#241 Tomorrow's picture: February 15, 1996
“citement mounts as NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft nears launch - currently scheduled for 3:53 ET on February 16. NEAR's mission is to become the first spacecraft to rendezvous with and orbit an asteroid, the asteroid designated 433 Eros. After achieving Eros orbit in 1999, project plans are to explore the asteroid for 1 year from this premiere vantage point, perhaps approaching to within 15 miles of the surface. For comparison, above is an image of the limb of asteroid Ida made by the Galileo spacecraft from a distance of about 1,500 miles, the highest resolution image of an asteroid surface - so far. It is hoped that NEAR will go far towards answering questions about the nature and origin of near Earth asteroids. These objects are thought to contain clues to the formation of the inner planets and influence the evolution of the atmosphere and life on Earth. Are asteroids and meteorites related? Do asteroids ever strike the Earth?"
Copyright: Public domain
#242 Tomorrow's picture: February 16, 1996
“What did our universe look like when it was young? To answer this, cosmologists run sophisticated computer programs tracking the locations of millions of particles. The above animated frame is the result of such a calculation and shows how our universe might have looked when it was just a fracton of its current age. The universe started out very smooth - matter and light are spread almost uniformly. As time progressed, gravity caused slight gatherings of mass to accrete so that ever greater conglomerations formed. Galaxies and long filaments formed - which are shown by the bright patches and streaks in the above frame. An IMAX movie including hundreds of these frames is currently under production and should be released this summer."
Copyright: Public domain
#243 Tomorrow's picture: February 17, 1996
“No person in history has had greater impact in determining the extent of our universe than Edwin Hubble. From proving that other galaxies existed to proving that galaxies move apart from one another, Hubble's work defined our place in the cosmos. Hubble lived from 1889 to 1953 and is shown above posing with the 48-inch telescope on Palomar Mountain and his famous pipe. In memory of his great work, the Orbiting Space Telescope was named after him. Today a great controversy rages on the rate of the universe's expansion, parameterized by a quantity known as Hubble's constant. A real live debate on this subject will take place in Washington, DC this April."
Copyright: Public domain
#244 Tomorrow's picture: February 18, 1996
“Are these galaxies near the center of the largest gravitationally bound concentration of mass yet known? Previously, the cluster of galaxies known as Abell 3627 was largely unstudied because dust in the disk of our own Galaxy obscured much of its light. Several galaxies from Abell 3627 appear above as fuzzy blue patches behind many stars in our Galaxy. Recent observations by Renee Kraan-Korteweg (Paris Observatory) and collaborators, however, indicate that this cluster of galaxies is near the center of the huge nearby conglomeration of mass known as the Great Attractor. Evidence for this was uncovered in new accurate measurements of the large extent and nearby distance of Abell 3627."
Copyright: STScIAAO
#245 Tomorrow's picture: February 19, 1996
“Comet Swift-Tuttle, shown above in false color, is the largest object known to make repeated passes near the Earth. It is also one of the oldest known periodic comets with sightings spanning two millennia. Last seen in 1862, its reappearance in 1992 was not spectacular, but the comet did become bright enough to see from many locations with binoculars. To create this composite telescopic image, four separate exposures have been combined, compensating for the motion of the comet. As a result, the stars appear slightly trailed. The inset shows details of the central coma. The unseen nucleus itself is essentially a chunk of dirty ice about ten kilometers in diameter. Comets usually originate in the Oort cloud in the distant Solar System - well past Pluto, most never venturing into the inner Solar System. When perturbed - perhaps by the gravity of a nearby star - a comet may fall toward the Sun. As a comet approaches the Sun, rocks, ice-chunks, gas, and dust boil away, sometimes creating impressive looking tails. In fact, debris from Comet Swift-Tuttle is responsible for the Perseids meteor shower visible every July and August. Comet Swift-Tuttle is expected to make an impressive pass near the earth in the year 2126, possibly similar to Comet Hyakutake this year or Comet Hale-Bopp next year."
Copyright: Public domain
#246 Tomorrow's picture: February 20, 1996
“Today marks the third anniversary of the launch of the Advanced Satellite for Cosmology and Astrophysics (ASCA; renamed from Astro D when launched). ASCA, seen here superposed on galaxy M31, is a Japanese satellite for which NASA has provided some scientific equipment. ASCA carries four large-area X-ray telescopes. At the focus of two of the telescopes is a Gas Imaging Spectrometer (GIS), while a Solid-state Imaging Spectrometer (SIS) is at the focus of the other two. ASCA has provided recent evidence that high energy cosmic rays are formed in the expanding gas from a supernova. During ASCA's three years of operation, it has also yielded valuable data on quasars, supernova remnants, dwarf novae, pulsars, clusters of galaxies, and the mysterious X-ray background radiation that appears to come from all directions."
Copyright: Public domain
#247 Tomorrow's picture: February 21, 1996
“Pictured above is the largest ball of stars in our Galaxy. About 10 million stars orbit the center of this globular cluster - named Omega Centauri - as this giant globular cluster orbits the center of our Galaxy. Recent evidence indicates that Omega Centauri is by far the most massive of the about 160 globular clusters in the Milky Way. The stars in globular clusters are generally older, redder and less massive than our Sun. Studying globular clusters tells us about the history of our Galaxy and the age of the universe."
Copyright: Public domain
#248 Tomorrow's picture: February 22, 1996
“The lunar module shown above, named "Falcon," served as home for Apollo 15 astronauts David Scott and James Irwin during their stay on the Moon in July and August 1971. Meanwhile, astronaut Alfred Worden circled in the command module overhead. Harsh sunlight on the grey lunar surface lends the image an eerie quality, while the Lunar Apennine Mountains frame the background with Mount Hadley Delta visible on the right. Visible in the foreground are tracks from the first Lunar Roving Vehicle, an electric car which enabled the astronauts to explore extended areas on the lunar surface. Apollo 15 confirmed that most lunar surface features were created by impacts. Rocks returned by the Apollo 15 crew included green glasses whose formation mechanism is still unclear."
Copyright: Public domain
#249 Tomorrow's picture: February 23, 1996
“Apollo 15 astronaut James Irwin works on the first Lunar Roving Vehicle, before he and fellow astronaut David Scott take it out for a drive. Sloping up behind the lunar module "Falcon" on the left are lunar mountains Hadley Delta and Apennine Front, while about 5 kilometers behind Irwin is St. George Crater. The explorations conducted during the Apollo lunar missions discovered much about our Moon, including that the Moon is made of ancient rock, that the Moon's composition is similar to Earth's, that life is not evident there, that the Moon underwent a great hot melting in its distant past, that the Moon has suffered from numerous impacts as shown by its craters, and that the Moon's surface is covered by a layer of rock fragments and dust."
Copyright: Public domain
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