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Dark Sun Sizzling
Title Dark Sun Sizzling
Explanation Is this our Sun? Yes. Even on a normal day, our Sun is sizzling [ http://antwrp.gsfc.nasa.gov/apod/ap970106.html ] ball [ http://antwrp.gsfc.nasa.gov/apod/ap970107.html ] of seething [ http://antwrp.gsfc.nasa.gov/apod/ap970108.html ] hot gas [ http://antwrp.gsfc.nasa.gov/apod/ap030729.html ]. Unpredictably, regions of strong and tangled magnetic fields [ http://www-spof.gsfc.nasa.gov/Education/whmfield.html ] arise, causing sunspots [ http://antwrp.gsfc.nasa.gov/apod/ap051106.html ] and bright active regions [ http://antwrp.gsfc.nasa.gov/apod/ap040726.html ]. The Sun's surface bubbles [ http://en.wikipedia.org/wiki/Granule_%28solar_physics%29 ] as hot hydrogen [ http://en.wikipedia.org/wiki/Hydrogen ] gas streams along looping magnetic fields. These active regions channel gas along magnetic loops [ http://antwrp.gsfc.nasa.gov/apod/ap050814.html ], usually falling back but sometimes escaping into the solar corona [ http://antwrp.gsfc.nasa.gov/apod/ap010408.html ] or out into space as the solar wind [ http://science.nasa.gov/ssl/pad/solar/sun_wind.htm ]. Pictured above is our Sun in three colors of ultraviolet [ http://imagers.gsfc.nasa.gov/ems/uv.html ] light. Since only active regions emit significant amounts of energetic ultraviolet light, most of the Sun appears dark. The colorful portions glow spectacularly, pinpointing the Sun's hottest and most violent regions [ http://antwrp.gsfc.nasa.gov/apod/ap060502.html ]. Although the Sun is constantly changing, the rate of visible [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html ] light it emits has been relatively stable [ http://en.wikipedia.org/wiki/Solar_constant ] over the past five billion years, allowing life to emerge [ http://www.pbs.org/wgbh/nova/origins/life-nf.html ] on Earth.
Smooth Sections of Asteroid …
Title Smooth Sections of Asteroid Itokawa
Explanation Why are parts of this asteroid's surface so smooth? No one is yet sure, but it may have to do with the dynamics of an asteroid [ http://en.wikipedia.org/wiki/Asteroid ] that is a loose pile of rubble [ http://www.daviddarling.info/encyclopedia/R/rubble-pile_asteroid.html ] rather than a solid rock. The unusual asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap051116.html ] has been visited recently by the Japan [ http://www.cia.gov/cia/publications/factbook/geos/ja.html ]ese spacecraft Hayabusa [ http://en.wikipedia.org/wiki/Hayabusa ] that has been documenting its unusual structure and mysterious lack of craters [ http://antwrp.gsfc.nasa.gov/apod/ap051121.html ]. Recent analyses of the border regions [ http://www.psi.edu/press/ ] between smooth and rugged sections of Itokawa indicate that jostling of the asteroid might be creating segregation between large and small rocks near the surface, like the Brazil nut effect [ http://en.wikipedia.org/wiki/Brazil_nut_effect ]. In late 2005, Hayabusa actually touched down [ http://www.planetary.org/news/2005/1126_Hayabusa_Spacecraft_Lands_on_Asteroid.html ] on one of the smooth patches, dubbed the MUSES Sea, and collected soil samples [ http://www.planetary.org/news/2005/1128_Hayabusa_Got_Sample_Yes.html ] that are to be returned to Earth for analysis. Hayabusa will start its three-year long return trip [ http://www.isas.jaxa.jp/e/snews/2007/0406.shtml ] to Earth this month. Computer simulations show that 500-meter asteroid Itokawa may impact the Earth [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005Icar..179..291M ] within the next few million years.
Circum-axial Leaf Trails
Title Circum-axial Leaf Trails
Explanation Are photographs of star trails [ http://www.astropix.com/HTML/I_ASTROP/TRIPOD/ TRIPOD2.HTM ] really evidence of the Earth's rotation [ http://www.astro.uiuc.edu/~kaler/celsph.html ] about its axis? Yes they are, and science journalist Trudy E. Bell discovered that there is a simple way to demonstrate this, if you have the stomach for it. First, find a playground equipped with a standard Merry-Go-Round [ http://scitation.aip.org/journals/doc/ PHTEAH-ft/vol_45/iss_2/85_1.html ] (MGR) located under or near a large, leafy tree. Seat yourself near the middle of the MGR platform. Ask a local playground expert (KID) to get you spinning very, very fast. As the scenery flashes by at a dizzying rate, point your camera skyward and take a picture with a slow shutter speed setting. The result will be similar to this excellent image of concentric, arcing leaf trails centered at a point corresponding to the MGR's axis of rotation - a convincing imitation of circumpolar star trails [ http://antwrp.gsfc.nasa.gov/apod/ap061202.html ] recorded in hours-long exposures [ http://antwrp.gsfc.nasa.gov/apod/ap060915.html ] of planet Earth's night sky. Then, just stand up and walk away ... if you still can [ http://youtube.com/watch?v=bWKUjKQxg0A ].
Barsoom
Title Barsoom
Explanation Yes, I have been to Barsoom again ..." begins John Carter in Edgar Rice Burroughs' 1913 science fiction classic "The Gods of Mars" [ http://www.literature.org/Works/Edgar-Rice-Burroughs/gods-of-mars/ ]. In Burroughs' novels describing Carter's adventures on Mars, "Barsoom" is the local inhabitants' name [ http://humbabe.arc.nasa.gov/mgcm/fun/pop.html ] for the Red Planet. Long after Burroughs' stories were published, Mars continues [ http://history.nasa.gov/SP-4212/on-mars.html ] to inspire Earthdweller [ http://nssdc.gsfc.nasa.gov/planetary/mars/mars_crew.html ]s' interests [ http://antwrp.gsfc.nasa.gov/apod/ap970627.html ] and imagination [ http://antwrp.gsfc.nasa.gov/apod/ap970528.html ]. Soon it will again be invaded by spacecraft from Earth [ http://mars.jpl.nasa.gov ]. This dramatic picture of a crescent Mars was taken by NASA's Viking 2 [ http://nssdc.gsfc.nasa.gov/cgi-bin/ database/www-nmc?75-083A ] spacecraft as it approached [ http://www2.jpl.nasa.gov/files/images/captions/ p17442.txt ] Barsoom in 1976.
The Moon and All the Crashes
Title The Moon and All the Crashes
Explanation A clear blue summer sky finally grows dark and the new telescope, hastily set up in the backyard, generates excitment and anticipation. "I bought it for the kids.", Dad assures himself as he anxiously supervises two young boys' efforts to center a bright, first quarter Moon [ http://tycho.usno.navy.mil/vphase.html ] in the finder. The evening's [ http://www.tufts.edu/as/wright_center/lessons/html/ moon.html ] first target acquired, James adjusts the focus knob and falls silent. Suddenly, "Wow, looks just like on Apollo 13 [ http://antwrp.gsfc.nasa.gov/apod/ap950708.html ]!". His younger brother Christopher takes his turn. "Do you see the Moon [ http://www.salzgeber.at/astro/moon/ index.html ]?", James asks, eager to provide guidance based on his own observing experience. Christopher echoes his brother's enthusiasm, "Yes, and I see all the crashes [ http://antwrp.gsfc.nasa.gov/apod/ap991208.html ] too!". The view they shared was not too different from this image of the seven day old moon, recorded in July 2000 by kids and staff during an observing session at Space Camp [ http://www.spacecampturkey.com/ ] in Izmir, Turkey. Along the terminator, the line between lunar night and day [ http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/ lo4_m123.html ], the shadows outline to advantage the spectacular craters -- caused by all the crashes [ http://antwrp.gsfc.nasa.gov/apod/ap990326.html ].
Diamond Ring in the Sun
Title Diamond Ring in the Sun
Explanation Today, earthbound skygazers can celebrate a solstice [ http://www-spof.gsfc.nasa.gov/stargaze/Sseason.htm ], a new Moon [ http://aa.usno.navy.mil/faq/docs/moon_phases.html ], the closest approach [ http://mars.jpl.nasa.gov/ ] of planet Mars since 1988 ... oh yes, and a total eclipse of the Sun, the first total solar eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/TSE2001/TSE2001.html ] of the third millennium. Of course for some, today's most spectacular celestial views will be of the eclipsed Sun [ http://science.nasa.gov/headlines/y2001/ast19jun_1.htm ] from along the path of totality as the new Moon's shadow tracks across southern Africa and Madagascar [ http://www.madagascar-eclipse2001.com/eclipse_.htm ]. This picture from the August 1999 total solar eclipse captures the shimmering solar corona just as that eclipse's total phase ended, as seen from eastern Turkey. The first rays of bright sunlight shinning through edge-on [ http://sunearth.gsfc.nasa.gov/eclipse/TSE2001/TSE2001fig/ TSE2001fig08.GIF ] lunar mountains and valleys create the fleeting appearance of glistening diamonds set in a ring around the Moon's silhouette. Do you want to see today's solar eclipse? Eclipse expeditions are offering live webcasts [ http://www.bit-net.com/~pauer/eclipse01/ ].
Two Million Galaxies
Title Two Million Galaxies
Explanation Our universe is filled with galaxies. Galaxies [ http://www.seds.org/messier/galaxy.html ] -- huge conglomerations of stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ], gas [ http://antwrp.gsfc.nasa.gov/apod/ap980301.html ], dust [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] -- and mysterious dark matter [ http://chandra.harvard.edu/xray_astro/dark_matter.html ] are the basic building blocks of the large-scale universe [ http://antwrp.gsfc.nasa.gov/apod/ap951108.html ]. Although distant galaxies move away from each other as the universe expands [ http://csep10.phys.utk.edu/astr162/lect/cosmology/expansion.html ], gravity attracts neighboring galaxies to each other, forming galaxy groups [ http://antwrp.gsfc.nasa.gov/apod/ap070727.html ], clusters of galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap060321.html ], and even larger expansive filaments. Some of these structures are visible on one of the most comprehensive maps of the sky ever made in galaxies: the APM galaxy survey map [ http://www.nottingham.ac.uk/~ppzsjm/apm/apm.html ] completed in the early 1990s. Over 2 million galaxies are depicted above in a region 100 degrees across centered toward our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ]'s south pole. Bright regions indicate more galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap061126.html ], while bluer colors denote larger average galaxies. Dark ellipses have been cut away where bright local stars [ http://antwrp.gsfc.nasa.gov/apod/ap030323.html ] dominate the sky. Many scientific discoveries [ http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&sim_query=YES&aut_xct=NO&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=AND&title=APM+galaxies&txt_logic=OR&text=&nr_to_return=100&start_nr=1&start_entry_day=&start_entry_mon=&start_entry_year=&min_score=&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&sort=SCORE&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1 ] resulted from analyses of the map data, including that the universe [ http://antwrp.gsfc.nasa.gov/apod/ap010904.html ] was surprisingly complex on large scales.
Tunguska: The Largest Recent …
Title Tunguska: The Largest Recent Impact Event
Explanation Yes, but can your meteor do this? The most powerful natural explosion [ http://en.wikipedia.org/wiki/Tunguska_event ] in recent Earth history occurred on 1908 June 30 when a meteor exploded [ http://antwrp.gsfc.nasa.gov/apod/ap011118.html ] above the Tunguska River in Siberia [ http://en.wikipedia.org/wiki/Siberia ], Russia [ http://en.wikipedia.org/wiki/Russian_Federation ]. Detonating with an estimated power [ http://en.wikipedia.org/wiki/Tsar_Bomba ] 1,000 times greater than the atomic bomb dropped [ http://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_and_Nagasaki ] over Hiroshima [ http://antwrp.gsfc.nasa.gov/apod/ap071114.html http://en.wikipedia.org/wiki/Hiroshima ], the Tunguska event [ http://antwrp.gsfc.nasa.gov/apod/ap071114.html http://www.psi.edu/projects/siberia/siberia.html ] leveled trees over 40 kilometers away and shook the ground in a tremendous earthquake. Eyewitness reports are astounding. [ http://en.wikipedia.org/wiki/Tunguska_event#Selected_eyewitness_reports ] The above picture was taken by a Russian expedition [ http://www.unmuseum.org/kulik.htm ] to the Tunguska site almost 20 years after the event, finding trees littering the ground like toothpicks. Estimates of the meteor's size range from 60 meters to over 1000 meters in diameter. Recent evidence [ http://news.nationalgeographic.com/news/2007/11/071107-russia-crater.html ] suggests that nearby Lake Cheko [ http://en.wikipedia.org/wiki/Lake_Cheko ] may even have been created by the impact [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ]. Although a meteor the size of the Tunguska can level a city [ http://www.youtube.com/watch?v=ls0ME-dX08c ], metropolitan areas take up such a small fraction of the Earth's surface that a direct impact on one is relatively unlikely. More likely is an impact in the water [ http://www.space.com/scienceastronomy/astronomy/asteroid_paine_september.html ] near a city that creates a dangerous tsunami [ http://www.youtube.com/watch?v=AlPqL7IUT6M ]. One focus of modern astronomy is to find Solar System objects [ http://neo.jpl.nasa.gov/neo/report2007.html ] capable of creating such devastation well before they impact the Earth.
Water-Ice Imaged in Martian …
Title Water-Ice Imaged in Martian Polar Cap
Explanation Does water exist today on Mars? Yes, although the only place on Mars [ http://www.nineplanets.org/mars.html ] known to have water [ http://science.nasa.gov/headlines/y2001/ast05jan_1.htm ] is the North Polar Cap [ http://antwrp.gsfc.nasa.gov/apod/ap981216.html ], and that water [ http://www.nyu.edu/pages/mathmol/modules/water/info_water.html ] is frozen. Views of this potentially life-enabling water-ice are usually obscured [ http://antwrp.gsfc.nasa.gov/apod/ap011017.html ] -- in the winter by darkness and in the summer by clouds [ http://antwrp.gsfc.nasa.gov/apod/ap010417.html ]. Last April, however, the orbiting Mars Global Surveyor spacecraft [ http://nssdc.gsfc.nasa.gov/planetary/marsurv.html ] was able to get a good glimpse of the water-bearing cap [ http://antwrp.gsfc.nasa.gov/apod/ap980924.html ] just before Martian spring. Low, dark layers in the above image [ http://www.msss.com/mars_images/moc/1yearExtend/npolar/index.html ] are thought to contain a large amount of sand [ http://waynesword.palomar.edu/ww0704b.htm ], while high, light layers likely contain higher amounts of water-ice [ http://antwrp.gsfc.nasa.gov/apod/ap010629.html ]. The image spans an area about 5 kilometers across.
S is for Sun
Title S is for Sun
Explanation Taken yesterday from the SOHO spacecraft, this false-color image shows [ http://sohowww.nascom.nasa.gov/explore/ Sun_Obs.html ] the active Sun near [ http://www.athropolis.com/sunrise/def-sol2.htm ] the March Equinox [ http://www2.worldbook.com/features/features.asp? feature=seasons&page=html/seasons.htm&direct=yes ], the beginning of Autumn in the south and Spring in the northern hemisphere. Recorded [ http://sohowww.nascom.nasa.gov/data/ latestimages.html# ] in a band of extreme ultraviolet light emitted by highly ionized iron [ http://antwrp.gsfc.nasa.gov/apod/ap010929.html ] atoms, the Sun's upper atmosphere or solar corona [ http://science.msfc.nasa.gov/ssl/pad/solar/ corona.htm ] shines with an array of active regions and plasma loops suspended in magnetic [ http://science.msfc.nasa.gov/ssl/pad/solar/ the_key.htm ] fields. The bright coronal structures and loops seen here have temperatures of about 1.5 million kelvins [ http://antoine.fsu.umd.edu/chem/senese/101/measurement/faq/ why-273.15-kelvin.shtml ]. By chance, the Sun's earth-facing [ http://antwrp.gsfc.nasa.gov/apod/ap010503.html ] side also seems to be marked with a twisting complex of dark filament channels [ http://sohowww.nascom.nasa.gov/explore/ filament.html ] shaped like a giant "S". Filaments represent relatively (!) cool material in the corona which show up as prominences when seen at the Sun's edge. For planet Earth, recent [ http://spaceweather.com/ ] solar activity has made auroral displays likely around this year's March Equinox [ http://antwrp.gsfc.nasa.gov/apod/ap010330.html ].
Hubble Telescope Maps Pluto
Title Hubble Telescope Maps Pluto
Explanation No spacecraft from Earth has yet explored Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap960212.html ] but astronomers have found ways of mapping its surface [ http://www.lowell.edu/users/buie/pluto/plutomap1.html ]. A stunning map of this distant, diminutive planet [ http://www.lowell.edu/users/buie/pluto/sites.html ], the first based on direct images, was revealed late last week in a Hubble Space Telescope press release [ http://www.stsci.edu/pubinfo/PR/96/09.html ]. Above are two opposite hemisphere views of the computer constructed map of Pluto's surface [ http://www.stsci.edu/pubinfo/PR/96/09/B.html ] (north is up). The grid pattern is due to the computer technique used where each grid element is over 100 miles across. The map is based on Hubble images made when Pluto [ http://www.lowell.edu/users/buie/pluto/pluto.html ] was a mere 3 billion miles distant. It shows strong brightness variations - confirming and substantially improving upon ground based observations [ http://eggfoo.arc.nasa.gov/HTML/PLUTO/PlutoSym/EFY/EFY.html ]. While the brightness variations may be due to surface features like craters and basins they are more likely caused by regions of nitrogen and methane frost. The frost regions should show "seasonal" changes which can be tracked in future Hubble observations. Yes, Pluto is a planet [ http://www.lowell.edu/users/buie/pluto/planet.html ] even though it is only 2/3 the size of Earth's Moon!
Ringed Planet Uranus
Title Ringed Planet Uranus
Explanation Yes it does look like Saturn, but Saturn is only one of four [ http://antwrp.gsfc.nasa.gov/apod/ap020616.html ] giant [ http://antwrp.gsfc.nasa.gov/apod/ap020215.html ] ringed [ http://antwrp.gsfc.nasa.gov/apod/ap981020.html ] planets [ http://ringmaster.arc.nasa.gov/neptune/neptune.html ] in our Solar System. And while Saturn has the brightest rings, this system of rings and moons actually belongs to planet Uranus, imaged here [ http://www.eso.org/outreach/press-rel/pr-2002/ phot-31-02.html ] in near-infrared light by the Antu [ http://antwrp.gsfc.nasa.gov/apod/ap000707.html ] telescope at the ESO Paranal Observatory in Chile. Since gas giant Uranus' [ http://www.seds.org/nineplanets/nineplanets/uranus.html ] methane-laced atmosphere absorbs sunlight at near-infrared wavelengths the planet appears substantially darkened, improving the contrast between the otherwise relatively bright planet and the normally faint rings. In fact, the narrow Uranian rings [ http://ringmaster.arc.nasa.gov/uranus/ uranus.html ] are all but impossible to see in visible light with earthbound telescopes and were discovered [ http://tdc-www.harvard.edu/occultations/ uranus25/ ] only in 1977 as careful astronomers noticed the then unknown rings blocking light from background stars. The rings are thought to be younger than 100 million years and may be formed of debris from the collision of a small moon with a passing comet or asteroid-like object. With moons [ http://antwrp.gsfc.nasa.gov/apod/ap000930.html ] named for characters [ http://antwrp.gsfc.nasa.gov/apod/ap990227.html ] in Shakespeare's plays, the distant ringed world Uranus [ http://vraptor.jpl.nasa.gov/voyager/vgrur_fs.html ] was last visited in 1986 by the Voyager 2 spacecraft.
The Heart in NGC 346
Title The Heart in NGC 346
Explanation Yes, it's Valentine's Day [ http://antwrp.gsfc.nasa.gov/apod/ap020214.html ] (!) and looking toward star cluster NGC 346 [ http://www.seds.org/~spider/ngc/ngc.cgi?346 ] in our neighboring galaxy the Small Magellanic Cloud [ http://www.seds.org/messier/xtra/ngc/smc.html ], astronomers have noted this heart-shaped cloud [ http://chandra.harvard.edu/photo/2003/ngc346/ index.html ] of hot, x-ray emitting gas in the cluster's central region. The false-color Chandra Observatory x-ray image also shows [ http://xxx.lanl.gov/abs/astro-ph/0212197 ] a strong x-ray source just above the heart-shaped cloud which corresponds to HD 5980, a remarkable, massive binary star system that lies within the cluster. HD 5980 [ http://heasarc.gsfc.nasa.gov/docs/objects/heapow/archive/stars/ hd5980_chandra.html ] has been known to undergo dramatic brightness variations, in 1994 briefly outshining all other stars in the Small Magellanic Cloud, and has been likened to the luminous, eruptive variable star Eta Carinae [ http://antwrp.gsfc.nasa.gov/apod/ap021010.html ] in our own Milky Way galaxy. At about 100 light-years across, NGC 346's [ http://www.asnsw.com/observing/clouds/tsmc5.htm ] heart-shaped cloud is probably the result of an ancient supernova explosion. Alternatively it may have been produced during past eruptions from the HD 5980 system, analogous to the nebula associated with Eta Carinae [ http://lheawww.gsfc.nasa.gov/users/corcoran/eta_car/ eta_car.html ].
The Moon and All the Crashes
Title The Moon and All the Crashes
Explanation A clear blue [ http://antwrp.gsfc.nasa.gov/apod/ap960730.html ] summer sky finally grows dark and the new telescope, hastily set up in the backyard, generates excitment and anticipation. "I bought it for the kids ...", Dad assures himself as he over-anxiously supervises the two young boys' efforts to center a bright, first quarter Moon [ http://antwrp.gsfc.nasa.gov/apod/lib/moon.html ], in the finder. The evening's first target acquired, James adjusts the focus knob and falls silent. Suddenly, "Wow, looks just like on Apollo 13 [ http://antwrp.gsfc.nasa.gov/apod/ap950707.html ]!". His younger brother Christopher takes his turn. "Do you see the Moon?", James asks, eager to provide guidance based on his own observing experience. Christopher echoes his brother's enthusiasm, "Yes, and I see all the crashes too!". The view they shared was not too different from the above image [ http://www.tiac.net/users/jhendric/6day.html ] of a six day old moon, recorded in July 1995 by Rhode Island amateur astronomer Jim Hendrickson [ http://www.tiac.net/users/jhendric/skyphoto.html ]. Along the terminator, the line between lunar night and day, the shadows outline to advantage the spectacular craters [ http://bang.lanl.gov/solarsys/edu/craters.htm ] -- caused by all the crashes [ http://antwrp.gsfc.nasa.gov/apod/ap960906.html ].
Explanation: Are planets com …
Title Explanation: Are planets common in our galaxy? Strong evidence that the answer is "yes" was provided in this 1994 image [ http://www.stsci.edu/pubinfo/PR/94/24.html ] made by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] . A close-up of the Orion Nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap951121.html ], it reveals what seem to be disks of dust and gas surrounding newly formed stars. These fuzzy blobs, called "proplyds [ http://www.stsci.edu/pubinfo/gif/OrionProplyds.txt ]", appear to be infant solar systems in the process of formation [ http://antwrp.gsfc.nasa.gov/apod/ap960119.html ]. Of the five stars in this field which spans about 0.14 light years, four appear to have associated proplyds - three bright ones and one dark one seen in silhouette against the bright nebula. A more complete survey of 110 stars in the region found 56 with proplyds. If extra-solar planetary systems are common place, are there extra-terrestrial civilizations out there as well? [ http://www.seti-inst.edu/ ]
Two Million Galaxies
Title Two Million Galaxies
Explanation Our universe is filled with galaxies. Galaxies [ http://www.seds.org/messier/galaxy.html ] -- huge conglomerations of stars [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ], gas [ http://antwrp.gsfc.nasa.gov/apod/ap980301.html ], dust [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ] -- and mysterious dark matter [ http://chandra.harvard.edu/xray_astro/dark_matter.html ] are the basic building blocks of the large-scale universe [ http://antwrp.gsfc.nasa.gov/apod/ap951108.html ]. Although distant galaxies move away from each other as the universe expands [ http://csep10.phys.utk.edu/astr162/lect/cosmology/expansion.html ], gravity attracts neighboring galaxies to each other, forming galaxy groups [ http://csep10.phys.utk.edu/astr162/lect/gclusters/groups.html ], clusters of galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap020203.html ], and even larger expansive filaments. Some of these structures are visible on one of the most comprehensive maps of the sky ever made in galaxies: the APM galaxy survey map [ http://astro.nott.ac.uk/~sjm/apm/ ] completed in the early 1990s. Over 2 million galaxies are depicted above in a region 100 degrees across centered toward our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ]'s south pole. Bright regions indicate more galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap021021.html ], while bluer colors denote larger average galaxies. Dark ellipses have been cut away where bright local stars [ http://antwrp.gsfc.nasa.gov/apod/ap030323.html ] dominate the sky. Many scientific discoveries [ http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&sim_query=YES&aut_xct=NO&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=AND&title=APM+galaxies&txt_logic=OR&text=&nr_to_return=100&start_nr=1&start_entry_day=&start_entry_mon=&start_entry_year=&min_score=&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&sort=SCORE&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1 ] resulted from analyses of the map data, including that the universe [ http://antwrp.gsfc.nasa.gov/apod/ap010904.html ] was surprisingly complex on large scales.
Sprint the Flying Space Came …
Title Sprint the Flying Space Camera
Explanation Yes, but can your soccer ball do this? The ball near the middle of the above photograph [ http://shuttle.nasa.gov/sts-87/images/esc/Flightday13/ ] is actually a robotic camera designed to float about a Space Shuttle [ http://antwrp.gsfc.nasa.gov/apod/ap950806.html ] and the International Space Station [ http://station.nasa.gov/ ] and take pictures. Named "Sprint", it is NASA's first Autonomous Extravehicular Activity Robotic Camera (AERCam) [ http://tommy.jsc.nasa.gov/~hnguyen/sprint_html/sprint_src.html ] and was tested earlier this month by the crew [ http://shuttle.nasa.gov/sts-87/crew/ ] of Space Shuttle Columbia. Sprint's diameter is actually about 50 percent larger than a soccer ball, and astronauts [ http://antwrp.gsfc.nasa.gov/apod/ap971210.html http://www.jsc.nasa.gov/Bios/astrobio.html ] make a goal of "not" kicking it.
A Planet Transits the Sun
Title A Planet Transits the Sun
Explanation Today an astronomical event will occur that no living person has ever seen: Venus will cross [ http://sunearth.gsfc.nasa.gov/sunearthday/2004/vt_edu2004_venus_back_his.htm ] directly in front of the Sun. A Venus crossing [ http://sunearth.gsfc.nasa.gov/sunearthday/2004/index_vthome.htm ], called a transit, last occurred in 1882 and was front-page [ http://image.gsfc.nasa.gov/poetry/venus/News/NYT12071882.pdf ] news [ http://image.gsfc.nasa.gov/poetry/venus/News/News.html ] around the world. Today's transit will be visible [ http://skyandtelescope.com/observing/objects/planets/article_1021_1.asp ] in its entirety throughout Europe and most of Asia and Africa. The northeastern half of North America [ http://science.nasa.gov/headlines/y2004/02jun_viewersguide.htm ] will see the Sun rise with the dark dot of Venus [ http://www.saao.ac.za/~wpk/tov1882/tovwell.html ] already superposed. Never look directly at the Sun [ http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety.html ], even when Venus is in front [ http://image.gsfc.nasa.gov/poetry/venus/TransitFAQs.html ]. Mercury's closer proximity to the Sun cause it to transit every few years. In fact, the above image mosaic of Mercury crossing the Sun [ http://www.space.com/scienceastronomy/venus_transit_2004.html ] is from two [ http://antwrp.gsfc.nasa.gov/apod/ap991119.html ] transits [ http://antwrp.gsfc.nasa.gov/apod/ap991210.html ] ago [ http://antwrp.gsfc.nasa.gov/apod/ap030513.html ], in November 1999. Will anyone living see the next Venus transit [ http://www.astronomy.com/content/dynamic/articles/000/000/001/745fvezh.asp ]? Surely yes since it occurs in 2012.
A Seemingly Square Sun
Title A Seemingly Square Sun
Explanation Isn't the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] round? Yes, but in the above picture, the Earth's atmosphere [ http://www.aspire.cs.uah.edu/~jonesj/r.html ] makes it appear almost square. Here a layer of air near the Earth was so warm it acted like a giant lens [ http://www.atm.damtp.cam.ac.uk/people/mgb/refraction.html ], creating increasingly distorted paths for sunlight to reach the camera. Similarly, on a long flat highway, it may appear that the road in the distance is covered with water. In this case, light from the blue sky [ http://math.ucr.edu/home/baez/physics/blue_sky.html ] is being unusually refracted [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/mch/refr/less.rxml ] by warm air just above the dry road. No matter how the Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ] makes the Sun appear, the Sun [ http://www.hawastsoc.org/solar/eng/sun.htm ] will always be spherical. This setting Sun was photographed [ http://www.psiaz.com/polakis/dayatmos/dayatmos.html ] over Lake Michigan [ http://www.epa.gov/grtlakes/lakemich/lampf.html ] in Muskegon [ http://www.ci.muskegon.mi.us/ ], MI.
NGC 4314: A Nuclear Starburs …
Title NGC 4314: A Nuclear Starburst Ring
Explanation Is this old galaxy up to new tricks? The barred spiral galaxy [ http://zebu.uoregon.edu/~js/ast123/lectures/lec13.html ] NGC 4314 is billions of years old, but its appearance has changed markedly over just the past few " millions " of years. During that time, a nuclear ring of bright young stars has been evolving. The inset picture of NGC 4314 [ http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?sim_query=YES&ned_query=YES&aut_xct=NO&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=1982&end_mon=&end_year=&ttl_logic=AND&title=NGC+4314&txt_logic=OR&text=&nr_to_return=50&start_nr=1&query_type=PAPERS&select_nr=50&select_start=1&start_entry_day=&start_entry_mon=&start_entry_year=&min_score=&jou_pick=ALL&ref_stems=&data_and=ALL&group_and=ALL&sort=SCORE&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&db_key=AST&version=1&nosetcookie=1 ] taken by McDonald Observatory [ http://numedia.tddc.net/hot/bigbend/mdo/ ] shows the whole galaxy and boxes the small region around the core imaged [ http://oposite.stsci.edu/pubinfo/pr/1998/21/content/prc9821.txt ] by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. This inner region [ http://oposite.stsci.edu/pubinfo/pr/1998/21/ ] appears much like a miniature spiral galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980606.html ] itself, complete with dust [ http://antwrp.gsfc.nasa.gov/apod/ap980104.html ] lanes and spiral arms, even though it is only a few thousand light-years across. Further study of NGC 4314 [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1996AJ%2E%2E%2E%2E111%2E1861B&nosetcookie=1 ] might help astronomers understand how the inner and outer parts of this galaxy interact, and what caused this unusual ring of star formation.
Barsoom
Title Barsoom
Explanation Yes, I have been to Barsoom again ..." begins John Carter in Edgar Rice Burroughs' 1913 science fiction classic "The Gods of Mars" [ http://www.literature.org/Works/Edgar-Rice-Burroughs/gods-of-mars/ ]. In Burroughs' novels describing Carter's adventures on Mars, "Barsoom" is the local inhabitants' name [ http://humbabe.arc.nasa.gov/mgcm/fun/pop.html ] for the Red Planet. Long after Burroughs' stories were published, Mars continues [ http://mars.jpl.nasa.gov/ ] to inspire Earthdweller [ http://nssdc.gsfc.nasa.gov/planetary/mars/mars_crew.html ]s' interests [ http://antwrp.gsfc.nasa.gov/apod/ap970627.html ] and imagination [ http://antwrp.gsfc.nasa.gov/apod/ap970528.html ]. Soon it will again be invaded by spacecraft from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990108.html ]. This dramatic picture of a crescent Mars was taken by NASA's Viking 2 [ http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?75-083A ] spacecraft in 1976.
Smooth Sections on Asteroid …
Title Smooth Sections on Asteroid Itokawa
Explanation Why are parts of this asteroid's surface so smooth? No one is yet sure, but it may have to do with the dynamics of an asteroid [ http://en.wikipedia.org/wiki/Asteroid ] that is a loose pile of rubble [ http://www.daviddarling.info/encyclopedia/R/rubble-pile_asteroid.html ] rather than a solid rock. The unusual asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap051116.html ] is currently being visited by the Japan [ http://www.cia.gov/cia/publications/factbook/geos/ja.html ]ese spacecraft Hayabusa [ http://en.wikipedia.org/wiki/Hayabusa ] that is documenting its unusual structure and mysterious lack of craters [ http://antwrp.gsfc.nasa.gov/apod/ap051121.html ]. Last month, Hayabusa actually touched down [ http://www.planetary.org/news/2005/1126_Hayabusa_Spacecraft_Lands_on_Asteroid.html ] on one of the smooth patches, dubbed the MUSES Sea, and collected soil samples [ http://www.planetary.org/news/2005/1128_Hayabusa_Got_Sample_Yes.html ] that will eventually be returned to Earth for analysis. Unfortunately, the robot Hayabusa craft [ http://www.isas.jaxa.jp/j/snews/2005/1101_hayabusa.shtml ] has been experiencing communications problems [ http://www.planetary.or.jp/en/ ] and so its departure for Earth [ http://www.planetary.org/news/2005/1214_Hayabusa_JAXA_Delays_Departure_of.html ] has been delayed until 2007. Computer simulations show that 500-meter asteroid Itokawa may impact the Earth [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005Icar..179..291M ] within the next few million years.
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