A Picturesque Venus Transit
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The rare transit of Venus across the face of the Sun earlier this month was one of the better-photographed events in sky history. Both scientific and artistic images have been flooding in from the areas that could see the transit: Europe and much of Asia, Africa, and North America. Scientifically, solar photographers confirmed that the black drop effect is really better related to the viewing clarity of the camera or telescope than the atmosphere of Venus. Artistically, images might be divided into several categories. One type captures the transit in front of a highly detailed Sun. Another category captures a double coincidence such as both Venus and an airplane simultaneously silhouetted, or Venus and the International Space Station in low Earth orbit. A third image type involves a fortuitous arrangement of interesting looking clouds, as shown by example in the above image taken from North Carolina, USA. There the distant orb of giant Venus might have been mistaken, at first glance, for a small but unusually circular cloud.
2004-06-23 David Cortner
Distant Supernova, Dark Energy
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A pinpoint of light from a star that exploded over 10 billion light-years away is centered in the panel at the lower right, a cosmic snapshot of the most distant supernova. The ancient stellar detonation was detected by digitally subtracting before and after images of a faint, yellowish, elliptical galaxy included in the Hubble Space Telescope Deep Field image illustrated at the top and left. Remarkable in itself as the farthest known supernova, its measured brightness provides astounding evidence for a strange universe - one which eventually defies gravity and expands at an accelerating rate. The unseen force driving this expansion is attributed to "dark energy" and discovering the fundamental nature of dark energy has been called the challenge of this millennium.
2001-04-04
Stars and Dust Across Corona Australis
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Cosmic dust clouds sprawl across a rich field of stars in this sweeping telescopic vista near the northern boundary of Corona Australis, the Southern Crown. Probably less than 500 light-years away and effectively blocking light from more distant, background stars in the Milky Way, the densest part of the dust cloud is about 8 light-years long. At its tip (upper right) is a group of lovely reflection nebulae cataloged as NGC 6726, 6727, 6729, and IC 4812. A characteristic blue color is produced as light from hot stars is reflected by the cosmic dust. The smaller yellowish nebula (NGC 6729) surrounds young variable star R Coronae Australis. Magnificent globular star cluster NGC 6723 is at the upper right corner of the view. While NGC 6723 appears to be part of the group, it actually lies nearly 30,000 light-years away, far beyond the Corona Australis dust clouds.
2009-06-05 Andrey Oreshko
How to Identify that Light in the Sky
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What is that light in the sky? Perhaps one of humanity's more common questions, an answer may result from a few quick observations. For example -- is it moving or blinking? If so, and if you live near a city, the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the din of artificial city lights. If not, and if you live far from a city, that bright light is likely a planet such as Venus or Mars -- the former of which is constrained to appear near the horizon just before dawn or after dusk. Sometimes the low apparent motion of a distant airplane near the horizon makes it hard to tell from a bright planet, but even this can usually be discerned by the plane's motion over a few minutes. Still unsure? The featured chart gives a sometimes-humorous but mostly-accurate assessment. Dedicated sky enthusiasts will likely note -- and are encouraged to provide -- polite corrections. Chart translations: Spanish, Italian, Polish, Tamil, Kannada, Latvian, and Norwegian
2017-09-24 HK (The League of Lost Causes)
The Shadow Of Phobos
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Hurtling through space above the Red Planet, potato-shaped Phobos completes an orbit of Mars in less than eight hours. In fact, since its orbital period is shorter than the planet's rotation period, Mars-based observers see Phobos rise in the west and set in the east - traveling from horizon to horizon in about 5 1/2 hours. These three images from the Mars Global Surveyor (MGS) spacecraft record the oval shadow of Phobos racing over western Xanthe Terra on August 26, 1999. The area imaged is about 250 kilometers across and is seen in panels from left to right as red filter, blue filter, and combined color composite views from the MGS wide-angle camera system. The three dark spots most easily seen in the red image are likely small fields of dark sand dunes on crater floors. Standing in the shadow of Phobos, you would see the Martian version of a solar eclipse!
1999-11-05
A Laser Strike at the Galactic Center
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Why are these people shooting a powerful laser into the center of our Galaxy? Fortunately, this is not meant to be the first step in a Galactic war. Rather, astronomers at the Very Large Telescope (VLT) site in Chile are trying to measure the distortions of Earth's ever changing atmosphere. Constant imaging of high-altitude atoms excited by the laser -- which appear like an artificial star -- allow astronomers to instantly measure atmospheric blurring. This information is fed back to a VLT telescope mirror which is then slightly deformed to minimize this blurring. In this case, a VLT was observing our Galaxy's center, and so Earth's atmospheric blurring in that direction was needed. As for inter-galaxy warfare, when viewed from our Galaxy's center, no casualties are expected. In fact, the light from this powerful laser would combine with light from our Sun to together appear only as bright as a faint and distant star.
2009-08-16
Cat's Eye
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Staring across interstellar space, the alluring Cat's Eye nebula lies three thousand light-years from Earth. A classic planetary nebula, the Cat's Eye (NGC 6543) represents a final, brief yet glorious phase in the life of a sun-like star. This nebula's dying central star may have produced the simple, outer pattern of dusty concentric shells by shrugging off outer layers in a series of regular convulsions. But the formation of the beautiful, more complex inner structures is not well understood. Seen so clearly in this sharp Hubble Space Telescope image, the truly cosmic eye is over half a light-year across. Of course, gazing into the Cat's Eye, astronomers may well be seeing the fate of our sun, destined to enter its own planetary nebula phase of evolution ... in about 5 billion years.
2005-09-24
N11B: Star Cloud of the LMC
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Massive stars, abrasive winds, mountains of dust, and energetic light sculpt one of the largest and most picturesque regions of star formation in the Local Group of Galaxies. Known as N11, the region is visible on the upper right of many images of its home galaxy, the Milky Way neighbor known as the Large Magellanic Clouds (LMC). The above image actually highlights N11B, part of the nebula that spans about 100 light years and is particularly active. The entire emission nebula N11 is second in LMC size only to 30 Doradus. Studying the stars in N11B has shown that it actually houses three successive generations of star formation. Compact globules of dark dust housing emerging young stars are also visible on the upper right.
2004-07-07
Solar Eclipse Shoes in the Classroom
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The total solar eclipse of March 8/9 will be the only total eclipse in 2016. Crossing the international date line, the New Moon's dark shadow traces a limited, narrow path for viewing the total phase, making landfall in Indonesia and mostly tracking across the Pacific Ocean. A much larger region will be witness to a partially eclipsed Sun though, during morning hours on March 9 for southeast Asia and northeast Australia, and before sunset March 8 for Hawaii and Alaska. Safely viewing the eclipse can actually be very easy. One technique is demonstrated in this shoe group portrait from a classroom in Rosenfeld, Germany, taken during March 2015's solar eclipse. With blinds closed to darken the room, each threaded hole in the window blind creates a pinhole camera, projecting multiple images of the eclipsed sun that march across the floor. Other viewing alternatives include eclipse glasses and a comfortable chair, but be sure to wear a fashionable eclipse shirt. NASA Television: Live Eclipse Coverage begins at 8pm ET.
2016-03-08 Progymnasium Rosenfeld
APOD is One Year Old Today
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The first Astronomy Picture of the Day (APOD) appeared one year ago today. Pictured above are Robert Nemiroff (left) and Jerry Bonnell (right), engaged in creating the APOD web pages. APOD started over speculative conversations on the ultimate value of the World Wide Web. In our (current) view, the WWW is the closest thing yet to an "Encyclopedia of Humanity," and we think it's important to contribute. We are proud to say that APOD has now annotated most of the famous astronomical pictures of our time and has made them available to the general public in an indexed and searchable archive. During it's first year, APOD's main daily picture page has been served over one million times. But APOD's mission continues. As space science progresses more pictures, fresh insights, and new educative links become available. Therefore, so long as public interest and NASA support continue, APOD will continue. We thank all whose gracious e-mail are continually a source of encouragement.
1996-06-16