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Very Large Array of Goddard Space Flight Center (GSFC)
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The Very Large Array of Radi
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| Title |
The Very Large Array of Radio Telescopes |
| Explanation |
The most photogenic array of radio telescopes [ http://csep10.phys.utk.edu/astr162/lect/light/radio.html ] in the world has also been one of the most productive. Each of the 27 radio telescopes [ http://www.r-clarke.org.uk/astrolinks_radio.htm ] in the Very Large Array [ http://en.wikipedia.org/wiki/Very_Large_Array ] (VLA) is the size of a house [ http://www.msue.msu.edu/msue/imp/mod02/master02.html ] and can be moved on train tracks. The above pictured [ http://www.aoc.nrao.edu/intro/vlapix/vlaviews.index.html ] VLA [ http://antwrp.gsfc.nasa.gov/apod/ap990620.html ], inaugurated in 1980 is situated in New Mexico [ http://www.state.nm.us/ ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. The VLA [ http://www.vla.nrao.edu/ ] has been used to discover water on planet Mercury [ http://www.nrao.edu/pr/2000/vla20/background/mercuryice/ ], radio-bright coronae around ordinary stars [ http://www.nrao.edu/pr/2000/vla20/background/radiostars/ ], micro-quasars in our Galaxy [ http://www.nrao.edu/pr/2000/vla20/background/superlum/ ], gravitationally-induced Einstein rings around distant galaxies [ http://www.nrao.edu/pr/2000/vla20/background/ering/ ], and radio counterparts to cosmologically distant gamma-ray bursts [ http://www.nrao.edu/pr/1998/grb/ ]. The vast size of the VLA [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?VLA ] has allowed astronomers to study the details of super-fast cosmic jets [ http://www.nrao.edu/pr/2000/vla20/background/jets/ ], and even map the center [ http://www.nrao.edu/pr/2000/vla20/background/galcenter/ ] of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ]. An upgrade of the VLA [ http://www.aoc.nrao.edu/evla/ ] is being planned. |
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The Very Large Array Turns T
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| Title |
The Very Large Array Turns Twenty |
| Explanation |
The most photogenic array of radio telescopes [ http://csep10.phys.utk.edu/astr162/lect/light/radio.html ] in the world has also been one of the most productive. Each of the 27 radio telescopes [ http://www.r-clarke.org.uk/astrolinks_radio.htm ] in the Very Large Array [ http://info.aoc.nrao.edu/doc/vla/html/VLAintro.shtml ] (VLA) is the size of a house [ http://www.msue.msu.edu/msue/imp/mod02/master02.html ] and can be moved on train tracks. The VLA [ http://antwrp.gsfc.nasa.gov/apod/ap990620.html ], celebrating its twentieth year [ http://www.aoc.nrao.edu/pr/vla20/vla20.html ] of operation, is pictured above [ http://www.aoc.nrao.edu/intro/vlapix/vlaviews.index.html ] in a compact formation in front of Tres Montosas [ http://angeleschapter.org/sps/summits/nm/socorro.htm ], New Mexico [ http://www.state.nm.us/ ], USA [ http://www.odci.gov/cia/publications/factbook/us.html ]. The VLA [ http://info.aoc.nrao.edu/vla/html/VLAhome.shtml ] has been used to discover water on planet Mercury [ http://www.aoc.nrao.edu/pr/vla20/mercury.ice.html ], radio-bright coronae around ordinary stars [ http://www.aoc.nrao.edu/pr/vla20/radiostars.html ], micro-quasars in our Galaxy [ http://www.aoc.nrao.edu/pr/vla20/superlum.html ], gravitationally-induced Einstein rings around distant galaxies [ http://www.aoc.nrao.edu/pr/vla20/einstein.ring.html ], and radio counterparts to cosmologically distant gamma-ray bursts [ http://www.aoc.nrao.edu/pr/vla20/grb.html ]. The vast size of the VLA [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?VLA ] has allowed astronomers to study the details of super-fast cosmic jets [ http://www.aoc.nrao.edu/pr/vla20/jets.html ], and even map the center of our Galaxy [ http://www.aoc.nrao.edu/pr/vla20/galcenter.html ]. An upgrade of the VLA [ http://www.aoc.nrao.edu/pr/evla.decadereview.html ] is being planned [ http://info.aoc.nrao.edu/vla/html/Upgrade/Upgrade_home.shtml ]. |
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A Big Dish at the VLA Radio
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| Title |
A Big Dish at the VLA Radio Observatory |
| Explanation |
They are so large, they are almost unreal. The radio dishes of the Very Large Array [ http://www.vla.nrao.edu/ ] (VLA) of radio telescopes [ http://csep10.phys.utk.edu/astr162/lect/light/radio.html ] might appear to some as a strange combination of a dinosaur skeleton [ http://www.bbc.co.uk/sn/prehistoric_life/games/skeleton_jigsaw/skeletal_jigsaws/index.shtml ] and common satellite-TV receiving dish [ http://en.wikipedia.org/wiki/Satellite_dish ]. Together, the 27 dishes of the VLA [ http://en.wikipedia.org/wiki/Very_Large_Array ] combine high sensitivity with high resolution, enabling a series of important astronomical discoveries, including water ice on planet Mercury [ http://www.nrao.edu/pr/2000/vla20/background/mercuryice/ ], micro-quasars in our Galaxy [ http://www.nrao.edu/pr/2000/vla20/background/superlum/ ], gravitationally-induced Einstein rings around distant galaxies [ http://www.nrao.edu/pr/2000/vla20/background/ering/ ], and radio counterparts to cosmologically distant gamma-ray bursts [ http://www.nrao.edu/pr/1998/grb/ ]. Pictured above, a dish from the VLA was photographed last week near Socorro [ http://en.wikipedia.org/wiki/Socorro%2C_New_Mexico ], New Mexico [ http://en.wikipedia.org/wiki/New_Mexico ], USA [ https://www.odci.gov/cia/publications/factbook/geos/us.html ]. |
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IC443's Neutron Star
| Title |
IC443's Neutron Star |
| Explanation |
Using x-ray data [ http://chandra.harvard.edu/photo/cycle1/1083/index.html ] from the orbiting Chandra Observatory [ http://chandra.harvard.edu/ ] along with radio data from the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap000530.html ], a team of researchers has discovered evidence for [ http://astro.ncssm.edu/ ] a new example of one of the most bizarre objects known to modern astrophysics -- a neutron star [ http://www.astro.umd.edu/~miller/ nstar.html#isolated ]. Embedded within supernova remnant IC443 [ http://antwrp.gsfc.nasa.gov/apod/ap970502.html ], the suspected neutron star appears as the reddish source at the lower right in this false-color x-ray image. Perhaps 20 kilometers across but with more mass than the Sun, this ultracompact object is the collapsed core of a massive star. The core collapsed when the star, located a reassuring 5,000 light-years [ http://www.howstuffworks.com/ question94.htm ] away in the constellation Gemini [ http://science.nasa.gov/headlines/y2000/ ast08dec_1.htm ], exploded long ago. How long ago? Judging from the characteristic bow wave [ http://antwrp.gsfc.nasa.gov/apod/ap001025.html ] shape of the x-ray nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980425.html ] the researchers have estimated the speed of the neutron star as it plows away from the explosion site. Comparing the speed to the measured distance traveled from the center of IC443, the team [ http://phywww1.ncssm.edu/physics/physics.htm ], three high school students and a teacher from the North Carolina School for Science and Mathematics, calculated that the light from the supernova explosion arrived at Earth about 30,000 years ago. |
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3C175: Quasar Cannon
| Title |
3C175: Quasar Cannon |
| Explanation |
3C175 is not only a quasar, it is a galaxy-fueled particle cannon. Visible as the central dot is quasar [ http://oposite.stsci.edu/pubinfo/PR/96/35/quasar.html ] 3C175, the active center of a galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap961125.html ] so distant [ http://isaac.exploratorium.edu/~pauld/activities/astronomy/cityuniversesize.html ] that the light we see from it was emitted when the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap001127.html ] was just forming [ http://www.astro.psu.edu/users/niel/scales/geohist1.ascii ]. The above image [ http://www.cv.nrao.edu/~abridle/3c175.htm ] was recorded in radio waves [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] by an array of house-sized telescopes called the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap000530.html ] (VLA). Shooting out from 3C175 is a thin jet [ http://antwrp.gsfc.nasa.gov/apod/ap000706.html ] of protons [ http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html ] and electrons [ http://www.aip.org/history/electron/ ] traveling near the speed of light [ http://www.what-is-the-speed-of-light.com/ ] that is over one million light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] long. The jet [ http://antwrp.gsfc.nasa.gov/apod/ap000619.html ] acts like a particle cannon [ http://www.pbs.org/tesla/ll/ll_wendwar.html ] and bores through gas cloud in its path. How this jet [ http://antwrp.gsfc.nasa.gov/apod/ap010816.html ] forms and why it is so narrow remain topics of current [ http://adsabs.harvard.edu/cgi-bin/bib_query?1994AJ....108..766B ] research [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999ApJ...511...84H ]. |
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Jets from Radio Galaxy 3C296
| Title |
Jets from Radio Galaxy 3C296 |
| Explanation |
Jets of streaming plasma [ http://www.plasmas.org/basics.htm ] expelled by the central black hole [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ] of a massive elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/elliptical_galaxies.html ] likely light up this composite image of 3C296 [ http://www.jb.man.ac.uk/atlas/object/3C296.html ]. The jets emanating from NGC 5532 [ http://www.mpa-garching.mpg.de/HIGHLIGHT/2001/highlight0103_e.html ] and are nearly a million light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] long. Exactly how the central black hole [ http://antwrp.gsfc.nasa.gov/apod/ap010508.html ] expels the infalling matter is still unknown. After clearing the galaxy, however, the jets [ http://antwrp.gsfc.nasa.gov/apod/ap991129.html ] inflate large radio bubbles that could glow for millions of years. If excited by a passing front, radio bubbles [ http://www.cv.nrao.edu/~abridle/images.htm ] can even light up again after a billion years. Visible light is depicted in the above image [ http://www.cv.nrao.edu/~abridle/3c296digss.htm ] in blue, while radio waves [ http://imagers.gsfc.nasa.gov/ems/radio.html ] are shown in red. The radio map was created with the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap000530.html ] of radio telescopes [ http://csep10.phys.utk.edu/astr162/lect/light/radio.html ]. |
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The Very Large Array of Radi
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| Title |
The Very Large Array of Radio Telescopes |
| Explanation |
The most photogenic array of radio telescopes [ http://csep10.phys.utk.edu/astr162/lect/light/radio.html ] in the world has also been one of the most productive. Each of the 27 radio telescopes [ http://www.r-clarke.org.uk/astrolinks_radio.htm ] in the Very Large Array [ http://info.aoc.nrao.edu/doc/vla/html/VLAintro.shtml ] (VLA) is the size of a house [ http://www.msue.msu.edu/msue/imp/mod02/master02.html ] and can be moved on train tracks. The above pictured [ http://www.nrao.edu/imagegallery/vla2/picture-006.html ] VLA [ http://antwrp.gsfc.nasa.gov/apod/ap990620.html ], celebrating its twenty-second year [ http://www.aoc.nrao.edu/pr/vla20/vla20.html ] of operation, is situated in New Mexico [ http://www.state.nm.us/ ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. The VLA [ http://info.aoc.nrao.edu/vla/html/VLAhome.shtml ] has been used to discover water on planet Mercury [ http://www.aoc.nrao.edu/pr/vla20/mercury.ice.html ], radio-bright coronae around ordinary stars [ http://www.aoc.nrao.edu/pr/vla20/radiostars.html ], micro-quasars in our Galaxy [ http://www.aoc.nrao.edu/pr/vla20/superlum.html ], gravitationally-induced Einstein rings around distant galaxies [ http://www.aoc.nrao.edu/pr/vla20/einstein.ring.html ], and radio counterparts to cosmologically distant gamma-ray bursts [ http://www.aoc.nrao.edu/pr/vla20/grb.html ]. The vast size of the VLA [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?VLA ] has allowed astronomers to study the details of super-fast cosmic jets [ http://www.aoc.nrao.edu/pr/vla20/jets.html ], and even map the center [ http://www.aoc.nrao.edu/pr/vla20/galcenter.html ] of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ]. An upgrade of the VLA [ http://www.aoc.nrao.edu/pr/evla.decadereview.html ] is being planned [ http://www.aoc.nrao.edu/evla/ ]. |
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The Galactic Center - A Radi
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| Title |
The Galactic Center - A Radio Mystery |
| Explanation |
Tuning in [ http://www.astrocappella.com/cosrad.shtml ] to the center of our Milky Way galaxy, radio astronomers [ http://www.aoc.nrao.edu/intro/ham.connection.html ] explore a complex, mysterious place. A premier high resolution view, this startlingly beautiful picture [ http://rsd-www.nrl.navy.mil/7213/lazio/GC/ ] covers a 4x4 degree region around the galactic center. It was constructed from 1 meter wavelength radio data obtained by telescopes of the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap020528.html ] near Socorro, New Mexico, USA. The galactic center [ http://science.nasa.gov/headlines/y2001/ast05sep_1.htm ] itself is at the edge of the extremely bright object labeled Sagittarius (Sgr) A, suspected of harboring a million solar mass black hole. Along the galactic plane which runs diagonally through the image are tortured clouds of gas energized by hot stars and bubble-shaped supernova remnants (SNRs) - hallmarks of a violent [ http://antwrp.gsfc.nasa.gov/apod/ap010910.html ] and energetic cosmic environment [ http://antwrp.gsfc.nasa.gov/apod/ap020110.html ]. But perhaps most intriguing are the arcs, threads, and filaments [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ] which abound in the scene. Their uncertain origins challenge present theories of the dynamics of the galactic center. |
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A Very Large Array of Radio
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| Title |
A Very Large Array of Radio Telescopes |
| Explanation |
Pictured above is one of the world's premiere radio astronomical observatories: The Very Large Array [ http://info.aoc.nrao.edu/doc/vla/html/VLAintro.shtml ] (VLA). Each antenna dish is as big as a house [ http://www.whitehouse.gov/WH/Welcome.html ] (25 meters across) and mounted on railroad tracks [ http://hamlet.phyast.pitt.edu/exhibit/neighborhoods/south/south_n226.html ]. The VLA consists of 27 dishes - together capable of spanning the size of a city (35 kilometers). The VLA [ http://www.nrao.edu/vla/html/VLAintro.shtml ] is the most sensitive radio telescope [ http://www.nro.nao.ac.jp/~kotaro/RTs/rts.html ] ever, and, through interferometry [ http://www.gps.caltech.edu/~eww/physics/node1037.html#SECTION000939000000000000000 ], can resolve a golf ball-sized radio source 150 kilometers away (0.04 arcsec). The VLA [ http://info.aoc.nrao.edu/doc/vla/obstatus/vlas/vlas.html ] is continually making new discoveries, including determining the composition of galaxies [ http://www.aoc.nrao.edu/doc/pr/press-1-11-95.html ], passing comets [ http://www.aoc.nrao.edu/doc/pr/press-3-14-96.html ], quasars [ http://adsabs.harvard.edu/cgi-bin/nph-article_query?bibcode=1993ApJ%2E%2E%2E402%2E%2E514K&page=1&plate_select=NO&type=GIF ], HII regions [ http://www.aas.org/ApJ/v449n2/5225/sc0.html ], and clusters of galaxies [ http://adsabs.harvard.edu/cgi-bin/nph-article_query?bibcode=1995AJ%2E%2E%2E%2E109%2E%2E853L&page=1&plate_select=NO&type=GIF ]. The VLA is also used to receive the weak radio signals broadcast from interplanetary spacecraft [ http://www.aoc.nrao.edu/doc/pr/press-11-16-95.html ]. The VLA is located in New Mexico [ http://www.viva.com/nm/nmhome.html ], USA. A significant upgrade [ http://www.aoc.nrao.edu/doc/pr/press-6-10-96.html ] of VLA's capabilities is planned. |
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Twin Proto-Planetary Disks
| Title |
Twin Proto-Planetary Disks |
| Explanation |
Sun-like stars [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/sun_parts.html ] are forming - and probably planets too [ http://wwwusr.obspm.fr/departement/darc/planets/encycl.html ] - hidden inside [ http://donald.phast.umass.edu/theses/dianne/chap1/node5.html ] Lynds 1551, an interstellar cloud of molecular gas and dust in the constellation [ http://www.mtwilson.edu/Education/ConQuiz/ ] Taurus. Using new receivers, coordinated radio telescopes at the Very Large Array [ http://www.nrao.edu/vla/html/VLAhome.shtml ] near Socorro, New Mexico, USA, can now sharply image the dusty proto-planetary disks surrounding these young stars at radio wavelengths. Just announced, this exciting example [ http://www.nrao.edu/pr/protodisks.html ] shows a false-color radio [ http://antwrp.gsfc.nasa.gov/apod/ap980917.html ] picture of twin disks in a double star system [ http://antwrp.gsfc.nasa.gov/apod/ap970219.html ]! A yellow bar indicates the scale in astronomical units (AUs) where one AU is the average distance between the Earth and Sun. The stars (unseen near the center of each disk) are about 45 AUs apart, comparable to the radius of the orbit of Pluto [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html ]. Similar proto-planetary disks [ http://antwrp.gsfc.nasa.gov/apod/ap980423.html ] have been seen around single stars, but these twin disks are much smaller, each limited in size by the gravity of the nearby companion star [ http://astrosun.tn.cornell.edu/courses/astro201/kepler_binary.htm ]. In fact, if large planets form orbiting near the edges of these disks they may be ejected from the binary system [ http://antwrp.gsfc.nasa.gov/apod/ap980529.html ]. |
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The Galactic Center - A Radi
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| Title |
The Galactic Center - A Radio Mystery |
| Explanation |
Tuning in [ http://www.pagecreations.com/astrocappella/welcome.html ] to the center of our Milky Way galaxy, radio astronomers explore a complex, mysterious place. A premier high resolution view, this startlingly beautiful picture [ http://rsd-www.nrl.navy.mil/7213/lazio/GC/ ] covers a 4x4 degree region around the galactic center. It was constructed from 1 meter wavelength radio data obtained by telescopes of the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap970727.html ] near Socorro, New Mexico, USA. The galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap971111.html ] itself is at the edge of the extremely bright object labeled Sagittarius (Sgr) A, suspected of harboring a million solar mass black hole. Along the galactic plane which runs diagonally through the image are tortured clouds of gas energized by hot stars and round-shaped supernova remnants (SNRs) - hallmarks of a violent [ http://www.astro.nwu.edu/astro/purcell/511kev_press_release/ ] and energetic cosmic environment [ http://antwrp.gsfc.nasa.gov/apod/ap980729.html ]. But perhaps most intriguing are the arcs, threads, and filaments [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991MNRAS%2E249%2E%2E262A&db_key=AST ] which abound in the scene. Their uncertain origins challenge present theories of the dynamics of the galactic center. |
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The Large and Small of M87
| Title |
The Large and Small of M87 |
| Explanation |
The small core of elliptical galaxy M87 [ http://antwrp.gsfc.nasa.gov/apod/ap950913.html ] appears to be energizing its whole galactic neighborhood. Recent images [ http://www.nrao.edu/pr/m87big.html ] from the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap970727.html ] (VLA) of radio telescopes [ http://www.nro.nao.ac.jp/~kotaro/RTs/rts.html ] indicate that huge bubbles of hot gas not only exist but are still being created. These bubbles measure 200,000 light-years across and surround the entire galaxy [ http://www.nrao.edu/~fowen/M87.html ]. The source creating and feeding the bubbles has been traced to jets [ http://www.jb.man.ac.uk/merlin/about/layman/jet.html ] pointing back to M87's center [ http://antwrp.gsfc.nasa.gov/apod/ap970405.html ], where a supermassive black hole [ http://antwrp.gsfc.nasa.gov/apod/ap970114.html ] is thought to live. The smallest scale on the above radio-map [ http://www.nrao.edu/~fowen/M87_halo.html ] is 0.2 light-years and imaged by many radio telescopes working together (VLBI [ http://www.jb.man.ac.uk/merlin/about/layman/vlbi.html ]). The labeled numbers refer to the wavelength of the radio waves observed. The exact composition of these jets is not known [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993MNRAS.264..228C&db_key=AST&high=34f6e1de7f07509 ], but thought to contain various subatomic particles [ http://pdg.lbl.gov/cpep/adventure_home.html ]. |
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A Very Large Array of Radio
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| Title |
A Very Large Array of Radio Telescopes |
| Explanation |
Pictured above is one of the world's premiere radio astronomical observatories: The Very Large Array [ http://info.aoc.nrao.edu/doc/vla/html/VLAintro.shtml ] (VLA). Each antenna dish is as big as a house [ http://www.whitehouse.gov/WH/Welcome.html ] (25 meters across) and mounted on railroad tracks. The VLA consists of 27 dishes - together capable of spanning the size of a city (35 kilometers). The VLA [ http://www.nrao.edu/vla/html/VLAintro.shtml ] is the most sensitive radio telescope [ http://www.nro.nao.ac.jp/~kotaro/RTs/rts.html ] ever, and, through interferometry [ http://www.sciam.com/0297issue/0297massonnet.html ], can resolve a golf ball-sized radio source 150 kilometers away (0.04 arcsec). The VLA [ http://info.aoc.nrao.edu/doc/vla/obstatus/vlas/vlas.html ] is continually making new discoveries, including determining the composition of galaxies [ http://www.aoc.nrao.edu/doc/pr/press-1-11-95.html ], passing comets [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998AJ....116..987D ], quasars [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1993ApJ...402..514K ], HII regions [ http://www.astro.uni-jena.de/Users/mfeldt/uchr/uchr.html ], and clusters of galaxies [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1995AJ....109..853L ]. The VLA is also used to receive the weak radio signals broadcast from interplanetary spacecraft [ http://www.aoc.nrao.edu/doc/pr/press-11-16-95.html ]. The VLA is located in New Mexico [ http://www.state.nm.us/ ], USA. A significant upgrade [ http://www.nrao.edu/vla/html/Upgrade/WhatIsIt.shtml ] of VLA's capabilities is planned. |
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Sundogs over the VLA
| Title |
Sundogs over the VLA |
| Explanation |
What if you woke up one morning and saw more than one Sun in the sky? Most probably, you would be seeing sundogs [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/sd.rxml ], extra-images of the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] created by falling ice-crystals [ http://dspace.dial.pipex.com/lc/halo/crystals.htm ] in the Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ]. As water freezes in the atmosphere, small, flat, six-sided, ice crystals [ http://kristall.uni-mki.gwdg.de/homep1.htm ] might be formed. As these crystals flutter to the ground, much time is spent with their faces flat, parallel to the ground. An observer may pass through the same plane as many of the falling ice crystals [ http://www.gi.alaska.edu/ScienceForum/ASF11/1180.html ] near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting [ http://wigner.byu.edu/LightRefract/LightRefract.html ] sunlight into our view and creating parhelia [ http://dspace.dial.pipex.com/lc/halo/plates.htm ], the technical term for sundogs. Sundogs [ http://www.members.tripod.com/~regenbogen/ee01ee02/ee02_11.htm ] were photographed here in a cloudy sky above the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap990620.html ] of radio telescopes [ http://casswww.ucsd.edu/physics/ph7/Radio_Tel.html ]. The real Sun is near the center above the train tracks. A bright sundog [ http://www.gi.alaska.edu/ScienceForum/ASF14/1422.html ] is visible on the far right, and a dim one on the far left. Ice-crystals can create other strange illusions of the Sun and Moon [ http://www.members.tripod.com/~regenbogen/indexe.htm ] including halos [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml ] and pillars [ http://antwrp.gsfc.nasa.gov/apod/ap990706.html ] |
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