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Galactic Fossil Revealed in
…
| Title |
Galactic Fossil Revealed in Infrared Light |
| Description |
This animation demonstrates the power of infrared light to see what visible light cannot -- a newfound bundle of stars called a globular cluster. The movie shifts from a visible-light image to a near-infrared image to a new mid-infrared image from NASA's Spitzer Space Telescope. The visible-light image is from the California Institute of Technology's Digitized Sky Survey and the near-infrared image is from the NASA-funded Two Micron All-Sky Survey (2MASS). Globular clusters date back to the birth of our galaxy, 13 or so billion years ago. There are about 150 clusters sprinkled around the core of the galaxy like seeds in a pumpkin. Astronomers use these galactic "fossils" as tools for studying the age and formation of the Milky Way. Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. Astronomers then searched for past references to the cluster and found only one undocumented image from the Two Micron All-Sky Survey. Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth -- closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered. The Two Micron All-Sky Survey false-color image was obtained using near-infrared wavelengths ranging from 1.3 to 2.2 microns. The Spitzer false-color image composite was taken on April 21, 2004, by its infrared array camera. It is composed of images obtained at four mid-infrared wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). The true-color image from the Digitized Sky Survey was acquired with red and blue filters. |
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Spitzer Digs Up Galactic Fos
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| Title |
Spitzer Digs Up Galactic Fossil |
| Description |
This false-color image taken by NASA's Spitzer Space Telescope shows a globular cluster previously hidden in the dusty plane of our Milky Way galaxy. Globular clusters are compact bundles of old stars that date back to the birth of our galaxy, 13 or so billion years ago. Astronomers use these galactic "fossils" as tools for studying the age and formation of the Milky Way. Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. A visible-light image (inset) shows only a dark patch of sky. The red streak behind the core of the cluster is a dust cloud, which may indicate the cluster's interaction with the Milky Way. Alternatively, this cloud may lie coincidentally along Spitzer's line of sight. Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth -- closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered. This image composite was taken on April 21, 2004, by Spitzer's infrared array camera. It is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). The visible-light image is from the Digitized Sky Survey, California University of Technology, Pasadena, Calif. |
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Spitzer Digs Up Galactic Fos
…
| Title |
Spitzer Digs Up Galactic Fossil |
| Description |
This false-color image taken by NASA's Spitzer Space Telescope shows a globular cluster previously hidden in the dusty plane of our Milky Way galaxy. Globular clusters are compact bundles of old stars that date back to the birth of our galaxy, 13 or so billion years ago. Astronomers use these galactic "fossils" as tools for studying the age and formation of the Milky Way. Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. A visible-light image (inset) shows only a dark patch of sky. The red streak behind the core of the cluster is a dust cloud, which may indicate the cluster's interaction with the Milky Way. Alternatively, this cloud may lie coincidentally along Spitzer's line of sight. Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth -- closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered. This image composite was taken on April 21, 2004, by Spitzer's infrared array camera. It is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). The visible-light image is from the Digitized Sky Survey, California University of Technology, Pasadena, Calif. |
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Spitzer Digs Up Galactic Fos
…
| Title |
Spitzer Digs Up Galactic Fossil |
| Description |
This false-color image taken by NASA's Spitzer Space Telescope shows a globular cluster previously hidden in the dusty plane of our Milky Way galaxy. Globular clusters are compact bundles of old stars that date back to the birth of our galaxy, 13 or so billion years ago. Astronomers use these galactic "fossils" as tools for studying the age and formation of the Milky Way. Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. A visible-light image (inset) shows only a dark patch of sky. The red streak behind the core of the cluster is a dust cloud, which may indicate the cluster's interaction with the Milky Way. Alternatively, this cloud may lie coincidentally along Spitzer's line of sight. Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth -- closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered. This image composite was taken on April 21, 2004, by Spitzer's infrared array camera. It is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). The visible-light image is from the Digitized Sky Survey, California University of Technology, Pasadena, Calif. |
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Galactic Fossil Found Behind
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| Title |
Galactic Fossil Found Behind Curtain of Dust |
| Description |
This image mosaic shows the same patch of sky in various wavelengths of light. While the visible-light image (left) shows a dark sky speckled with stars, infrared images (middle and right), reveal a never-before-seen bundle of stars, called a globular cluster. The left panel is from the California Institute of Technology's Digitized Sky Survey, the middle panel includes images from the NASA-funded Two Micron All-Sky Survey and the University of Wyoming Infrared Observatory (circle inset), and the right panel is from NASA's Spitzer Space Telescope. Globular clusters date back to the birth of our galaxy, 13 or so billion years ago. There are about 150 clusters sprinkled around the core of the galaxy like seeds in a pumpkin. Astronomers use these galactic "fossils" as tools for studying the age and formation of the Milky Way. Most clusters orbit around the center of the galaxy well above its dust-enshrouded disc, or plane, while making brief, repeated passes through the plane that each last about a million years. Spitzer, with infrared eyes that can see into the dusty galactic plane, first spotted the newfound cluster during its current pass. Astronomers then searched for past references to the cluster and found only one undocumented image from the Two Micron All-Sky Survey. Follow-up observations with the University of Wyoming Infrared Observatory helped set the distance of the new cluster at about 9,000 light-years from Earth -- closer than most clusters -- and set the mass at the equivalent of 300,000 Suns. The cluster's apparent size, as viewed from Earth, is comparable to a grain of rice held at arm's length. It is located in the constellation Aquila. Astronomers believe that this cluster may be one of the last in our galaxy to be uncovered. The Two Micron All-Sky Survey false-color image was obtained using near-infrared wavelengths ranging from 1.3 to 2.2 microns. The University of Wyoming Observatory false-color image was captured on July 31, 2004, at wavelengths ranging from 1.2 to 2.2 microns. The Spitzer false-color image composite was taken on April 21, 2004, by its infrared array camera. It is composed of images obtained at four mid-infrared wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). |
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The Tycho Catalog Skymap
| Title |
The Tycho Catalog Skymap |
| Abstract |
This image set is a skymap of stars from the Tycho and Hipparcos star catalogs. The maps are plotted in Platte-Carre projection (Cylindrical-Equidistant) using celestial coordinates making them suitable for mapping onto spheres in many popular animation programs. The stars are plotted as gaussian point-spread functions (PSF) so the size and amplitude of the stars corresponds to their relative intensity. The stars are also elongated in Right Ascension (celestial longitude) based on declination (celestial latitude) so stars in the polar regions will still be round when projected on a sphere. Stars fainter than the "threshold magnitude", usually selected as 5th magnitude, have their magnitude-intensity curve adjusted so they appear brighter than they really are. This makes the band of the Milky Way more visible. Stellar colors are assigned based on B and V magnitudes (B and V are stellar magnitudes measured through different filters). If Tycho B and V magnitudes are unavailable, Johnson B and V magnitudes are used instead. From these, an effective stellar temperature is derived using the algorithms described in Flower (ApJ 469, 355 1996). Corrections were noted from Siobahn Morgan (UNI). The effective temperature was then converted to CIE tristimulus X,Y,Z triples assuming a blackbody emission distribution. The X,Y,Z values are then converted to red-green-blue color pixels. About 2.4 million stars are plotted, but many may be below the pixel intensity resolution. The three most conspicuously missing objects on these maps are the Andromeda galaxy (M31) and the two Magellanic Clouds. [The images in this visualization were updated August 28, 2007 to fix a bug in the star generation algorithm.] |
| Completed |
2007-08-14 |
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Celebrating Hubble With NGC
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| Title |
Celebrating Hubble With NGC 6751 |
| Explanation |
Planetary nebulae do [ http://antwrp.gsfc.nasa.gov/apod/ap991023.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubble.stsci.edu/ ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap991031.html ] of dying Sun-like stars to possess a staggering variety [ http://oposite.stsci.edu/pubinfo/pr/97/pn/index.html ] of detailed symmetries and shapes. This composite color Hubble image of NGC 6751 [ http://oposite.stsci.edu/pubinfo/pr/2000/12/index.html ] is a beautiful example of a classic planetary nebula with complex features and was selected to commemorate the tenth anniversary [ http://pao.gsfc.nasa.gov/gsfc/spacesci/hst10/hst_main.htm ] of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star [ http://antwrp.gsfc.nasa.gov/apod/ap990703.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.cchem.berkeley.edu/ChemResources/ temperature.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/public/2000apr6/ ngc6751table.html ] actual diameter is approximately 0.8 light-years or about 600 times the size [ http://antwrp.gsfc.nasa.gov/apod/ap990916.html ] of our solar system. NGC 6751 is 6,500 light-years distant in the constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ]. |
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A Tale of Comet Holmes
| Title |
A Tale of Comet Holmes |
| Explanation |
A beautiful blue ion tail has become visible in deep telescopic images of Comet Holmes [ http://antwrp.gsfc.nasa.gov/apod/ap071109.html ]. Pointing generally away from the Sun and also planet Earth, the comet's ion tail [ http://www.ifa.hawaii.edu/~jewitt/tail.html ] is seriously foreshortened [ http://en.wikipedia.org/wiki/ Perspective_(graphical)#Foreshortening ] by our extreme viewing angle. Still, enthusiastic [ http://spaceweather.com/comets/ gallery_holmes_page12.htm ] comet watchers have remarked that on the whole, the compact but tentacled appearance suggests a jellyfish or even a cosmic calamari [ http://en.wikipedia.org/wiki/Squid ]. This stunning view [ http://eder.csillagaszat.hu/digital/C17P_Holmes/20071104/ 17P_Holmes_20071104_eder_en.htm ] of the comet's greenish coma and blue tail was recorded on November 4 in clear skies near Budapest, Hungary. The colors are caused by molecules in [ http://www.spaceweather.com/swpod2007/26jul07/ John-Cordiale1.jpg ] the tenuous gas, like C2 (green) and CO+ (blue), fluorescing [ http://www.ifa.hawaii.edu/~jewitt/ spectral-excitation.html ] in sunlight. In a more recent development, the dramatic inset is a deep image from L'Aquila in central Italy on November 8, showing the ion tail disconnecting [ http://antwrp.gsfc.nasa.gov/apod/ap071003.html ] from the comet. |
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The Local Bubble and the Gal
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| Title |
The Local Bubble and the Galactic Neighborhood |
| Explanation |
What surrounds the Sun in this neck of the Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ]? Our current best guess is depicted in the above map [ http://www.sigmaxi.org/amsci/articles/00articles/Frischcap3.html ] of the surrounding 1500 light year [ http://chandra.harvard.edu/photo/cosmic_distance.html ]s constructed from various observations and deductions [ http://www.sigmaxi.org/amsci/articles/00articles/Frisch.html ]. Currently, the Sun is passing through a Local Interstellar Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ] (LIC), shown in violet, which is flowing away from the Scorpius-Centaurus Association [ http://www.mpifr-bonn.mpg.de/staff/tpreibis/scocen.html ] of young stars. The LIC resides in a low-density hole in the interstellar medium [ http://spacsun.rice.edu/~twg/lism.html ] (ISM) called the Local Bubble [ http://spacsun.rice.edu/~twg/pc120.html ], shown in black. Nearby, high-density molecular clouds [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] including the Aquila Rift [ http://www.a.phys.nagoya-u.ac.jp/~ohnishi/aquila/aquila.html ] surround star forming regions, each shown in orange. The Gum Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap001107.html ], shown in green, is a region of hot ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. Inside the Gum Nebula [ http://www.edpsciences.org/articles/astro/abs/1997/07/ads1235/ads1235.html ] is the Vela Supernova Remnant [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ], shown in pink, which is expanding to create fragmented shells of material like the LIC [ http://antwrp.gsfc.nasa.gov/apod/ap020217.html http://www-ssg.sr.unh.edu/tof/Outreach/Interstellar/index.html ]. Future observations should help astronomers discern more about the local Galactic Neighborhood [ http://www.sigmaxi.org/amsci/articles/00articles/frischmaterial.html#environment ] and how it might have affected Earth's past climate [ http://whyfiles.news.wisc.edu/017planet/gas_cloud2.html ]. |
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The E Nebula in Aquila
| Title |
The E Nebula in Aquila |
| Explanation |
Several unusual strands of darkness [ http://antwrp.gsfc.nasa.gov/apod/ap020526.html ] are prominent toward the constellation of Aquila [ http://chandra.harvard.edu/photo/constellations/aquila.html ]. This particular dark nebula [ http://zebu.uoregon.edu/~js/glossary/dark_nebula.html ] is known as the E Nebula, for its evocative shape, or B142 and B143, for its position(s) on a list of such nebula compiled by Barnard [ http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html ]. The E Nebula [ http://www.eastbayastro.org/articles/lore/aquila.htm ] spans roughly the angle of a full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ] and lies about 2000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] distant. The nebula [ http://www.abmedia.com/astro/current/b142-b143-fs102.html ] can be seen with binoculars and is particularly visible during the summer months in Earth's northern hemisphere. Other names for dark nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ] include absorption nebula [ http://www.glyphweb.com/esky/concepts/absorptionnebula.html ], as they efficiently absorb visible light emitted behind them, and molecular clouds [ http://etacha.as.arizona.edu/~eem/ttau/gmc.html ], as they frequently attain temperatures low enough so that several different types of stable molecules [ http://www.chem.ox.ac.uk/mom/ ] can exist. The low temperatures of these interstellar clouds [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ] facilitate the formation of dense knots [ http://antwrp.gsfc.nasa.gov/apod/ap011125.html ] of gas that may then collapse into bright stars. |
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Glimpse of a Globular Star C
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| Title |
Glimpse of a Globular Star Cluster |
| Explanation |
Not a glimpse of this cluster [ http://www.spitzer.caltech.edu/Media/releases/ ssc2004-16/quickfacts.shtml ] of stars can be seen [ http://www.spitzer.caltech.edu/Media/releases/ssc2004-16/ ssc2004-16b.shtml ] in the inset visible light image (lower right). Still, the infrared view [ http://www.spitzer.caltech.edu/Media/releases/ssc2004-16/ release.shtml ] from the Spitzer [ http://www.spitzer.caltech.edu/ ] Space Telescope reveals a massive globular star cluster of about 300,000 suns in an apparently empty region of sky in the constellation Aquila. When astronomers used infrared [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ light_lessons/our_world_different_light/ ] cameras to peer through obscuring dust [ http://antwrp.gsfc.nasa.gov/apod/ap030928.html ] in the plane of our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap040701.html ] galaxy, they were rewarded with the surprise discovery of the star cluster, likely one of the last such star clusters [ http://www.seds.org/messier/glob.html ] to be found. Globular star clusters [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2002/10/astrofile/ ] normally roam [ http://www.belmontnc.4dw.net/globulars.htm ] the halo of the Milky Way, ancient relics [ http://antwrp.gsfc.nasa.gov/apod/ap040918.html ] of our galaxy's formative years. Yet the Spitzer image shows this otherwise hidden cluster crossing through [ http://antwrp.gsfc.nasa.gov/apod/ap030125.html ] the middle of the galactic plane some 10,000 light-years away. At that distance, the picture spans only about 20 light-years. In the false color infrared image, the red streak is a dust cloud which seems to lie behind the cluster core. |
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Celebrating Hubble With NGC
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| Title |
Celebrating Hubble With NGC 6751 |
| Explanation |
Planetary nebulae can [ http://antwrp.gsfc.nasa.gov/apod/ap040424.html ] look simple, round, and planet-like in small telescopes. But images from the orbiting Hubble Space Telescope [ http://hubblesite.org/reference_desk/faq/ category.php.cat=hst ] have become well known for showing these fluorescent gas shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap050311.html ] of dying Sun-like stars to possess a staggering variety [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ image_category/nebula/planetary/ ] of detailed symmetries and shapes [ http://antwrp.gsfc.nasa.gov/apod/ap040910.html ]. This composite color Hubble image of NGC 6751 [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2000/12/ ] is a beautiful example of a classic planetary nebula with complex features. It was selected in April of 2000, to commemorate the tenth anniversary [ http://hubblesite.org/newscenter/newsdesk/future/ ] of Hubble in orbit. The colors were chosen to represent the relative temperature of the gas - blue, orange, and red indicating the hottest to coolest gas. Winds and radiation from the intensely hot central star [ http://antwrp.gsfc.nasa.gov/apod/ap050123.html ] (140,000 degrees [ http://www.unidata.ucar.edu/staff/ blynds/tmp.html ] Celsius [ http://www.astro.uu.se/history/Celsius_eng.html ]) have apparently created the nebula's streamer-like features. The nebula's [ http://heritage.stsci.edu/2000/12/fast_facts.html ] actual diameter is approximately 0.8 light-years or about 600 times the size of our solar system. NGC 6751 is 6,500 light-years distant in the high-flying constellation Aquila [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Aquila.html ]. |
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Loop I in the Northern Sky
| Title |
Loop I in the Northern Sky |
| Explanation |
One of the largest coherent structures on the sky is known simply as Loop I [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1980ApJ...242..533H ] and can best be seen in radio [ http://antwrp.gsfc.nasa.gov/apod/ap990403.html ] and X-ray [ http://antwrp.gsfc.nasa.gov/apod/ap961008.html ] maps. Spanning over 100 degrees, part of Loop I [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998AGM....14..K04B ] appears so prominent in northern sky maps that it is known as the North Polar Spur (NPS). Loop I, shown above [ http://heasarc.gsfc.nasa.gov/Images/rosat/snr_loop1.html ] in X-ray light [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ], is a thin bubble of gas about 700 light-years across with a center located only about 400 light-years away. Surprisingly, the cause of this immense structure is still debated, but is possibly related to expanding gas from a million-year old supernova [ http://antwrp.gsfc.nasa.gov/apod/ap981230.html ]. Loop I [ http://www.msi.umn.edu/Projects/twj/snrmeet/node17.html ] gas is impacting the nearby Aquila Rift [ http://antwrp.gsfc.nasa.gov/apod/ap980225.html ] molecular cloud [ http://dept.physics.upenn.edu/~myers/ASTR001/L25.html ], and may create relatively dense fragments of the local interstellar medium [ http://pegasus.phast.umass.edu/a100/handouts/ism.html ]. Were our Sun to pass through one of these fragments in the next few million years, it might affect Earth's climate [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996AAS...188.4408F ]. |
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A Nova In Aquila
| Title |
A Nova In Aquila |
| Explanation |
On December 1st [ http://www.aavso.org/alerts/alert264text.stm ], experienced observers patroling [ http://www.aavso.org/alerts/alert265text.stm ] the night sky with binoculars noticed what seemed to be a new star in the constellation of Aquila (The Eagle) [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Aquila.html ]. It wasn't really a new star though. A comparison [ http://aibn47.astro.uni-bonn.de/~gallery/various/novablink.html ] with detailed skymaps revealed the amazing truth, there was a known star at that position in the sky ... its brightness had simply increased by about "70,000 times". The star, now fondly known to variable star observers [ http://www.aavso.org/ ] as Nova V1494 Aquilae, continued to grow brighter for several days, becoming easily visible to the unaided eye before starting to slowly fade away. Its position within the constellation is indicated on this wide-angle picture [ http://aibn47.astro.uni-bonn.de/~gallery/various/novaaql.html ] taken on December 4th, near the time it was brightest. What would cause a star to undergo such a cataclysmic change? This "new star" appears to be a classical nova [ http://antwrp.gsfc.nasa.gov/apod/ap990524.html ]. Classical novae are thought to be interacting binary star systems [ http://oposite.stsci.edu/pubinfo/pr/97/29/slide-show-js.html ] in which one of the pair is a dense, hot white dwarf. Material from the companion falls onto the surface of the white dwarf, building up until it triggers a thermonuclear blast. A stunning increase in brightness and an expanding shell of debris result - but the binary system is likely not destroyed! Classical novae are believed to recur [ http://antwrp.gsfc.nasa.gov/apod/ap970925.html ] as the flow of material resumes and produces another outburst in perhaps hundreds of years time. |
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