NASA APOD #1036-1043
#1036 Name This Satellite April 20, 1998
“Can you name this satellite? In December, NASA's third Great Observatory is planned for launch. The two NASA Great Observatories currently in orbit are the Hubble Space Telescope and the Compton Gamma-Ray Observatory, both now named for famous scientists. But after whom should the Advanced X-ray Astrophysics Facility (AXAF) be named? If your submitted suggestion conforms with contest rules and is chosen, you will have named the most powerful X-ray satellite ever built, and may even win a prize. AXAF is the size of a bus, has strange mirrors polished to atomic smoothness, and will produce X-ray images five times clearer of objects twice as faint as any previous X-ray satellite. This should allow AXAF the ability to see X-rays emitted near small black holes, from distant active galaxies, and inside huge clusters of galaxies. Astronomers now hope for an uneventful launch, routine operations, and spectacular discoveries."
Copyright: Public domain
#1037 Water in Orion April 21, 1998
“Is Orion all wet? Recent observations have confirmed that water molecules now exist in the famous Orion Nebula, and are still forming. The Orion Nebula (M42, shown above) is known to be composed mostly of hydrogen gas, with all other atoms and molecules being comparatively rare. The nebula is so vast, though, that even the measured minuscule production rate creates enough water to fill Earth's oceans 60 times over every day, speculate discoverers led by M. Harwit (Cornell). The water that composes comets, the oceans of Earth, and even humans may have been created in a cloud like the Orion Nebula."
Copyright: Anglo-Australian Telescope
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#1038 HR 4796A: A Recipe for Planets April 22, 1998
“Two hundred and twenty light years from Earth, planets are forming. Recent observations of the binary star system HR 4796 have shown that one of the stars is surrounded by a dusty gaseous disk. This disk is of the right size, age, and density for dust pellets to accrete surrounding matter. A hole in the disk's center indicates that increasingly larger condensates are colliding and sticking together, coalescing into moons and planets. Pictured above is a false-color image of the system, with the bright star HR 4796A indicated by a cross. The disk measures about five times the size of our Solar System, and is seen nearly edge-on. HR 4796 is in the southern constellation Centaurus."
Copyright: Public domain
#1039 Three Dusty Stars April 23, 1998
“These separate radio images reveal three dusty debris disks surrounding three bright, young, nearby stars - evidence for solar systems in formation. From left to right are the stars Fomalhaut, Beta Pictoris, and Vega, their positions indicated by star symbols. The false color maps show the intensity of submillimeter radio emission from the surrounding dust. Next to each dust "disk", a vertical bar illustrates the present size of our own solar system. These observations are likely examples of what our solar system would have looked like to distant radio astronomers when it was only a few hundred million years old! Astronomers speculate that bright blobs of emission near Vega and Beta Pictoris may represent dust clouds around developing giant planets. The radio images were made using detectors cooled to near absolute zero and the James Clerk Maxwell Telescope at Mauna Kea Observatory in Hawaii."
Copyright: Public domain
#1040 Infrared Saturn April 24, 1998
“This delightfully detailed false color image of Saturn has been earmarked to celebrate the 8th anniversary of the orbiting Hubble Space Telescope. The picture is a combination of three images taken in January of this year with the Hubble's new NICMOS instrument and shows the lovely ringed planet in reflected infrared light. Different colors indicated varying heights and compositions of cloud layers generally thought to consist of ammonia ice crystals. The eye-catching rings cast a shadow on Saturn's upper hemisphere, while the bright stripe seen within the left portion of the shadow is infrared sunlight streaming through the large gap in the rings known as the Cassini Division. Two of Saturn's many moons have also put in an appearance, Tethys just beyond the planet's disk at the upper right, and Dione at the lower left."
Copyright: Public domain
#1041 Supernova Remnant and Neutron Star April 25, 1998
“A massive star ends life as a supernova, blasting its outer layers back to interstellar space. The spectacular death explosion is initiated by the collapse of what has become an impossibly dense stellar core. However, this core is not necessarily destroyed. Instead, it may be transformed into an exotic object with the density of an atomic nucleus but more total mass than the sun - a neutron star. A neutron star is hard to detect directly because it is small (roughly 10 miles in diameter) and therefore dim, but newly formed in this violent crucible it is intensely hot, glowing in X-rays. These X-ray images from the orbiting ROSAT observatory may offer a premier view of such a recently formed neutron stars' X-ray glow. Pictured is the supernova remnant Puppis A, one of the brightest sources in the X-ray sky, with shocked gas clouds still expanding and radiating X-rays. In the inset close-up view, a faint pinpoint source of X-rays is visible which is most likely the young neutron star, kicked out by the asymmetric explosion and moving away from the site of the original supernova at about 600 miles per second."
Copyright: Public domain
#1042 NGC 2440: Cocoon of a New White Dwarf April 26, 1998
“Like a butterfly, a white dwarf star begins its life by casting off a cocoon that enclosed its former self. In this analogy, however, the Sun would be a caterpillar and the ejected shell of gas would become the prettiest of all! The above cocoon, the planetary nebula designated NGC 2440, contains one of the hottest white dwarf stars known. The white dwarf can be seen as the bright dot near the photo's center. Our Sun will eventually become a "white dwarf butterfly", but not for another 5 billion years. The above false color image and was post-processed by F. Hamilton."
Copyright: Public domain
#1043 IC 4406: A Seemingly Square Nebula April 27, 1998
“How can a round star make a square nebula? This conundrum came to light with the discovery of planetary nebulae like IC 4406. IC 4406 is most probably cylindrical, with its square appearance the result of our vantage point in viewing the cylinder. Hot gas is known to be flowing out the ends of the cylinder, while filaments of dark dust and molecular gas lace the bounding walls. The star primarily responsible for this interstellar sculpture can be found in the nebula's center. In a few million years, the only thing left visible in IC 4406 will be a fading white dwarf star."
Copyright: Public domain
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