the stars also reflects their optical light [ http://fuse.pha.jhu.edu/~wpb/spectroscopy/em_spec.html ], giving NGC 1333 [ http://www.robgendlerastropics.com/NGC1333text.html ]'s predominantly blue glow the general designation of a reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ]. A highly detailed image of the nebula, shown above [ http://www.noao.edu/image_gallery/html/im1037.html ], was taken recently by the Mayall 4-meter telescope [ http://www.noao.edu/outreach/kptour/mayall.html ] on Kitt Peak [ http://www.noao.edu/kpno/ ] in Arizona [ http://en.wikipedia.org/wiki/Arizona ], USA [ http://en.wikipedia.org/wiki/United_States ] and released to honor astronomer Stephen Strom [ http://www.noao.edu/outreach/press/pr07/pr0706.html ] on his retirement. Visible near the image top are vast blue regions of dust [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ] predominantly reflecting the light from bright massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ]. Visible in the thick central dust are not only newly formed stars but red jets [ http://antwrp.gsfc.nasa.gov/apod/ap070430.html ] and red-glowing gas energized by the light and winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] from recently formed young stars. The NGC 1333 [ http://adsabs.harvard.edu/abs/2002ApJ...580..959N ] nebula contains [ http://antwrp.gsfc.nasa.gov/apod/ap061006.html ] hundreds of newly formed stars that are less than one million years old. Reflection nebula [ http://en.wikipedia.org/wiki/Reflection_nebula ] NGC 1333 lies about 1,000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation of Perseus [ http://chandra.harvard.edu/photo/constellations/perseus.html ]. |
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Bright Galaxy NGC 2903
| Title |
Bright Galaxy NGC 2903 |
| Explanation |
Spiral galaxy NGC 2903 is [ http://seds.lpl.arizona.edu/messier/xtra/ngc/ n2903.html ] only some 20 million light-years distant in the constellation Leo [ http://www.wikisky.org/?ra=10.667106650000001 &de=13.138711900000004 &zoom=2&locale=EN&show_grid=1&show_constellation_lines=1 &show_constellation_boundaries=1&show_const_names=1 &show_galaxies=1 ]. One of the brighter galaxies visible from the northern hemisphere, it is surprisingly missing [ http://seds.lpl.arizona.edu/messier/xtra/similar/ similar.html ] from Charles Messier's famous catalog of celestial sights [ http://antwrp.gsfc.nasa.gov/apod/ap000311.html ]. This impressively sharp color image [ http://www.cosmotography.com/images/small_ngc2903.html ] shows off the galaxy's beautiful blue spiral arms. Included in the ground-based telescopic view are intriguing details of NGC 2903's [ http://antwrp.gsfc.nasa.gov/apod/ap010321.html ] central regions -- a remarkable mix of old and young star clusters with immense dust and gas clouds. In fact [ http://arxiv.org/abs/astro-ph/0010522 ], NGC 2903 exhibits an exceptional rate of star formation activity near its center, also bright in radio, infrared [ http://antwrp.gsfc.nasa.gov/apod/ap990322.html ], ultraviolet, and x-ray bands [ http://science.hq.nasa.gov/kids/imagers/ems/ index.html ]. Just a little smaller than our own Milky Way, NGC 2903 is about 80,000 light-years across. |
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Spiral Galaxy NGC 7742
| Title |
Spiral Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap000920.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years [ http://www.treasure-troves.com/astro/Light-Year.html ] away in the constellation Pegasus [ http://www.seds.org/Maps/Stars_en/Fig/pegasus.html ], NGC 7742 is known to be a Seyfert galaxy [ http://www.astro.soton.ac.uk/PH308/AGN/Seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://amazing-space.stsci.edu/light/index.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/m077_hst.html ] of Seyferts [ http://www.seds.org/~spider/spider/ScholarX/seyferts.html ] can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/subjectindex.html ]. |
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NGC 1977: Blue Reflection Ne
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| Title |
NGC 1977: Blue Reflection Nebula in Orion |
| Explanation |
The Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980127.html ] is visible to the unaided eye as a fuzzy patch near the famous belt of three stars [ http://antwrp.gsfc.nasa.gov/apod/ap970820.html ] in the |
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NGC 1850: Not Found in the M
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| Title |
NGC 1850: Not Found in the Milky Way |
| Explanation |
A mere 168,000 light-years distant, this large, lovely cluster of stars, NGC 1850 [ http://antwrp.gsfc.nasa.gov/apod/ap000729.html ], is located near the outskirts of the central bar structure in our neighboring galaxy, the Large Magellanic Cloud [ http://www.seds.org/messier/xtra/ngc/lmc.html ]. A first glance at this [ http://oposite.stsci.edu/pubinfo/PR/2001/25/fastfacts.html ] Hubble Space Telescope composite image suggests [ http://oposite.stsci.edu/pubinfo/PR/2001/25/index.html ] that this cluster's size and shape are reminiscent of the ancient globular star clusters which roam our own Milky Way Galaxy's halo [ http://www.limber.org/globs.html ]. But NGC 1850's stars are young ... making it a type of star cluster [ http://csep10.phys.utk.edu/guidry/violence/ starclusters.html ] with no known counterpart in the Milky Way [ http://www.seds.org/messier/glob.html ]. NGC 1850 is also a double star cluster, with a second, compact cluster of stars visible here below and to the right of the large cluster's central region. Stars in the large cluster are estimated to be 50 million years young [ http://oposite.stsci.edu/pubinfo/PR/97/34/af4.html ], while stars in the compact cluster are younger still, with an age of about 4 million years. In fact, the smaller cluster contains T-Tauri stars [ http://xxx.lanl.gov/abs/astro-ph/0106321 ], thought to be low mass, solar-type stars still in the process [ http://etacha.as.arizona.edu/~eem/ttau/ ] of formation. The glowing nebula at the left, like the supernova remnants [ http://antwrp.gsfc.nasa.gov/apod/ap010623.html ] in our own galaxy, testifies to [ http://www.eso.org/outreach/press-rel/pr-1999/ phot-15-99.html ] violent stellar explosions, indicating short-lived massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap991130.html ] were also present in NGC 1850 [ http://antwrp.gsfc.nasa.gov/apod/ap001224.html ]. |
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NGC 4631: The Whale Galaxy
| Title |
NGC 4631: The Whale Galaxy |
| Explanation |
NGC 4631 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n4631.html ] is a big beautiful spiral galaxy seen edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] only 25 million light-years away towards the small northern constellation Canes Venatici [ http://seds.lpl.arizona.edu/messier/map/CVn.html ]. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way [ http://www.aemann.pwp.blueyonder.co.uk/paintings/ galaxy.html ], it is similar in size to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ]. In this gorgeous color image [ http://www.noao.edu/outreach/aop/observers/ n4631.html ], the Whale's dark interstellar dust clouds, young bright blue star clusters, and purplish star forming regions are easy to spot [ http://antwrp.gsfc.nasa.gov/apod/ap990507.html ]. A companion [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ] galaxy, the small elliptical NGC 4627 appears above the Whale Galaxy. Out of view off the lower left corner of the picture lies another distorted galaxy, the hockey stick-shaped NGC 4656 [ http://www.noao.edu/outreach/aop/observers/n4656.html ]. The distortions and mingling trails [ http://antwrp.gsfc.nasa.gov/apod/ap970224.html ] of gas and dust [ http://www.astro.uni-bonn.de/~nneini/coldust.html ] detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays [ http://chandra.harvard.edu/press/01_releases/press_071901.html ]. |
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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. |
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NGC 2237: The Rosette Nebula
| Title |
NGC 2237: The Rosette Nebula |
| Explanation |
Would the Rosette [ http://c.gp.cs.cmu.edu:5103/prog/webster?rosette ] nebula by any other name " look " as sweet [ http://the-tech.mit.edu/Shakespeare/Tragedy/romeoandjuliet/ romeoandjuliet.all.html ]? The bland New General Catalog [ http://www.physics.sfsu.edu/asp/ngc.html ] designation of NGC 2237 [ http://seds.lpl.arizona.edu/billa/twn/n2237x.html ] doesn't appear to diminish the appearance of the this flowery emission nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#emis_neb ]. Inside the nebula lies an open cluster [ http://antwrp.gsfc.nasa.gov/apod/ap960116.html ] of bright young stars designated NGC 2244. These stars recently formed from the nebular material and their stellar "wind" has cleared a hole in the nebula's center, insulated by a layer of dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] and hot gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ]. Ultraviolet [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#uv ] light from the hot cluster stars causes the surrounding nebula to glow. |
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NGC 253: The Sculptor Galaxy
| Title |
NGC 253: The Sculptor Galaxy |
| Explanation |
NGC 253 [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?ngc+253 ] is not only one of the brightest spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980922.html ] visible, it is also one of the dustiest [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ]. Discovered in 1783 by Caroline Herschel [ http://history.math.csusb.edu/Mathematicians/Herschel_Caroline.html ] in the constellation of Sculptor [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sculptor.html ], NGC 253 [ http://astro.nmsu.edu/~choopes/research.html ] lies only about ten million light-years distant. NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ] is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/sclgr.html ], the nearest group to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/local.html ]. The dense dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] accompanies a high star formation [ http://antwrp.gsfc.nasa.gov/apod/ap020717.html ] rate, giving NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap990121.html ] the designation of starburst galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...505..639E ]. Visible in the above photograph [ http://oposite.stsci.edu/pubinfo/pr/1998/42/a.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] is the active central nucleus [ http://www.astr.ua.edu/keel/agn/text.html ], also known to be a bright source of X-rays [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] and gamma rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
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NGC 1818: Pick A Star
| Title |
NGC 1818: Pick A Star |
| Explanation |
This is NGC 1818 [ http://antwrp.gsfc.nasa.gov/apod/ap980307.html ], a youthful, glittering cluster of 20,000 stars residing in the Large Magellanic Cloud [ http://seds.lpl.arizona.edu/messier/xtra/ngc/lmc.html ], 180,000 light-years away. Pick a star. Any star. Astronomers might pick [ http://oposite.stsci.edu/pubinfo/pr/1998/16/ ] the unassuming bluish-white one (circled) which appears [ http://hubblesite.org/sci.d.tech/behind_the_pictures/ wacky_shape/index.shtml ] to be a hot newly formed white dwarf star. What makes it so interesting? The standard astronomical wisdom suggests that stars over 5 times as massive as the sun rapidly exhaust [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/ StarDeath.html ] their nuclear fuel and end their lives in a spectacular supernova explosion [ http://antwrp.gsfc.nasa.gov/apod/ap030528.html ]. With less than this critical mass [ http://heasarc.gsfc.nasa.gov/docs/ xmm_lc/edu/lessons/background-lifecycles.html ] they evolve into red giants, pass through a relatively peaceful planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020302.html ] phase, and calmly fade away as white dwarf stars [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] like this one. Except that as a member of the NGC 1818 cluster, this new white dwarf would have evolved from a red giant star [ http://www.historyoftheuniverse.com/starold.html ] over 7.6 times as massive as the sun -- which should have exploded! Its discovery [ http://xxx.lanl.gov/abs/astro-ph/9802117 ] will likely force astronomers to revise the limiting mass estimate for supernovae upward. |
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Spiral Galaxy NGC 7742
| Title |
Spiral Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap000920.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years [ http://www.treasure-troves.com/astro/ Light-Year.html ] away in the constellation Pegasus [ http://www.seds.org/Maps/Stars_en/Fig/ pegasus.html ], NGC 7742 is known to be a Seyfert galaxy [ http://www.seds.org/~spider/spider/ScholarX/ seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://amazing-space.stsci.edu/light/index.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/ m077_hst.html ] of Seyferts can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/ subjectindex.html ]. |
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NGC 4631: The Whale Galaxy
| Title |
NGC 4631: The Whale Galaxy |
| Explanation |
NGC 4631 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n4631.html ] is a big beautiful spiral galaxy seen edge-on [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] only 25 million light-years away towards the small northern constellation Canes Venatici [ http://seds.lpl.arizona.edu/messier/map/CVn.html ]. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. Either way [ http://www.aemann.pwp.blueyonder.co.uk/paintings/ galaxy.html ], it is similar in size to our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ]. In this gorgeous color image [ http://www.noao.edu/outreach/aop/observers/ n4631.html ], the Whale's dark interstellar dust clouds, young bright blue star clusters, and purplish star forming regions are easy to spot [ http://antwrp.gsfc.nasa.gov/apod/ap990507.html ]. A companion [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ] galaxy, the small elliptical NGC 4627 appears above the Whale Galaxy. Out of view off the lower left corner of the picture lies another distorted galaxy, the hockey stick-shaped NGC 4656 [ http://www.noao.edu/outreach/aop/observers/n4656.html ]. The distortions and mingling trails [ http://antwrp.gsfc.nasa.gov/apod/ap970224.html ] of gas and dust [ http://www.astro.uni-bonn.de/~nneini/coldust.html ] detected at other wavelengths suggest that all three galaxies have had close encounters with each other in their past. The Whale Galaxy is also known to have spouted a halo of hot gas glowing in x-rays [ http://chandra.harvard.edu/press/01_releases/press_071901.html ]. |
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NGC 1977: Blue Reflection Ne
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| Title |
NGC 1977: Blue Reflection Nebula in Orion |
| Explanation |
The Orion Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980127.html ] is visible to the unaided eye as a fuzzy patch near the famous belt of three stars [ http://antwrp.gsfc.nasa.gov/apod/ap951114.html ] in the constellation [ http://galileo.gmu.edu/constellation/constellation.html ] Orion [ http://antwrp.gsfc.nasa.gov/apod/ap970523.html ]. The above picture captures a part of the Orion Nebula [ http://seds.lpl.arizona.edu/billa/twn/n1976x.html ] that primarily reflects light from bright Orion stars. This reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/index/ReflectionNebulae.html ] appears blue because the blue light from the neighboring stars scatters more efficiently from nebula gas than does red light. The dark lanes are composed of mostly interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] - fine needle-shaped carbon grains. |
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Seyfert Galaxy NGC 7742
| Title |
Seyfert Galaxy NGC 7742 |
| Explanation |
This might resemble [ http://oposite.stsci.edu/pubinfo/pr/1998/28/index.html ] a fried egg you've had for breakfast [ http://antwrp.gsfc.nasa.gov/apod/ap980320.html ], but it's actually much larger. In fact, ringed by blue-tinted star forming [ http://antwrp.gsfc.nasa.gov/apod/ap980701.html ] regions and faintly visible spiral arms [ http://antwrp.gsfc.nasa.gov/apod/ap980326.html ], the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across. About 72 million light-years away in the constellation Pegasus, NGC 7742 is known to be a Seyfert galaxy [ http://www.astro.soton.ac.uk/PH308/AGN/Seyferts.html ] - a type of active spiral galaxy [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.html ] with a center or nucleus which is very bright at visible wavelengths [ http://oposite.stsci.edu/pubinfo/education/amazing-space/ light/ems-frames.html ]. Across the spectrum, the tremendous brightness [ http://seds.lpl.arizona.edu/messier/more/m077_hst.html ] of Seyferts can change over periods of just days to months and galaxies like NGC 7742 are suspected of harboring massive black holes at their cores [ http://oposite.stsci.edu/pubinfo/pr/97/18.html ]. This beautiful color picture is courtesy of the newly inaugurated Hubble Space Telescope Heritage Project [ http://heritage.stsci.edu/public/commonpages/subjectindex.html ]. |
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Sideways Galaxy NGC 3628
| Title |
Sideways Galaxy NGC 3628 |
| Explanation |
Dark dust lanes cutting across the middle of this gorgeous island universe strongly hint that NGC 3628 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/ n3628.html ] is a spiral galaxy seen sideways [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ]. About 35 million light-years away in the northern springtime constellation Leo [ http://www.pacificsites.com/~hakuna/leo.html ], NGC 3628 also bears the distinction of being the only member of the well known Leo triplet [ http://seds.lpl.arizona.edu/messier/more/m066gr.html ] of galaxies not in Charles Messier's famous catalog [ http://seds.lpl.arizona.edu/messier/xtra/history/ m-cat.html ]. Otherwise similar in size to our Milky Way galaxy, the disk of NGC 3628 is clearly seen to fan out near the galaxy's edge. A faint arm of material also extends up and to the left in this deep view [ http://www.rc-astro.com/galaxies/ngc3628.html ] of the region. The distorted shape and tidal tail [ http://antwrp.gsfc.nasa.gov/apod/ap040515.html ] suggest that NGC 3628 [ http://www.aao.gov.au/images/captions/aat063.html ] is interacting gravitationally with the other spiral galaxies in the Leo triplet, M66 [ http://antwrp.gsfc.nasa.gov/apod/ap040407.html ] and M65 [ http://antwrp.gsfc.nasa.gov/apod/ap980807.html ]. |
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NGC 253: The Sculptor Galaxy
| Title |
NGC 253: The Sculptor Galaxy |
| Explanation |
NGC 253 is not only one of the brightest spiral galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap980922.html ] visible, it is also one of the dustiest [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ]. Discovered in 1783 by Caroline [ http://history.math.csusb.edu/Mathematicians/Herschel_Caroline.html ] Herschel [ http://www.scottlan.edu/LRIDDLE/WOMEN/herschel.htm ] in the constellation of Sculptor [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sculptor.html ], NGC 253 [ http://astro.nmsu.edu/~choopes/research.html ] lies only about ten million light-years distant. NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ] is the largest member of the Sculptor Group of Galaxies [ http://seds.lpl.arizona.edu/messier/xtra/ngc/sclgr.html ], the nearest group to our own Local Group of Galaxies [ http://seds.lpl.arizona.edu/messier/more/local.html ]. The dense dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] accompanies a high star formation [ http://antwrp.gsfc.nasa.gov/apod/ap981207.html ] rate, giving NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap961102.html ] the designation of starburst galaxy [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...505..639E&db_key=AST&nosetcookie=1&high=33613e8e5801623 ]. Visible in the above photograph [ http://oposite.stsci.edu/pubinfo/pr/1998/42/a.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] is the active central nucleus, also known to be a bright source of X-rays [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] and gamma rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
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Spiral Galaxy NGC 253
| Title |
Spiral Galaxy NGC 253 |
| Explanation |
A camera with [ http://www.eso.org/lasilla/Telescopes/2p2T/E2p2M/ WFI/news/WFI_P63.html ] over 67 million pixels (digital picture elements) was used to record this stunning image [ http://www.eso.org/outreach/press-rel/pr-1999/pr-02-99.html ] of spiral galaxy NGC 253 [ http://antwrp.gsfc.nasa.gov/apod/ap981209.html ]. Known as the Wide Field Imager (WFI), the camera is the latest instrument to be installed at the European Southern Observatory's 2.2 meter telescope [ http://www.ls.eso.org/lasilla/Telescopes/2p2T/E2p2M/E2p2M.html ] in La Silla, Chile [ http://search.eso.org:8080/lasilla/generalinfo/html/aboutls.html ]. Constructed from exposures made by the WFI in December 1998, this picture has been cropped from the full field to emphasize the galaxy and contrast adjusted to follow the graceful, winding arms and dramatic [ http://antwrp.gsfc.nasa.gov/apod/ap951001.html ] dust lanes of this photogenic island universe [ http://seds.lpl.arizona.edu/messier/xtra/similar/cher.html ]. Relatively bright foreground stars produce the sharp vertical streaks seen here while higher resolution versions of the image show intriguing, faint, background galaxies and likely globular star clusters [ http://www.limber.org/globs.html ] associated with NGC 253 [ http://seds.lpl.arizona.edu/messier/xtra/ngc/n0253.html ]. Two faint satellite trails are also visible. NGC 253, an Sc type spiral [ http://antwrp.gsfc.nasa.gov/apod/ap980314.html ], is about 8 million light-years away in the southern constellation Sculptor. |
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Stars of NGC 206
| Title |
Stars of NGC 206 |
| Explanation |
Nestled within the dusty arms of the large spiral galaxy Andromeda [ http://www.seds.org/messier/m/m031.html ] (M31), the star cluster NGC 206 is one of the largest star forming regions known in our local group of galaxies. The beautiful bright blue stars of NGC 206 [ http://www.fera.com/M31.html ] betray its youth - but close, systematic studies of variable stars [ http://redfrog.norconnect.no/~poems/poems/00535.html ] in and around NGC 206 will also accurately reveal its distance. Astronomers are searching [ http://xxx.lanl.gov/abs/astro-ph/9902382 ] for variable stars in NGC 206, particularly pulsating stars known as Cepheids [ http://antwrp.gsfc.nasa.gov/apod/ap960110.html ] and eclipsing binary star [ http://astrosun.tn.cornell.edu/courses/astro201/bin_eclipse.htm ] systems. Distances for these types of stars can be effectively determined by following the periodic changes [ http://www.pbs.org/wgbh/aso/databank/entries/dp12le.html ] in their brightness and spectra. About 3 million light-years away, an accurately known distance to NGC 206 and thus M31 [ http://antwrp.gsfc.nasa.gov/apod/ap960406.html ] is critical to the larger understanding of galaxy formation, galaxy evolution, and ultimately the distance scale of the Universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate96.html ]. |
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Star Wars in NGC 664
| Title |
Star Wars in NGC 664 |
| Explanation |
Long ago in a galaxy far, far away, locked in their final desperate struggle against the force of gravity [ http://heasarc.gsfc.nasa.gov/docs/snr.html ] ... two stars exploded! stellar explosions - Supernovae [ http://www.limber.org/SN1993J.html ] - are among the most powerful [ http://antwrp.gsfc.nasa.gov/apod/ap990420.html ] events in the Universe, estimated to release an equivalent energy [ http://www.physics.arizona.edu/physics/newsletter/summer95/sn.html ] of up to 1 million trillion trillion (1 followed by 30 zeros) megatons of TNT. After the explosion [ http://antwrp.gsfc.nasa.gov/apod/ap960726.html ], an expanding supernova envelope is observed to brighten [ http://astrosun.tn.cornell.edu/staff/wynnho/papers/sn94iopt.html ] over a a period of days to a maximum light output which rivals that of an entire galaxy before fading from view over the following months. Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf supernovae occur in average spiral galaxies [ http://oir-www.harvard.edu/cfa/oir/Research/supernova/RecentSN.html ] only about once every 25-100 years [ http://antwrp.gsfc.nasa.gov/apod/ap960623.html ]. But a recent observation of NGC 664, a spiral galaxy about 300 million light years distant, captured a rare and colorful performance - two supernovae from the same galaxy. In this monitoring exposure the two supernovae [ http://cfa-www.harvard.edu/cfa/hotimage/ngc664.html ], one reddish yellow and one blue, form a close pair just below the image center (to the right of the galaxy nucleus). The color difference is due to temperature - blue is hotter [ http://antwrp.gsfc.nasa.gov/apod/ap961202.html ]. |
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One-Armed Spiral Galaxy NGC
…
| Title |
One-Armed Spiral Galaxy NGC 4725 |
| Explanation |
While most spiral galaxies, including our own Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ], have two or more spiral arms, peculiar galaxy NGC 4725 [ http://www.noao.edu/outreach/aop/observers/n4725.html ] has only one. In this false-color Spitzer [ http://www.spitzer.caltech.edu/Media/mediaimages/sig/ sig05-011.shtml ] Space Telescope infrared [ http://coolcosmos.ipac.caltech.edu/cosmic_games/what/ ] image, the galaxy's solo spira mirabilis [ http://antwrp.gsfc.nasa.gov/apod/ap030925.html ] is seen in red, highlighting the emission from dust clouds warmed by newborn stars. The blue color is light from NGC 4725's population of old stars. Also sporting a prominent ring and a central bar, this galaxy is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices [ http://www.hawastsoc.org/deepsky/com/index.html ]. Computer simulations [ http://arxiv.org/abs/astro-ph/9705078 ] of the formation of single spiral arms suggest that they can be either leading or trailing arms with respect to a galaxy's overall rotation [ http://antwrp.gsfc.nasa.gov/apod/ap040221.html ]. |
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NGC 1309 and Friends
| Title |
NGC 1309 and Friends |
| Explanation |
A gorgeous [ http://heritage.stsci.edu/ ] spiral galaxy some 100 million light-years distant, NGC 1309 [ http://seds.lpl.arizona.edu/~spider/ngc/ngc.cgi?NGC1309 ] lies on the banks of the constellation Eridanus [ http://www.hawastsoc.org/deepsky/eri/index.html ]. NGC 1309 spans about 30,000 light-years, one third the size of our larger Milky Way galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap050825.html ]. Bluish clusters of young stars [ http://antwrp.gsfc.nasa.gov/apod/ap990402.html ] and dust lanes are seen to trace out NGC 1309's spiral arms as they wind around an older yellowish star population at its core. Not just another pretty face-on [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ] spiral galaxy, observations of NGC 1309's recent [ http://www.rochesterastronomy.org/sn2002/ sn2002fk.html ] supernova and cepheid stars contribute to the calibration [ http://cassfos02.ucsd.edu/public/tutorial/ Distances.html ] of the expansion [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2001/09/astrofile/ ] of the Universe. Still, after you get over this beautiful galaxy's grand [ http://curious.astro.cornell.edu/ question.php?number=199 ] design, check out [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/07/ image/c+zoom ] the array of more distant background galaxies also recorded in the sharp Hubble Space Telescope view [ http://hubblesite.org/newscenter/newsdesk/ archive/releases/2006/07/ ]. |
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