juliensimon/nasa-apod huggingface dataset:
In the Center of Reflection Nebula NGC 1333 (2007-05-21)

The dust is so thick in the center of NGC 1333 that you can hardly see the stars forming.  Conversely, the very dust clouds that hide the stars also reflects their optical light, giving NGC 1333's predominantly blue glow the general designation of a reflection nebula. A highly detailed image of the nebula, shown above, was taken recently by the Mayall 4-meter telescope on Kitt Peak in Arizona, USA and released to honor astronomer Stephen Strom on his retirement. Visible near the image top are vast blue regions of dust predominantly reflecting the light from bright massive stars.  Visible in the thick central dust are not only newly formed stars but red jets and red-glowing gas energized by the light and winds from recently formed young stars.   The NGC 1333 nebula contains hundreds of newly formed stars that are less than one million years old. Reflection nebula NGC 1333 lies about 1,000 light years away toward the constellation of Perseus.

Image credit: T. Rector
Orange Sun Oozing (2007-05-22)

The Sun's surface keeps changing.  Click the central arrow and watch how the Sun's surface oozes during a single hour.  The Sun's photosphere has thousands of bumps called granules and usually a few dark depressions called sunspots.  The above time-lapse movie centered on Sunspot 875 was taken last year by the Vacuum Tower Telescope in the Canary Islands of Spain using adaptive optics to resolve details below 500 kilometers across.  Each of the numerous granules is the size of an Earth continent, but much shorter lived.  A granule slowly changes its shape over an hour, and can even completely disappear.  Hot hydrogen gas rises in the bright center of a granule, and falls back into the Sun along a dark granule edge.  The above movie and similar movies allow solar scientists to study how granules and sunspots evolve as well as how magnetic sunspot regions produce powerful solar flares.
Venus Near the Moon (2007-05-23)

The two brightest objects in the night sky appeared to go right past each other last week.  On the night of May 19, Earth's Moon and the planet Venus were visible in the same part of the sky, and at closest approach were less than one degree apart.  The conjunction was captured in the above image taken from near Quebec City, Quebec, Canada.  Venus appears on the lower left of the above photo.  The spires that appear to emanate from Venus are diffraction spikes caused by the camera itself.   The image is so clear that craters on the Moon are resolved.  Of course, the real physical distance between the two heavenly bodies was not unusually small -- the apparent conjunction was really just an illusion of perspective. Although Earth's Moon passes Venus once each month, such a close passing visible in the evening sky is more rare.

Image credit: Jay Ouellet
The Tulip in the Swan (2007-05-24)

This expansive (1-degree wide) telescopic view looks out along the plane of our Milky Way Galaxy toward the nebula rich constellation Cygnus the Swan. It is centered on a bright hydrogen emission region recorded in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101. About 8,000 light-years distant the nebula is popularly known as the Tulip Nebula, understandably not the only cosmic cloud to evoke the imagery of flowers. Complex and beautiful in visible light, the area also includes one of the brightest, most famous sources in the x-ray sky, Cygnus X-1. Discovered in the early 1970s, Cygnus X-1 is a bizarre binary system consisting of a massive, hot, supergiant star (seen here) in close orbit with a stellar mass black hole. The Cygnus X-1 system is also estimated to lie a comfortable 8,000 light-years away.

Image credit: Neil Fleming
Jupiter, Vesta, and the Milky Way (2007-05-25)

In this gorgeous skyscape, gas giant Jupiter along with the stars and cosmic dust clouds of the Milky Way hang over the southern horizon in the early morning hours as seen from Stagecoach, Colorado, USA. Recorded on Thursday, Jupiter is the brightest object near picture center. Along with the stunning Milky Way, Jupiter is hard to miss, but a careful inspection of the view also reveals main belt asteroid Vesta. Of all the asteroids Vesta is the brightest and is now just bright enough to be visible to the naked eye from locations with very dark, clear skies. Vesta (as well as Jupiter) appears relatively bright now because it is near opposition, literally opposite the Sun in planet Earth's sky and closest to Earth in its orbit. For Vesta, this opposition offers the best viewing in many years. The year 2007 also coincides with the 200th anniversary of the asteroid's discovery. Starting late next month, NASA plans to launch the Dawn mission intended to explore Vesta (and Ceres) and the main asteroid belt.

Image credit: Jimmy Westlake
(Colorado
Mountain College)
The Moon's Saturn (2007-05-26)

On May 22nd, just days after sharing the western evening sky with Venus, the Moon moved on to Saturn - actually passing in front of the ringed planet when viewed in skies over Europe, northern Africa, and western Asia. Because the Moon and bright planets wander through the sky near the ecliptic plane, such occultation events are not uncommon, but they are dramatic, especially in telescopic views. For example, in this sharp image Saturn is captured emerging from behind the Moon, giving the illusion that it lies just beyond the Moon's bright edge. Of course, the Moon is a mere 400 thousand kilometers away, compared to Saturn's distance of 1.4 billion kilometers. Taken with a digital camera and 20 inch diameter telescope at the Weikersheim Observatory in southern Germany, the picture is a single exposure adjusted to reduce the difference in brightness between Saturn and the cratered lunar surface.

Image credit: Jens Hackmann
The Horsehead Nebula (2007-05-27)

One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud.  Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s.  The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis.  The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left.  Streams of gas leaving the nebula are funneled by a strong magnetic field.  Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.  Light takes about 1500 years to reach us from the Horsehead Nebula.   The above image was taken with the 0.9-meter telescope at  Kitt Peak National Observatory.

Image credit: Nigel Sharp
A Hole in Mars (2007-05-28)

Black spots have been discovered on Mars that are so dark that nothing inside can be seen. Quite possibly, the spots are entrances to deep underground caves capable of protecting Martian life, were it to exist.  The unusual hole pictured above was found on the slopes of the giant Martian volcano Arsia Mons. The above image was captured three weeks ago by the HiRISE instrument onboard the Mars Reconnaissance Orbiter currently circling Mars.  The holes were originally identified on lower resolution images from the Mars Odyssey spacecraft, The above hole is about the size of a football field and is so deep that it is completely unilluminated by the Sun.  Such holes and underground caves might be prime targets for future spacecraft, robots, and even the next generation of human interplanetary explorers.
Bright Spiral Galaxy M81 from Hubble (2007-05-29)

The Hubble Space Telescope has resolved individual stars in a spectacular new image of nearby spiral galaxy M81.  The feat is similar to Edwin Hubble's historic images with the Mt. Wilson 100-inch Hooker Telescope in the 1920s that resolved stars in neighboring galaxy M31.  Edwin Hubble was able to use individual Cepheid variable stars to show that M31 was not nearby swirling gas but rather an entire galaxy like our Milky Way Galaxy.   This above image in visible light taken by the Hubble Space Telescope is being used in conjunction with images being taken in ultraviolet by Galex, infrared by Spitzer, and X-rays with Chandra to study how stars have formed and died over the history M81.  Light takes about 12 million years to reach us from M81.  M81 is visible with binoculars toward the constellation of the Great Bear (Ursa Major).
Liquid Sea on Saturn's Titan (2007-05-30)

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.
Dwarf Galaxies in the Coma Cluster (2007-05-31)

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.
Messier 65 (2007-06-01)

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.

Image credit: Volker Wendel
3D Full Moon (2007-06-02)

Get out your red/blue glasses and check out this satisfying stereo anaglyph of the Full Moon. A corresponding stereo image pair, intended for cross-eyed viewing, is also available through this link. Regardless of your preferred technique for stereo viewing, the 3D effect comes from combining pictures of the same scene taken at different angles -- mimicking the slightly different perspective of each eye. Perhaps surprisingly for Earthdwellers, getting two pictures of the Full Moon from different angles only requires a little patience. In this case, photographer Laurent Laveder used pictures taken months apart, one in November 2006 and one in January 2007. He relied on the Moon's continuous libration or wobble as it orbits to produce two shifted images of a Full Moon.

Image credit: Laurent Laveder
(PixHeaven.net)
Shuttle Plume Shadow Points to Moon (2007-06-03)

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.
IC 4603: Reflection Nebula in Ophiuchius (2007-06-04)

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.

Image credit: Takayuki Yoshida
Jet Approaching a Crescent Moon (2007-06-05)

No natural clouds appear in this picture.  On the left, an airplane cruises through the atmosphere leaving a contrail in its wake.  The contrail would normally appear white, but the large volume of air toward the setting Sun preferentially knocks away blue light, giving the reflected trail a bright orange hue.  Far in the distance, to the right of the plane, is the young Moon.  This vast world shows only a sliver of itself because the Sun is nearly lined up behind it.  The above image is framed by an eerie gray sky, too far from day to be blue, too far from night to be black.  Within minutes the impromptu sky show ended.  The plane crossed the Moon. The contrail dispersed. The Sun set. The Moon set.  The sky faded to black, only to reveal thousands of stars that had been hiding below the gray din.

Image credit: Vincent Jacques
Dust Sculptures in the Rosette Nebula (2007-06-06)

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).

Image credit: Ignacio de la Cueva Torregrosa
Great Mountain Moonrise (2007-06-07)

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.

Image credit: Tunc Tezel
Markarian's Eyes (2007-06-08)

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.

Image credit: Ken Crawford  
(Rancho Del Sol Observatory)
Globular Star Cluster M3 (2007-06-09)

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.

Image credit: Karel Teuwen
Looking Back at an Eclipsed Earth (2007-06-10)

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.

Image credit: CNES
The Merope Reflection Nebula (2007-06-11)

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.

Image credit: Jean-Charles
Cuillandre
Shuttle Plume (2007-06-12)

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.
Warped Sky: Star Trails Panorama (2007-06-13)

What's happened to the sky?  A time warp, of sorts, and a digital space warp too.  The time warp occurs because the above image captured in a single frame a four hour exposure of the night sky.  Prominent and picturesque star trails are visible.   The space warp occurs because the above image is actually a full 360 degree panorama, horizontally compressed to fit your browser.   As the Earth rotated, stars appeared to circle both the South Celestial Pole, on the left, and the North Celestial Pole, which occurs just below the horizon on the right.   The above image captured the sky over Mudgee, New South Wales, Australia, including the domes of two large telescopes artificially lit by red light. A horizontally unwarped image is visible by clicking on the above image.

Image credit: Peter Ward
vdB 152: Reflection Nebula in Cepheus (2007-06-14)

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.

Image credit: Giovanni Benintende
Messier 96 (2007-06-15)

Dust lanes seem to swirl around the core of Messier 96 in this colorful, detailed portrait of the beautiful island universe. Of course M96 is a spiral galaxy, and counting the faint arms extending beyond the brighter central region it spans 100 thousand light-years or so, about the size of our own Milky Way. M96 is known to be 38 million light-years distant, a dominant member of the Leo I galaxy group. Background galaxies and smaller Leo I group members can be found by examining the picture, but accomplished astro-imager Adam Block notes he is most intrigued by the edge-on spiral galaxy that apparently lies behind the outer spiral arm near the 10 o'clock position. The edge-on spiral appears to be about 1/5 the size of M96. If the spiral is similar in actual size to M96, then it lies about 5 times farther away.

Image credit: Adam Block
(Caelum Observatory),

Acknowledgement: R. Jay GaBany
Lunar Orbiter Views Crater Copernicus (2007-06-16)

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!