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  #136  
Παλιά 30-05-07, 08:20
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Liquid Sea on Saturn's Titan
Credit: Cassini Radar Mapper, JPL, ESA, NASA

Explanation: What is this vast dark region on Titan? Quite possible a sea of liquid hydrocarbons. The region was imaged earlier this month when the robotic Cassini spacecraft swooped past Saturn's cloudy moon and illuminated part of it with radar. The dark region in the above image reflected little radar, an effect expected were the dark surface relatively flat, as expected for a liquid. Other indications that the vast dark area is liquid include the coastline-like topology of the brighter regions, which appear to include islands, inlets, and tributary channels. The uninterrupted smoothness of much of the dark sea may indicate that the sea runs deep, with speculation holding a depth estimate of tens of meters. A hydrocarbon sea on Titan holds particular interest for exobiologists as it might be a place where life could develop. In 2005 the Huygens probe landed on Titan and returned the first surface images. Cassini will continue to explore Titan, as 13 more flybys are planned.

Tomorrow's picture: open space

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  #137  
Παλιά 31-05-07, 11:49
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Dwarf Galaxies in the Coma Cluster
Credit: Leigh Jenkins, Ann Hornschemeier (Goddard Space Flight Center) et al.,
JPL-Caltech, SDSS, NASA

Explanation: In visible light images, over a thousand galaxies are seen to lie within a volume about 20 million light-years across in the rich Coma Galaxy Cluster. But infrared images of the Coma Cluster have now been used to add thousands more to the Coma's galaxy count in the form of previously undiscovered dwarf galaxies. This composite combines infrared Spitzer Space Telescope image data (red and green) with visible light Sloan Sky Survey data (blue) for the central part of the cluster. Over 1 degree wide, the field is dominated by two giant elliptical galaxies in blue. Still, many of the small green smudges (see magnified inset) are identified as dwarf galaxies, roughly comparable to the Small Magellanic Cloud. Dwarf galaxies are thought to form first, providing building blocks for larger galaxies. The well-studied, friendly, Coma Cluster is 320 million light-years away.

Tomorrow's picture: pixels in space

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  #138  
Παλιά 01-06-07, 08:17
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Messier 65
Credit & Copyright: Volker Wendel

Explanation: M65 is a big, beautiful spiral galaxy, the sixty-fifth object in the famous astronomical catalog compiled by 18th century cosmic tourist Charles Messier. It's also a member of a picturesque trio of large spiral galaxies known as the Leo Triplet, about 35 million light-years away. This sharp view of M65 shows off the galaxy in remarkable detail, with tightly wound spiral arms and dust lanes stretching into a core dominated by the yellowish light from an older population of stars. In fact, M65 seems to be the least disturbed of the Leo Trio, though it is close enough to be interacting gravitationally with the other two galaxies (not seen here). Very nearly edge-on to our line-of-sight, M65 is about 100,000 light-years across, similar in size to our Milky Way Galaxy.

Tomorrow's picture: red/blue moon

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  #139  
Παλιά 03-06-07, 08:48
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Shuttle Plume Shadow Points to Moon
Credit: Pat McCracken, NASA

Explanation: Why would the shadow of a space shuttle launch plume point toward the Moon? In early 2001 during a launch of Atlantis, the Sun, Earth, Moon, and rocket were all properly aligned for this photogenic coincidence. First, for the space shuttle's plume to cast a long shadow, the time of day must be either near sunrise or sunset. Next, just at sunset, the shadow is the longest and extends all the way to the horizon. Finally, during a Full Moon, the Sun and Moon are on opposite sides of the sky. Just after sunset, for example, the Sun is slightly below the horizon, and, in the other direction, the Moon is slightly above the horizon. Therefore, as Atlantis blasted off, just after sunset, its shadow projected away from the Sun toward the opposite horizon, where the Full Moon just happened to be.

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  #140  
Παλιά 04-06-07, 08:18
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IC 4603: Reflection Nebula in Ophiuchius
Credit & Copyright: Takayuki Yoshida

Explanation: Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars. The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light, can combine to form areas seemingly created on an artist's canvas. Photographed above is roughly four square degrees of the nebula IC 4603 near the bright star Antares toward the constellation of Ophiuchus.

Tomorrow's picture: streak crescent

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  #141  
Παλιά 06-06-07, 08:19
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Dust Sculptures in the Rosette Nebula
Credit & Copyright: Ignacio de la Cueva Torregrosa

Explanation: What creates the cosmic dust sculptures in the Rosette Nebula? Noted for the common beauty of its overall shape, parts of the Rosette Nebula, also known as NGC 2244, show beauty even when viewed up close. Visible above are globules of dark dust and gas that are slowly being eroded away by the energetic light and winds by nearby massive stars. Left alone long enough, the molecular-cloud globules would likely form stars and planets. The above image was taken in very specific colors of Sulfur (shaded red), Hydrogen (green), and Oxygen (blue). The Rosette Nebula spans about 50 light-years across, lies about 4,500 light-years away, and can be seen with a small telescope towards the constellation of the Unicorn (Monoceros).

Tomorrow's picture: open space

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  #142  
Παλιά 07-06-07, 08:35
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Great Mountain Moonrise
Credit & Copyright: Tunc Tezel

Explanation: On May 31st, a gorgeous Full Moon rose over Uludag Mountain in Bursa Province, Turkey. This alluring telephoto view of the twilight scene is a composite of images taken roughly every two minutes beginning shortly after Sunset, following the rising Moon as it moves up and to the right. Of course, as the Moon rises it gets brighter and changes color, becoming less reddened as the sight-line through the dense atmosphere is steadily reduced. Each of the final two exposures also captured a rising planet Jupiter. Like the Full Moon, the bright, wandering planet is nearly opposite the Sun in Earth's sky and was caught on the lefthand side of the picture in two places, just above a small peak in the mountain side. Intriguingly, some considered this Full Moon a Blue Moon.

Tomorrow's picture: pixels in space

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  #143  
Παλιά 08-06-07, 08:38
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Markarian's Eyes
Credit & Copyright: Ken Crawford (Rancho Del Sol Observatory)

Explanation: Across the heart of the Virgo Galaxy Cluster lies a string of galaxies known as Markarian's Chain. Prominent in Markarian's Chain are these two interacting galaxies, NGC 4438 (left) and NGC 4435 - also known as The Eyes. About 50 million light-years away, the two galaxies appear to be about 100,000 light-years apart in this sharp close-up, but have likely approached to within an estimated 16,000 light-years of each other in their cosmic past. Gravitational tides from the close encounter have ripped away at their stars, gas, and dust. The more massive NGC 4438 managed to hold on to much of the material torn out in the collision, while material from the smaller NGC 4435 was more easily lost. The remarkably deep image of this crowded region of the universe also includes many more distant background galaxies.

Tomorrow's picture: light-weekend

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  #144  
Παλιά 09-06-07, 09:27
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Globular Star Cluster M3
Credit & Copyright: Karel Teuwen

Explanation: This immense ball of half a million stars older than the Sun lies over 30,000 light-years away. Cataloged as M3 (and NGC 5272), it is one of about 150 globular star clusters that roam the halo of our Milky Way Galaxy. Even in this impressively sharp image, individual stars are difficult to distinguished in the densely packed core, but colors are apparent for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take on a yellowish cast, while hotter giants and pulsating variable stars look light blue. A closer look at the deep telescopic view also reveals a host of background galaxies. Itself about 200 light-years across, the giant star cluster is a relatively bright, easy target for binoculars in the northern constellation Canes Venatici, The Hunting Dogs, and not far from Arcturus.

Tomorrow's picture: earth spot

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  #145  
Παλιά 10-06-07, 09:42
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Looking Back at an Eclipsed Earth
Credit: Mir 27 Crew; Copyright: CNES

Explanation: Here is what the Earth looks like during a solar eclipse. The shadow of the Moon can be seen darkening part of Earth. This shadow moved across the Earth at nearly 2000 kilometers per hour. Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon. This spectacular picture of the 1999 August 11 solar eclipse was one of the last ever taken from the Mir space station. The two bright spots that appear on the upper left are possibly Jupiter and Saturn, although this has yet to be proven. Mir was deorbited in a controlled re-entry in 2001.

Tomorrow's picture: reflecting merope

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  #146  
Παλιά 11-06-07, 09:14
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The Merope Reflection Nebula
Credit & Copyright: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT

Explanation: Reflection nebulas reflect light from a nearby star. Many small carbon grains in the nebula reflect the light. The blue color typical of reflection nebula is caused by blue light being more efficiently scattered by the carbon dust than red light. The brightness of the nebula is determined by the size and density of the reflecting grains, and by the color and brightness of the neighboring star(s). NGC 1435, pictured above, surrounds Merope (23 Tau), one of the brightest stars in the Pleiades (M45). The Pleiades nebulosity is caused by a chance encounter between an open cluster of stars and a molecular cloud.

Tomorrow's picture: saturn five

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  #147  
Παλιά 12-06-07, 08:49
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Shuttle Plume
Credit: NASA, Ken Thornsley

Explanation: What kind of cloud is that? Not a naturally occurring one. Pictured above is the drifting smoke plume left over from last Friday's launch of the Space Shuttle Atlantis. The twisted plume was captured shortly after launch high above NASA's massive Vehicle Assembly Building, the largest single story building in the world. Rockets frequently create picturesque plumes during launch. The Space Shuttle is currently visiting the International Space Station and delivering a new backbone truss segment to the continually developing and occupied spaceport. This trip, officially labeled STS-117, is the 118th space shuttle flight overall and the 28th for the Atlantis Orbiter.

Tomorrow's picture: open space

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  #148  
Παλιά 14-06-07, 08:22
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vdB 152: Reflection Nebula in Cepheus
Credit & Copyright: Giovanni Benintende

Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula vdB 152 really is very faint. It lies about 1400 light-years away, along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of cosmic dust in the region block light from background stars or scatter light from the embedded bright star (top) giving parts of the nebula a characteristic blue color. Ultraviolet light from the star is also thought to cause a dim reddish luminescence in the nebular dust. Though stars do form in molecular clouds, this star seems to have only accidentally wandered into the area, as its measured velocity through interstellar space is very different from the cloud's velocity. This deep telescopic image spans about 7 light-years at the estimated distance of vdB 152.

Tomorrow's picture: M96 and friends

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  #149  
Παλιά 16-06-07, 08:26
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Lunar Orbiter Views Crater Copernicus
Credit: NASA, U.S. Geological Survey

Explanation: To prepare for the Apollo landings, five Lunar Orbiter spacecraft were launched during 1966 and 1967 to gather detailed images of our fair planet's large, natural satellite. Dramatic views returned by the spacecraft cameras included this stark moonscape. The mosaic of 93 kilometer wide impact crater Copernicus features central peaks rising above the crater floor and rugged crater walls.

Note: As of today, June 16, the APOD editors have enjoyed presenting images from space missions, major observatories, and professional and amateur cosmic tourists alike for twelve years. A sincere thanks to our web site operators, translators, and to all for the gracious email and continued APOD submissions!

Tomorrow's picture: Ana's Argument

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  #150  
Παλιά 17-06-07, 09:15
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Analemma over the Ukraine
Credit & Copyright: Vasilij Rumyantsev ( Crimean Astrophysical Obsevatory)

Explanation: If you took a picture of the Sun at the same time each day, would it remain in the same position? The answer is no, and the shape traced out by the Sun over the course of a year is called an analemma. The Sun's apparent shift is caused by the Earth's motion around the Sun when combined with the tilt of the Earth's rotation axis. The Sun will appear at its highest point of the analemma during summer and at its lowest during winter. Analemmas created from different Earth latitudes would appear at least slightly different, as well as analemmas created at a different time each day. The analemma pictured to the left was built up by Sun photographs taken from 1998 August through 1999 August from Ukraine. The foreground picture from the same location was taken during the early evening in 1999 July.

Tomorrow's picture: space butter

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