|
|
The Pipe Dark Nebula
| Title |
The Pipe Dark Nebula |
| Explanation |
The dark nebula predominant at the lower left of the above photograph is known as the Pipe Nebula. The dark clouds, suggestively shaped like smoke rising from a pipe, are caused by absorption of background starlight by dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ]. These dust clouds can be traced all the way to the Rho Ophiuchi nebular clouds [ http://antwrp.gsfc.nasa.gov/apod/ap970922.html ] on the right. The brightest star in the field is Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ]. Many types of nebula are highlighted here: the red are emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], the blue are reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ], and the dark are absorption nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ]. This picture has been digitally enhanced [ http://www.astropix.com/HTML/J_DIGIT/ETHICS.HTM ]. |
|
Antares and Rho Ophiuchi
| Title |
Antares and Rho Ophiuchi |
| Explanation |
Why is the sky near Antares and Rho Ophiuchi [ http://www.seds.org/billa/twn/antx.html ] so colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap990829.html ]. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap000111.html ]. Backlit dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] clouds block starlight and so appear dark [ http://antwrp.gsfc.nasa.gov/apod/ap990511.html ]. Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ], a red supergiant [ http://www.lcse.umn.edu/research/RedGiant/ ] and one of the brighter stars in the night sky [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ], lights up the yellow-red clouds on the upper left. Rho Ophiuchi [ http://antwrp.gsfc.nasa.gov/apod/ap960312.html ] lies at the center of the blue nebula on the right. The distant globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] M4 is visible just below Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ], and to the left of the red cloud engulfing Sigma Scorpii [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992A%26A...261..203P ]. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
|
M4: The Closest Known Globul
…
| Title |
M4: The Closest Known Globular Cluster |
| Explanation |
M4 is a globular cluster [ http://www.seds.org/messier/glob.html ] visible in dark skies about one degree west of the bright star Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ] in the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] Scorpius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Scorpius.html ]. M4 is perhaps the closest globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] at 7000 light years [ http://www.treasure-troves.com/astro/Light-Year.html ], meaning that we see M4 [ http://www.seds.org/messier/m/m004.html ] only as it was 7000 years ago, near the dawn of recorded human history [ http://www.hyperhistory.com/online_n2/History_n2/a.html ]. Although containing hundreds of thousands of stars and spanning over 50 light-years, M4 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1993MNRAS.265..395D ] is one of the smallest and sparsest globular clusters [ http://ast.leeds.ac.uk/research/gcs.html ] known. A particularly unusual aspect for a globular cluster is M4 [ http://www.astr.ua.edu/gifimages/m4v.html ]'s central bar of stars. M4, pictured above [ http://www.noao.edu/image_gallery/html/im0598.html ], is one of the oldest objects for which astronomers can estimate age directly. Cluster white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/ap971102.html ] appear to be at least nine billion years old - so ancient they limit the youth of our entire universe [ http://www.astro.ucla.edu/~wright/cosmology_faq.html ]. |
|
The Colorful Clouds of Rho O
…
| Title |
The Colorful Clouds of Rho Ophiuchi |
| Explanation |
This stunning mosiac [ http://www.robgendlerastropics.com/Rhomosaic.html ] of the sky around bright stars Antares (Alpha Scorpii [ http://www.hawastsoc.org/deepsky/sco/index.html ]) and Rho Ophiuchi [ http://astro.nineplanets.org/twn/antx.html ] reveals spectacular colors in a cosmic starscape. Near the top, Rho Ophiuchi and nearby stars are immersed in blue reflection nebulae - dust clouds that shine primarily by reflected starlight [ http://antwrp.gsfc.nasa.gov/apod/ap060109.html ]. Cool supergiant star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ] (lower left) is itself shedding the material that reflects the evolved star's yellowish hue. Characteristic of star forming regions, the telltale red emission from hydrogen gas [ http://antwrp.gsfc.nasa.gov/apod/ap060519.html ] also permeates the view along with dark, obscuring dust clouds seen [ http://antwrp.gsfc.nasa.gov/apod/ap060623.html ] in silhouette against the background stars and brighter nebulosities. About 500 light-years away, the Rho Ophiuchi star clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000521.html ], are well in front of the nearby globular [ http://www.seds.org/messier/glob.html ] star cluster M4 [ http://antwrp.gsfc.nasa.gov/apod/ap030718.html ], visible just below and right of center. The wide view spans about 6 degrees on the sky. |
|
IC 4628: The Prawn Nebula
| Title |
IC 4628: The Prawn Nebula |
| Explanation |
South of Antares [ http://antwrp.gsfc.nasa.gov/apod/ap060714.html ], in the tail of the nebula-rich [ http://antwrp.gsfc.nasa.gov/apod/ap060628.html ] constellation Scorpius, lies emission nebula IC 4628 [ http://www.aao.gov.au/images/captions/aat105.html ]. Nearby hot, massive stars, millions of years young, radiate the nebula [ http://en.wikipedia.org/wiki/H_II_region ] with invisible ultraviolet light, stripping electrons from atoms. The electrons eventually recombine with the atoms to produce the visible nebular glow [ http://vis.sdsc.edu/research/hayden2.html ]. This narrow band [ http://antwrp.gsfc.nasa.gov/apod/ap060324.html ] image adopts a typical false-color mapping [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/eagle.shtml ] of the atomic emission, showing hydrogen emission in green hues, sulfur as red and oxygen as blue. At an estimated distance of 6,000 light-years, the region shown is about 250 light-years across. The nebula is also cataloged as [ http://antwrp.gsfc.nasa.gov/apod/ap060519.html ] Gum 56 for Australian astronomer Colin Stanley Gum, but seafood-loving astronomers might know [ http://seds.lpl.arizona.edu/messier/xtra/supp/ d-names.html ] this cosmic cloud as The Prawn Nebula [ http://www.martinpughastrophotography.id.au/ Nebulae/IC4628.htm ]. |
|
Nova Over Iran
| Title |
Nova Over Iran |
| Explanation |
A bright new nova is being studied by astronomers. The officially dubbed Nova Scorpii 2007 [ http://www.aavso.org/publications/specialnotice/33.shtml ] has become so bright in recent days that it is now visible [ http://skytonight.com/observing/home/Nova-Sco-2007.html ] to the unaided eye. Adventurous early morning sky enthusiasts [ http://antwrp.gsfc.nasa.gov/apod/ap040808.html ] should look in dark skies toward the constellation of the Scorpion [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Scorpius.html ], just below Jupiter and Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ]. The above image may help as a sky chart. A nova [ http://antwrp.gsfc.nasa.gov/apod/ap060224.html ] this bright occurs only every few [ http://en.wikipedia.org/wiki/Nova#Bright_novae_since_1890 ] years. Novas [ http://csep10.phys.utk.edu/astr162/lect/novae/novae.html ] are caused by thermonuclear explosions [ http://www.youtube.com/watch?v=1KoZS-PX3VM ] casting off the outer layers of a white dwarf [ http://en.wikipedia.org/wiki/White_dwarf ] star. Pictured above on Friday, the nova was being studied through a small telescope [ http://antwrp.gsfc.nasa.gov/apod/ap050413.html ] as it appeared over the Varzaneh Desert in Isfahan [ http://en.wikipedia.org/wiki/Isfahan ], Iran [ http://en.wikipedia.org/wiki/Iran ]. The nova [ http://curious.astro.cornell.edu/question.php?number=234 ] will likely fade but remain visible with binoculars [ http://www.aavso.org/cgi-bin/newql.pl?name=V1280%20Sco&output=html ] for at least a few more days. |
|
IC 4603: Reflection Nebula i
…
| Title |
IC 4603: Reflection Nebula in Ophiuchius |
| Explanation |
Why does this starfield photograph resemble an impressionistic painting [ http://www.ibiblio.org/wm/paint/glo/impressionism/ ]? The effect is created not by digital trickery [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ] but by large amounts of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ]. Dust, minute globs rich in carbon [ http://www.nyu.edu/pages/mathmol/modules/carbon/carbon1.html ] and similar in size [ http://www.lakeair.com/particle.html ] to cigarette smoke [ http://amos.indiana.edu/library/scripts/smoke.html ], frequently starts in the outer atmospheres of large, cool, young stars. The dust [ http://nedwww.ipac.caltech.edu/level5/March02/Li/Li_contents.html ] is dispersed as the star dies and grows as things stick to it in the interstellar medium [ http://www-ssg.sr.unh.edu/ism/intro.html ]. Dense dust clouds are opaque [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] to visible light [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue [ http://www.why-is-the-sky-blue.org/why-is-the-sky-blue.html ] starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], can combine to form areas seemingly created on an artist's canvas. Photographed above [ http://ryutao.main.jp/english/stl_ant.html ] is roughly four square degrees of the nebula IC 4603 [ http://antwrp.gsfc.nasa.gov/apod/ap060714.html ] near the bright star Antares [ http://en.wikipedia.org/wiki/Antares ] toward the constellation [ http://en.wikipedia.org/wiki/Constellation ] of Ophiuchus [ http://www.seds.org/Maps/Stars_en/Fig/ophiuchus.html ]. |
|
A Close Encounter Of The Ste
…
| Title |
A Close Encounter Of The Stellar Kind |
| Explanation |
The unassuming star centered in this sky view [ http://skyview.gsfc.nasa.gov ] will one day be our next door [ http://antwrp.gsfc.nasa.gov/apod/ap010318.html ] stellar neighbor. The faint 9th magnitude red dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap991120.html ], currently 63 light-years away in the constellation Ophiucus [ http://www.seds.org/Maps/Stars_en/Fig/ophiuchus.html ], was recently discovered to be approaching our Solar System. Known in catalogs of nearby stars [ http://cdsweb.u-strasbg.fr/htbin/myqcat3?V/70A/ ] as Gliese (Gl) 710 it is predicted to come within nearly 1 light-year of the Sun ... about 1.5 million years from now. At that distance this star, presently much too faint to be seen [ http://liftoff.msfc.nasa.gov/academy/universe/MAG.HTML ] by the naked eye, will blaze at 0.6 magnitude - rivaling the apparent brightness of the mighty red giant Antares [ http://antwrp.gsfc.nasa.gov/apod/ap970624.html ]. Ultimately Gliese 710 poses no direct collision danger itself although its gravitational influence will likely scatter comets out of the Solar System's reservoir, the Oort cloud [ http://www.windows.umich.edu/cgi-bin/tour_def/comets/ Oort_cloud.html ], sending some inbound. This future stellar encounter [ http://adsabs.harvard.edu/cgi-bin/ nph-bib_query?bibcode=1999AJ....117.1042G&db_key=AST&high=3af6c03e8102908 ] was discovered by researchers Joan Garcia-Sanchez and Robert Preston (JPL [ http://www.jpl.nasa.gov ]), and collaborators while studying stars in the solar neighborhood [ http://www.clockwk.com/stars/ ] using data from the Hipparcos Astrometry Satellite [ http://astro.estec.esa.nl/SA-general/Projects/Hipparcos/ hipparcos.html ]. The star field shown is based on the Palomar Digitized Sky Survey [ http://www-gsss.stsci.edu/Dss/dss_home.HTM ] and is 1/4 degree wide (about half the diameter of the full moon). |
|
A Scorpius Sky Spectacular
| Title |
A Scorpius Sky Spectacular |
| Explanation |
If Scorpius looked this good to the unaided eye, humans might remember it better. Scorpius [ http://www.allthesky.com/constellations/scorpius/ ] more typically appears as a few bright stars in a well known but rarely pointed out zodiacal [ http://en.wikipedia.org/wiki/Zodiac ] constellation [ http://www.fillingthesky.com/constellationhistory.html ]. To get a spectacular image like this [ http://astrosurf.com/sguisard/Pagim/Scorpius_constellation-LHRVB-50mm.html ], though, one needs a good camera [ http://electronics.howstuffworks.com/digital-camera.htm ], color filters [ http://en.wikipedia.org/wiki/Filter_%28optics%29 ], and a digital image processor. To bring out detail, the above image [ http://astrosurf.com/sguisard/Pagim/Scorpius_constellation-LHRVB-50mm.html ] not only involved long duration exposures taken in several colors, but one exposure in a very specific red color [ http://antwrp.gsfc.nasa.gov/apod/ap050930.html ] emitted by hydrogen [ http://periodic.lanl.gov/elements/1.html ] that brings out great detail. The resulting image [ http://astrosurf.com/sguisard/Pagim/Scorpius_constellation-LHRVB-50mm.html ] shows many breathtaking features. Vertically across the image left is part of the plane [ http://antwrp.gsfc.nasa.gov/apod/ap050605.html ] of our Milky Way Galaxy [ http://seds.org/messier/more/mw.html ]. Visible there are vast clouds of bright stars and long filaments of dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ]. Jutting out diagonally from the Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap070123.html ] in the image center are dark dust bands known as the Dark River [ http://antwrp.gsfc.nasa.gov/apod/ap040809.html ]. This river connects to several bright stars on the right that are part of Scorpius' head and claws [ http://www.ianridpath.com/startales/scorpius.htm ], and include the bright star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ]. Above and right of Antares is an even brighter planet Jupiter. Numerous red emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] and blue reflection nebulas [ http://en.wikipedia.org/wiki/Reflection_nebula ] are visible throughout the image. Scorpius [ http://en.wikipedia.org/wiki/Scorpion ] appears prominently in southern skies after sunset during the middle of the year. |
|
The Colorful Clouds of Rho O
…
| Title |
The Colorful Clouds of Rho Ophiuchi |
| Explanation |
The many spectacular colors of the Rho Ophiuchi [ http://www.seds.org/billa/twn/antx.html ] (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star Rho Ophiuchi [ http://coolcosmos.ipac.caltech.edu/image_galleries/legacy/iras_rhooph_gc/captio n.html ] and nearby stars reflects [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue [ http://www.why-is-the-sky-blue.org/why-is-the-sky-blue.html ] for the same reason. The red and yellow regions shine primarily because of emission [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ] - knocks electrons [ http://www-istp.gsfc.nasa.gov/Education/welect.html ] away from the gas, which then shines when the electrons recombine with the gas. The dark regions [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] are caused by dust grains [ http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis1.html ] - born in young stellar atmospheres - which effectively block light emitted behind them. The Rho Ophiuchi star clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000521.html ], well in front of the globular cluster [ http://www.seds.org/messier/glob.html ] M4 [ http://antwrp.gsfc.nasa.gov/apod/ap000523.html ] visible above [ http://www.noao.edu/outreach/aop/observers/antares.html ] on far lower left, are even more colorful than humans can see [ http://www.colormatters.com/optics.html ] - the clouds emits light in every wavelength band [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] from the radio [ http://imagers.gsfc.nasa.gov/ems/radio.html ] to the gamma-ray [ http://imagers.gsfc.nasa.gov/ems/gamma.html ]. |
|
The Milky Way at 5000 Meters
| Title |
The Milky Way at 5000 Meters |
| Explanation |
Climb up to 5000 meters (16,500 feet) above sea level, near Cerro Chajnantor [ http://www.alma.nrao.edu/development/site/Chajnantor/ photos/ ] in the northern Chilean Andes [ http://www.solarviews.com/cap/earth/chile.htm ], and your night sky could encompass this cosmic vista. Recorded from that high and dry locale [ http://www.alma.nrao.edu/development/site/ ], the spectacular fish-eye image features the myriad stars and sprawling dust clouds of our Milky Way Galaxy [ http://www.atlasoftheuniverse.com/galaxy.html ]. The direction toward the center of the Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap070210.html ] is near the zenith and center of the picture, but the Galactic Center [ http://antwrp.gsfc.nasa.gov/apod/ap021018.html ] itself is hidden from view, located far behind the obscuring dust. Brilliant Jupiter rules this scene just above the Milky Way's [ http://antwrp.gsfc.nasa.gov/apod/ap071020.html ] central bulge with the noticeably fainter, yellowish, giant star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ] to its right. Small and faint, near the right edge of the picture is one of the Milky Way's many satellite galaxies [ http://www.atlasoftheuniverse.com/sattelit.html ], the Small Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap050617.html ]. The Amateur Astronomers Association of New York Presents: APOD Editor's Lecture: Tonight [ http://www.aaa.org/ ] - American Museum of Natural History |
|
The Colorful Clouds of Rho O
…
| Title |
The Colorful Clouds of Rho Ophiuchi |
| Explanation |
The many spectacular colors of the Rho Ophiuchi [ http://www.seds.org/billa/twn/ant.html ] (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions [ http://antwrp.gsfc.nasa.gov/apod/lib/reflection.html ] shine primarily by reflected light. Blue light from the star rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue for the same reason. The red and yellow regions [ http://antwrp.gsfc.nasa.gov/apod/lib/emission.html ] shine primarily because of emission of the nebula's atomic and molecular gas [ http://donald.phast.umass.edu/latex/oph/oph.html ]. Light from nearby stars - particularly the bright star Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ] in this case - knocks electrons [ http://pdg.lbl.gov/cpep/adventure.html ] away from the gas, which then shines when the electrons recombine with the gas [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#hydrogen ]. The dark regions are caused by dust grains [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] - born in young stellar atmospheres - which effectively block light emitted behind them. The Rho Ophiuchi star clouds [ http://www-astro.phast.umass.edu/latex/oph/section3_3.html ], well in front of the globular cluster M4 visible on far lower left, are even more colorful than humans can see - the clouds emits light in every wavelength band [ http://www.astro.washington.edu/strobel/lightnotes/lightnotes.html ] from the radio to the gamma-ray. |
|
The Pipe Dark Nebula
| Title |
The Pipe Dark Nebula |
| Explanation |
The dark nebula predominant at the lower left of the above photograph is known as the Pipe Nebula [ http://www.astropix.com/piperho.htm ]. The dark clouds, suggestively shaped like smoke rising from a pipe, are caused by absorption of background starlight by dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ]. These dust clouds can be traced all the way to the Rho Ophiuchi nebular clouds [ http://antwrp.gsfc.nasa.gov/apod/ap960312.html ] on the right. The brightest star in the field is Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ]. Many types of nebula are highlighted here: the red are emission nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/emission.html ], the blue are reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/reflection.html ], and the dark are absorption nebula [ http://antwrp.gsfc.nasa.gov/apod/lib/dark.html ]. This picture has been digitally enhanced [ http://www.astropix.com/digtechs.htm ]. |
|
Mt. Etna Lava Plumes
| Title |
Mt. Etna Lava Plumes |
| Explanation |
Mt. Etna [ http://www.volcanolive.com/etna.html ] has been erupting for hundreds of thousands of years. Located in Sicily [ http://www.siol.it/Ricerca/Sicily_map.htm ], Italy [ http://www.cia.gov/cia/publications/factbook/geos/it.html ], the volcano [ http://www.geography.learnontheinternet.co.uk/topics/etna.html ] produces lava fountains over one kilometer high. Mt. Etna [ http://volcano.und.nodak.edu/vwdocs/current_volcs/etna/ ] is not only one of the most active volcanoes [ http://www.volcanolive.com/active2.html ] on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ], it is one of the largest, measuring over 50 kilometers at its base and rising nearly 3 kilometers high. Pictured in 2001 May, the tops of two lava plumes [ http://antwrp.gsfc.nasa.gov/apod/ap020121.html ] are visible near the center of the frame, while hot lava [ http://volcano.und.nodak.edu/vwdocs/glossary.html#lava ] flowing down the volcano [ http://volcano.und.nodak.edu/ ] is visible on the left. This panoramic shot [ http://www.educeth.ch/stromboli/etna/etna01/etna0105-en.html ] also includes the city lights of Calabria and Taormina on the left, and Catania on the right. The Earth's rotation [ http://antwrp.gsfc.nasa.gov/apod/ap010110.html ] is discernable on this long duration image [ http://www.educeth.ch/stromboli/etna/etna01/etna0105-en.html ] as star trails [ http://antwrp.gsfc.nasa.gov/apod/ap000905.html ]. Orange Mars [ http://www.nineplanets.org/mars.html ] can be seen rising just below the star Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ] far in the distance. |
|
IC 4603: Reflection Nebula i
…
| Title |
IC 4603: Reflection Nebula in Ophiuchius |
| Explanation |
Why does this starfield photograph resemble an impressionistic painting [ http://www.ibiblio.org/wm/paint/glo/impressionism/ ]? The effect is created not by digital trickery [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ] but by large amounts of interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ]. Dust, minute globs rich in carbon [ http://www.nyu.edu/pages/mathmol/modules/carbon/carbon1.html ] and similar in size [ http://www.lakeair.com/particle.html ] to cigarette smoke [ http://amos.indiana.edu/library/scripts/smoke.html ], frequently starts in the outer atmospheres of large, cool, young stars. The dust [ http://nedwww.ipac.caltech.edu/level5/March02/Li/Li_contents.html ] is dispersed as the star dies and grows as things stick to it in the interstellar medium [ http://www-ssg.sr.unh.edu/tof/Outreach/Interstellar/index.html?what1.html ]. Dense dust clouds are opaque [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] to visible light [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue [ http://www.why-is-the-sky-blue.org/why-is-the-sky-blue.html ] starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], can combine to form areas seemingly created on an artist's canvas. Photographed above [ http://home.earthlink.net/~gstevens916/pic4603.htm ] is roughly one square degree of the nebula IC 4603 [ http://www.psiaz.com/Schur/astro/filmimagepages/rho.html ] near the bright star Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ] toward the constellation [ http://www.adlerplanetarium.org/history/exhibits/constellations/timeline.html ] of Ophiuchus [ http://www.seds.org/Maps/Stars_en/Fig/ophiuchus.html ]. |
|
Antares
| Title |
Antares |
| Explanation |
Antares [ http://scienceweb.dao.nrc.ca/astro/skygaze060696.html ] is a huge star. In a class called red supergiant [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1992AJ%2E%2E%2E%2E104%2E%2E821M&db_key=AST&nosetcookie=1 ], Antares is about 700 times the size of our own Sun [ http://antwrp.gsfc.nasa.gov/apod/lib/sun.html ], 15 times more massive, and 10,000 times brighter. Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ] is the brightest star in the constellation of Scorpius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Scorpius.html ] and one of the brighter stars [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ] in all the night sky. Antares [ http://www.seds.org/billa/twn/antx.html ] is surrounded by a nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983ApJ%2E%2E%2E275%2E%2E704H&db_key=AST&nosetcookie=1 ] of gas which it has itself expelled. Radiation from Antares [ http://stardate.utexas.edu/radio/StarDateDB.FM$RETRIEVE?value=06/11/1996&field=ScriptAirDate&html=Test+Request+Date ]' blue stellar companion helps cause the nebular gas to glow, as photographed above. Antares [ http://www.travel-net.com/mickey/mh41.html ] is located about 500 light years away. |
|
A Close Encounter of the Ste
…
| Title |
A Close Encounter of the Stellar Kind |
| Explanation |
The unassuming star centered in this sky view [ http://skyview.gsfc.nasa.gov ] will one day be our next door [ http://www.bigear.org/vol1no2/kraus.htm ] stellar neighbor [ http://www.astro.wisc.edu/~dolan/constellations/extra/nearest.html ]. The faint 9th magnitude red dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap970605.html ] currently 63 light-years away [ http://zebu.uoregon.edu/~soper/Stars/parallax_ly.html ] in the constellation Ophiucus [ http://www.astro.wisc.edu/~dolan/constellations/extra/nearest.html ] was recently discovered to be on a course toward our Solar System. Known in catalogs of nearby stars [ http://proxima.astro.virginia.edu/~pai/Recons/index.html ] as Gliese 710 it is predicted to come within 1 light-year of the Sun ... a million years from now. At that distance this star, presently much too faint to be seen [ http://liftoff.msfc.nasa.gov/academy/universe/MAG.HTML ] by the naked eye, will blaze at 0.6 magnitude - rivaling the apparent brightness of the mighty red giant Antares [ http://antwrp.gsfc.nasa.gov/apod/ap970624.html ]. Gliese 710 poses no direct collision danger [ http://ccf.arc.nasa.gov/sst/main.html ] itself although its gravitational influence will likely scatter comets out of the Solar System's reservoir, the Oort cloud, sending some inbound [ http://antwrp.gsfc.nasa.gov/apod/ap961219.html ]. This future stellar encounter was discovered by researchers Joan Garcia-Sanchez and Robert Preston (JPL [ http://www.jpl.nasa.gov ]), and collaborators while studying stars in the solar neighborhood [ http://www.clockwk.com/stars/ ] using data from the Hipparcos Astrometry Satellite [ http://astro.estec.esa.nl/SA-general/Projects/Hipparcos/ hipparcos.html ]. The star field shown is based on the Palomar Digitized Sky Survey [ http://www-gsss.stsci.edu/dss/dss.html ] and is 1/4 degree wide (about half the diameter of the full moon). |
|
Antares and Rho Ophiuchi
| Title |
Antares and Rho Ophiuchi |
| Explanation |
Why is the sky near Antares and Rho Ophiuchi [ http://www.seds.org/billa/twn/antx.html ] so colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap960903.html ]. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap960606.html ]. Backlit dust [ http://antwrp.gsfc.nasa.gov/apod/ap961119.html ] clouds block starlight and so appear dark [ http://antwrp.gsfc.nasa.gov/apod/ap961005.html ]. Antares [ http://antwrp.gsfc.nasa.gov/apod/ap970624.html ], a red supergiant [ http://antwrp.gsfc.nasa.gov/apod/ap970922.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1992AJ%2E%2E%2E%2E104%2E%2E821M&db_key=AST&nosetcookie=1 ] and one of the brighter stars in the night sky [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ], lights up the yellow-red clouds on the upper left. Rho Ophiuchi [ http://antwrp.gsfc.nasa.gov/apod/ap960312.html ] lies at the center of the blue nebula on the right. The distant globular cluster [ http://antwrp.gsfc.nasa.gov/apod/ap970916.html ] M4 is visible just below Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ], and to the left of the red cloud engulfing Sigma Scorpii [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1992A%26A%2E%2E%2E261%2E%2E203P&db_key=AST&nosetcookie=1 ]. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum [ http://heasarc.gsfc.nasa.gov/docs/learning_center/basic/emspectrum.html ]. |
|
Venus On The Horizon
| Title |
Venus On The Horizon |
| Explanation |
The month of October [ http://www.skypub.com/whatsup/oct97sky.html ] features a sky full of planets, including Venus as the brilliant evening star. Besides the sun and moon, Venus is the brightest object [ http://www.seds.org/billa/nineplanets/venus.html ] visible in Earth's sky. This month, Venus appears in early evening near the red planet Mars [ http://antwrp.gsfc.nasa.gov/apod/ap970528.html ] and Mars' red giant rival Antares [ http://antwrp.gsfc.nasa.gov/apod/ap970922.html ] above the southwestern horizon. Because it is closer to the sun than Earth, Venus never strays far from the sun in its apparent position [ http://quasar.as.utexas.edu/courses/ast309/misc/DresdenCodex.html ] and is seen during the year as either a bright morning or evening star [ http://rowlf.cc.wwu.edu:8080/~skywise/legends.html#Evening Star ]. This beautiful sunset imaged from low earth orbit by the Atlantis space shuttle [ http://www.ksc.nasa.gov/shuttle/resources/orbiters/atlantis.html ] crew in May 1989 also reveals the planet Venus blazing above Earth's horizon. It is a fitting image [ http://images.jsc.nasa.gov/images/pao/STS30/10063311.htm ] for this mission and crew [ http://www.ksc.nasa.gov/shuttle/missions/sts-30/sts-30-press-kit.txt ]. It was recorded following the successful release of the robot Venus-explorer Magellan [ http://nssdc.gsfc.nasa.gov/planetary/magellan.html ], the first planetary probe to be deployed from a space shuttle. |
|
Antares and Rho Ophiuchi
| Title |
Antares and Rho Ophiuchi |
| Explanation |
Why is the sky near Antares and Rho Ophiuchi [ http://www.seds.org/billa/twn/antx.html ] so colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap031229.html ]. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap000111.html ]. Backlit dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] clouds block starlight and so appear dark [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ]. Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ], a red supergiant [ http://hyperphysics.phy-astr.gsu.edu/hbase/astro/redsup.html ] and one of the brighter stars in the night sky [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ], lights up the yellow-red clouds on the upper left. Rho Ophiuchi [ http://www.iso.vilspa.esa.es/galleries/ism/rhooph.html ] lies at the center of the blue nebula on the right. The distant globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] M4 [ http://antwrp.gsfc.nasa.gov/apod/ap000523.html ] is visible just below Antares [ http://www.astro.wisc.edu/~dolan/constellations/hr/6134.html ], and to the left of the red cloud engulfing Sigma Scorpii [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1992A%26A...261..203P ]. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ]. |
|
The Colorful Clouds of Rho O
…
| Title |
The Colorful Clouds of Rho Ophiuchi |
| Explanation |
The many spectacular colors of the Rho Ophiuchi [ http://www.seds.org/billa/twn/antx.html ] (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the star Rho Ophiuchi [ http://coolcosmos.ipac.caltech.edu/image_galleries/legacy/iras_rhooph_gc/caption.html ] and nearby stars reflects [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue [ http://www.why-is-the-sky-blue.org/why-is-the-sky-blue.html ] for the same reason. The red and yellow regions shine primarily because of emission [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ] - knocks electrons [ http://www-istp.gsfc.nasa.gov/Education/welect.html ] away from the gas, which then shines when the electrons recombine with the gas. The dark regions [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ] are caused by dust grains [ http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis1.html ] - born in young stellar atmospheres - which effectively block light emitted behind them. The Rho Ophiuchi star clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000521.html ], well in front of the globular cluster [ http://www.seds.org/messier/glob.html ] M4 [ http://antwrp.gsfc.nasa.gov/apod/ap000523.html ] visible above [ http://www.noao.edu/outreach/aop/observers/antares.html ] on far lower left, are even more colorful than humans can see [ http://www.colormatters.com/optics.html ] - the clouds emits light in every wavelength band [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] from the radio [ http://imagers.gsfc.nasa.gov/ems/radio.html ] to the gamma-ray [ http://imagers.gsfc.nasa.gov/ems/gamma.html ]. |
|
The Dark River to Antares
| Title |
The Dark River to Antares |
| Explanation |
Connecting the Pipe Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap020526.html ] to the bright star Antares is a flowing dark cloud nicknamed the Dark River [ http://www.astropix.com/HTML/D_SUM_S/PIPE.HTM ]. The murkiness of the Dark River [ http://antwrp.gsfc.nasa.gov/apod/ap030928.html ] is caused by absorption of background starlight by dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ], although the nebula contains mostly hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] and molecular gas. Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ], the brightest star in the frame, is embedded in the colorful Rho Ophiuchi [ http://antwrp.gsfc.nasa.gov/apod/ap040602.html ] nebula clouds. The Dark River, pictured above [ http://www.starryscapes.com/nebula/rho_ophiuchus.html ] across the upper left, spans over 20 times the angular diameter of the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ] and lies about 500 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] distant. Other types of nebula [ http://www.seds.org/billa/twn/antx.html ] visible here include red emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] and the blue reflection [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] nebula. |
|
Moon Lightning
| Title |
Moon Lightning |
| Explanation |
Moonsets [ http://antwrp.gsfc.nasa.gov/apod/ap020921.html ] are not often quite as exciting as this one. But amateur astronomer Marc-Andre Besel was impressed by the brilliant lighting displays that joined the first quarter [ http://antwrp.gsfc.nasa.gov/apod/ap010428.html ] Moon and stars of the constellation Scorpius [ http://hawastsoc.org/deepsky/sco/index.html ] in western skies. On August 22, 2004, his view looked [ http://people.freenet.de/besel/ Fotoalben/Blitz/PAGE1.HTM ] across the Gulf of Mexico from Anna Maria Island, Florida, USA, a region that would experience even more stormy [ http://antwrp.gsfc.nasa.gov/apod/ap040903.html ] weather in the coming days. The alluring digital image is a time exposure, by chance [ http://images.jsc.nasa.gov/luceneweb/ fullimage.jsp?photoId=S83-40452 ] capturing the details of a brief flash of lightning [ http://thunder.msfc.nasa.gov/primer/primer2.html ] along with an overexposed Moon and dramatic cloud formations. In fact, the exposure is long enough to show the background stars as short streaks or trails [ http://www.astropix.com/HTML/ I_ASTROP/I06/I0601/I0601.HTM ]. The bright yellowish star trail, just above and right of the lightning flash, is red giant star Antares [ http://www.astro.uiuc.edu/~kaler/sow/antares.html ]. |
|
Comet Hyakutake and the Milk
…
| Title |
Comet Hyakutake and the Milky Way |
| Explanation |
Two years ago, the Great Comet of 1996 [ http://antwrp.gsfc.nasa.gov/apod/ap960208.html ], Comet Hyakutake [ http://www.jpl.nasa.gov/comet/hyakutake/ ], inched across our northern sky during its long orbit [ http://antwrp.gsfc.nasa.gov/apod/ap960314.html ] around the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. Visible above as the bright spot with the faint tail [ http://antwrp.gsfc.nasa.gov/apod/ap960326.html ] near the picture [ http://www.psiaz.com/polakis/gco/gco.html ]'s center, Comet Hyakutake [ http://encke.jpl.nasa.gov/comets_long/96B2.html ] shares the stage with part of the central band of the Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970517.html ], prominent in the picture's upper right. Also visible are Antares [ http://antwrp.gsfc.nasa.gov/apod/ap980726.html ], the bright orange star in the upper right, Arcturus [ http://www.windows.umich.edu/the_universe/Arcturus.html ], the bright star on the lower left, and the Pipe Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970621.html ], which is perhaps harder to find. Comet Hyakutake [ http://antwrp.gsfc.nasa.gov/apod/index/Hyakutake.html ]'s unusually close approach [ http://antwrp.gsfc.nasa.gov/apod/ap960325.html ] to the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980204.html ] allowed astronomers to learn many things, including that comets can emit much X-ray light [ http://antwrp.gsfc.nasa.gov/apod/ap960411.html ]. |
|
A Close Encounter Of The Ste
…
| Title |
A Close Encounter Of The Stellar Kind |
| Explanation |
The unassuming star centered in this sky view [ http://skyview.gsfc.nasa.gov ] will one day be our next door [ http://www.bigear.org/vol1no2/kraus.htm ] stellar neighbor [ http://www.astro.wisc.edu/~dolan/constellations/extra/nearest.html ]. The faint 9th magnitude red dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap991120.html ], currently 63 light-years away [ http://zebu.uoregon.edu/~soper/Stars/parallax_ly.html ] in the constellation Ophiucus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Ophiuchus.html ], was recently discovered to be approaching our Solar System. Known in catalogs of nearby stars [ http://tarkus.pha.jhu.edu/~thenry/RECONS.html ] as Gliese 710 it is predicted to come within 1 light-year of the Sun ... a million years from now. At that distance this star, presently much too faint to be seen [ http://liftoff.msfc.nasa.gov/academy/universe/MAG.HTML ] by the naked eye, will blaze at 0.6 magnitude - rivaling the apparent brightness of the mighty red giant Antares [ http://antwrp.gsfc.nasa.gov/apod/ap970624.html ]. Ultimately Gliese 710 poses no direct collision danger itself although its gravitational influence will likely scatter comets out of the Solar System's reservoir, the Oort cloud [ http://www.windows.umich.edu/cgi-bin/tour_def/comets/ Oort_cloud.html ], sending some inbound. This future stellar encounter [ http://cass.jsc.nasa.gov/meetings/dps97/html/H2501/H2501.html ] was discovered by researchers [ http://www.newscientist.com/ns/970524/doomstar.html ] Joan Garcia-Sanchez and Robert Preston (JPL [ http://www.jpl.nasa.gov ]), and collaborators while studying stars in the solar neighborhood [ http://www.clockwk.com/stars/ ] using data from the Hipparcos Astrometry Satellite [ http://astro.estec.esa.nl/SA-general/Projects/Hipparcos/ hipparcos.html ]. The star field shown is based on the Palomar Digitized Sky Survey [ http://www-gsss.stsci.edu/dss/dss.html ] and is 1/4 degree wide (about half the diameter of the full moon). |
|
East of Antares
| Title |
East of Antares |
| Explanation |
East of Antares [ http://antwrp.gsfc.nasa.gov/apod/ap020526.html ], dark markings seem to sprawl through the crowded star fields toward the center of our Milky Way Galaxy. Cataloged in [ http://adsabs.harvard.edu/cgi-bin/ bib_query?1919ApJ....49....1B ] the early 20th century by astronomer E. E. Barnard [ http://astro.uchicago.edu/yerkes/virtualmuseum/ Barnardfull.html ], the obscuring interstellar dust clouds include [ http://www.saguaroastro.org/content/ Best-of-Barnards-Dark-Nebulae.htm ] B72 [ http://antwrp.gsfc.nasa.gov/apod/ap050521.html ], B77, B78, and B59, seen in silhouette [ http://antwrp.gsfc.nasa.gov/apod/ap001229.html ] against the starry background. Here, their combined shape suggests smoke rising from a pipe, and so the dark nebula's popular name is the Pipe Nebula. This gorgeous and expansive view [ http://panther-observatory.com/gallery/deepsky/doc/ Pipe_200mm.htm ] was recorded in very dark skies over Hakos, Namibia [ http://www.fallingrain.com/world/WA/40/Hakos.html ]. It covers a full 10 by 7 degree field in the pronounceable [ http://www.astronomyclub.org/learn/Say_What.htm ] constellation Ophiuchus. |
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