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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. |
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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. |
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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 ]. |
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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. |
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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. |
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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 ]. |
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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! |
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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. |
|
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. |
|
Humans, El Nino Conspire to
…
nasa, nasaimageofthedaygalle
…
Who is responsible when smok
…
globalco_mop_200511_geo
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of the National Center for Atmospheric Research (NCAR) and the University of Toronto www.eos.ucar.edu/mopitt/ MOPITT Teams. |
| identifier |
globalco_mop_200511_geo |
|
Humans, El Nino Conspire to
…
nasa, nasaimageofthedaygalle
…
Who is responsible when smok
…
globalco_mop_200511_geo
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of the National Center for Atmospheric Research (NCAR) and the University of Toronto www.eos.ucar.edu/mopitt/ MOPITT Teams. |
| identifier |
globalco_mop_200511_geo |
|
Humans, El Nino Conspire to
…
nasa, nasaimageofthedaygalle
…
Who is responsible when smok
…
globalco_mop_200511_geo
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of the National Center for Atmospheric Research (NCAR) and the University of Toronto www.eos.ucar.edu/mopitt/ MOPITT Teams. |
| identifier |
globalco_mop_200511_geo |
|
Humans, El Nino Conspire to
…
nasa, nasaimageofthedaygalle
…
Who is responsible when smok
…
globalco_mop_200511_geo
| mediatype |
IMAGE |
| mediatype |
image |
| date |
2006 |
| creator |
NASA -- NASA image created by Jesse Allen, using data provided courtesy of the National Center for Atmospheric Research (NCAR) and the University of Toronto www.eos.ucar.edu/mopitt/ MOPITT Teams. |
| identifier |
globalco_mop_200511_geo |
|
|
