________________________________________________________________
Please vote for the TWO best Astronomy Pictures of the Day (image and text) of November 28-December 4.
(Repeated APODs are not included in the poll.)
All titles are clickable and link to the original APOD page.
We ask for your help in choosing an APOW, as this helps Jerry and Robert create "year in APOD images" review lectures, creates APOM polls that can be used to create a free PDF calendar at year's end, and provides feedback on which images and APODs were relatively well received. You can select two top images for the week.
Please do not vote repeatedly to boost the votes on a particular image; doing so invalidates the poll results.
Thank you!
________________________________________________________________
<- Previous week's poll
Why are planet-circling clouds disappearing and reappearing on Jupiter? Although the ultimate cause remains unknown, planetary
meteorologists are beginning to better understand what is happening. Earlier this year, unexpectedly, Jupiter's dark
Southern Equatorial Belt (SEB) disappeared. The
changes were first noted by amateurs dedicated to watching Jupiter full time. The South Equatorial Band has been
seen to change colors before, although the
change has never been recorded in such detail. Detailed professional observations revealed that high-flying light-colored
ammonia-based clouds formed over the
planet-circling dark belt. Now those light clouds are dissipating,
again unveiling the lower dark clouds.
Pictured above two weeks ago, far
infrared images -- depicted in false-color red -- show a
powerful storm system active above the returning dark belt.
Continued observations of Jupiter's current
cloud opera, and our understanding of it, is sure to continue.
Is that a spaceship or a cloud? Although it may seem like an
alien mothership, it's actually a impressive thunderstorm cloud called a
supercell. Such
colossal storm systems center on
mesocyclones -- rotating updrafts that can span several kilometers and deliver
torrential rain and high winds including
tornadoes. Jagged sculptured clouds adorn the supercell's
edge, while wind swept dust and rain
dominate the center. A tree
waits patiently in the foreground. The
above supercell cloud was photographed in July west of
Glasgow,
Montana,
USA, caused minor damage, and lasted several hours before moving on.
Why is Phobos so dark?
Phobos, the largest and innermost of two Martian moons, is the darkest moon in the entire
Solar System. Its unusual orbit and color indicate that it may be a captured
asteroid composed of a mixture of ice and dark rock. The
above picture of Phobos near the limb of Mars was
captured last month by the robot spacecraft
Mars Express currently orbiting Mars.
Phobos is a heavily cratered and
barren moon, with its
largest crater located on the far side. From images like this,
Phobos has been determined to be covered by perhaps a meter of
loose dust. Phobos
orbits so close to Mars that from some places it would appear to rise and set twice a day, but from other places it would not be visible at all.
Phobos' orbit around Mars is continually decaying -- it will likely
break up with pieces crashing to the Martian surface in about 50 million years.
Early in November, small
but active Comet Hartley 2 (103/P Hartley) became the
fifth comet imaged close-up by a
spacecraft from planet Earth. Continuing its own
tour of the solar system with a 6 year
orbital period, Hartley 2 is now appearing in the
nautical constellation Puppis. Still a target for binoculars or small telescopes from dark sky locations, the comet is captured in this composite image from November 27, sharing the rich 2.5 degree wide
field of view with some
star clusters well known to earthbound skygazers. Below and right of the comet's alluring green coma lies
bright M47, a young open star cluster some 80 milion years old, about 1,600 light-years away. Below and left open cluster
M46 is older, around 300 million years of age, and 5,400 light-years distant. Hartley 2's short, faint tail even extends up and right toward another fainter star cluster in the scene, NGC 2423. On November 27, Comet Hartley 2 was about 2.25
light-minutes from Earth.
Sweeping toward the bottom of this field, by November 28 the
comet's path had carried it between M46 and M47.
The small, northern constellation
Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the
Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the
Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the
Andromeda Galaxy and
astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth,
this sharp, detailed image nicely shows off M33's blue star clusters and pinkish
star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the
cavernous NGC 604 is the brightest star forming region, seen here at about the 4 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a
cosmic yardstick for
establishing the distance
scale of the Universe.
In dwindling twilight at an August day's end, these broad dark bands appeared in the sky for a moment, seen from
Robert Smithson's Spiral Jetty on the eastern shore of Utah's
Great Salt Lake. Outlined by rays of sunlight known as
crepuscular rays, they are actually shadows cast by clouds near the distant western horizon, the setting Sun having disappeared from direct view behind them. The cloud shadows are parallel, but seem to converge in the distance
because of perspective. Coiled in the salt-encrusted lake surface,
Smithson's most famous earthwork provides a dramatic contrast to the converging lines. The Spiral Jetty was constructed in 1970, when the water level was unusually low and was completely submerged in a few years as the level rose. Now just above water again, it has spent much of its existence submerged in
the briny lake.
<- Previous week's poll
[size=200][color=#FF0000]________________________________________________________________[/color][/size]
Please vote for the TWO best Astronomy Pictures of the Day (image and text) of November 28-December 4.
(Repeated APODs are not included in the poll.)
All titles are clickable and link to the original APOD page.
We ask for your help in choosing an APOW, as this helps Jerry and Robert create "year in APOD images" review lectures, creates APOM polls that can be used to create a free PDF calendar at year's end, and provides feedback on which images and APODs were relatively well received. You can select two top images for the week.
Please do not vote repeatedly to boost the votes on a particular image; doing so invalidates the poll results.
Thank you!
[size=200][color=#FF0000]________________________________________________________________[/color][/size]
[size=110][url=http://asterisk.apod.com/viewtopic.php?f=29&t=22149][color=#4040FF][b]<- Previous week's poll[/b][/color][/url][/size]
[c][url=http://apod.nasa.gov/apod/ap101129.html][b][size=150]Dark Belt Reappearing on Jupiter (2010 Nov 29)[/size][/b][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1011/jupiterstorm_gemini.jpg[/img2][/float]Why are planet-circling clouds disappearing and reappearing on Jupiter? Although the ultimate cause remains unknown, planetary [url=http://www.ametsoc.org/careercenter/index.html]meteorologists[/url] are beginning to better understand what is happening. Earlier this year, unexpectedly, Jupiter's dark [url=http://en.wikipedia.org/wiki/File:Jupiter_cloud_bands.svg]Southern Equatorial Belt (SEB)[/url] disappeared. The [url=http://www.youtube.com/watch?v=uPjNFIJUZT0]changes[/url] were first noted by amateurs dedicated to watching Jupiter full time. The South Equatorial Band has been [url=http://blogs.discovermagazine.com/badastronomy/2010/11/25/astronomers-thankful-for-return-of-jupiters-belt/]seen to change[/url] colors before, although the [url=http://apod.nasa.gov/apod/ap001123.html]change[/url] has never been recorded in such detail. Detailed professional observations revealed that high-flying light-colored [url=http://en.wikipedia.org/wiki/Ammonia]ammonia[/url]-based clouds formed over the [url=http://apod.nasa.gov/apod/ap100124.html]planet-circling[/url] dark belt. Now those light clouds are dissipating, [url=http://www.universetoday.com/79931/how-jupiter-is-getting-its-belt-back/]again unveiling[/url] the lower dark clouds. [url=http://www.berkeley.edu/news/media/releases/2010/11/24_jupiter_stripe.shtml]Pictured above[/url] two weeks ago, far [url=http://science.hq.nasa.gov/kids/imagers/ems/infrared.html]infrared[/url] images -- depicted in false-color red -- show a [url=http://www.youtube.com/watch?v=NS6uYY53NGo]powerful storm system[/url] active above the returning dark belt. [url=http://cosmos4u.blogspot.com/2010/11/rapid-progress-in-sebs-revival-jupiter.html]Continued observations[/url] of Jupiter's current [url=http://www.youtube.com/watch?v=e3fqE01YYWs]cloud opera[/url], and our understanding of it, is sure to continue.
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[c][url=http://apod.nasa.gov/apod/ap101130.html][size=150][b]A Supercell Thunderstorm Cloud Over Montana (2010 Nov 30)[/b][/size][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1011/thundercell_heavey.jpg[/img2][/float] Is that a spaceship or a cloud? Although it may seem like an [url=http://www.ugo.com/movies/100-best-movie-spaceships]alien mothership[/url], it's actually a impressive thunderstorm cloud called a [url=http://en.wikipedia.org/wiki/Supercell]supercell[/url]. Such [url=http://www.youtube.com/watch?v=lvSHGx1ZO50]colossal storm[/url] systems center on [url=http://en.wikipedia.org/wiki/Mesocyclone]mesocyclones[/url] -- rotating updrafts that can span several kilometers and deliver [url=http://www.youtube.com/watch?v=UBTb5Yd20cM]torrential rain[/url] and high winds including [url=http://apod.nasa.gov/apod/ap060702.html]tornadoes[/url]. Jagged sculptured clouds adorn the supercell's [url=http://apod.nasa.gov/apod/ap080122.html]edge[/url], while wind swept dust and rain [url=http://www.youtube.com/watch?v=HFW7PABbJYQ]dominate[/url] the center. A tree [url=http://media1.break.com/dnet/media/2008/10/67%20Bear%20Waiting%20Patiently%20For%20Picnic.jpg]waits patiently[/url] in the foreground. The [url=http://www.alconartz.com/AlconArtz/Storm.html#1]above supercell cloud[/url] was photographed in July west of [url=http://en.wikipedia.org/wiki/Glasgow,_MT]Glasgow[/url], [url=http://en.wikipedia.org/wiki/Montana]Montana[/url], [url=https://www.cia.gov/library/publications/the-world-factbook/geos/us.html]USA[/url], caused minor damage, and lasted several hours before moving on.
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[c][url=http://apod.nasa.gov/apod/ap101201.html][size=150][b]Martian Moon Phobos from Mars Express (2010 Dec 01)[/b][/size][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1012/phoboslimb_marsexpress.jpg[/img2][/float]Why is Phobos so dark? [url=http://en.wikipedia.org/wiki/Phobos_%28moon%29]Phobos[/url], the largest and innermost of two Martian moons, is the darkest moon in the entire [url=http://solarsystem.nasa.gov/planets/]Solar System[/url]. Its unusual orbit and color indicate that it may be a captured [url=http://asterisk.apod.com/viewtopic.php?f=24&t=18014]asteroid[/url] composed of a mixture of ice and dark rock. The [url=http://www.unmannedspaceflight.com/index.php?showtopic=480&st=195&p=167059&#entry167059]above picture[/url] of Phobos near the limb of Mars was [url=http://www.planetary.org/blog/article/00002791/]captured[/url] last month by the robot spacecraft [url=http://www.esa.int/SPECIALS/Mars_Express/SEMFU55V9ED_0.html]Mars Express[/url] currently orbiting Mars. [url=http://apod.nasa.gov/apod/ap080414.html]Phobos[/url] is a heavily cratered and [url=http://apod.nasa.gov/apod/ap031109.html]barren[/url] moon, with its [url=http://apod.nasa.gov/apod/ap080410.html]largest crater[/url] located on the far side. From images like this, [url=http://apod.nasa.gov/apod/ap061203.html]Phobos[/url] has been determined to be covered by perhaps a meter of [url=http://apod.nasa.gov/apod/ap980914.html]loose dust[/url]. Phobos [url=http://www.youtube.com/watch?v=7rxqZcO-0uI]orbits[/url] so close to Mars that from some places it would appear to rise and set twice a day, but from other places it would not be visible at all. [url=http://apod.nasa.gov/apod/ap990313.html]Phobos[/url]' orbit around Mars is continually decaying -- it will likely [url=http://adsabs.harvard.edu/abs/2008AGUFM.P51C1423H]break up[/url] with pieces crashing to the Martian surface in about 50 million years.
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[c][url=http://apod.nasa.gov/apod/ap101202.html][size=150][b]Hartley 2 Star Cluster Tour (2010 Dec 02)[/b][/size][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1012/103P_101127ligustri900c.jpg[/img2][/float]Early in November, small [url=http://planetary.org/blog/article/00002781/]but active[/url] Comet Hartley 2 (103/P Hartley) became the [url=http://photojournal.jpl.nasa.gov/catalog/PIA13576]fifth comet[/url] imaged close-up by a [url=http://www.nasa.gov/mission_pages/epoxi/index.html]spacecraft from planet Earth[/url]. Continuing its own [url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=103p&orb=1]tour of the solar system[/url] with a 6 year [url=http://pdssbn.astro.umd.edu/comet_data/periodic_comets.html]orbital period[/url], Hartley 2 is now appearing in the [url=http://www.hawastsoc.org/deepsky/pup/index.html]nautical constellation[/url] Puppis. Still a target for binoculars or small telescopes from dark sky locations, the comet is captured in this composite image from November 27, sharing the rich 2.5 degree wide [url=http://apod.nasa.gov/apod/image/1012/103P_101127ligustri_label.jpg]field of view[/url] with some [url=http://apod.nasa.gov/apod/ap060910.html]star clusters well known[/url] to earthbound skygazers. Below and right of the comet's alluring green coma lies [url=http://www.seds.org/messier/m/m047.html]bright M47[/url], a young open star cluster some 80 milion years old, about 1,600 light-years away. Below and left open cluster [url=http://www.seds.org/messier/m/m046.html]M46 is[/url] older, around 300 million years of age, and 5,400 light-years distant. Hartley 2's short, faint tail even extends up and right toward another fainter star cluster in the scene, NGC 2423. On November 27, Comet Hartley 2 was about 2.25 [url=http://www.haydenplanetarium.org/universe/duguide/app_light_travel_time_dista.php]light-minutes[/url] from Earth. [url=http://picasaweb.google.com/astroligu/CometeDiRolandoLigustriCASTItalia#5545806047210206514]Sweeping toward the bottom[/url] of this field, by November 28 the [url=http://www.skyandtelescope.com/observing/home/102632669.html]comet's path[/url] had carried it between M46 and M47.
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[c][url=http://apod.nasa.gov/apod/ap101203.html][size=150][b]M33: Triangulum Galaxy (2010 Dec 03)[/b][/size][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1012/m33_konrad_900c.jpg[/img2][/float]The small, northern constellation [url=http://www.hawastsoc.org/deepsky/tri/index.html]Triangulum[/url] harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the [url=http://www.seds.org/messier/m/m033.html]Triangulum Galaxy[/url]. M33 is over 50,000 light-years in diameter, third largest in the [url=http://atlasoftheuniverse.com/localgr.html]Local Group[/url] of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the [url=http://apod.nasa.gov/apod/ap021021.html]Andromeda Galaxy[/url] and [url=http://arxiv.org/abs/astro-ph?papernum=0506609]astronomers[/url] in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, [url=http://www.astrofotografie-laupheim.de/bilder.php?bild_anzeige=382&urubrik=]this sharp, detailed image[/url] nicely shows off M33's blue star clusters and pinkish [url=http://apod.nasa.gov/apod/ap061123.html]star forming[/url] regions that trace the galaxy's loosely wound spiral arms. In fact, the [url=http://www.seds.org/messier/more/m033_n604.html]cavernous NGC 604[/url] is the brightest star forming region, seen here at about the 4 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a [url=http://cfa-www.harvard.edu/~kstanek/DIRECT/]cosmic yardstick[/url] for [url=http://adsabs.harvard.edu/cgi-bin/bib_query?1926ApJ....63..236H]establishing[/url] the distance [url=http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate96.html]scale[/url] of the Universe.
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[c][url=http://apod.nasa.gov/apod/ap101204.html][size=150][b]Sunset at the Spiral Jetty (2010 Dec 04)[/b][/size][/url][/c]
[float=left][img2]http://antwrp.gsfc.nasa.gov/apod/image/1012/SpiralRays_erisoty.jpg[/img2][/float][url=http://apod.nasa.gov/apod/ap030424.html]In dwindling twilight[/url] at an August day's end, these broad dark bands appeared in the sky for a moment, seen from [url=http://www.diaart.org/sites/main/spiraljetty]Robert Smithson's Spiral Jetty[/url] on the eastern shore of Utah's [url=http://epod.usra.edu/blog/2010/07/spiral-jetty-and-great-salt-lake.html]Great Salt Lake[/url]. Outlined by rays of sunlight known as [url=http://www.atoptics.co.uk/atoptics/ray1.htm]crepuscular rays[/url], they are actually shadows cast by clouds near the distant western horizon, the setting Sun having disappeared from direct view behind them. The cloud shadows are parallel, but seem to converge in the distance [url=http://www.atoptics.co.uk/atoptics/rayform.htm]because of perspective[/url]. Coiled in the salt-encrusted lake surface, [url=http://www.robertsmithson.com/introduction/introduction.htm]Smithson's most famous earthwork[/url] provides a dramatic contrast to the converging lines. The Spiral Jetty was constructed in 1970, when the water level was unusually low and was completely submerged in a few years as the level rose. Now just above water again, it has spent much of its existence submerged in [url=http://earthobservatory.nasa.gov/IOTD/view.php?id=4148]the briny lake[/url].
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[size=110][url=http://asterisk.apod.com/viewtopic.php?f=29&t=22149][color=#4040FF][b]<- Previous week's poll[/b][/color][/url][/size]