NGC 1068 and the X-Ray Flashlight
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At night, tilting a flashlight up under your chin hides the glowing bulb from the direct view of your friends. Light from the bulb still reflects from your face though, and can give you a startling appearance. Spiral Galaxy NGC 1068 may be playing a similar trick on a cosmic scale, hiding a central powerful source of x-rays -- likely a supermassive black hole -- from direct view. X-rays are still scattered into our line-of-sight though, by a dense torus of material surrounding the black hole. The scenario is supported by x-ray data from the Chandra Observatory combined with a Hubble Space Telescope optical image in this false-color composite picture. Optical data in red shows spiral structure across NGC 1068's inner 7 thousand light-years with the x-ray data overlaid in blue and green. A hot wind of gas streaming from the galaxy's core is seen as the broad swath of x-ray emission while material lit up by the hidden black hole source is within the central cloud of more intense x-rays. Also well known as M77, NGC 1068 lies a mere 50 million light-years away toward the constellation Cetus.
2003-07-11
The Case of the Missing Supernova
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Would you notice a second Moon in the sky? About 700 years ago, light from a tremendous explosion reached Earth that should have appeared almost as bright as a full Moon. The bright spot should have lasted for weeks, yet no notation of such an occurrence has been found in historical records. The mystery was uncovered by Wan Chen and Neil Gehrels (NASA/GSFC) when studying the source of radioactive elements toward the Vela supernova remnant. They deduced that an explosion much younger and closer than the supernova that caused Vela must have occurred, and even computed explosion characteristics from the amounts of radioactive elements present. They calculate that GRO/RX J0852 should have dazzled medieval stargazers. Perhaps people were too busy, surviving records are too incomplete, or the explosion was somehow too dim. The above picture of GRO/RX J0852 was taken in gamma-ray light with the Compton Gamma-Ray Observatory and is shown in false-color. Astronomers and historians continue to contemplate the clues.
1999-04-13
Shadow Cone of a Total Solar Eclipse
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Sometimes, during a total eclipse of the Sun, a strange shadow of darkness can be seen stretching off into the distance. Called a shadow cone, they are visible because the Earth's atmosphere is not completely transparent, scattering sunlight and hence appearing blue during the day. Shadow cones are particularly dramatic for eclipses near the horizon, as geometry creates a long corridor of sun-blocked air. Visible above is a shadow cone caught during a total solar eclipse visible last month from South Australia. The eclipsed Sun itself still appears bright because of light from the surrounding corona. The digital camera on the left is zoomed in to show a better image of the actual eclipse.
2003-01-06 Olivier Staiger (High Moon)
A Flock of Stars
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Only a few stars can be found within ten light-years of our lonely Sun, situated near an outer spiral arm of the Milky Way galaxy. But if the Sun were found within one of our galaxy's star clusters, thousands of stars might occupy a similar space. What would the night sky look like in such a densely packed stellar neighborhood? When Roger Hopkins took this picture at the Montezuma National Wildlife Refuge in the Finger Lakes region of western New York, USA, he was struck by this same notion. Appropriately, he had photographed a flock of starlings against the backdrop of a serene sunset. He then manipulated the image so that the black bird silhouettes were changed to white. The final picture dramatically suggests the tantalizing spectacle of approaching night in crowded skies above a cluster star world.
2003-12-13 Roger A. Hopkins
A Cerro Tololo Sky
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High atop a Chilean mountain lies one of the premier observatories of the southern sky: Cerro Tololo. Pictured above is one of the premier telescopes of the Cerro Tololo Inter-American Observatory (CTIO) and of the past quarter-century: the 4-meter Blanco Telescope. Far behind the telescope are thousands of individual stars and diffuse light from three galaxies: the Small Magellanic Cloud (upper left), the Large Magellanic Cloud (lower left), and our Milky Way Galaxy (right). Visible just to Blanco's right is the famous superposition of four bright stars known as the Southern Cross. The observatory structures are lit solely by starlight.
2001-05-14 Roger Smith
The Virgo Cluster of Galaxies
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Pictured are several galaxies of the Virgo Cluster, the closest cluster of galaxies to our Milky Way Galaxy. The Virgo Cluster spans more than 5 degrees on the sky - about 10 times the angle made by a full Moon. It contains over 100 galaxies of many types - including spirals, ellipticals, and irregular galaxies. The Virgo Cluster is so massive that it is noticeably pulling our Galaxy toward it. The cluster contains not only galaxies filled with stars but also gas so hot it glows in X-rays. Motions of galaxies in and around clusters indicate that they contain more dark matter than any visible matter we can see. Notable bright galaxies in the Virgo Cluster include bright Messier objects such as M61, M87, M90, and M100.
2000-02-20 Digitized Sky Survey, Palomar Observatory, STScI
PKS 1127-145: Quasar View
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The quasar known as PKS 1127-145 lies ten billion light-years from our fair planet. A Hubble Space Telescope view in the left panel shows this quasar along with other galaxies as they appear in optical light. The quasar itself is the brightest object in the lower right corner. In the right panel is a Chandra Observatory x-ray picture, exactly corresponding to the Hubble field. While the more ordinary galaxies are not seen in the Chandra image, a striking jet, nearly a million light-years long, emerges from the quasar to dominate the x-ray view. Bright in both optical and x-ray light, the quasar is thought to harbor a supermassive black hole which powers the jet and makes PKS 1127-145 visible across the spectrum -- a beacon from the distant cosmos.
2002-02-08
The ĂandĂș in the Milky Way
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Have you seen the bird in the Milky Way? Beyond the man in the Moon, the night sky is filled with stories, and cultures throughout history have projected some of their most enduring legends onto the stars and dust above. Generations of people see these celestial icons, hear their associated stories, and pass them down. Pictured here is not only a segment of the central band of our Milky Way galaxy, but, according to folklore of several native peoples of Uruguay, the outline of a great bird called ĂandĂș. Furthermore, ĂandĂș's footprint is associated with the Southern Cross asterism. In the foreground, in silhouette, is a statue of MarĂa Micaela Guyunusa, an indigenous woman of the CharrĂșa people who lived in the 1800s and endures as a symbol of colonial resistance. The composite image was taken in mid-April in Cabo Polonio, Uruguay, with the Atlantic Ocean in the background.
2023-06-20 Fefo Bouvier; Line Drawing: Alfonso Rosso
NGC 253: Close Up
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This dusty island universe is one of the brightest spiral galaxies in planet Earth's sky. Seen nearly edge-on, NGC 253 is only 13 million light-years away, the largest member of the Sculptor Group of galaxies, neighbor to our own local galaxy group. The detailed close-up view is a five frame mosaic based on data assembled from the Hubble Legacy Archive. Beginning on the left near the galaxy's core, the sharp panorama follows dusty filaments, interstellar gas clouds, and even individual stars toward the galaxy's edge at the right. The magnificent vista spans nearly 50,000 light-years. The frame at the far right has been compressed slightly to bring into view an intriguing pair of background galaxies. Designated a starburst galaxy because of its frantic star forming activity, NGC 253 features tendrils of dust rising from a galactic disk laced with young star clusters and star forming regions. NGC 253 is also known to be a strong source of high-energy x-rays and gamma rays, likely due to massive black holes near the galaxy's center.
2011-05-19
Tombaugh 4
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Clyde Tombaugh discovered planet Pluto in 1930 while surveying the skies with the 13-inch Lawrence Lowell Telescope. But the skilled and careful astronomer also went on to discover star clusters, comets, asteroids, and clusters of galaxies. For example, pictured is galactic or open star cluster Tombaugh 4 in the northern constellation Cassiopeia. Published in 1941, Tombaugh's description, based on his photographic images from the Lowell 13-inch, indicates the cluster is small and faint, and comprised of about 30 stars. Using the apparent brightness of the cluster stars he estimated the distance to be 20 to 30 thousand light-years, making Tombaugh 4 over 10 light-years in diameter. This deep color image, made with a modern ccd camera and another 13-inch telescope, includes the region's foreground stars and faint nebulosities.
2006-10-21 Dean Rowe