Astronomy and Stars
Discussions about astronomy and stars. As we look further out what can we find in the universe beyond Earth's atmosphere?
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Though ozone may be diminishing on Earth, it is being manufactured one-half billion miles away, on Jupiter's largest satellite, Ganymede. NASA's Hubble Space Telescope found ozone's spectral "fingerprint" during observations of Ganymede made by Keith Noll and colleagues at the Space Telescope Science Institute in Baltimore, Maryland. These Hubble Faint Object Spectrograph results were presented at the American Astronomical Society's 27th Annual Meeting of the Division of Planetary Sciences in Kona, Hawaii. View the full article
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This pair of images of Jupiter's volcanic moon Io, taken with the Hubble telescope, shows the surprising emergence of a 200-mile-wide, yellowish-white feature near the center of the moon's disk [photo on the right]. This represents a more dramatic change in 16 months than any seen over the previous 15 years, say researchers. They suggest the spot may be a new class of transient feature on the moon. For comparison the photo on the left was taken in March 1994, before the spot emerged. The photo indicates that Io's surface had undergone only subtle changes since it was last seen close-up by the Voyager 2 probe in 1979. View the full article
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This Hubble telescope image of a portion of a vast dust disk around the star Beta Pictoris [top picture] shows that the disk is thinner than previously thought. Estimates based on the Hubble snapshot place the disk's thickness as no more than one billion miles (600 million kilometers). For comparison the disk appears four times thicker in a ground-based image. The disk is tilted nearly edge-on to Earth and may be older than some previous estimates because its dust has had enough time to settle into a flat plane. A thin disk also increases the probability that comet-sized or larger bodies have formed through accretion in the disk. Both conditions are believed to be chara…
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The Hubble telescope has taken the first picture of bright aurorae at Saturn's northern and southern poles [top picture]. The picture at the bottom was taken in visible light. Hubble's far-ultraviolet-light image resolves a luminous, circular band centered on the north pole, where an enormous curtain of light rises as far as 1,200 miles (2,000 kilometers) above the cloud tops. This curtain changed rapidly in brightness and extent over the two-hour period of observations. View the full article
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These two surface maps of the asteroid Vesta are derived from Hubble telescope images taken between November 28 and December 1, 1994. The pictures show surface details as small as 35 miles across. Vesta is 320 miles in diameter, and the map covers the asteroid's entire surface area, about 200,000 miles. The top panel indicates sharp contrasts in Vesta's surface color. The surface markings may represent ancient volcanic activity such as lava flows and, in addition, regions where major collisions have stripped away the surface. The bottom panel reveals that Vesta's surface is made up of igneous rock, indicating that either the entire surface was once melted or lava flowin…
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These Hubble telescope pictures of comet Hale-Bopp show a remarkable "pinwheel" pattern and a blob of free-flying debris near its center. The image at left shows the entire comet; the picture at right is a close-up of the nucleus. The bright clump of light along the spiral [just above the center of the picture] may be a piece of the comet's icy crust. Although the "blob" is about 3.5 times fainter than the brightest portion at the comet's center, the lump appears brighter because it covers a larger area. The debris follows a spiral pattern outward because the solid center is rotating like a lawn sprinkler, completing a single rotation about once per week. View th…
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This Hubble telescope picture reveals one of the least massive and coolest stars ever seen [upper right]. This star is a diminutive companion to the K dwarf star called GL 105A (also known as HD 16160), seen at lower left. The pair is located 27 light-years from Earth in the constellation Cetus. Based on the Hubble observation, astronomers calculate that the cool, lightweight star, called GL 105C, is 25,000 times fainter than GL 105A in visible light. If the dim companion were at the distance of our Sun, it would be only four times brighter than the full moon. View the full article
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Peering deep into the globular star cluster M4 with the Hubble telescope, Canadian and American astronomers have discovered a large number of "stellar corpses," called white dwarf stars, which may be used eventually to refine age estimates of the universe. The observation was so sensitive that even the brightest of the detected white dwarfs was no more luminous than a 100-watt light bulb seen at the moon's distance (239,000 miles). A Hubble color image of a small portion of the cluster reveals eight white dwarf stars [inside the white circles] among the cluster's much brighter population of yellow, Sun-like stars and cooler red dwarf stars. Hubble reveals a total of 75 …
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Saturn's magnificent ring system is seen tilted edge-on - for the second time in 1995 - in this Hubble telescope picture taken Aug. 10, when the planet was 895 million miles (1,440 million kilometers) away from Earth. Hubble snapped the image as Earth sped back across Saturn's ring plane to the sunlit side of the rings. Several of Saturn's icy moons are visible as tiny star-like objects in or near the ring plane. On May 22, 1995 Earth dipped below the ring plane, giving observers a brief look at the backlit side of the rings. Ring-plane crossing events occur approximately every 15 years. Earthbound observers won't have as good a view until the year 2038. View the…
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Probing some of the most distant and energetic galaxies in the universe, the Hubble telescope has uncovered surprisingly varied and intricate structures of stars and gas, suggesting that the processes powering these so-called radio galaxies are more complex than previously thought. The radio galaxies observed are far across the cosmos, existing when the universe was half its present age. Light from these galaxies is just now reaching Earth. The Hubble observations should shed light on galaxy evolution and on the nature of active galaxies, which may be powered by immense black holes at their cores. These Hubble images, combined with radio maps produced by the Very Large …
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Astronomers have announced the discovery of at least two, and possibly as many as four, new moons orbiting the giant planet Saturn. This discovery was based upon Hubble telescope images that were taken when Saturn's rings were tilted edge-on to Earth. Two of the satellites seen by Hubble are in orbits similar to those of Atlas and Prometheus, a pair of moons discovered in 1980 by the Voyager 1 spacecraft. Additional Hubble observations of Saturn will provide more images that can be used to determine whether two of the four satellites detected by Hubble are truly new or not. This four-picture sequence shows one of the new moons discovered by Hubble. Saturn appears as a b…
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NASA's Hubble Space Telescope has imaged a variety of galaxies with normal, irregular and peculiar shapes. These galaxies are so far away that they are seen when the universe was a fraction of its current age. These images are part of a serendipitous sky survey which has been conducted over the past three years by an international team of astronomers. The survey is one of the key projects for Hubble. View the full article
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Astronomers using the Hubble telescope have solved a 20-year-old mystery by showing that a class of galaxies once thought to be rare is actually the most common type of galaxy in the universe. Analyzing some of the deepest images ever taken of the heavens, the astronomers conclude that small irregular objects called "blue dwarfs" were more numerous several billion years ago, outnumbering giant elliptical galaxies and spiral galaxies like our Milky Way. This means that blue dwarfs are a more important constituent of the universe and figure more prominently in the evolution of galaxies than previously thought. View the full article
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This Hubble telescope photo mosaic shows a field of distant galaxies. The brightest object in this picture is NGC 4881 [just above center], an elliptical galaxy in the outskirts of the Coma Cluster, a great cluster of galaxies more than five times farther away than the Virgo Cluster. The distance to the Coma Cluster is an important cosmic yardstick for scaling the overall size of the universe. View the full article
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Two groups have recently used the Hubble telescope to acquire high-resolution images of the planet Neptune. These images represent the clearest views of Neptune since the Voyager 2 flyby in August 1989. The observations are providing a wealth of new information about the structure, composition, and meteorology of this distant planet's atmosphere. The pictures show several bright clouds, which are thought to be high above the main cloud deck and above much of the absorbing methane gas. The edge of the planet's disk also appears somewhat bright, indicating the presence of a ubiquitous high-altitude haze layer. View the full article
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The Hubble telescope has detected a long-sought population of comets dwelling at the icy fringe of the solar system. The observation, which is the astronomical equivalent to finding the proverbial needle-in-a-haystack, bolsters proof for a primordial comet reservoir just beyond Neptune. The circles pinpoint one of the candidate Kuiper belt objects. The dotted lines represent a possible orbit that this Kuiper belt comet is following. Based on the Hubble observations, a team of astronomers estimate that the belt contains at least 200 million comets, which have remained essentially unchanged since the birth of the solar system 4.5 billion years ago. View the full ar…
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Astronomers using the Hopkins Ultraviolet Telescope (HUT), flown aboard the Shuttle ASTRO-2 mission, have been able to exclude one explanation for the mysterious far ultraviolet background radiation that existed when the universe was young. They find that starburst galaxies -- galaxies forming new stars at an extremely high rate -- were largely opaque to the UV radiation from hot newborn stars embedded within them. Contrary to earlier ideas, this means that starburst galaxies did not contribute significantly to heating, or ionizing, the early universe. View the full article
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Observations with the Hopkins Ultraviolet Telescope (HUT) of the most massive star currently known have revealed new features of its hot outer layers, which are being blown away from the star at speeds of up to 2300 miles per second due to its extreme luminous energy output. These features in turn provide information about physical characteristics of the star, such as its temperature, luminosity, chemical composition, age, and mass, or the total amount of matter it contains. View the full article
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The Hubble telescope has provided a detailed look at the fitful, eruptive, and dynamic processes accompanying the final stages of a star's "construction." These three images provide a dramatically clear look at collapsing circumstellar disks of dust and gas that build stars and provide the ingredients for a planetary system. The pictures also show blowtorch-like jets of hot gas funneled from deep within several embryonic systems and machine gun-like bursts of material fired from the stars at speeds of a half-million mph. The Hubble observations shed new light on one of modern astronomy's central questions: How do tenuous clouds of interstellar gas and dust make stars li…
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This sequence of images from the Hubble telescope documents a rare astronomical alignment: Saturn's magnificent ring system turned edge-on. This event occurs when the Earth passes through Saturn's ring plane, as it does about every 15 years. In these pictures, Hubble can see details on Saturn as small as 450 miles (725 kilometers) across. In each image the dark band across Saturn is the ring shadow cast by the Sun, which is still slightly above the planet's ring plane. The bright dots to the left of Saturn and in the boxes to the right are some of the planet's moons. The boxes around the western portion of the rings [on the right] indicate the area in which the faint li…
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Peering into the heart of two recently exploded double-star systems, the Hubble telescope has surprised researchers by finding that the white dwarf stars at the center of the fireworks are cooler than expected and spin more slowly than previously thought. Each dwarf - dense, burned-out stars that have collapsed to the size of Earth - is in a compact binary system, called a cataclysmic variable, where its companion is a normal star similar to, but smaller than the Sun. The stars are so close together that the entire binary system would fit inside the Sun. Their closeness allows gas to flow from the normal star onto the dwarf, where it swirls into a pancake-shaped disk [s…
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Hubble telescope images of the asteroid Vesta are providing astronomers with a glimpse of the oldest terrain ever seen in the solar system and a peek into a broken-off section of the "mini-planet," which exposes its interior. Hubble's pictures provide the best view yet of Vesta's complex surface, which has geologic features similar to those of terrestrial worlds such as Earth or Mars. The asteroid's ancient surface, battered by collisions eons ago, allows astronomers to peer below the asteroid's crust and into its past. These images trace the asteroid through a full rotation. View the full article
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The distant, blue-green planet Neptune has again surprised astronomers with the emergence of a new great dark spot in the cloudy planet's Northern Hemisphere, discovered by the Hubble telescope. Only last June, Hubble images revealed that a great dark spot in the Southern Hemisphere discovered by the Voyager 2 spacecraft during its 1989 flyby had mysteriously disappeared. The new dark spot is a near mirror image of the one found in the Southern Hemisphere. Bright, high-altitude clouds accompany the new northern dark spot. Atmospheric gases that flow up over the spot cool to form the methane-ice crystal clouds. The new spot might be a hole in Neptune's methane cloud tops…
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This is a Hubble telescope image of the tattered debris of a star that exploded 3,000 years ago as a supernova. This supernova remnant, called N132D, lies 169,000 light-years from Earth in the satellite galaxy, the Large Magellanic Cloud. A Hubble snapshot of the supernova's inner regions shows the complex collisions that take place as fast-moving material slams into cool, dense interstellar clouds. This level of detail in the expanding filaments could only be seen previously in much closer supernova remnants. Now, Hubble's capabilities extend the detailed study of supernovae to the distance of a neighboring galaxy. View the full article
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This Hubble telescope image of a rich cluster of galaxies called Abell 2218 is a spectacular example of gravitational lensing. The arc-like pattern spread across the picture like a spider web is an illusion caused by the cluster's gravitational field. This cluster of galaxies is so massive and compact that light rays passing through it are deflected by its enormous gravitational field, much as a camera's lens bends light to form an image. This phenomenon magnifies, brightens, and distorts images of those faraway objects, providing a powerful "zoom lens" for viewing galaxies that are so far away they could not normally be observed with the largest telescopes. View…
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