|
|
A Cauldron of Stars at the G
…
| Title |
A Cauldron of Stars at the Galaxy's Center |
| Description |
This dazzling infrared image from NASA's Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because dust lying between Earth and the galactic center blocks our view. In this false-color picture, old and cool stars are blue, while dust features lit up by blazing hot, massive stars are shown in a reddish hue. Both bright and dark filamentary clouds can be seen, many of which harbor stellar nurseries. The plane of the Milky Way's flat disk is apparent as the main, horizontal band of clouds. The brightest white spot in the middle is the very center of the galaxy, which also marks the site of a supermassive black hole. The region pictured here is immense, with a horizontal span of 890 light-years and a vertical span of 640 light-years. Earth is located 26,000 light-years away, out in one of the Milky Way's spiral arms. Though most of the objects seen in this image are located at the galactic center, the features above and below the galactic plane tend to lie closer to Earth. Scientists are intrigued by the giant lobes of dust extending away from the plane of the galaxy. They believe the lobes may have been formed by winds from massive stars. This image is a mosaic of thousands of short exposures taken by Spitzer's Infrared Array Camera (IRAC), showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). The entire region was imaged in less than 16 hours. |
|
A Cauldron of Stars at the G
…
| Title |
A Cauldron of Stars at the Galaxy's Center |
| Description |
This dazzling infrared image from NASA's Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because dust lying between Earth and the galactic center blocks our view. In this false-color picture, old and cool stars are blue, while dust features lit up by blazing hot, massive stars are shown in a reddish hue. Both bright and dark filamentary clouds can be seen, many of which harbor stellar nurseries. The plane of the Milky Way's flat disk is apparent as the main, horizontal band of clouds. The brightest white spot in the middle is the very center of the galaxy, which also marks the site of a supermassive black hole. The region pictured here is immense, with a horizontal span of 890 light-years and a vertical span of 640 light-years. Earth is located 26,000 light-years away, out in one of the Milky Way's spiral arms. Though most of the objects seen in this image are located at the galactic center, the features above and below the galactic plane tend to lie closer to Earth. Scientists are intrigued by the giant lobes of dust extending away from the plane of the galaxy. They believe the lobes may have been formed by winds from massive stars. This image is a mosaic of thousands of short exposures taken by Spitzer's Infrared Array Camera (IRAC), showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). The entire region was imaged in less than 16 hours. |
|
The Milky Way Center Aglow w
…
| Title |
The Milky Way Center Aglow with Dust |
| Description |
Our Milky Way is a dusty place. So dusty, in fact, that we cannot see the center of the galaxy in visible light. But when NASA's Spitzer Space Telescope set its infrared eyes on the galactic center, it captured this spectacular view. Taken with just one of Spitzer's cameras (at a wavelength of 8 microns), the image highlights the region's exceptionally bright and dusty clouds, lit up by young massive stars. Individual stars can also be seen as tiny dots scattered throughout the dust. The top mosaic shows a portion of the galactic center that stretches across a distance of 760 light-years. Thanks to Spitzer's excellent resolution, the dusty features within the galactic center are seen in unprecedented detail. Four examples are shown in the magnified insets at the bottom. The farthest left box shows a pair of star-forming regions resembling owl-like cosmic eyes. To the left of the "eyes," dark lanes of dust can be seen. This object is probably located in a spiral arm between Earth and the galactic center, in contrast to the following examples, which are all located at the galactic center. The next inset to the right includes the extremely luminous "Quintuplet" stars, a set of five massive stars believed to have buried themselves in cocoons of dust. Just below and to the right of the Quintuplet is the "Pistol" nebula, a bubble of ejected material from the central, massive Pistol star. The finger-like pillars to the left are part of a structure known as "Sickle." They are similar in size and shape to those in the famous picture of the Eagle Nebula taken by NASA's Hubble Space Telescope. Pillars like these are sculpted out of dense dust clouds by radiation and winds from hot stars. The pillars in the Sickle were likely to have been formed by a cluster of hot stars located to their right but not readily visible here. The third inset highlights a system of long, stringy structures that are seen for the first time near the base of a region known as the "Arched Filaments." These long filaments are about 10 light-years long and less than 1 light-year wide. The bright star-forming regions to the right are some of the brightest in the infrared sky. The final inset to the right shows the center of our galaxy, which is the brightest spot in the entire mosaic. The brightness is a result of dust being heated up by a compact cluster of hot stars. The bright spot also marks the location of a supermassive black hole, around which a rotating ring of gas and dust known as the circumnuclear disk can be seen. This image was taken with Spitzer's Infrared Array Camera (IRAC), using its 8-micron detector. It shows emissions from heated-up molecules in dust clouds called polycyclic aromatic hydrocarbons. |
|
The Milky Way Center Aglow w
…
| Title |
The Milky Way Center Aglow with Dust |
| Description |
Our Milky Way is a dusty place. So dusty, in fact, that we cannot see the center of the galaxy in visible light. But when NASA's Spitzer Space Telescope set its infrared eyes on the galactic center, it captured this spectacular view. Taken with just one of Spitzer's cameras (at a wavelength of 8 microns), the image highlights the region's exceptionally bright and dusty clouds, lit up by young massive stars. Individual stars can also be seen as tiny dots scattered throughout the dust. The top mosaic shows a portion of the galactic center that stretches across a distance of 760 light-years. Thanks to Spitzer's excellent resolution, the dusty features within the galactic center are seen in unprecedented detail. Four examples are shown in the magnified insets at the bottom. The farthest left box shows a pair of star-forming regions resembling owl-like cosmic eyes. To the left of the "eyes," dark lanes of dust can be seen. This object is probably located in a spiral arm between Earth and the galactic center, in contrast to the following examples, which are all located at the galactic center. The next inset to the right includes the extremely luminous "Quintuplet" stars, a set of five massive stars believed to have buried themselves in cocoons of dust. Just below and to the right of the Quintuplet is the "Pistol" nebula, a bubble of ejected material from the central, massive Pistol star. The finger-like pillars to the left are part of a structure known as "Sickle." They are similar in size and shape to those in the famous picture of the Eagle Nebula taken by NASA's Hubble Space Telescope. Pillars like these are sculpted out of dense dust clouds by radiation and winds from hot stars. The pillars in the Sickle were likely to have been formed by a cluster of hot stars located to their right but not readily visible here. The third inset highlights a system of long, stringy structures that are seen for the first time near the base of a region known as the "Arched Filaments." These long filaments are about 10 light-years long and less than 1 light-year wide. The bright star-forming regions to the right are some of the brightest in the infrared sky. The final inset to the right shows the center of our galaxy, which is the brightest spot in the entire mosaic. The brightness is a result of dust being heated up by a compact cluster of hot stars. The bright spot also marks the location of a supermassive black hole, around which a rotating ring of gas and dust known as the circumnuclear disk can be seen. This image was taken with Spitzer's Infrared Array Camera (IRAC), using its 8-micron detector. It shows emissions from heated-up molecules in dust clouds called polycyclic aromatic hydrocarbons. |
|
The Trifid Nebula: Stellar S
…
| Title |
The Trifid Nebula: Stellar Sibling Rivalry |
|
Stars and Dust Across Corona
…
| Title |
Stars and Dust Across Corona Australis |
| Explanation |
A cosmic dust cloud sprawls across a rich field of stars in this gorgeous wide field telescopic vista [ http://www.caelumobservatory.com/obs/n6727.html ] looking toward Corona Australis [ http://www.botproductions.com/stellar/ corona_australis.html ], the Southern Crown. Probably less than 500 light-years away and effectively blocking light [ http://antwrp.gsfc.nasa.gov/apod/ap030620.html ] from more distant, background stars in the Milky Way [ http://members.nova.org/~sol/chview/chv5.htm ], the densest part of the dust cloud is about 8 light-years long. At its tip (lower left) is a series of lovely blue nebulae cataloged as NGC 6726, 6727, 6729 [ http://www.aao.gov.au/images/captions/ aat073.html ], and IC [ http://www.ngcic.org/pubdb.htm ] 4812. Their characteristic blue color is produced as light from hot stars is reflected by [ http://antwrp.gsfc.nasa.gov/apod/ap011228.html ] the cosmic dust. The tiny but intriguing yellowish arc visible near the blue nebulae marks young [ http://antwrp.gsfc.nasa.gov/apod/ap031226.html ] variable star R Coronae Australis [ http://antwrp.gsfc.nasa.gov/apod/ap001016.html ]. Magnificent globular star cluster [ http://antwrp.gsfc.nasa.gov/apod/ap040511.html ] NGC 6723 is seen here below and left of the nebulae. While NGC 6723 appears [ http://www.seds.org/~spider/spider/ MWGC/n6723.html ] to be just outside Corona Australis in the constellation Sagittarius, it actually lies nearly 30,000 light-years [ http://en.wikipedia.org/wiki/Light_years ] away, far beyond the Corona Australis dust cloud. |
|
M20: The Trifid Nebula
| Title |
M20: The Trifid Nebula |
| Explanation |
Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula [ http://www.seds.org/messier/m/m020.html ]. Also known as M20, this photogenic nebula [ http://www.noao.edu/image_gallery/html/im0587.html ] is visible with good binoculars towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. The energetic processes of star formation [ http://antwrp.gsfc.nasa.gov/apod/ap990502.html ] create not only the colors but the chaos. The red-glowing gas [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ] results from high-energy starlight striking interstellar hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. The dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] filaments [ http://antwrp.gsfc.nasa.gov/apod/ap990607.html ] that lace M20 [ http://antwrp.gsfc.nasa.gov/apod/ap970828.html ] were created in the atmospheres of cool giant stars [ http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html ] and in the debris [ http://antwrp.gsfc.nasa.gov/apod/ap990803.html ] from supernovae [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] explosions. Which bright young stars light up the blue reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] is still being investigated [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986AJ.....92.1125L ]. The light from M20 [ http://www.aao.gov.au/local/www/dfm/aat069.html ] we see today left perhaps 3000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20 [ http://www.seds.org/billa/twn/n6514x.html ]. |
|
The Galactic Center in Infra
…
| Title |
The Galactic Center in Infrared |
| Explanation |
The center of our Galaxy is a busy place. In visible light [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html ], much of the Galactic Center [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] is obscured by opaque dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ]. In infrared light [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/discovery.html ], however, dust glows more and obscures less, allowing nearly one million stars to be recorded in the above photograph [ http://www.ipac.caltech.edu/2mass/gallery/images_misc.html ]. The Galactic Center [ http://antwrp.gsfc.nasa.gov/apod/ap020803.html ] itself appears [ http://antwrp.gsfc.nasa.gov/apod/ap020707.html ] on the right and is located about 30,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away towards the constellation of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. The Galactic Plane [ http://antwrp.gsfc.nasa.gov/apod/ap000130.html ] of our Milky Way Galaxy [ http://www.damtp.cam.ac.uk/user/gr/public/gal_milky.html ], the plane in which the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] orbits, is identifiable by the dark diagonal dust lane [ http://antwrp.gsfc.nasa.gov/apod/ap020703.html ]. The absorbing dust [ http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis1.html ] grains are created in the atmospheres of cool red-giant stars [ http://www.historyoftheuniverse.com/starold.html ] and grow in molecular cloud [ http://antwrp.gsfc.nasa.gov/apod/ap030202.html ]s. The region directly surrounding the Galactic Center [ http://antwrp.gsfc.nasa.gov/apod/ap000422.html ] glows brightly in radio [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ] and high-energy radiation [ http://antwrp.gsfc.nasa.gov/apod/ap000819.html ], and is thought to house a large black hole [ http://hubblesite.org/discoveries/black_holes/home.html ]. |
|
Galactic Center Star Cluster
…
| Title |
Galactic Center Star Clusters |
| Explanation |
If [ http://www.csie.ntu.edu.tw/~ntucs82/PEOPLE/b2506017/ sf/4t.html ] you had x-ray vision [ http://chandra.harvard.edu/xray_astro/medxray.html ], the central regions [ http://antwrp.gsfc.nasa.gov/apod/ap010627.html ] of our Galaxy would not be hidden from view by cosmic dust clouds. Instead [ http://adc.gsfc.nasa.gov/mw/ ], the Milky Way [ http://www.seds.org/messier/more/mw.html ] toward Sagittarius [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] might look something like this. Pleasing to look at, the gorgeous false-color representation of x-ray data [ http://xxx.lanl.gov/abs/astro-ph/0606414 ] from the Chandra Observatory shows high energies in blue, medium in green, and low energy [ http://antwrp.gsfc.nasa.gov/apod/ap010511.html ] x-rays in red. The mosaic spans [ http://chandra.harvard.edu/photo/2006/gcenter/ ] about 130 light-years at the 26,000 light-year distance of the Galactic Center. It reveals massive, x-ray emitting star clusters in a crowded environment. In particular, the Galactic Center cluster and the enormous black hole [ http://antwrp.gsfc.nasa.gov/apod/ap051023.html ] Sagittarius A* are within the bright region near the bottom. Two other star clusters, the Arches [ http://antwrp.gsfc.nasa.gov/apod/ap010614.html ], and the Quintuplet [ http://antwrp.gsfc.nasa.gov/apod/ap990921.html ] lie near the top. Cluster interactions with dense molecular clouds in the region may produce some of the diffuse emission detected in the Chandra x-ray view. |
|
Blue Lagoon
| Title |
Blue Lagoon |
| Explanation |
Stars come and go as you slide your cursor over this engaging image of M8, aka the Lagoon Nebula [ http://www.seds.org/messier/m/m008.html ]. Of course, the nebula is itself a star-forming region [ http://antwrp.gsfc.nasa.gov/apod/ap030908.html ], but the stars that appear and disappear here include background and foreground stars that by chance lie along the same line of sight. In this "for fun" [ http://www.rc-astro.com/php/displayImage.htm?id=1169 ] comparison of two nearly identical digital images, the stellar point sources were removed from one image [ http://www.rc-astro.com/php/displayImage.htm?id=1168 ] by computer processing to leave only the diffuse emission from the glowing gas clouds. In both pictures, red emission (H-alpha emission [ http://antwrp.gsfc.nasa.gov/apod/ap050930.html ]) from atomic hydrogen dominates the cosmic lagoon's visible light, but narrow band [ http://antwrp.gsfc.nasa.gov/apod/ap060324.html ] filters were used to record the image data and map the hydrogen emission to green hues, with emission from sulfur atoms in red and oxygen in blue. The lovely [ http://www.mistisoftware.com/astronomy/ Compare_m8_Med.htm ] Lagoon Nebula spans about 30 light-years at an estimated distance of 5,000 light-years toward the constellation Sagittarius [ http://www.hawastsoc.org/deepsky/sgr/index.html ]. |
|
Galactic Centre Starscape
| Title |
Galactic Centre Starscape |
| Explanation |
Thirty thousand light-years distant, beyond the majestic dust clouds [ http://antwrp.gsfc.nasa.gov/apod/ap960605.html ] of the constellation Sagittarius, lies the centre of our Milky Way Galaxy. Hidden from optical view by the dust, the Galactic Centre [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ] region is a relatively unexplored [ http://antwrp.gsfc.nasa.gov/apod/ap000422.html ] starscape. But infrared [ http://www.ipac.caltech.edu/Outreach/Edu/ univ_index.html ] light can more easily penetrate the dust and this recently released [ http://www.iso.vilspa.esa.es/science/galleries/ism/ isogalgc.htm ] Infrared Space Observatory (ISO [ http://www.ipac.caltech.edu/iso/iso.html ]) mosaic, together with other similar images, shows about 100,000 previously unseen stars of the Milky Way's central regions. Huge obscuring dust clouds still seem to crowd the area especially in the left part of the infrared picture. Marked by the white circle, the centre itself is missing from the mosaic because it is so bright that it would saturate ISO's sensitive camera. The stars [ http://mrcohen1.keel.physics.ship.edu/108/evol.htm ] are mostly evolved red giants [ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/ 971016.html ], intrinsically cool, large, bright stars that have swollen after exhausting their central supply of hydrogen fuel. The detailed properties of the red [ http://aibn47.astro.uni-bonn.de/~gallery/color.html ] giant stars can be very revealing [ http://sci.esa.int/content/news/ index.cfm?aid=18&cid=599&oid=20040 ] as these stars contribute to the interstellar gas and dust clouds, enriching their galactic environment with carbon [ http://antwrp.gsfc.nasa.gov/apod/ap981218.html ] and other elements. Their motions also trace the mass distribution in the Galactic Centre and may support the idea that our Galaxy grew by swallowing smaller [ http://antwrp.gsfc.nasa.gov/apod/ap980216.html ], nearby galaxies. |
|
The Hubble SWEEPS Field
| Title |
The Hubble SWEEPS Field |
| Explanation |
This crowded star field [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2006/34/ ] towards the center of our Milky Way Galaxy turns out to be a great place to search for planets beyond [ http://www.alienearths.org/online/ starandplanetformation/planetfamilies.php ] our solar system. In fact, repeatedly imaging about 180,000 stars in the field [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2006/34/fastfacts/ ] over a one week period, the Hubble Space Telescope enabled astronomers to conduct the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Their search looked for brief, periodic dips in brightness caused as a large planet eclipses [ http://antwrp.gsfc.nasa.gov/apod/ap991115.html ] or transits its parent star. Since chances [ http://imgsrc.hubblesite.org/hu/db/2006/34/images/g/ formats/web_print.jpg ] of seeing such an eclipse are slim, it was a definite advantage to examine as many stars as possible. In the end, SWEEPS astronomers found [ http://arxiv.org/abs/astro-ph/0610098 ] 16 candidate stars (green circles identify 11 in this cropped picture) that are likely closely orbited by large Jupiter-sized planets with periods of a few days or less. Large planets orbiting so close to their stars are termed hot Jupiters [ http://www.spitzer.caltech.edu/Media/releases/ ssc2006-18/release.shtml ]. Kepler [ http://www.kepler.arc.nasa.gov/ ], a future NASA mission, is intended to extend the transit technique to search for Earth-sized planets [ http://planetquest.jpl.nasa.gov/index.cfm ]. |
|
M17: Omega Nebula Star Facto
…
| Title |
M17: Omega Nebula Star Factory |
| Explanation |
In the depths of the dark clouds of dust and molecular gas known as M17, stars continue to form. Visible in the above recently released representative-color photograph [ http://www.eso.org/outreach/press-rel/pr-2000/phot-24-00.html ] of M17 [ http://www.seds.org/messier/m/m017.html ] by the New Technology Telescope [ http://www.ls.eso.org/lasilla/Telescopes/NEWNTT/telescope/esontt.html ] are clouds so dark that they appear almost empty of near infrared light [ http://www.ipac.caltech.edu/Outreach/Edu/discovery.html ]. The darkness of these molecular clouds [ http://antwrp.gsfc.nasa.gov/apod/ap990511.html ] results from background starlight being absorbed by thick carbon-based smoke-sized dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]. As bright massive stars form, they produce intense and energetic light that slowly boils away [ http://antwrp.gsfc.nasa.gov/apod/ap990502.html ] the dark shroud. M17 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999AAS...195.7914K ]'s unusual appearance [ http://www.limber.org/m17fid.html ] has garnered it such nicknames as the Omega Nebula, the Horseshoe Nebula, and the Swan Nebula. M17 [ http://antwrp.gsfc.nasa.gov/apod/ap990126.html ], visible with binoculars towards the constellation of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ], lies 5000 light-years [ http://www.howstuffworks.com/question94.htm ] away and spans 20 light-years across. |
|
M55: Globular Star Cluster
| Title |
M55: Globular Star Cluster |
| Explanation |
The fifty-fifth entry [ http://antwrp.gsfc.nasa.gov/apod/ap991023.html ] in Charles Messier's catalog, M55 is [ http://www.seds.org/messier/m/m055.html ] a large and lovely globular cluster [ http://www.seds.org/messier/glob.html ] of around 100,000 stars. Only 20,000 light-years away in the constellation Sagittarius [ http://www.astronomical.org/constellations/ sgr.html ], M55 appears to earth-bound observers to be nearly 2/3 the size of the full moon. Globular star clusters like M55 roam the halo [ http://www.limber.org/globs.html ] of our Milky Way Galaxy as gravitationally bound populations of stars known to be much older than stellar groups found in the galactic disk. Astronomers who make detailed studies [ http://arXiv.org/abs/astro-ph/?9812302 ] of globular cluster stars can accurately measure the cluster ages and distances. Their results ultimately constrain the age of the Universe [ http://antwrp.gsfc.nasa.gov/diamond_jubilee/debate.html ] (... it must be older than the stars in it! ), and provide a fundamental rung on the astronomical distance [ http://casswww.ucsd.edu/public/tutorial/ Distances.html ] ladder. This stunning three-color image [ http://aibn47.astro.uni-bonn.de/~gallery/ articles/imagecolor.html ] made with astronomical (BVI [ http://herbie.ucolick.org/techdocs/filters/ phot_filt_curves.html ]) filters spans about 100 light-years across the globular cluster M55. |
|
Stars of the Galactic Center
| Title |
Stars of the Galactic Center |
| Explanation |
The center [ http://antwrp.gsfc.nasa.gov/apod/ap040411.html ] of our Milky Way Galaxy is hidden [ http://antwrp.gsfc.nasa.gov/apod/ap051004.html ] from the prying eyes of optical telescopes by clouds of obscuring dust and gas. But in this stunning vista [ http://www.spitzer.caltech.edu/Media/releases/ ssc2006-02/ssc2006-02a.shtml ], the Spitzer Space Telescope's infrared [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ ir_tutorial/importance.html ] cameras, penetrate much of the dust revealing the stars of the crowded galactic center region. A mosaic of many smaller snapshots, the detailed, false-color image shows [ http://www.spitzer.caltech.edu/Media/releases/ ssc2006-02/release.shtml ] older, cool stars in bluish hues. Reddish glowing dust clouds are associated with young, hot stars in stellar nurseries. The galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap051023.html ] lies some 26,000 light-years away, toward the constellation Sagittarius [ http://hawastsoc.org/deepsky/sgr/index.html ]. At that distance, this picture spans about 900 light-years. |
|
M8: In the Center of the Lag
…
| Title |
M8: In the Center of the Lagoon Nebula |
| Explanation |
In the center of the Lagoon Nebula [ http://www.seds.org/messier/m/m008.html ] one finds glowing gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], star clusters, and dense knots of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap961229.html ] just now forming stars. The young open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars, designated NGC 6523, can be seen in the center of the above image [ http://www.janis.or.jp/users/kitahara/e-m8-95.jpg.html ]. These stars emit energetic light [ http://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ] that ionizes [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] the surrounding hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. As this gas reacquires electrons [ http://www.aip.org/history/electron/ ], it emits red light [ http://csep10.phys.utk.edu/astr162/lect/light/absorption.html ]. The Lagoon Nebula [ http://www.seds.org/billa/twn/n6523x.html ] lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away and spans about 100 light-years across. The nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980707.html ] occupies an area on the sky larger than a full moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ], and can be seen even without binoculars from a dark location towards the constellation [ http://www.allthesky.com/constellations/const.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
Constellations and Cloudy Sk
…
| Title |
Constellations and Cloudy Skies |
| Explanation |
Recorded earlier in July, the clouds of planet Earth [ http://earthobservatory.nasa.gov/ ] reflect moonlight and a faint, reddish glow in this serene sea and skyscape. Beyond them lie the cosmic dust and star clouds of the Milky Way [ http://seds.org/messier/more/mw.html ]. The near-midnight view looks south from a beach in northern France and finds the constellation Sagittarius [ http://en.wikipedia.org/wiki/ Sagittarius_%28constellation%29 ], the Archer, peaking above the horizon [ http://www.pixheaven.net/photo_us.php? nom=070705_6674-79constellation ]. Bright planet Jupiter rules [ http://antwrp.gsfc.nasa.gov/apod/ap070525.html ] on the right, wandering among the stars of the constellation Scorpius [ http://hawastsoc.org/deepsky/sco/index.html ]. Of course, the Galactic Center [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] itself is hidden behind the Milky Way clouds in Sagittarius. To find them, just put your cursor over the picture and follow the arrow. |
|
Infrared Trifid
| Title |
Infrared Trifid |
| Explanation |
The Trifid Nebula, aka Messier 20 [ http://www.seds.org/messier/m/m020.html ], is easy to find with a small telescope, a well known stop in the nebula rich [ http://antwrp.gsfc.nasa.gov/apod/ap040909.html ] constellation Sagittarius [ http://www.hawastsoc.org/deepsky/sgr/index.html ]. But where visible light pictures [ http://antwrp.gsfc.nasa.gov/apod/ap020424.html ] show the nebula divided into three parts by dark, obscuring dust lanes, this penetrating infrared image [ http://www.spitzer.caltech.edu/Media/releases/ssc2005-02/ ssc2005-02a.shtml ] reveals filaments of glowing dust clouds and newborn stars. The spectacular false-color view is courtesy of the Spitzer Space Telescope [ http://www.spitzer.caltech.edu/spitzer/index.shtml ]. Astronomers have used the Spitzer infrared image [ http://coolcosmos.ipac.caltech.edu/ ] data to count newborn and embryonic [ http://photojournal.jpl.nasa.gov/catalog/PIA07226 ] stars which otherwise can lie hidden in the natal dust and gas clouds of this intriguing stellar nursery [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/ StarForm.html ]. As seen here, the Trifid is about 30 light-years across and lies only 5,500 light-years away. |
|
Sagittarius Star Cloud
| Title |
Sagittarius Star Cloud |
| Explanation |
Stars come in all different colors. The color of a star [ http://zebu.uoregon.edu/~soper/Stars/color.html ] indicates its surface temperature [ http://csep10.phys.utk.edu/astr162/lect/stars/cindex.html ], an important property used to assign each star a spectral type [ http://www.skypub.com/tips/basics/spectra.html ]. Most stars in the above Sagittarius Star Cloud [ http://heritage.stsci.edu/public/Oct22/sgr1/sgrtable.html ] are orange or red and relatively faint, as our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap980830.html ] would appear. The blue [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ] and greenish stars are hotter, many being relatively young and massive. The bright red stars are cool Red Giants [ http://plabpc.csustan.edu/astro/stars/giant.htm ], bloated stars once similar to our Sun that have entered a more advanced stage of evolution [ http://www.aegis1.demon.co.uk/tutorials/stellar.htm ]. Stars of this Sagittarius Cloud lie towards the center of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap990621.html ] - tantalizing cosmic jewels [ http://antwrp.gsfc.nasa.gov/apod/ap961111.html ] viewed through a rift in the dark [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ], pervasive, interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/ap001119.html ]. This famous stellar grouping houses some of the oldest [ http://antwrp.gsfc.nasa.gov/apod/ap001029.html ] stars known. |
|
The Lagoon Nebula in Gas, Du
…
| Title |
The Lagoon Nebula in Gas, Dust, and Stars |
| Explanation |
Stars are battling gas and dust in the Lagoon Nebula but the photographers are winning. Also known as M8, this photogenic nebula [ http://astrosurf.com/afernandez/gallery/deepsky/m8/m8_lrgb_asa_70.htm ] is visible [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] even without binoculars towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. The energetic processes of star formation [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ] create not only the colors but the chaos [ http://antwrp.gsfc.nasa.gov/apod/ap031228.html ]. The red-glowing gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] results from high-energy starlight striking interstellar hydrogen [ http://en.wikipedia.org/wiki/Hydrogen ] gas. The dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] filaments [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ] that lace M8 [ http://www.seds.org/messier/m/m008.html ] were created in the atmospheres of cool giant stars [ http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html ] and in the debris [ http://antwrp.gsfc.nasa.gov/apod/ap990803.html ] from supernovae [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] explosions. The light from M8 [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?m8 ] we see today left about 5,000 years ago [ http://en.wikipedia.org/wiki/3rd_millennium_BC ]. Light takes about 50 years to cross this section of M8 [ http://www.seds.org/billa/twn/n6523.html ]. |
|
Messiers and Mars
| Title |
Messiers and Mars |
| Explanation |
A telescopic tour of the constellation Sagittarius [ http://www.seds.org/Maps/Stars_en/Fig/ sagittarius.html ] offers the many bright clusters and nebulae of dimensioned space [ http://antwrp.gsfc.nasa.gov/apod/ap010418.html ] in a starscape [ http://antwrp.gsfc.nasa.gov/apod/ap000629.html ] surrounding the galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ]. This gorgeous color deep-sky photograph [ http://members.home.net/fct150/mars_visits_messier.htm ] visits two such lovely sights, cataloged by the 18th century cosmic tourist Charles Messier [ http://www.seds.org/messier/xtra/history/biograph.html ] as M8 and M20. M20 (upper left), the Trifid Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap000328.html ], presents a striking contrast in red/blue colors and dark dust lanes. Just below and to the right is the expansive, alluring red glow of M8, the Lagoon Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010103.html ]. Both nebulae are a few thousand light-years distant but at the far right, the dominant celestial beacon is a "local" source, the planet Mars [ http://www.seds.org/nineplanets/nineplanets/mars.html ]. Just passing through Sagittarius and strongly overexposed in this picture, the Red Planet [ http://mars.jpl.nasa.gov/ ] is a short 4 light-minutes away. Now near its closest approach [ http://www.skypub.com/sights/moonplanets/0105marsreturn.shtml ] to planet Earth since 1988, Mars rises around sunset and can be seen [ http://members.nbci.com/marsprev/mpenglish.htm ] for most of the night shining [ http://cfa-www.harvard.edu/iauc/07600/07642.html#Item1 ] brightly at about -2.3 magnitude [ http://csep10.phys.utk.edu/astr162/lect/stars/ magnitudes.html ]. Urban imager [ http://members.home.net/mrcolewa/cartoon.htm ] Michael Cole recorded this photograph at 3:00 AM on May 20th in clear skies over Camp Hancock, Oregon, USA. |
|
Sagittarius Triplet
| Title |
Sagittarius Triplet |
| Explanation |
These three bright nebulae are often featured in telescopic tours of the constellation Sagittarius [ http://www.hawastsoc.org/deepsky/sgr/ index.html ] and the crowded starfields of the central Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ]. In fact, 18th century cosmic tourist Charles Messier [ http://www.seds.org/messier/xtra/history/ biograph.html ] cataloged two of them, M8, the nebula below and right of center, and colorful M20 at the upper right. The third, NGC 6559 [ http://antwrp.gsfc.nasa.gov/apod/ap011023.html ], is left of M8, separated from the the larger nebula by a dark dust lane. All three are stellar nurseries about five thousand light-years or so distant. The expansive M8, over a hundred light-years across, is also known as the Lagoon Nebula [ http://www.seds.org/messier/m/ m008.html ] while M20's popular moniker is the Trifid [ http://antwrp.gsfc.nasa.gov/apod/ap050526.html ]. This stunning digital view [ http://www.fourthdimensionastroimaging.com/ LagoonTrifid.html ] is actually a collaborative composite recorded by 2 cameras and 2 telescopes about 2 thousand miles apart. The deep, wide image field was captured under dark Arizona skies [ http://www.mistisoftware.com/astronomy/Site.htm ]. Both M8 and M20 were recorded in more detail from an observatory [ http://www.fourthdimensionastroimaging.com/Observatory.html ] in Pennsylvania. Glowing hydrogen gas creates the dominant red color of the emission nebulae, with contrasting blue hues, most striking in the Trifid, due to dust reflected starlight. |
|
Unusual Flashes Toward Globu
…
| Title |
Unusual Flashes Toward Globular Cluster M22 |
| Explanation |
What is causing the unusual flashes behind globular cluster M22? This teeming ball of stars is the brightest globular cluster [ http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html ] visible from Earth's northern hemisphere. M22 [ http://www.seds.org/messier/m/m022.html ], shown in full in the inset, spans about 50 light-years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies 8,500 light-years away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. M22's center was recently imaged repeatedly [ http://oposite.stsci.edu/pubinfo/PR/2001/20/index.html ] by the high resolution Hubble Space Telescope [ http://www.stsci.edu/hst/ ]. Behind M22 [ http://www.mt.net.au/~southsky/astronomy/m22.html ] are many more stars near the center of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000705.html ]. Unexpectedly, several stars near the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ] -- well behind M22 [ http://www.noao.edu/image_gallery/html/im0575.html ] -- appeared to nearly double in brightness and return to normal within 20 hours. One hypothesis [ http://www.nature.com/nature/links/010628/010628-5.html ] posed to explain these quick brightness changes is the gravitational lens effect [ http://www.iam.ubc.ca/~newbury/lenses/research.html ] of large planets roaming freely in the cluster. One problem with this is that no such planetary population [ http://exoplanets.org/index.html ] was previously known! Future observations are planned to better understand these mysterious flashes. |
|
Around The Arches Cluster
| Title |
Around The Arches Cluster |
| Explanation |
The most compact cluster of stars known in our galaxy, the Arches cluster [ http://oposite.stsci.edu/pubinfo/pr/1999/30/content/ 9930w.jpg ], boasts 100 or so massive, young stars contained within a diameter of one light-year. Seen toward the constellation Sagittarius [ http://chandra.harvard.edu/photo/constellations/ sagittarius.html ], the Arches cluster is [ http://oposite.stsci.edu/pubinfo/pr/1999/30/ pr.html ] about 25,000 light-years from planet Earth and lies within a scant 100 light-years of the supermassive black hole [ http://antwrp.gsfc.nasa.gov/apod/ap001220.html ] believed to lurk in our Milky Way Galaxy's center [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ]. This combination of [ http://chandra.harvard.edu/photo/cycle1/arches/index.html ] images in radio [ http://imagers.gsfc.nasa.gov/ems/radio.html ], infrared [ http://imagers.gsfc.nasa.gov/ems/infrared.html ], and x-ray [ http://imagers.gsfc.nasa.gov/ems/xrays.html ] light illustrates this star cluster's bizarre galactic neighborhood. Shown in [ http://chandra.harvard.edu/photo/cycle1/arches/more.html ] red, radio emission traces the filamentary arching structures near the galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap990128.html ] around the Arches cluster [ http://www.aas.org/publications/baas/v33n2/aas198/ 191.htm ] location. Within the zoomed inset box, infrared image data shows some of the cluster's individual stars as bright point-like sources. The diffuse emission in blue surrounding the cluster stars is a false-color [ http://chandra.harvard.edu/photo/false_color.html ] x-ray image of an enveloping cloud of 60 million degree gas -- the first time [ http://www.physics.nwu.edu/news/reuters.html ] such an energetic star cluster halo has been detected. Astronomers consider [ http://www.physics.nwu.edu/news/starfactory.html ] the tightly packed and relatively nearby Arches cluster, an analog of the furious star forming regions in galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap010606.html ] millions of light-years away. |
|
Star Factory Messier 17
| Title |
Star Factory Messier 17 |
| Explanation |
Sculpted by [ http://www.astrogranada.org/astroimagen/html/pag_img/ccd/ m17_cisne_sii-oiii-ha.htm ] stellar winds and radiation, the star factory known as Messier 17 [ http://seds.org/messier/m/m017.html ] lies some 5,500 light-years away in the nebula-rich constellation Sagittarius [ http://www.hawastsoc.org/deepsky/sgr/index.html ]. At that distance, this 30 arcminute field of view spans almost 50 light-years. Stellar winds and energetic light from hot, massive stars formed from M17's stock of cosmic gas and dust have slowly carved away at the remaining interstellar material producing the cavernous appearance [ http://antwrp.gsfc.nasa.gov/apod/ap030821.html ] and undulating [ http://antwrp.gsfc.nasa.gov/apod/ap040828.html ] shapes. Colors [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/eagle.php ] in the gorgeous image were picked to emphasize light emitted by specific elements in the nebula excited by the energetic starlight [ http://antwrp.gsfc.nasa.gov/apod/ap050930.html ]. Red indicates emission from sulfur, green from hydrogen, and blue from oxygen. M17 is also [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ multiwavelength_astronomy/multiwavelength_museum/m17.html ] known as the Omega Nebula or the Swan Nebula. |
|
Moonlight, Mars, and Milky W
…
| Title |
Moonlight, Mars, and Milky Way |
| Explanation |
Aloha [ http://www.mhpcc.edu/~erobello/homepage_ernie/ernie1.html ] and welcome to a breath-taking skyscape. In this celestial scene, a four day old Moon illuminates a dreamlike foreground while bright planet Mars [ http://antwrp.gsfc.nasa.gov/apod/ap010615.html ] (above center) rules and the Milky Way's [ http://www.maths.tcd.ie/~jaymin/chview/chv5.htm ] cosmic clouds of stars and dust seem to stretch from horizon to horizon. The picture was taken on May 27th from what may be the best amateur astronomy observing site on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980725.html ], near the Mauna Kea, Hawai'i Visitor Center [ http://www.ifa.hawaii.edu/info/vis/ ], 9,600 feet above sea level. Remarkable in the volcanic foreground are moonlit clouds and an "ahu hoku" - a star marker or star altar - built up of rocks topped with a white piece of coral gently glowing in the moonlight. Now near its closest approach in 13 years, Mars still lingers [ http://www.skypub.com/sights/moonplanets/ 0105marsreturn.shtml ] between the Milky Way constellations of [ http://antwrp.gsfc.nasa.gov/apod/ap990911.html ] Sagittarius and Scorpius. High above the horizon by midnight, the Red Planet [ http://members.nbci.com/marsprev/mpenglish.htm ] is exceptionally well placed for earthdwellers to [ http://antwrp.gsfc.nasa.gov/apod/ap010331.html ] admire it. Astrophotographer Barney Magrath [ mailto:magraths@kona.net ] comments that this splendid sky view represents one of the joys of photography [ http://antwrp.gsfc.nasa.gov/apod/ap001104.html ] itself. When making the time exposure he did not realize that the ahu hoku would become such a beautiful element in his celestial composition. |
|
The Trifid Nebula in Stars a
…
| Title |
The Trifid Nebula in Stars and Dust |
| Explanation |
Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula [ http://www.seds.org/messier/m/m020.html ]. Also known as M20, this photogenic nebula [ http://www.cosmotography.com/images/lrg_m20.html ] is visible [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] with good binoculars towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. The energetic processes of star formation [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ] create not only the colors but the chaos [ http://en.wikipedia.org/wiki/Chaos_%28physics%29 ]. The red-glowing gas [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ] results from high-energy starlight striking interstellar hydrogen [ http://periodic.lanl.gov/elements/1.html ] gas. The dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] filaments [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ] that lace M20 [ http://antwrp.gsfc.nasa.gov/apod/ap970828.html ] were created in the atmospheres of cool giant stars [ http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html ] and in the debris [ http://antwrp.gsfc.nasa.gov/apod/ap990803.html ] from supernovae [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] explosions. Which bright young stars light up the blue reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] is still being investigated [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986AJ.....92.1125L ]. The light from M20 [ http://www.noao.edu/image_gallery/html/im0587.html ] we see today left perhaps 3000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20 [ http://www.seds.org/billa/twn/n6514x.html ]. |
|
The Red Spider Planetary Neb
…
| Title |
The Red Spider Planetary Nebula |
| Explanation |
Oh what a tangled web [ http://www.bartleby.com/100/338.25.html ] a planetary nebula [ http://www.seds.org/messier/planetar.html ] can weave. The Red Spider Planetary Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980106.html ] shows the complex structure that can result when a normal star [ http://antwrp.gsfc.nasa.gov/apod/ap000815.html ] ejects its outer gases and becomes a white dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap000910.html ] star. Officially tagged NGC [ http://www.encyclopedia.com/printablenew/33395.html ] 6537 [ http://www.astro.washington.edu/balick/WFPC2/n6537.caption.html ], this two-lobed symmetric planetary nebula [ http://antwrp.gsfc.nasa.gov/apod/planetary_nebulae.html ] houses one of the hottest white dwarfs [ http://antwrp.gsfc.nasa.gov/apod/ap000730.html ] ever observed, probably as part of binary star [ http://astrosun.tn.cornell.edu/courses/astro201/binstar.htm ] system. Internal winds [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] emanating from the central stars, visible in the center, have been measured in excess of 1000 kilometers per second. These winds [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] expand the nebula, flow along the nebula's walls, and cause waves of hot gas [ http://pearl1.lanl.gov/periodic/elements/1.html ] and dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] to collide. Atoms [ http://education.jlab.org/atomtour/ ] caught in these colliding shocks radiate light shown in the above representative-color picture [ http://www.spacetelescope.org/pressroom/embargo/heic0109_embargo.html ]. The Red Spider Nebula [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000A%26A...362L..17P ] lies toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. It's distance is not well known but estimated by some [ http://cdsads.u-strasbg.fr/cgi-bin/bib_query?1986A&A...157..191G ] to be about 4000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ]. |
|
A Galactic Star Forming Regi
…
| Title |
A Galactic Star Forming Region in Infrared |
| Explanation |
How do stars form? To help study this complex issue, astronomers took a deep image in infrared light of an active part of our Milky Way Galaxy [ http://cassfos02.ucsd.edu/public/tutorial/MW.html ] where star formation is rampant. In IRDC G11.11-0.11, thick clouds of dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] and gas are congealing into stars that are so dark that humans living there would see an empty night sky. The image [ http://www.spitzer.caltech.edu/Media/releases/ssc2006-20/ ssc2006-20a.shtml ], though, taken last year by the Spitzer Space Telescope [ http://en.wikipedia.org/wiki/Spitzer_Space_Telescope ] in infrared light [ http://science.hq.nasa.gov/kids/ imagers/ems/infrared.html ], shows vast glowing fields of gas and dust, indicating that much of this dust is heated by forming stars. The centers of some clouds, such as the snake-like structure [ http://antwrp.gsfc.nasa.gov/apod/ap050521.html ] on the upper left, are so thick and cold that they are dark even in infrared light [ http://en.wikipedia.org/wiki/Infrared ]. Many of the red dots are glowing dust shrouds [ http://antwrp.gsfc.nasa.gov/apod/ap030816.html ] centered on very young newly formed stars. The unusual red sphere below the snake is actually a supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/ap051226.html ], the glowing shell of a young star so massive it evolved rapidly and exploded. The region [ http://www.spitzer.caltech.edu/Media/releases/ssc2006-20/ ssc2006-20a.shtml ] spans about 150 light years and lies about 10,000 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away toward the constellation of Sagittarius [ http://www.astronomical.org/portal/modules/wfsection/ article.php?articleid=72 ]. APOD editor to review best space pictures in Philadelphia Wednesday night [ http://www.rittenhouseastronomicalsociety.org/ ] |
|
The Lagoon Nebula in Three C
…
| Title |
The Lagoon Nebula in Three Colors |
| Explanation |
The bright Lagoon Nebula [ http://www.seds.org/messier/m/m008.html ] is home to a diverse array of astronomical objects. Particularly interesting sources include a bright open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars and several energetic star-forming regions [ http://antwrp.gsfc.nasa.gov/apod/stellar_nursuries.html ]. When viewed by eye, cluster light [ http://antwrp.gsfc.nasa.gov/apod/ap980707.html ] is dominated by an overall red glow that is caused by luminous hydrogen gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], while the dark filaments are caused by absorption by dense lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]. The above picture [ http://antwrp.gsfc.nasa.gov/apod/ap010820.html http://lilen.fcaglp.unlp.edu.ar/ ], from the Curtis-Schmidt Telescope [ http://www.noao.edu/image_gallery/html/im0131.html ], however, shows the nebula's emission in three exact colors specifically emitted by hydrogen [ http://www.eren.doe.gov/hydrogen/ ], oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ], and sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ]. The Lagoon Nebula [ http://www.seds.org/billa/twn/n6523x.html ], also known as M [ http://www.seds.org/messier/xtra/history/CMessier.html ]8 and NGC [ http://www.ngcic.org/mission.htm ] 6523, lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away. The Lagoon Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010103.html ] can be located with binoculars in the constellation of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ] spanning a region over three times the diameter of a full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ]. |
|
The Small Cloud of Magellan
| Title |
The Small Cloud of Magellan |
| Explanation |
Portuguese navigator Ferdinand Magellan [ http://www.mariner.org/educationalad/ageofex/ magellan.php ] and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two celestial wonders easily visible for southern hemisphere skygazers are known as the Clouds of Magellan. These cosmic clouds are now understood to be dwarf irregular galaxies, satellites of our larger spiral [ http://www.atlasoftheuniverse.com/ ] Milky Way Galaxy. The Small Magellanic Cloud [ http://www.seds.org/messier/xtra/ngc/smc.html ] pictured above actually spans 15,000 light-years or so and contains several hundred million stars. About 210,000 light-years distant in the constellation Tucana [ http://www.hawastsoc.org/deepsky/tuc/ ], it is the fourth closest of the Milky Way's known satellite galaxies, after the Canis Major [ http://www.seds.org/messier/more/cma_dw.html ] and Sagittarius Dwarf [ http://www.seds.org/messier/more/sagdeg.html ] galaxies and the Large Magellanic Cloud [ http://www.seds.org/messier/xtra/ngc/lmc.html ]. This gorgeous view [ http://astrosurf.com/sguisard/Pagim/SMC-LHRVB-300mm-V1.html ] also includes two foreground globular star clusters NGC 362 (bottom right) and 47 Tucanae. Spectacular 47 Tuc [ http://antwrp.gsfc.nasa.gov/apod/ap010422.html ]anae is a mere 13,000 light-years away and seen here to the left of the Small Magellanic Cloud [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ multiwavelength_astronomy/multiwavelength_museum/ smc.html ]. |
|
Galactic Center Flicker Indi
…
| Title |
Galactic Center Flicker Indicates Black Hole |
| Explanation |
Why would the center of our Galaxy flicker? Many astronomers believe the only credible answer involves a black hole [ http://cfpa.berkeley.edu/BHfaq.html ]. During observations of Sagittarius A* [ http://www.mpifr-bonn.mpg.de/staff/hfalcke/bh/sld5.html ] with the orbiting Chandra X-ray Observatory [ http://asc.harvard.edu/udocs/overview_cxo.html ], the bright X-ray [ http://chandra.harvard.edu/xray_astro/xrays.html ] source at the very center [ http://antwrp.gsfc.nasa.gov/apod/ap990128.html ] of our Milky Way [ http://www.seds.org/messier/more/mw.html ] brightened dramatically for a few minutes. Sagittarius A* [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001A%26A...375L..18C ] is visible as the bright dot near the center of the above image [ http://chandra.harvard.edu/photo/cycle1/0204flare/index.html ]. Since large objects cannot vary quickly, a small source is implicated in the variation. Evidence [ http://csep10.phys.utk.edu/astr162/lect/active/smblack.html ] including the motions of central stars [ http://antwrp.gsfc.nasa.gov/apod/ap001220.html ] indicates that the center of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap010708.html ] is a massive place, however, estimated to be over a million times the mass of our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]. Only one known type of object can fit so much mass in so small a volume: a black hole [ http://antwrp.gsfc.nasa.gov/apod/ap010119.html ]. This short flicker therefore provides additional evidence that a black hole [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ] does indeed reside at our Galaxy's center [ http://antwrp.gsfc.nasa.gov/apod/ap000120.html ]. If true, the flicker [ http://science.nasa.gov/headlines/y2001/ast05sep_1.htm ] might have been caused by an object disrupting as it fell toward the disruptive monster [ http://antwrp.gsfc.nasa.gov/apod/ap010508.html ]. |
|
The Closest Galaxy: Canis Ma
…
| Title |
The Closest Galaxy: Canis Major Dwarf |
| Explanation |
What is the closest galaxy to the Milky Way? The new answer to this old question is the Canis Major dwarf galaxy [ http://astro.u-strasbg.fr/images_ri/canm-e.html ]. For many years astronomers thought the Large Magellan Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010804.html ] (LMC) was closest, but its title was supplanted in 1994 by the Sagittarius dwarf galaxy [ http://www.seds.org/messier/more/sagdeg.html ]. Recent measurements indicate that the Canis Major [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Canis_Major.html ] dwarf is only 42 [ http://en2.wikipedia.org/wiki/The_Answer_to_Life,_the_Universe,_and_Everything ],000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] from the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ], about three quarters of the distance to the Sagittarius dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap030930.html ] and a quarter of the distance to the LMC. The discovery was made in data from the 2MASS [ http://www.ipac.caltech.edu/2mass/overview/about2mass.html#about ]-sky survey, where infrared [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/discovery.html ] light allows a better view through our optically opaque Galactic plane [ http://antwrp.gsfc.nasa.gov/apod/ap070930.html ]. The labeled illustration above [ http://astro.u-strasbg.fr/images_ri/canm-e.html ] shows the location of the newly discovered Canis Major dwarf and its associated tidal stream [ http://antwrp.gsfc.nasa.gov/apod/ap030930.html ] of material in relation to our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ]. The Canis Major dwarf [ http://en.wikipedia.org/wiki/Canis_Major_Dwarf ] and other satellite galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap001023.html ] are slowly being gravitationally ripped apart [ http://www-astronomy.mps.ohio-state.edu/~pogge/Ast162/Unit4/interact.html ] as they travel around and through our Galaxy. |
|
Three Nebulae in Narrow Band
| Title |
Three Nebulae in Narrow Band |
| Explanation |
Narrow band filters and a false-color palette [ http://antwrp.gsfc.nasa.gov/apod/ap060324.html ] give these three nebulae a stunning appearance against the cosmic canvas of the central Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap071020.html ]. All three are stellar nurseries about 5,000 light-years [ http://www.atlasoftheuniverse.com/5000lys.html ] or so distant, toward the nebula rich constellation Sagittarius [ http://antwrp.gsfc.nasa.gov/apod/ap070711.html ]. In the 18th century, astronomer Charles Messier cataloged [ http://messier.obspm.fr/ ] two of them, colorful M8, above and right of center, and compact M20 at the left. The third, NGC 6559 [ http://antwrp.gsfc.nasa.gov/apod/ap040629.html ], is at bottom right. Over a hundred light-years across, M8 is also known as the Lagoon Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap060825.html ]. Divided by obscuring dust lanes, M20's popular moniker is the Trifid [ http://antwrp.gsfc.nasa.gov/apod/ap070813.html ]. In the composite image, narrow emission lines [ http://csep10.phys.utk.edu/astr162/lect/light/ absorption.html ] from sulfur, hydrogen, and oxygen atoms recorded through the filters, are mapped into broader red, green, and blue colors respectively. The color scheme [ http://hubblesite.org/gallery/behind_the_pictures/ meaning_of_color/eagle.php ] was made popular in Hubble Space Telescope images. But for ground-based telescopes, narrow band filters also make it possible to reject overwhelming light-pollution and capture compelling images of the cosmos from urban skies [ http://mayda.com/astro/Index.html ]. |
|
Emission and Reflection in N
…
| Title |
Emission and Reflection in NGC 6559 |
| Explanation |
Bright gas and dark dust permeate the space between stars in a nebula known as NGC 6559 [ http://robgendler.astrodigitals.com/6559.html ]. The gas, primarily hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ], is responsible for the diffuse red glow of the emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ]. As energetic light from neighboring stars ionizes interstellar hydrogen [ http://antwrp.gsfc.nasa.gov/apod/ap010113.html ], protons [ http://www.neutron.anl.gov/hyper-physics/proton.html ] and electrons [ http://www.aip.org/history/electron/ ] recombine to emit light [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] of very specific colors [ http://csep10.phys.utk.edu/astr162/lect/light/absorption.html ], including the red [ http://antwrp.gsfc.nasa.gov/apod/ap010214.html ] hue observed. Small dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] particles reflect blue starlight efficiently and so creates the blue reflection nebulosity [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] seen near two of the bright stars. Dust [ http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis9.html ] also absorbs visible light, causing the dark clouds [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] and filaments [ http://antwrp.gsfc.nasa.gov/apod/ap990919.html ] visible. NGC 6559 [ http://www.aao.gov.au/images/captions/uks003.html ] lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
Stars and Dust through Baade
…
| Title |
Stars and Dust through Baade's Window |
| Explanation |
Billions of stars light up the direction toward the center of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap021018.html ]. The vast majority of these stars are themselves billions of years old, rivaling their home Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] in age. Together with interstellar dust, these old stars [ http://www.damtp.cam.ac.uk/user/gr/public/gal_milky.html ] combine to create this yellowish starscape [ http://astrosurf.com/sguisard/Pagim/ Baade_window-LRVB-300mm.html ]. Although the opaque dust [ http://antwrp.gsfc.nasa.gov/apod/ap020707.html ] obscures the true Galactic center in visible light [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ], there is a low density hole in the dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.html ] on the right of the image. The region, named Baade's Window [ http://en.wikipedia.org/wiki/Baade%27s_Window ] for the German astronomer [ http://antwrp.gsfc.nasa.gov/apod/ap071219.html http://www.phys-astro.sonoma.edu/BruceMedalists/Baade/ index.html ] who studied it, is used [ http://antwrp.gsfc.nasa.gov/apod/ap960201.html ] to inspect distant stars and to determine the internal geometry [ http://www.obspm.fr/actual/nouvelle/nov01/ alard.en.shtml ] of the Milky Way. Baade's Window [ http://antwrp.gsfc.nasa.gov/apod/ap071219.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1996A%26A...315..116N ] lies toward the constellation [ http://en.wikipedia.org/wiki/Constellation ] of the Archer (Sagittarius [ http://www.astronomical.org/portal/modules/wfsection/article.php?articleid=72 ]). |
|
Star Forming Region Hubble-V
| Title |
Star Forming Region Hubble-V |
| Explanation |
How did stars form in the early universe? Astronomers are gaining insight by studying NGC 6822 [ http://www.seds.org/messier/xtra/ngc/n6822.html ], a nearby galaxy classified as irregular [ http://www.seds.org/messier/irre.html ] by modern standards but appearing more typical of galaxies billions of years ago [ http://antwrp.gsfc.nasa.gov/apod/ap000709.html ]. Inspection of NGC 6822 shows several bright star groups, including two dubbed Hubble-X [ http://antwrp.gsfc.nasa.gov/apod/ap010216.html ] and Hubble-V. Pictured above [ http://heritage.stsci.edu/2001/39/index.html ], the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] has resolved Hubble V [ http://heritage.stsci.edu/2001/39/table.html ] into the energetic stars that are lighting up the surrounding gas. Each star in the central dense knot of Hubble V [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999PASP..111.1382O ] shines brighter than 100,000 Sun [ http://www.nineplanets.org/sol.html ]s. The Hubble V [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001AJ....121.2020B ] gas cloud spans about 200 light years [ http://www.treasure-troves.com/astro/Light-Year.html ] and lies about 1.5 million light-years away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
X-Ray Milky Way
| Title |
X-Ray Milky Way |
| Explanation |
If [ http://www.csie.ntu.edu.tw/~ntucs82/PEOPLE/b2506017/ sf/4t.html ] you had x-ray vision, the center regions [ http://antwrp.gsfc.nasa.gov/apod/ap010627.html ] of our Galaxy would not be hidden from view by immense cosmic dust clouds opaque to visible light. Instead [ http://nvo.gsfc.nasa.gov/mw/milkyway.html ], the Milky Way [ http://www.seds.org/messier/more/mw.html ] toward Sagittarius [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] might look something like this stunning mosaic [ http://chandra.harvard.edu/photo/2002/gcenter/ index.html ] of images from the orbiting Chandra Observatory [ http://chandra.harvard.edu/chronicle/ index.html ]. Pleasing to look at, the gorgeous false-color representation of the x-ray data shows [ http://chandra.harvard.edu/press/02_releases/ press_010902.html ] high energy x-rays in blue, medium energies in green, and low energies [ http://antwrp.gsfc.nasa.gov/apod/ap010511.html ] in red. Hundreds of white dwarf stars, neutron stars, and black holes immersed in a fog of multimillion-degree gas are included in the x-ray vista. Within the white patch at the image center lies the Galaxy's central supermassive black hole [ http://science.nasa.gov/headlines/y2001/ ast05sep_1.htm ]. Chandra's sharp x-ray vision [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ history1_xray.html ] will likely lead to a new appreciation of our Milky Way's most active neighborhood and has already indicated that the hot gas itself may have a temperature of a mere 10 million degrees Celsius instead of 100 million degrees as previously thought. The full mosaic is composed of 30 separate images and covers a 900 by 400 light-year swath at the galactic center [ http://chandra.harvard.edu/photo/2002/gcenter/more.html ]. |
|
The Annotated Galactic Cente
…
| Title |
The Annotated Galactic Center |
| Explanation |
The sky toward the center of our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap980523.html ] is filled with a wide variety of celestial wonders [ http://www.allthesky.com/ ]. Many are easily visible with binoculars. Constellations [ http://www.emufarm.org/~cmbell/myth/myth.html ] near the galactic center include Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Sagittarius.html ], Libra [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Libra.html ], Scorpius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Scorpius.html ], Scutum [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Scutum.html ], and Ophiuchus [ http://www.astro.wisc.edu/~dolan/constellations/constellations/ Ophiuchus.html ]. Nebulae include Messier [ http://antwrp.gsfc.nasa.gov/apod/ap960626.html ] Objects M8 [ http://antwrp.gsfc.nasa.gov/apod/ap960127.html ], M16 [ http://antwrp.gsfc.nasa.gov/apod/ap970118.html ], M17 [ http://antwrp.gsfc.nasa.gov/apod/ap960829.html ], M20 [ http://antwrp.gsfc.nasa.gov/apod/ap950723.html ] and the Pipe Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap970621.html ]. Open star clusters [ http://www.seds.org/messier/cluster.html ] include M6 [ http://www.seds.org/messier/m/m006.html ], M7 [ http://www.seds.org/messier/m/m007.html ], M18 [ http://www.seds.org/messier/m/m018.html ], M21 [ http://www.seds.org/messier/m/m021.html ], M23 [ http://www.seds.org/messier/m/m023.html ], M24 [ http://seds.lpl.arizona.edu/messier/m/m024.html ], M25 [ http://www.seds.org/messier/m/m025.html ]. Globular star clusters include M9 [ http://seds.lpl.arizona.edu/messier/m/m009.html ], M22 [ http://seds.lpl.arizona.edu/messier/m/m022.html ], M28 [ http://seds.lpl.arizona.edu/messier/m/m028.html ], M54 [ http://seds.lpl.arizona.edu/messier/m/m054.html ], M69 [ http://seds.lpl.arizona.edu/messier/m/m069.html ], M70 [ http://seds.lpl.arizona.edu/messier/m/m070.html ]. And don't forget Baade's Window [ http://antwrp.gsfc.nasa.gov/apod/ap960201.html ]. Click on the photo to get the un-annotated version. |
|
Local Group Galaxy NGC 6822
| Title |
Local Group Galaxy NGC 6822 |
| Explanation |
Nearby galaxy NGC 6822 [ http://www.seds.org/messier/xtra/ngc/n6822.html ] is irregular in several ways. First, the galaxy's star distribution merits a formal classification of dwarf [ http://antwrp.gsfc.nasa.gov/apod/ap001023.html ] irregular [ http://www.seds.org/messier/irre.html ], and from our vantage-point the small galaxy appears nearly rectangular. What strikes astronomers as more peculiar, however, is NGC 6822 [ http://www.ctio.noao.edu/REU/ctioreu_2001/shay/pagelgs.html ]'s unusually high abundance of HII regions [ http://antwrp.gsfc.nasa.gov/apod/ap011218.html ], locales of ionized [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] that surround young stars. Large HII regions, also known as emission nebulas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], are visible [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1925ApJ....62..409H ] surrounding the small galaxy, particularly toward the upper right. Toward the lower left are bright stars that are loosely grouped into an arm. Pictured above [ http://www.noao.edu/image_gallery/html/im0698.html ], NGC 6822, also known as Barnard's Galaxy [ http://www.noao.edu/outreach/aop/observers/n6822.html ], is located only about 1.5 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away and so is a member of our Local Group of Galaxies [ http://www.seds.org/messier/more/local.html ]. The galaxy [ http://www.aao.gov.au/images/captions/aat026.html ], home to famous nebulas including Hubble V [ http://antwrp.gsfc.nasa.gov/apod/ap011225.html ], is visible with a small telescope toward the constellation [ http://www.adlerplanetarium.org/history/exhibits/constellations/ ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. |
|
The Trifid Nebula from AAO
| Title |
The Trifid Nebula from AAO |
| Explanation |
Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula [ http://www.seds.org/messier/m/m020.html ]. Also known as M20, this photogenic nebula [ http://www.aao.gov.au/images/captions/aat012.html ] is visible [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] with good binoculars towards the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. The energetic processes of star formation [ http://antwrp.gsfc.nasa.gov/apod/ap020108.html ] create not only the colors but the chaos [ http://antwrp.gsfc.nasa.gov/apod/ap011230.html ]. The red-glowing gas [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ] results from high-energy starlight striking interstellar hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. The dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] filaments [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ] that lace M20 [ http://antwrp.gsfc.nasa.gov/apod/ap970828.html ] were created in the atmospheres of cool giant stars [ http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html ] and in the debris [ http://antwrp.gsfc.nasa.gov/apod/ap990803.html ] from supernovae [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] explosions. Which bright young stars light up the blue reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] is still being investigated [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986AJ.....92.1125L ]. The light from M20 [ http://www.noao.edu/image_gallery/html/im0587.html ] we see today left perhaps 3000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20 [ http://www.seds.org/billa/twn/n6514x.html ]. |
|
East of the Lagoon Nebula
| Title |
East of the Lagoon Nebula |
| Explanation |
To the east of the Lagoon Nebula [ http://www.astropix.com/HTML/D_SUM_S/M8.HTM ] is a star field rich in diversity. On the lower left are clouds rich in dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] that hide background stars [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] and young star systems [ http://antwrp.gsfc.nasa.gov/apod/ap010604.html ] still forming. Dark clouds [ http://antwrp.gsfc.nasa.gov/apod/ap020409.html ] include LDN 227 [ http://homepage.interaccess.com/~purcellm/lcas/Articles/darkne.htm ] on the left and IC 1275 on the right, with a bright star near its tip. On the upper right are clouds rich in hot glowing gas [ http://antwrp.gsfc.nasa.gov/apod/ap010103.html ], including part of the emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] NGC 6559 [ http://www.astropix.com/HTML/D_SUM_S/NGC6559.HTM ]. On the right, between the two regions, is a nebula reflecting [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] light from a group of massive blue stars [ http://antwrp.gsfc.nasa.gov/apod/ap970128.html ]. The NGC 6559 complex pictured above spans about 3 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and likely has a common history with the Lagoon Nebula [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?Lagoon ]. The complex [ http://www.seds.org/messier/m/m008.html ] lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away toward the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
The Galactic Center Radio Ar
…
| Title |
The Galactic Center Radio Arc |
| Explanation |
What causes this unusual structure near the center of our Galaxy? The long parallel rays slanting across the top of the above radio image [ http://chandra.harvard.edu/photo/2002/gradioarc/more.html ] are known collectively as the Galactic Center Radio Arc [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989ApJ...343..177L ] and jut straight out from the Galactic plane [ http://antwrp.gsfc.nasa.gov/apod/ap011020.html ]. The Radio Arc [ http://www.northwestern.edu/univ-relations/observer/stories/01_24_02/astronomers.html ] is connected to the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap990128.html ] by strange curving filaments known as the Arches. The bright radio structure at the bottom right likely surrounds a black hole [ http://cosmology.berkeley.edu/Education/BHfaq.html ] at the Galactic center [ http://antwrp.gsfc.nasa.gov/apod/ap001220.html ] and is known as Sagittarius A* [ http://www.mpifr-bonn.mpg.de/staff/hfalcke/bh/sld5.html ]. One origin hypothesis [ http://adsabs.harvard.edu/cgi-bin/bib_query?1994ApJ...424L..91S ] holds that the Radio Arc and the Arches have their geometry because they contain hot plasma [ http://www.plasmas.org/what-are-plasmas.htm ] flowing along lines of constant magnetic field [ http://liftoff.msfc.nasa.gov/academy/space/mag_field.html ]. Recent images [ http://chandra.harvard.edu/photo/2002/gradioarc/index.html ] from the Chandra X-ray Observatory [ http://chandra.nasa.gov/ ] appear to show this plasma colliding [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001AAS...19910902Y ] with a nearby cloud of cold gas. |
|
In the Center of the Trifid
…
| Title |
In the Center of the Trifid Nebula |
| Explanation |
Clouds of glowing gas mingle with lanes of dark dust in the Trifid Nebula [ http://www.seds.org/messier/m/m020.html ], a star forming region toward the constellation [ http://www.att.virtualclassroom.org/vc99/vc_04/cons_stars/cons/hist_cons.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. In the center, the three huge dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] lanes that give the Trifid [ http://antwrp.gsfc.nasa.gov/apod/ap020424.html ] its name all come together. Mountains [ http://antwrp.gsfc.nasa.gov/apod/ap011230.html ] of opaque dust appear on the lower left, while filaments of dust are visible threaded throughout the nebula. A single massive star [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001ApJ...562..446R ] visible near the center causes much of the Trifid's glow [ http://antwrp.gsfc.nasa.gov/apod/ap980828.html ]. The Trifid, also known as M20 [ http://www.astrocruise.com/m20.htm ], is only about 300,000 years old, making it among the youngest emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] known. The nebula lies about 5000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away and part pictured above spans about 20 light years. The above false-color digitally enhanced image [ http://www.gemini.edu/media/images_2002-10.html ] was taken with the Gemini North telescope [ http://antwrp.gsfc.nasa.gov/apod/ap990629.html ] earlier this month. |
|
Gomez's Hamburger: A Proto-P
…
| Title |
Gomez's Hamburger: A Proto-Planetary Nebula |
| Explanation |
What, in heaven, is that? Sometimes astronomers [ http://www.aas.org/education/career.html ] see things on the sky they don't immediately understand [ http://antwrp.gsfc.nasa.gov/apod/ap990928.html ]. In 1985 this happened to Arturo Gomez [ http://heritage.stsci.edu/2002/19/bio/bio_gomez_english.html ], and the object became known as Gomez's Hamburger [ http://www.lib.ucdavis.edu/exhibits/food/panel6.html ] for its distinctive yet familiar shape. After some investigation, the object was identified as a proto-planetary nebula [ http://www.astro.washington.edu/palen/Research/nsf/intro.html ], a gas cloud emitted by a Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ]-like star just after its central hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] fuel has all been fused [ http://casswww.ucsd.edu/physics/ph7/StevI.html ] to helium [ http://pearl1.lanl.gov/periodic/elements/2.html ]. Gomez's Hamburger is on its way [ http://instruct1.cit.cornell.edu/courses/astro101/java/evolve/evolve.htm ] to becoming a full-fledged planetary nebula [ http://www.seds.org/messier/planetar.html ] in a few thousand years. The light seen (the bun) is reflected [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ] by dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] from the central star, although the star itself is obscured by a thick dust disk [ http://antwrp.gsfc.nasa.gov/apod/ap000208.html ] that runs across the middle (the patty). Gomez's Hamburger [ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1987ApJ...316L..21R ], pictured above [ http://heritage.stsci.edu/2002/19/table.html ] in a recent image from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ], is only a fraction of a light year [ http://www.howstuffworks.com/question94.htm ] across but located approximately 10,000 light years away towards the constellation of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ]. |
|
Open Cluster NGC 6520 from C
…
| Title |
Open Cluster NGC 6520 from CFHT |
| Explanation |
Did you ever have a day when it felt like a dark cloud [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] was following you around? For the open cluster [ http://www.seds.org/messier/open.html ] of stars NGC 6520, every day is like this. On the left of the above picture [ http://www.cfht.hawaii.edu/HawaiianStarlight/AIOM/English/CFHT-Coelum-AIOM.html ] are many of NGC 6520's bright blue stars. They formed only millions of years ago - much more recently than our ancient Sun which formed billions of years ago. On the right is an absorption nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ], molecular cloud [ http://origins.jpl.nasa.gov/poster/bigbang3.html ] Barnard 86 [ http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html ], from which the stars of NGC 6520 surely formed. This nebula contains much opaque dust [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] that blocks light from the many stars that would have been visible in the background. Surrounding NGC 6520 [ http://www.ast.cam.ac.uk/AAO/images/captions/aat092.html ] is part of the tremendously dense starscape in the bulge of our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap970315.html ], the extended halo of stars that surrounds the center [ http://antwrp.gsfc.nasa.gov/apod/ap010708.html ] of our Galaxy. NGC 6520 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1982S%26T....63..254M ] spans about 10 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and lies about 5500 light years away toward the direction of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
The Galactic Center - A Radi
…
| Title |
The Galactic Center - A Radio Mystery |
| Explanation |
Tuning in [ http://www.astrocappella.com/cosrad.shtml ] to the center of our Milky Way galaxy, radio astronomers [ http://www.aoc.nrao.edu/intro/ham.connection.html ] explore a complex, mysterious place. A premier high resolution view, this startlingly beautiful picture [ http://rsd-www.nrl.navy.mil/7213/lazio/GC/ ] covers a 4x4 degree region around the galactic center. It was constructed from 1 meter wavelength radio data obtained by telescopes of the Very Large Array [ http://antwrp.gsfc.nasa.gov/apod/ap020528.html ] near Socorro, New Mexico, USA. The galactic center [ http://science.nasa.gov/headlines/y2001/ast05sep_1.htm ] itself is at the edge of the extremely bright object labeled Sagittarius (Sgr) A, suspected of harboring a million solar mass black hole. Along the galactic plane which runs diagonally through the image are tortured clouds of gas energized by hot stars and bubble-shaped supernova remnants (SNRs) - hallmarks of a violent [ http://antwrp.gsfc.nasa.gov/apod/ap010910.html ] and energetic cosmic environment [ http://antwrp.gsfc.nasa.gov/apod/ap020110.html ]. But perhaps most intriguing are the arcs, threads, and filaments [ http://antwrp.gsfc.nasa.gov/apod/ap020521.html ] which abound in the scene. Their uncertain origins challenge present theories of the dynamics of the galactic center. |
|
A Sagittarius Starscape
| Title |
A Sagittarius Starscape |
| Explanation |
Many vast star fields [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] in the plane [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] of our Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] are rich in clouds of stars, dust, and gas. First and foremost, visible in the above picture [ http://www.aao.gov.au/images/captions/uks022.html ] are millions of stars, many of which are similar to our Sun [ http://www.nineplanets.org/sol.html ]. Next huge filaments of dark interstellar dust [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#dust ] run across the image and block the light from millions of more stars yet further across our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap000629.html ]. The bright red region on the left is the Omega Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap990126.html ], an emission nebula [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] of mostly hot hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas also known as M17 [ http://antwrp.gsfc.nasa.gov/apod/ap020501.html ]. A small bright grouping of stars near the image center is the open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] M18 [ http://www.seds.org/messier/m/m018.html ], while the long bright streak of stars just right of center is M24 [ http://www.seds.org/messier/m/m024.html ]. On the far right of the image is the picturesque red emission nebula [ http://www.noao.edu/image_gallery/emission_nebulae.html ] IC 1283 flanked by two blue reflection nebula [ http://antwrp.gsfc.nasa.gov/apod/reflection_nebulae.html ]s NGC 6589 [ http://www.aao.gov.au/images/captions/aat020.html ] and NGC 6590 [ http://antwrp.gsfc.nasa.gov/apod/ap970810.html ]. These objects are visible with a small telescope [ http://antwrp.gsfc.nasa.gov/apod/ap011014.html ] toward the constellation [ http://www.adlerplanetarium.org/history/exhibits/constellations/timeline.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
|
The Lagoon Nebula in Three C
…
| Title |
The Lagoon Nebula in Three Colors |
| Explanation |
The bright Lagoon Nebula [ http://www.seds.org/messier/m/m008.html ] is home to a diverse array of astronomical objects. Particularly interesting sources include a bright open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars and several energetic star-forming regions [ http://antwrp.gsfc.nasa.gov/apod/ap020829.html ]. When viewed by eye, cluster light [ http://antwrp.gsfc.nasa.gov/apod/ap980707.html ] is dominated by an overall red glow that is caused by luminous hydrogen gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], while the dark filaments are caused by absorption by dense lanes [ http://antwrp.gsfc.nasa.gov/apod/ap980116.html ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]. The above picture [ http://antwrp.gsfc.nasa.gov/apod/ap021006.html http://lilen.fcaglp.unlp.edu.ar/ ], from the Curtis-Schmidt Telescope [ http://www.noao.edu/image_gallery/html/im0131.html ], however, shows the nebula's emission in three exact colors specifically emitted by hydrogen [ http://www.eren.doe.gov/hydrogen/ ], oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ], and sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ]. The Lagoon Nebula [ http://www.seds.org/billa/twn/n6523x.html ], also known as M [ http://www.seds.org/messier/xtra/history/CMessier.html ]8 and NGC [ http://www.ngcic.org/mission.htm ] 6523, lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away. The Lagoon Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010103.html ] can be located with binoculars in the constellation of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ] spanning a region over three times the diameter of a full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ]. |
|
M17: Omega Nebula Star Facto
…
| Title |
M17: Omega Nebula Star Factory |
| Explanation |
In the depths of the dark clouds [ http://antwrp.gsfc.nasa.gov/apod/ap010923.html ] of dust [ http://antwrp.gsfc.nasa.gov/apod/ap010813.html ] and molecular gas [ http://antwrp.gsfc.nasa.gov/apod/ap970430.html ] known as M17 [ http://www.seds.org/messier/m/m017.html ], stars continue to form. The similarity to the Greek letter [ http://www.nadin00.freeserve.co.uk/maths/greek.htm ] capital Omega gives the molecular cloud [ http://oposite.stsci.edu/pubinfo/pr/97/34/af2.html ] its popular name, but the nebula is also known as the Swan Nebula, the Horseshoe Nebula, and M17. The darkness of these molecular clouds [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/GMC.html ] results from background starlight being absorbed by thick carbon-based smoke-sized dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ]. As bright massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap011125.html ] form, they produce intense and energetic light [ http://imagers.gsfc.nasa.gov/ems/uv.html ] that slowly boils away the dark shroud. M17, pictured above [ http://www.cfht.hawaii.edu/HawaiianStarlight/AIOM/English/CFHT-Coelum-AIOM-Dec2002.html ], is visible with binoculars towards the constellation [ http://www.dibonsmith.com/constel.htm ] of Sagittarius [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html ], lies 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away, and spans 20 light-years across. |
|
|
