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A different astronomy and space science related image is featured each day, along with a brief explanation.
Contemplating the Sun
Have you contemplated your home star recently? Featured here, a Sun partially eclipsed on the top left by the Moon is also seen eclipsed by earthlings contemplating the eclipse below. The spectacular menagerie of silhouettes was taken in 2012 from the Glen Canyon National Recreation Area near Page, Arizona, USA, where park rangers and astronomers expounded on the unusual event to interested gatherers. Also faintly visible on the Sun's disk, just to the lower right of the dark Moon's disk, is a group of sunspots. Although a partial solar eclipse by the Moon is indeed a good chance to contemplate the Sun, a great chance -- and one that is significantly more rare -- will occur next week when the Sun undergoes a partial eclipse by the planet Mercury.
Fermi's Gamma-ray Moon
If you could only see gamma-rays, photons with up to a billion or more times the energy of visible light, the Moon would be brighter than the Sun! That startling notion underlies this novel image of the Moon, based on data collected by the Fermi Gamma-ray Space Telescope's Large Area Telescope (LAT) instrument during its first seven years of operation (2008-2015). Fermi's gamma-ray vision doesn't distinguish details on the lunar surface, but a gamma-ray glow consistent with the Moon's size and position is clearly found at the center of the false color map. The brightest pixels correspond to the most significant detections of lunar gamma-rays. Why is the gamma-ray Moon so bright? High-energy charged particles streaming through the Solar System known as cosmic rays constantly bombard the lunar surface, unprotected by a magnetic field, generating the gamma-ray glow. Because the cosmic rays come from all sides, the gamma-ray Moon is always full and does not go through phases. The first gamma-ray image of the Moon was captured by the EGRET instrument onboard the Compton Gamma-ray Observatory, launched 25 years ago.
Omega Centauri: The Brightest Globular Star Cluster
This huge ball of stars predates our Sun. Long before humankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy. Of the 200 or so globular clusters that survive today, Omega Centauri is the largest, containing over ten million stars. Omega Centauri is also the brightest globular cluster, at apparent visual magnitude 3.9 it is visible to southern observers with the unaided eye. Cataloged as NGC 5139, Omega Centauri is about 18,000 light-years away and 150 light-years in diameter. Unlike many other globular clusters, the stars in Omega Centauri show several different ages and trace chemical abundances, indicating that the globular star cluster has a complex history over its 12 billion year age.
Simeis 147: Supernova Remnant
It's easy to get lost following the intricate strands of the Spaghetti Nebula. A supernova remnant cataloged as Simeis 147 and Sh2-240, the glowing gas filaments cover nearly 3 degrees -- 6 full moons -- on the sky. That's about 150 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. This sharp composite includes image data taken through a narrow-band filter to highlight emission from hydrogen atoms tracing the shocked, glowing gas. The supernova remnant has an estimated age of about 40,000 years, meaning light from the massive stellar explosion first reached Earth about 40,000 years ago. But the expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.
Milky Way in Moonlight
A waning crescent moon, early morning twilight, and Al Hamra's city lights on the horizon can't hide the central Milky Way in this skyscape from planet Earth. Captured in a single exposure, the dreamlike scene looks southward across the region's grand canyon from Jabal Shams (Sun Mountain), near the highest peak in Oman, on the Arabian Peninsula. Mist, moonlight, and shadows still play along the steep canyon walls. Dark rifts along the luminous band of the Milky Way are the galaxy's cosmic dust clouds. Typically hundreds of light-years distant, they obscure starlight along the galactic plane, viewed edge-on from the Solar System's perspective.
The Comet, the Owl, and the Galaxy
Comet C/2014 S2 (PanSTARRS) poses for a Messier moment in this telescopic snapshot from April 18. In fact it shares the 1.5 degree wide field-of-view with two well-known entries in the 18th century comet-hunting astronomer's famous catalog. Outward bound and sweeping through northern skies just below the Big Dipper, the fading visitor to the inner Solar System was about 18 light-minutes from our fair planet. Dusty, edge-on spiral galaxy Messier 108 (upper right) is more like 45 million light-years away. A planetary nebula with an aging but intensely hot central star, the owlish Messier 97 is only about 12 thousand light-years distant though, still well within our own Milky Way galaxy. Astronomers expect the orbit of this comet PanSTARRS to return it to the inner Solar System around the year 4226.
Asperatus Clouds Over New Zealand
What kind of clouds are these? Although their cause is presently unknown, such unusual atmospheric structures, as menacing as they might seem, do not appear to be harbingers of meteorological doom. Known informally as Undulatus asperatus clouds, they can be stunning in appearance, unusual in occurrence, are relatively unstudied, and have even been suggested as a new type of cloud. Whereas most low cloud decks are flat bottomed, asperatus clouds appear to have significant vertical structure underneath. Speculation therefore holds that asperatus clouds might be related to lenticular clouds that form near mountains, or mammatus clouds associated with thunderstorms, or perhaps a foehn wind -- a type of dry downward wind that flows off mountains. Such a wind called the Canterbury arch streams toward the east coast of New Zealand's South Island. The featured image, taken above Hanmer Springs in Canterbury, New Zealand, in 2005, shows great detail partly because sunlight illuminates the undulating clouds from the side.
Mercury and Crescent Moon Set
Innermost planet Mercury and a thin crescent Moon are never found far from the Sun in planet Earth's skies. Taken near dusk on April 8, this colorful evening skyscape shows them both setting toward the western horizon just after the Sun. The broad Tagus River and city lights of Lisbon, Portugal run through the foreground under the serene twilight sky. Near perigee or closest approach to Earth, the Moon's bright, slender crescent represents about 3 percent of the lunar disk in sunlight. Of course as seen from the Moon, a nearly full Earth would light up the lunar night, and that strong perigee earthshine makes the rest of the lunar disk visible in this scene. Bright Mercury stays well above the western horizon at sunset for northern skywatchers in the coming days. The fleeting planet reaches maximum elongation, or angular distance from the Sun, on April 18. But Mercury will swing back toward the Sun and actually cross the solar disk on May 9, the first transit of Mercury since November 8, 2006.
Orion in Red and Blue
When did Orion become so flashy? This colorful rendition of part of the constellation of Orion comes from red light emitted by hydrogen and sulfur (SII), and blue-green light emitted by oxygen (OIII). Hues on the featured image were then digitally reassigned to be indicative of their elemental origins -- but also striking to the human eye. The breathtaking composite was painstakingly composed from hundreds of images which took nearly 200 hours to collect. Pictured, Barnard's Loop, across the image bottom, appears to cradle interstellar constructs including the intricate Orion Nebula seen just right of center. The Flame Nebula can also be quickly located, but it takes a careful eye to identify the slight indentation of the dark Horsehead Nebula. As to Orion's flashiness -- a leading explanation for the origin of Barnard's Loop is a supernova blast that occurred about two million years ago.
The Comet and the Star Cluster
Comet Linear has become unexpectedly bright. The comet, discovered in 2000, underwent a 100-fold outburst just a week before it passed a mere 14 lunar distances from Earth late last month. The comet was captured here last week at about magnitude 6 -- just bright enough to be seen by the unaided eye -- passing in front of the distant globular star cluster M14. Comet 252/P LINEAR is one of a rare group of comets that vacillate between the Earth and Jupiter every 5 years. How the comet will evolve from here is unknown, but hopes run high that it will remain a good object for binoculars in northern skies for the next week or two.
A Green Flash of Spring
Taken on March 20 from the top of Haleakala on the isle of Maui, planet Earth, the first sunrise of northern spring is pictured in this vacation snapshot. The telephoto view from the volcanic caldera above a sea of clouds also captures an elusive green flash near the Sun's upper limb. Atmospheric layers with sharp temperature changes cause the colorful flash as the Sun rises behind a distant cloud bank. Refraction along sight lines through the layers creates multiple distorted images of the Sun, and for a moment, can visibly deflect shorter wavelength green light.
Wolf-Lundmark-Melotte
Named for the three astronomers instrumental in its discovery and identification, Wolf - Lundmark - Melotte (WLM) is a lonely dwarf galaxy. Seen toward the mostly southern constellation Cetus, about 3 million light-years from the Milky Way, it is one of the most remote members of our local galaxy group. In fact, it may never have interacted with any other local group galaxy. Still, telltale pinkish star forming regions and hot, young, bluish stars speckle the isolated island universe. Older, cool yellowish stars fade into the small galaxy's halo, extending about 8,000 light-years across. This sharp portrait of WLM was captured by the 268-megapixel OmegaCAM widefield imager and survey telescope at ESO's Paranal Observatory.
Lucid Dreaming
Is this the real world? Or is it just fantasy? The truth started with a dream -- a dream that the spectacular Seljarlandsfoss waterfall in southern Iceland could be photographed with a backdrop of an aurora-filled sky. Soon after a promising space weather report, the visionary astrophotographer and his partner sprang into action. After arriving, capturing an image of the background sky, complete with a cool green aurora, turned out to be the easy part. The hard part was capturing the waterfall itself, for one reason because mist kept fogging the lens! Easy come, easy go -- it took about 100 times where someone had to go back to the camera -- on a cold night and over slippery rocks -- to see how the last exposure turned out, wipe the lens, and reset the camera for the next try. Later, the best images of land and sky were digitally combined. Visible in the sky, even well behind the aurora, are numerous stars of the northern sky. The resulting title -- given by the astrophotographer -- was influenced by a dream-like quality of the resulting image, possibly combined with the knowledge that some things really mattered in this effort to make a dream come true.
Pluto s Bladed Terrain in 3D
Get out your red/blue glasses and gaze across a mountainous region informally known as Tartarus Dorsa. This scene sprawls some 300 kilometers (about 180 miles) across the Plutonian landscape. The color anaglyph creates a stereo view by combining parts of two images taken about 14 minutes apart during the New Horizons historic flyby of Pluto last July. Along with shadows near the terminator, or line between Pluto's dim day and night, the 3D perspective emphasizes the alignment of narrow, steep ridges. The region's remarkable bladed landforms typically extend 500 meters high and are 3 to 5 kilometers apart. Referring to a part of Hades in ancient Greek mythology, Tartarus Dorsa borders Tombaugh Regio to the east.
Big Dipper to Southern Cross
Welcome to an equatorial night. This remarkable 24 frame night skyscape was captured from Maba Beach on the Indonesian island of Halmahera during the evening of March 4. Seen from a mere 0.7 degrees northern latitude, both famous northern and southern asterisms and navigational aids lie within the panoramic view. The Big Dipper is on the far left and Southern Cross at the far right. Beyond the fading campfire on that night a yellow-orange celestial triangle is set by Mars, Antares, and Saturn. It stands above the rising central Milky Way, or "Miett" in the local Maba language. Of course, you can follow the pole pointing stars in the cup of the Big Dipper or body of the Southern Cross to the north and south celestial poles. Both lie just at the horizon in the view from the island's equatorial beach.
Moon over Makemake
Makemake, second brightest dwarf planet of the Kuiper belt, has a moon. Nicknamed MK2, Makemake's moon reflects sunlight with a charcoal-dark surface, about 1,300 times fainter than its parent body. Still, it was spotted in Hubble Space Telescope observations intended to search for faint companions with the same technique used to find the small satellites of Pluto. Just as for Pluto and its satellites, further observations of Makemake and orbiting moon will measure the system's mass and density and allow a broader understanding of the distant worlds. About 160 kilometers (100 miles) across compared to Makemake's 1,400 kilometer diameter, MK2's relative size and contrast are shown in this artist's vision. An imagined scene of an unexplored frontier of the Solar System, it looks back from a spacecraft's vantage as the dim Sun shines along the Milky Way. Of course, the Sun is over 50 times farther from Makemake than it is from planet Earth.
A Dust Angel Nebula
The combined light of stars along the Milky Way are reflected by these cosmic dust clouds that soar some 300 light-years or so above the plane of our galaxy. Dubbed the Angel Nebula, the faint apparition is part of an expansive complex of dim and relatively unexplored, diffuse molecular clouds. Commonly found at high galactic latitudes, the dusty galactic cirrus can be traced over large regions toward the North and South Galactic poles. Along with the refection of starlight, studies indicate the dust clouds produce a faint reddish luminescence, as interstellar dust grains convert invisible ultraviolet radiation to visible red light. Also capturing nearby Milky Way stars and an array of distant background galaxies, the deep, wide-field 3x5 degree image spans about 10 Full Moons across planet Earth's sky toward the constellation Ursa Major.
NGC 6872: A Stretched Spiral Galaxy
What makes this spiral galaxy so long? Measuring over 700,000 light years across from top to bottom, NGC 6872, also known as the Condor galaxy, is one of the most elongated barred spiral galaxies known. The galaxy's protracted shape likely results from its continuing collision with the smaller galaxy IC 4970, visible just above center. Of particular interest is NGC 6872's spiral arm on the upper left, as pictured here, which exhibits an unusually high amount of blue star forming regions. The light we see today left these colliding giants before the days of the dinosaurs, about 300 million years ago. NGC 6872 is visible with a small telescope toward the constellation of the Peacock (Pavo).
M16: Pillars of Star Creation
Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars' end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away. The pillars of creation were imaged again in 2007 by the orbiting Spitzer Space Telescope in infrared light, leading to the conjecture that the pillars may already have been destroyed by a local supernova, but light from that event has yet to reach the Earth.
NGC 7635: The Bubble Nebula
Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 7 light-year diameter bubble offers evidence of violent processes at work. Above and left of the Bubble's center is a hot, O-type star, several hundred thousand times more luminous and around 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula and associated cloud complex lie a mere 7,100 light-years away toward the boastful constellation Cassiopeia. This sharp, tantalizing view of the cosmic bubble is a composite of Hubble Space Telescope image data from 2016, released to celebrate the 26th anniversary of Hubble's launch.
Galaxy Einstein Ring
Can one galaxy hide behind another? Not in the case of SDP.81. Here the foreground galaxy, shown in blue in an image taken by the Hubble Space Telescope, acts like a huge gravitational lens, pulling light from a background galaxy, shown in red in an image taken in radio waves by the Atacama Large Millimeter Array (ALMA), around it, keeping it visible. The alignment is so precise that the distant galaxy is distorted into part of a ring around the foreground galaxy, a formation known as an Einstein ring. Detailed analysis of the gravitational lens distortions indicate that a small dark satellite galaxy participates in the deflections, bolstering indication that many satellite galaxies are quite dim and dominated by dark matter. That small galaxy is depicted by a small white dot on the left. Although spanning only a few arcseconds, the featured Einstein ring is really tens of thousands of light years across.
Heliopause Electrostatic Rapid Transit System
Want to take a fast trip to the edge of the Solar System? Consider a ride on a Heliopause Electrostatic Rapid Transit System (HERTS). The concept is currently being tested and it might take only 10 to 15 years to make the trip of over 100 Astronomical Units (15 billion kilometers). That's fast compared to the 35 years it took Voyager 1, presently humanity's most distant spacecraft, to approach the heliopause or outer boundary of the influence of the solar wind. HERTS would use an advanced electric solar sail that works by extending multiple, 20 kilometer or so long, 1 millimeter thin, positively charged wires from a rotating spacecraft. The electrostatic force generated repels fast moving solar wind protons to create thrust. Compared to a reflective solar light sail, another propellantless deep space propulsion system, the electric solar wind sail could continue to accelerate at greater distances from the Sun, still developing thrust as it cruised toward the outer planets.
Full Venus and Crescent Moon Rise
Inner planet Venus and a thin crescent Moon are never found far from the Sun in planet Earth's skies. Taken near dawn on April 6, this timelapse composite shows them both rising just before the Sun. The mountaintop Teide Observatory domes on the fortunate island of Tenerife appear in silhouette against the twilight. In fact, the series of telephoto exposures follows the occultation of Venus by the Moon in three frames. Far from Earth in its orbit and in a nearly full phase, Venus was 96 percent illuminated. Near perigee or closest approach to Earth, the Moon's slender crescent represents about 2 percent of the lunar disk in sunlight. Seen in the first two exposures, the brilliant morning star only vanishes in the third as it winks out behind the bright lunar limb. Five minutes of the dramatic occultation at dawn is compressed into 15 seconds in this timelapse video (vimeo).
Combined Solar Eclipse Corona from Earth and Space
Sometimes, a total eclipse is a good time to eye the Sun. Taking advantage of an unusual juxtaposition of Earth, Moon and Sun, the featured image depicts the total solar eclipse that occurred last month as it appeared -- nearly simultaneously -- from both Earth and space. The innermost image shows the total eclipse from the ground, with the central pupil created by the bright Sun covered by a comparatively dark Moon. Surrounding the blocked solar disk is the tenuous corona of Sun imaged in white light, easily visible from the ground only during an eclipse. Normally, this corona is hard to track far from the Sun, but the featured montage matches it to false-colored observations of the Sun from NASA and ESA's space-based, Sun-orbiting, Solar and Heliospheric Observatory (SOHO). Observations like this allow the study of the constantly changing magnetic activity both near and far from the Sun, the same activity that ultimately drives Earth's auroras.
Cassini Approaches Saturn
Cassini, a robot spacecraft launched in 1997 by NASA, became close enough in 2002 to resolve many rings and moons of its destination planet: Saturn. At that time, Cassini snapped several images during an engineering test. Several of those images were combined into the contrast-enhanced color composite featured here. Saturn's rings and cloud-tops are visible toward the image bottom, while Titan, its largest moon, is visible as the speck toward the top. When arriving at Saturn in July 2004, the Cassini orbiter began to circle and study the Saturnian system. A highlight was when Cassini launched the Huygens probe that made an unprecedented landing on Titan in 2005, sending back detailed pictures. Now nearing the end of its mission, Cassini is scheduled to embark on a Grand Finale phase in late 2016 where it will repeatedly dive between the giant planet and its innermost rings.
Lapland Northern Lights
Early spring in the northern hemisphere is good season for aurora hunters. Near an equinox Earth's magnetic field is oriented to favor interactions with the solar wind that trigger the alluring glow of the northern lights. On March 28/29 the skies over Kaunispää Hill, Lapland, Finland did not disappoint. That night's expansive auroral curtains are captured in this striking panoramic view that covers a full 360 degrees. Local skywatchers were mesmerized by bright displays lasted throughout the dark hours, shimmering with colors easily visible to the naked eye.
Auroras and the Magnetosphere of Jupiter
Jupiter has auroras. Like near the Earth, the magnetic field of our Solar System's largest planet compresses when impacted by a gust of charged particles from the Sun. This magnetic compression funnels charged particles towards Jupiter's poles and down into the atmosphere. There, electrons are temporarily excited or knocked away from atmospheric gases, after which, when de-exciting or recombining with atmospheric ions, auroral light is emitted. The featured illustration portrays the magnificent magnetosphere around Jupiter in action. In the inset image released last month, the Earth-orbiting Chandra X-ray Observatory shows unexpectedly powerful X-ray light emitted by Jovian auroras, depicted in false-colored purple. That Chandra inset is superposed over an optical image taken at a different time by the Hubble Space Telescope. This aurora on Jupiter was seen in October 2011, several days after the Sun emitted a powerful Coronal Mass Ejection (CME).
Close up of the Bubble Nebula
It's the bubble versus the cloud. NGC 7635, the Bubble Nebula, is being pushed out by the stellar wind of massive central star BD 602522. Next door, though, lives a giant molecular cloud, visible to the right. At this place in space, an irresistible force meets an immovable object in an interesting way. The cloud is able to contain the expansion of the bubble gas, but gets blasted by the hot radiation from the bubble's central star. The radiation heats up dense regions of the molecular cloud causing it to glow. The Bubble Nebula, featured here in scientifically mapped colors to bring up contrast, is about 10 light-years across and part of a much larger complex of stars and shells. The Bubble Nebula can be seen with a small telescope towards the constellation of the Queen of Aethiopia (Cassiopeia).
Europa: Discover Life Under the Ice
Looking for an interplanetary vacation destination? Consider a visit to Europa, one of the Solar System's most tantalizing moons. Ice-covered Europa follows an elliptical path in its 85 hour orbit around our ruling gas giant Jupiter. Heat generated from strong tidal flexing by Jupiter's gravity keeps Europa's salty subsurface ocean liquid all year round. That also means even in the absence of sunlight Europa has energy that could support simple life forms. Unfortunately, it is currently not possible to make reservations at restaurants on Europa, where you might enjoy a dish of the local extreme shrimp. But you can always choose another destination from Visions of the Future.
NGC 6188 and NGC 6164
Fantastic shapes lurk in clouds of glowing gas in the giant star forming region NGC 6188. The emission nebula is found about 4,000 light years away near the edge of a large molecular cloud unseen at visible wavelengths, in the southern constellation Ara. Massive, young stars of the embedded Ara OB1 association were formed in that region only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. Joining NGC 6188 on this cosmic canvas, visible toward the lower right, is rare emission nebula NGC 6164, also created by one of the region's massive O-type stars. Similar in appearance to many planetary nebulae, NGC 6164's striking, symmetric gaseous shroud and faint halo surround its bright central star near the bottom edge. The impressively wide field of view spans over 3 degrees (six full Moons), corresponding to over 200 light years at the estimated distance of NGC 6188. Three image sets have been included in the featured composite.
