Aitoff projection of the three-color composite JHKs source count map of the entire sky, based on 95,851,173 stars with Ks 13.5. What appears most prominently are the Galactic plane and the Galactic bulge. The plane is cut by dark dust lanes and clouds, even in the near-infrared, and several dusty regions, including Orion, are conspicuous. One can also see the two Magellanic Clouds, Large and Small. (Note the prominent bar and incipient spiral structure of the Large Cloud.) Near the Small Magellanic Cloud is the globular cluster 47 Tucanae. Cutting almost north-south through one side of the bulge is the dwarf Sagittarius galaxy, which, along with the Clouds, is a satellite of the Milky Way. 2MASS has completed the observational part of the survey and is now preparing to reprocess all of the data for a Final public Release, in late 2002. The source generation was performed by M.F. Skrutskie (UMass, Principal Investigator, 2MASS), the flux maps were compiled by J.M. Carpenter (Caltech), and the color composite was assembled by R. Hurt (IPAC/Caltech). It is this composite flux map that comprises the new 2MASS logo, seen above.
Date
12.01.1999
Solar System Portrait - 60 F
…
PIA00451
Imaging Science Subsystem -
…
Title
Solar System Portrait - 60 Frame Mosaic
Original Caption Released with Image
The cameras of Voyager 1 on Feb. 14, 1990, pointed back toward the sun and took a series of pictures of the sun and the planets, making the first ever "portrait" of our solar system as seen from the outside. In the course of taking this mosaic consisting of a total of 60 frames, Voyager 1 made several images of the inner solar system from a distance of approximately 4 billion miles and about 32 degrees above the ecliptic plane. Thirty-nine wide angle frames link together six of the planets of our solar system in this mosaic. Outermost Neptune is 30 times further from the sun than Earth. Our sun is seen as the bright object in the center of the circle of frames. The wide-angle image of the sun was taken with the camera's darkest filter (a methane absorption band) and the shortest possible exposure (5 thousandths of a second) to avoid saturating the camera's vidicon tube with scattered sunlight. The sun is not large as seen from Voyager, only about one-fortieth of the diameter as seen from Earth, but is still almost 8 million times brighter than the brightest star in Earth's sky, Sirius. The result of this great brightness is an image with multiple reflections from the optics in the camera. Wide-angle images surrounding the sun also show many artifacts attributable to scattered light in the optics. These were taken through the clear filter with one second exposures. The insets show the planets magnified many times. Narrow-angle images of Earth, Venus, Jupiter, Saturn, Uranus and Neptune were acquired as the spacecraft built the wide-angle mosaic. Jupiter is larger than a narrow-angle pixel and is clearly resolved, as is Saturn with its rings. Uranus and Neptune appear larger than they really are because of image smear due to spacecraft motion during the long (15 second) exposures. From Voyager's great distance Earth and Venus are mere points of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size. Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the sun.
Terrestrial Planet Interiors
title
Terrestrial Planet Interiors
description
*Mercury* Mercury has an average density of 5430 kilograms per cubic meter, which is second only to Earth among all the planets. It is estimated that the planet Mercury, like Earth, has a ferrous core with a size equivalent to two-thirds to three-fourths that of the planet's overall radius. The core is believed to be composed of an iron-nickel alloy covered by a mantle and surface crust. *Venus* It is believed that the composition of the planet Venus is similar to that of Earth. The planet crust extends to around 10-30 kilometers below the surface, under which the mantle reaches to a depth of some 3000 kilometers. The planet core comprises a liquid iron-nickel alloy. Average planet density is 5240 kilograms per cubic meter. *Earth* The Earth comprises three separate layers: a crust, a mantle, and a core (in descending order from the surface). The crust thickness averages 30 kilometers for land masses and 5 kilometers for seabeds. The mantle extends from just below the crust to some 2900 kilometers deep. The core below the mantle begins at a depth of around 5100 kilometers, and comprises an outer core (liquid iron-nickel alloy) and inner core (solid iron-nickel alloy). The crust is composed mainly of granite in the case of land masses and basalt in the case of seabeds. The mantle is composed primarily of peridotite and high-pressure minerals. Average planet density is 5520 kilograms per cubic meter. *Mars* Mars is roughly one-half the diameter of Earth. Due to its small size, it is believed that the martian center has cooled. Geological structure is mainly rock and metal. The mantle below the crust comprises iron-oxide-rich silicate. The core is made up of an iron-nickel alloy and iron sulfide. Average planet density is 3930 kilograms per cubic meter. *Pluto* The structure of Pluto is not very well understood at present. Nevertheless, spectroscopic observation from Earth in the 1970s has revealed that the planet surface is covered with methane ice. Surface temperature is -230?C (-382?F), and the frozen methane exhibits a bright coloration. However, with the exception of the polar caps, the frozen methane surface is seen to change to a dark red when eclipsed by its moon Charon. Average planet density is 2060 kilograms per cubic meter. The low average density requires that the planet must be a mix of ice and rock. *Image Credit*: Lunar and Planetary Institute
Solar System Montage
Title
Solar System Montage
Full Description
This is a montage of planetary images taken by spacecraft managed by the Jet Propulsion Laboratory in Pasadena, CA. Included are (from top to bottom) images of Mercury, Venus, Earth (and Moon), Mars, Jupiter, Saturn, Uranus and Neptune. The spacecraft responsible for these images are as follows: the Mercury image was taken by Mariner 10, the Venus image by Magellan, the Earth image by Galileo, the Mars image by Viking, and the Jupiter, Saturn, Uranus and Neptune images by Voyager. Pluto is not shown as no spacecraft has yet visited it. The inner planets (Mercury, Venus, Earth, Moon, and Mars) are roughly to scale to each other, the outer planets (Jupiter, Saturn, Uranus, and Neptune) are roughly to scale to each other. Actual diameters are given below: Sun 1,390,000 km Mercury 4,879 km Venus 12,104 km Earth 12,756 km Moon 3,475 km Mars 6,794 km Jupiter 142.984 km Saturn 120,536 km Uranus 51,118 km Neptune 49,528 km Pluto 2,390 km
Date
04/09/1999
NASA Center
Jet Propulsion Laboratory
Terrestrial Planet Sizes
title
Terrestrial Planet Sizes
description
The terrestrial planets are the four innermost planets in the solar system, Mercury, Venus, Earth, and Mars. They are called terrestrial because they have a compact, rocky surface like the Earth's. The planets Venus, Earth, and Mars have significant atmospheres, while Mercury has almost none. This diagram shows the approximate relative sizes of the terrestrial planets. Distances are not to scale. *Image Credit*: Lunar and Planetary Institute
All Planet Sizes
title
All Planet Sizes
description
This illustration shows the approximate sizes of the planets relative to each other. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Jupiter's diameter is about 11 times that of the Earth's and the Sun's diameter is about 10 times Jupiter's. Pluto's diameter is slightly less than one-fifth of Earth's. The planets are not shown at the appropriate distance from the Sun. *Image Credit*: Lunar and Planetary Laboratory
Far Side of the Moon
title
Far Side of the Moon
description
This image of the moon was obtained by the Galileo Solid State imaging system on Dec. 8 at 7 p.m. PST as the Galileo spacecraft passed the Earth and was able to view the lunar surface from a vantage point not possible from the Earth. On the right-hand side of the image is seen the dark maria of Oceanus Procellarum, also visible from the Earth. The dark spots in the center are Mare Orientale, on the western limb of the nearside of the moon, a region barely visible from the Earth. This region and the bright far side highlands on the left have not been seen previously by a camera system such as the one on the Galileo spacecraft, which provides multispectral images of the lunar limb and far side which have not previously been obtained. Comparison of such images to those of the near-side areas from which Apollo astronauts have returned samples will help us understand the spectral properties and composition of the lunar far side. *Image Credit*: JPL
Stellar Quakes
title
Stellar Quakes
date
12.27.2004
description
On December 27, 2004, a neutron star flared up so brightly, it temporarily blinded all the X-ray satellites in space for an instant, and lit up the Earth's upper atmosphere. This tremendous blast of energy was from a giant flare created by the neutron star's twisting magnetic field. Objects like this are called magnetars, and they produce magnetic fields trillions of time more powerful than those here on Earth. These fields are so strong they can actually buckle the surface of the neutron star causing these powerful star quakes.
Massive Terrestrial Strike
title
Massive Terrestrial Strike
description
Artist's concept of a catastrophic asteroid impact with the early Earth. An impact with a 500-km-diameter asteroid would effectively sterilize the planet. The Earth may have experienced such gigantic impacts in its youth, but fortunately today there are no projectiles this large to threaten our planet. *Image Credit*: Don Davis, NASA
Coastline Remodeling
title
Coastline Remodeling
description
An illustration of a massive asteroid crashing into Earth. The Earth may have experienced such gigantic impacts in its youth, but fortunately today there are no projectiles this large to threaten our planet. *Image Credit*: Don Davis, NASA
Eclipsed Earth
title
Eclipsed Earth
date
03.29.2006
description
The shadow of the moon falls on Earth as seen from the International Space Station, 230 miles above the planet, during a total solar eclipse at about 4:50 a.m. EST March 29. This digital photo was taken by the Expedition 12 crew, who are wrapping up a six-month mission on the ISS. Visible near the shadow are portions of Cyprus in the Mediterranean Sea and the coast of Turkey. *Credit:* NASA
Andromeda in Ultraviolet
In a break from its usual ta
…
10/14/09
Description
In a break from its usual task of searching for distant cosmic explosions, NASA's Swift satellite acquired the highest-resolution view of a neighboring spiral galaxy ever attained in the ultraviolet. The galaxy, known as M31 in the constellation Andromeda, is the largest and closest spiral galaxy to our own. This mosaic of M31 merges 330 individual images taken by Swift's Ultraviolet/Optical Telescope. The image shows a region 200,000 light-years wide and 100,000 light-years high (100 arcminutes by 50 arcminutes). Image Credit: NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)
Date
10/14/09
Three Faces of Andromeda
Title
Three Faces of Andromeda
Description
NASA's Spitzer Space Telescope has captured stunning infrared views of the famous Andromeda galaxy to reveal insights that were only hinted at in visible light. Spitzer's 24-micron mosaic (top panel) is the sharpest image ever taken of the dust in another spiral galaxy. This is possible because Andromeda is a close neighbor to the Milky Way at a mere 2.5 million light-years away. The Spitzer multiband imaging photometer's 24-micron detector recorded 11,000 separate snapshots to create this new comprehensive picture. Asymmetrical features are seen in the prominent ring of star formation. The ring appears to be split into two pieces, forming the hole to the lower right. These features may have been caused by interactions with satellite galaxies around Andromeda as they plunge through its disk. Spitzer also reveals delicate tracings of spiral arms within this ring that reach into the very center of the galaxy. One sees a scattering of stars within Andromeda, but only select stars that are wrapped in envelopes of dust light up at infrared wavelengths. This is a dramatic contrast to the traditional view at visible wavelengths (lower left panel), which shows the starlight instead of the dust. The center of the galaxy in this view is dominated by a large bulge that overwhelms the inner spirals seen in dust. The dust lanes are faintly visible in places, but only where they can be seen in silhouette against background stars. The multi-wavelength view of Andromeda (lower right panel) combines images taken at 24 microns (blue), 70 microns (green), and 160 microns (red). Using all three bands from the multiband imaging photometer allows astronomers to measure the temperature of the dust by its color. The warmest dust is brightest at 24 microns while the coolest is most evident at 160 microns. The blue/white areas have the hottest dust, as seen in the bulge and in the star-forming areas along the arms. The cooler dust floating further out in the ring and arms are in the redder regions. The data were taken on August 25, 2004, the one-year anniversary of the launch of the space telescope. The observations have been transformed into this remarkable gift from Spitzer -- the most detailed infrared image of the spectacular galaxy to date.
Amazing Andromeda Galaxy
Title
Amazing Andromeda Galaxy
Description
The many "personalities" of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope. The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's "fiery" nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively "cool" side, which includes embryonic stars hidden in their dusty cocoons. Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars. Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them. Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist. Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across. This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).
Kitt Peak Optical Image of M
…
Name
Kitt Peak Optical Image of M33
Deepest View of Space Yields
…
Title
Deepest View of Space Yields Young Stars in Andromeda Halo
Deepest View of Space Yields
…
Title
Deepest View of Space Yields Young Stars in Andromeda Halo
Orion Nebula: Peering into t
…
Name
Orion Nebula: Peering into the Orion Nebula
Category
Normal Stars & Star Clusters
Release Date
October 03, 2007
Image is 7 arcmin on a side.
…
Name
Image is 7 arcmin on a side., Orion Nebula Infrared
Hubble Optical Image of Orio
…
Name
Hubble Optical Image of Orion Nebula, Close-up
Hubble Optical Image of Orio
…
Name
Hubble Optical Image of Orion Nebula
Sirius: The Brightest Star i
…
Title
Sirius: The Brightest Star in the Night
Explanation
Sirius is the brightest star [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ] in the night sky. Sirius [ http://www.louisville.edu/~aoclar01/ancient/astronomy/Sirius.htm ] is visible on the far left of the above photograph, to the left of the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Orion [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Orion.html ] and Comet Hale-Bopp [ http://antwrp.gsfc.nasa.gov/apod/ap970429.html ]. Intrinsically, Sirius [ http://www.physics.purdue.edu/astr263l/forum/Sirius.html ] is over 20 times brighter than our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] and over twice as massive. As Sirius [ http://www.wshs.fcps.k12.va.us/academic/science/bjewell/ocean/zittel/final/stars.htm ] is 8.7 light years distant, it is not the closest star system - the Alpha Centauri [ http://antwrp.gsfc.nasa.gov/apod/ap960526.html ] system holds this distinction. Sirius [ http://www.star.le.ac.uk/edu/ask/stars_faq.html#9 ] is called the Dog Star because of its prominence in the constellation of Canis Majoris [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Canis_Major.html ] (Big Dog). In 1862, Sirius [ http://www.astro.wisc.edu/~dolan/constellations/hr/2491.html ] was discovered to be a binary star system with a companion star, Sirius B [ http://www.dcn.davis.ca.us/~btcarrol/skeptic/dogon.html ], 10,000 times dimmer than the bright primary, Sirius A. Sirius B was the first white dwarf star discovered, a type of star first understood by Subrahmanyan Chandrasekhar [ http://antwrp.gsfc.nasa.gov/apod/ap950901.html ] in 1930. While studying Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap960902.html ] in 1718, Edmond Halley [ http://antwrp.gsfc.nasa.gov/apod/ap960706.html ] discovered that stars move with respect to each other. There is conflicting evidence that Sirius appeared more red [ http://www.louisville.edu/~aoclar01/ancient/astronomy/Sirius.htm ] only 2000 years ago.
Other Worlds and HD 38529
Title
Other Worlds and HD 38529
Explanation
After the latest round of discovery announcements [ http://www.iau.org/ga24press/ ], the list of known worlds of distant suns [ http://www.spaceart.org/lcook/extrasol.html ] has grown to 50 [ http://www.spaceref.com/news/viewnews.html?id=200 ]. While extrasolar planet [ http://exoplanets.org/ ] discoveries are [ http://obswww.unige.ch/~udry/planet/planet.html ] sure to continue, none - so far [ http://sim.jpl.nasa.gov/ ] - points clearly to another planetary system like our own [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ]. Take, for example, the newly discovered parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] star HD38529 [ http://www.obspm.fr/encycl/HD38529.html ]. Shining in Earth's night sky at 6th magnitude, this sun-like star lies 137 light-years away in the constellation Orion [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/orion/ main.html ]. Like most of the known extrasolar planets [ http://www.obspm.fr/encycl/encycl.html ], HD38529's planet was discovered by detecting the telltale Doppler wobble [ http://exoplanets.org/doppler.html ] in the parent star's spectrum. The data reveal that this planet orbits once every 14.3 days at an average of only 0.13 times the Earth-Sun distance and has a minimum of 0.77 Jupiter masses (about 240 Earth masses). There is even evidence [ http://www.iau.org/ga24press/pr000807_3.html#1 ] in the wobble data that HD38529, and other stars with one known planet have additional massive planets orbiting them. In this dramatic artist's vision, HD38529 and its newfound world are viewed from the moon of another massive ringed planet [ http://antwrp.gsfc.nasa.gov/apod/ap000330.html ] orbiting farther out. The ringed planet's moon is imagined to have a thin atmosphere and a surface covered with icy sheets and ridges similar to those found on Jupiter's moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ].
Hale-Bopp from Indian Cove
Title
Hale-Bopp from Indian Cove
Explanation
Good cameras [ http://www.chimacum.wednet.edu/highschool/jeff/Photo/camera/camera3.html ] were able to obtain impressive photographs of Comet Hale-Bopp [ http://galileo.ivv.nasa.gov/comet/ ] when at its brightest earlier this year. In the above photograph [ http://galileo.ivv.nasa.gov/comet/pach9.html ] taken April 5th, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Forest [ http://www.nps.gov/jotr/ ] in California, USA. A flashlight was used to momentarily illuminate foreground rocks in this 30 second exposure. Comet Hale-Bopp is still visible [ http://www.eso.org/outreach/info-events/hale-bopp/comet-hale-bopp-summary-aug01-97-rw.html ] to the unaided eye in Earth's Southern Hemisphere [ http://antwrp.gsfc.nasa.gov/apod/ap951222.html ], with observers there reporting it to be about 4th magnitude [ http://liftoff.msfc.nasa.gov/academy/universe/MAG.HTML ]. The comet is now passing nearly in front of the star Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap960902.html ], and shows only a slight dust tail [ http://antwrp.gsfc.nasa.gov/apod/ap970403.html ].
The Winter Hexagon
Title
The Winter Hexagon
Explanation
Some of the brightest stars [ http://www.seds.org/Maps/Stars_en/ ] form a large and easily found pattern [ http://astronomy.swin.edu.au/~pbourke/geometry/hexagon/ ] in the winter sky [ http://www.astro.uu.nl/~bassa/gallery/wintersky.htm ] of Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ]'s northern hemisphere [ http://www.sel.noaa.gov/pmap/pmapN.html ]. Dubbed the Winter Hexagon [ http://www.earthvisions.net/bcp/aster/constellations/win6.htm ], the stars involved can usually be identified even in the bright night skies [ http://antwrp.gsfc.nasa.gov/apod/ap010827.html ] of a big city. The six stars that compose the Winter Hexagon are Aldebaren [ http://www.astro.uiuc.edu/~kaler/sow/aldebaran.html ], Capella [ http://www.astro.wisc.edu/~dolan/constellations/hr/1708.html ], Castor [ http://einstein.stcloudstate.edu/Dome/constellns/castor.html ], Procyon [ http://www.solstation.com/stars/procyon2.htm ], Rigel [ http://www.sciencenet.org.uk/astron/const/orion/Rigel.html ], and Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap000611.html ]. Rolling your cursor over the above image [ http://www.astropix.com/HTML/SHOWCASE/HEXAGON.HTM ] will identify them. The Winter Hexagon [ http://newton.dep.anl.gov/newton/askasci/1993/astron/AST015.HTM ] asterism [ http://www.seds.org/Maps/Const/asterism.html ] engulfs several constellations [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] including Orion [ http://www.seds.org/Maps/Stars_en/Fig/orion.html ] and Canis Major [ http://www.astronomical.org/constellations/cma.html ].
Canaries Sky
Title
Canaries Sky
Explanation
This gorgeous view of [ http://www.mclink.it/personal/MC7872/deepvoid/deepskyen.htm ] stars, nebulae, and the Milky Way comes from the dark night sky [ http://www.mclink.it/personal/MC7872/deepvoid/index.html ] above the lovely island of La Palma in the Canaries archipelago [ http://www.ing.iac.es/lapalma/history.html ]. The picture was made by a group of experienced astrophotographers who traveled there to take advantage of the ideal observing conditions [ http://www.ing.iac.es/ ] near La Palma's Observatorio del Roque de los Muchachos [ http://www.ing.iac.es/orm/orm.html ]. Skygazers can easily pick out several of their favorite astronomical objects [ http://antwrp.gsfc.nasa.gov/apod/ap980214.html ] in this wide angle time exposure which covers about 40 degrees on winter the sky. Faint stars along the plane of our Galaxy compose the delicate, luminous band of the Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap980226.html ] stretching across the image from the bottom left. The familiar constellation [ http://www.adler.uchicago.edu/ISE/menu.html ] of Orion [ http://antwrp.gsfc.nasa.gov/apod/ap970817.html ] the hunter is also easy to find, with glowing nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap980127.html ] highlighting [ http://antwrp.gsfc.nasa.gov/apod/ap980201.html ] the hunter's belt and sword. Orion's [ http://antwrp.gsfc.nasa.gov/apod/ap961202.html ] famous red giant star Betelgeuse [ http://antwrp.gsfc.nasa.gov/apod/ap970216.html ], near picture center, has a yellowish cast and Rigel is [ http://antwrp.gsfc.nasa.gov/apod/ap980209.html ] the bright star in Orion at lower right. Brilliant white Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap960902.html ], near the bottom, is the brightest star in the picture (and in Earth's night sky). Sirius, is part of the constellation Canis Major [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Canis_Major.html ] (Big Dog). Across the Milky Way, above and to the left of Sirius, is slightly less brilliant Procyon, brightest star of Canis Minor [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Canis_Minor.html ]. A V-shaped group [ http://www.adler.uchicago.edu/ISE/HYAPLEIA.HTM ] of yellowish stars at the upper right, part of Taurus the bull [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Taurus.html ], is dominated by the red giant Aldebaran [ http://www.bo.astro.it/copernic/alde-eng.html ].
Upsilon Andromedae: An Extra
…
Title
Upsilon Andromedae: An Extra-Solar System
Explanation
Yesterday, astronomers announced [ http://cfa-www.harvard.edu/afoe/upsAnd_pr.html ] the discovery of the first system of planets around a normal star other than our Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. Previously, only single planet star systems [ http://www.physics.sfsu.edu/~gmarcy/planetsearch/ ] had been found. Subtle changes in the wobble of Upsilon Andromedae [ http://www.physics.sfsu.edu/~gmarcy/planetsearch/upsand/upsand.html ], a Sun-like star in the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html ] of Andromeda [ http://www.astro.wisc.edu/~dolan/constellations/constellations/Andromeda.html ], allowed astronomers led by R. Paul Butler [ http://astro.berkeley.edu/~paul/vita.html ] (AAO [ http://www.aao.gov.au/aaohomepage.html ]) and Geoffrey W. Marcy [ http://cannon.sfsu.edu/~gmarcy/ ] (SFSU [ http://cannon.sfsu.edu/ ] /UCB [ http://astron.berkeley.edu/home.html ]) to make the breakthrough. This star system is quite different from our own Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap980517.html ], however. All three detected planets have masses near or above Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. The discovery [ http://science.nasa.gov/newhome/headlines/ast15apr99_1.htm ] implies that multiple-planet systems [ http://antwrp.gsfc.nasa.gov/apod/ap961019.html ] are quite common, increasing speculation that life-bearing [ http://cmex-www.arc.nasa.gov/VikingCD/Puzzle/EvoLife.htm ] planets similar to Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ] may one day be found. The drawing above is an artist's depiction of the Upsilon Andromedae [ http://antwrp.gsfc.nasa.gov/apod/ap990416.html http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJ...474L.119B ] system and its innermost planet. This planet orbits unexpectedly close to its parent star.
In the Shade of a Historic P
…
Title
In the Shade of a Historic Planet
Explanation
For the first time, astronomers have recovered [ http://astron.berkeley.edu/~gmarcy/transit.html ] independent evidence that distant planetary systems [ http://cannon.sfsu.edu/~gmarcy/planetsearch/planetsearch.html ] exist. Last Friday, a team led by G. W. Henry [ http://schwab.tsuniv.edu/henrypage.html ] (Tenn. State [ http://coe.tsuniv.edu/ ]) and G. Marcy [ http://astron.berkeley.edu/~gmarcy/ ] (UC Berkeley [ http://astron.berkeley.edu/ ]) announced the discovery [ http://www.urel.berkeley.edu/urel_1/CampusNews/PressReleases/releases/11-12-1999a.html ] of a shadow of a planet crossing a distant star. Little known HD 209458 [ http://skyview.gsfc.nasa.gov/cgi-bin/nnskcall.pl?Interface=eform&VCOORD=HD+209458&SURVEY=Digitized+Sky+Survey&SCOORD=Equatorial&EQUINX=2000&MAPROJ=Gnomonic&SFACTR=Default&ISCALN=Log%2810%29&GRIDDD=No&RETURN=simple ], a Sun-like star 150 light-years away, had been suspected of harboring planets from a slight wobble [ http://antwrp.gsfc.nasa.gov/apod/ap961019.html ] found in its motion. Henry et al. now find that this wobble [ http://astron.berkeley.edu/~gmarcy/hd/doppler.html ] exactly corresponds to a planet crossing the face of the star, creating the slight dimming effect of a partial eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap970903.html ]. The astronomers were then able to make a groundbreaking estimate [ http://astron.berkeley.edu/~gmarcy/hd/iau.html ] of the mass and radius of the extra-solar planet [ http://obswww.unige.ch/~udry/planet/planet.html ], which they find to have about two-thirds the mass of Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] but about 60 percent larger radius. The drawing above [ http://www.spaceart.org/lcook/extrasol.html ] is an artist's depiction of a planetary eclipse in the HD 209458 system.
A Sirius Leonid Meteor
Title
A Sirius Leonid Meteor
Explanation
In the sky [ http://leonid.arc.nasa.gov/ ] or on the web, did you watch [ http://leonids.hq.nasa.gov/leonids/ ] this year's Leonid meteor shower? If you did, meteors flashing [ http://science.nasa.gov/newhome/headlines/ast17nov99_1.htm ] through the night sky should be a familiar sight. Recorded last year during the 1998 apparition [ http://science.nasa.gov/newhome/headlines/ast27nov98_1.htm ] of the Leonids, this time-exposure of the sky around the constellation Canis Major [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Canis_Major.html ] (big dog) shows the trail of a spectacular fireball meteor. The meteor, by chance, seems to leap from the constellation's brightest star Sirius [ http://antwrp.gsfc.nasa.gov/apod/ap960902.html ], near the top right. In the foreground is the beautiful desert scenery of Joshua Tree [ http://www.nps.gov/jotr/home.html ] National Park. At this year's peak of the cosmic dust storm, observers in Europe and Africa reported intense rates [ http://science.nasa.gov/newhome/headlines/ast18nov99_1.htm ] of over "1600 meteors per hour" for a brief period near 0215 November 18 (UTC [ http://tycho.usno.navy.mil/zones.html ]). Awe inspiring as they were, the Leonids posed [ http://www.spacescience.com/newhome/headlines/ast10nov99_1.htm ] no danger to earthbound skywatchers.
Symphony in Blue
Like early explorers mapping
…
8/27/09
Description
Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA's Spitzer Space Telescope, scientists have discovered that the Milky Way's elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms. This artist's concept illustrates the new view of the Milky Way, along with other findings presented at the 212th American Astronomical Society meeting. The galaxy's two major arms (Scutum-Centaurus and Perseus) can be seen attached to the ends of a thick central bar, while the two now-demoted minor arms (Norma and Sagittarius) are less distinct and located between the major arms. The major arms consist of the highest densities of both young and old stars, the minor arms are primarily filled with gas and pockets of star-forming activity. Image credit: NASA/JPL-Caltech
Date
8/27/09
Into the Heart of Darkness
Astronomers have long known
…
01/06/10
Description
Astronomers have long known that the supermassive black hole at the center of the Milky Way Galaxy, known as Sagittarius A* (or Sgr A* for short), is a particularly poor eater. The fuel for this black hole comes from powerful winds blown off dozens of massive young stars that are concentrated nearby. These stars are located a relatively large distance away from Sgr A*, where the gravity of the black hole is weak, and so their high-velocity winds are difficult for the black hole to capture and swallow. Scientists have previously calculated that Sgr A* should consume only about 1 percent of the fuel carried in the winds. However, it now appears that Sgr A* consumes even less than expected -- ingesting only about one percent of that one percent. Why does it consume so little? The answer may be found in a new theoretical model developed using data from a very deep exposure made by NASA's Chandra X-ray Observatory. This model considers the flow of energy between two regions around the black hole: an inner region that is close to the so-called event horizon (the boundary beyond which even light cannot escape), and an outer region that includes the black hole's fuel source -- the young stars -- extending up to a million times farther out. Collisions between particles in the hot inner region transfer energy to particles in the cooler outer region via a process called conduction. This, in turn, provides additional outward pressure that makes nearly all of the gas in the outer region flow away from the black hole. The model appears to explain well the extended shape of hot gas detected around Sgr A* in X-rays as well as features seen in other wavelengths. This Chandra image of Sgr A* and the surrounding region is based on data from a series of observations lasting a total of about one million seconds, or almost two weeks. Such a deep observation has given scientists an unprecedented view of the supernova remnant near Sgr A* (known as Sgr A East) and the lobes of hot gas extending for a dozen light years on either side of the black hole. These lobes provide evidence for powerful eruptions occurring several times over the last ten thousand years. The image also contains several mysterious X-ray filaments, some of which may be huge magnetic structures interacting with streams of energetic electrons produced by rapidly spinning neutron stars. Such features are known as pulsar wind nebulas. This new model of Sgr A* was presented at the 215th meeting of the American Astronomical Society in January 2009 by Roman Shcherbakov and Robert Penna of Harvard University and Frederick K. Baganoff of the Massachusetts Institute of Technology. Image Credit: NASA/CXC/MIT/F. Baganoff, R. Shcherbakov et al.
Date
01/06/10
Sagittarius A* with Scale Ba
…
Name
Sagittarius A* with Scale Bar
Chandra Image of Sgr A* with
…
Name
Chandra Image of Sgr A* with Labels
Sagittarius A*: Milky Way Mo
…
Name
Sagittarius A*: Milky Way Monster Stars in Cosmic Reality Show
Category
Black Hole
Release Date
January 06, 2003
Hubble Finds Extrasolar Plan
…
Title
Hubble Finds Extrasolar Planets Far Across Galaxy
General Information
What is a NASA Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a NASA Science Update (NSU), broadcast on NASA television. The NSU includes a question and answer session with members of the media. NASA's Hubble Space Telescope has discovered 16 extrasolar planet candidates orbiting a variety of distant stars in the central region of our Milky Way galaxy. The planet bonanza was uncovered during a Hubble survey, called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble looked farther than has ever successfully been searched for extrasolar planets. Hubble peered at 180,000 stars in the crowded central bulge of our galaxy 26,000 light-years away or one-quarter the diameter of the Milky Way's spiral disk. The results will appear in the Oct. 5 issue of the journal Nature. Read more: * NASA Press Release [ http://hubblesite.org/newscenter/archive/releases/2006/34/text/ ]
Hubble Finds Extrasolar Plan
…
Title
Hubble Finds Extrasolar Planets Far Across Galaxy
General Information
What is a NASA Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a NASA Science Update (NSU), broadcast on NASA television. The NSU includes a question and answer session with members of the media. NASA's Hubble Space Telescope has discovered 16 extrasolar planet candidates orbiting a variety of distant stars in the central region of our Milky Way galaxy. The planet bonanza was uncovered during a Hubble survey, called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble looked farther than has ever successfully been searched for extrasolar planets. Hubble peered at 180,000 stars in the crowded central bulge of our galaxy 26,000 light-years away or one-quarter the diameter of the Milky Way's spiral disk. The results will appear in the Oct. 5 issue of the journal Nature. Read more: * NASA Press Release [ http://hubblesite.org/newscenter/archive/releases/2006/34/text/ ]
Hubble Finds Extrasolar Plan
…
Title
Hubble Finds Extrasolar Planets Far Across Galaxy
General Information
What is a NASA Science Update? Major Hubble discoveries on NASA television ... Astronomers explain their Hubble discoveries at a press conference, called a NASA Science Update (NSU), broadcast on NASA television. The NSU includes a question and answer session with members of the media. NASA's Hubble Space Telescope has discovered 16 extrasolar planet candidates orbiting a variety of distant stars in the central region of our Milky Way galaxy. The planet bonanza was uncovered during a Hubble survey, called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble looked farther than has ever successfully been searched for extrasolar planets. Hubble peered at 180,000 stars in the crowded central bulge of our galaxy 26,000 light-years away or one-quarter the diameter of the Milky Way's spiral disk. The results will appear in the Oct. 5 issue of the journal Nature. Read more: * NASA Press Release [ http://hubblesite.org/newscenter/archive/releases/2006/34/text/ ]
Hubble Identifies Stellar Co
…
Title
Hubble Identifies Stellar Companion to Distant Planet
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 ].
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 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 ].
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.
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.
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 ].
X-Rays from the Galactic Cor
…
Title
X-Rays from the Galactic Core
Explanation
Using the orbiting Chandra [ http://chandra.harvard.edu/chronicle/ ] X-ray Observatory, astronomers have taken this long look [ http://chandra.harvard.edu/press/03_releases/ press_010603.html ] at the core of our Milky Way galaxy, some 26,000 light-years away. The spectacular false-color view [ http://chandra.harvard.edu/photo/2003/0203long/ index.html ] spans about 130 light-years. It reveals an energetic region [ http://antwrp.gsfc.nasa.gov/apod/ap020803.html ] rich in x-ray sources and high-lighted by the central source, Sagittarius A*, known to be a supermassive black hole [ http://antwrp.gsfc.nasa.gov/apod/ap021018.html ] with 3 million times the mass of the Sun [ http://www.sunblock99.org.uk/sb99/fact/heavy.html ]. Given its tremendous mass, Sagittarius A* is amazingly faint in x-rays in comparison to central black holes observed in distant galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap021128.html ], even during its frequent x-ray flares. This suggests that this supermassive black hole has been starved [ http://science.nasa.gov/headlines/y2001/ast05sep_1.htm ] by a lack of infalling material. In fact, the sharp Chandra image shows clouds of multi-million degree gas dozens of light-years across flanking (upper right and lower left) the central region -- evidence that violent events have cleared much material from the vicinity [ http://chandra.harvard.edu/resources/ illustrations/blackholes.html ] of the black hole.
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.
M17: A Hubble Close-Up
Title
M17: A Hubble Close-Up
Explanation
Sculpted by stellar winds and radiation, these fantastic, undulating shapes lie within the stellar nursery [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/StarForm.html ] known as M17 [ http://www.seds.org/messier/m/m017.html ], the Omega Nebula, some 5,500 light-years away in the nebula-rich [ http://antwrp.gsfc.nasa.gov/apod/ap011229.html ] constellation Sagittarius. The lumpy features [ http://antwrp.gsfc.nasa.gov/apod/ap011230.html ] in the dense cold gas and dust are illuminated by stars off the upper left of the image and may themselves represent sites of future star formation. Colors in the fog of surrounding hotter material indicate M17's [ http://sirtf.caltech.edu/EPO/Messier/m17.html ] chemical make up. The predominately green glow corresponds to abundant hydrogen, with trace sulfur and oxygen atoms contributing red and blue hues. The picture spans about 3 light-years and was released to celebrate [ http://hubblesite.org/newscenter/archive/2003/13/ ] the thirteenth year of the Hubble Space Telescope's [ http://hubblesite.org/newscenter/archive/2003/13/ astrofile ] cosmic voyage of exploration.
Messiers and Mars
Title
Messiers and Mars
Explanation
A telescopic tour of the constellation Sagittarius [ http://www.hawastsoc.org/deepsky/sgr/index.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://home.earthlink.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/ ] was a short 4 light-minutes away. Now headed [ http://www.lpl.arizona.edu/~rhill/alpo/mars.html ] for its closest approach [ http://skyandtelescope.com/observing/objects/planets/ article_985_1.asp ] to planet Earth in recorded history, Mars rises in the east southeast by midnight shining brightly at about -1.4 magnitude [ http://csep10.phys.utk.edu/astr162/lect/stars/ magnitudes.html ]. Urban imager [ http://home.earthlink.net/~urbanimager/cartoon.htm ] Michael Cole recorded this photograph at 3:00 AM on May 20th, 2001 in clear skies over Camp Hancock, Oregon, USA.
A Beautiful Trifid
Title
A Beautiful Trifid
Explanation
The beautiful Trifid Nebula (aka M20) [ http://www.seds.org/messier/m/m020.html ], a photogenic study in cosmic contrasts, lies about 5,000 [ http://www.anzwers.org/free/universe/5000lys.html ] light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid alone illustrates three basic types of astronomical nebulae, red emission nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap020317.html ] dominated by light from hydrogen atoms, blue reflection nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap990301.html ] produced by dust reflecting starlight, and dark absorption nebulae [ http://antwrp.gsfc.nasa.gov/apod/ap030620.html ] where dense dust clouds appear in silhouette. The bright emission nebula on the right, separated into three parts by obscuring dust lanes, lends the nebula its popular name. Many details are apparent in this gorgeous high-resolution image [ http://www.noao.edu/outreach/aop/observers/m20.html ] of the Trifid. For example, light-year long pillars and jets sculpted by newborn stars - visible here in the upper right-hand corner of the emission nebula - appear in Hubble Space Telescope close-up images [ http://antwrp.gsfc.nasa.gov/apod/ap011230.html ] of the region.
Elements of the Swan Nebula
Title
Elements of the Swan Nebula
Explanation
In the depths of the dark clouds [ http://antwrp.gsfc.nasa.gov/apod/ap030202.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. Also known as the Omega Nebula and Horseshoe Nebula, the darkness of M17's molecular clouds [ http://archive.ncsa.uiuc.edu/Cyberia/Bima/GMC.html ] results from background starlight being absorbed by thick filaments of carbon-based smoke-sized dust [ http://antwrp.gsfc.nasa.gov/apod/ap030706.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. Colors in the above image [ http://www.rc-astro.com/nebulae/m17_2003-07-30.htm ] were picked to highlight specific element [ http://www.hyperdictionary.com/dictionary/element ]s that emit nebular light: red indicates emission from sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ], green from hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ], and blue from oxygen [ http://pearl1.lanl.gov/periodic/elements/8.html ]. The Swan Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030425.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.
