Dark Matter in a Simulated UniverseOctober 31, 2017
Is our universe haunted? It might look that way on this dark matter map. The gravity of unseen dark matter is the leading explanation for why galaxies rotate so fast, why galaxies orbit clusters so fast, why gravitational lenses so strongly deflect light, and why visible matter is distributed as it is both in the local universe and on the cosmic microwave background. The featured image from the American Museum of Natural History's Hayden Planetarium Space Show Dark Universe highlights one example of how pervasive dark matter might haunt our universe. In this frame from a detailed computer simulation, complex filaments of dark matter, shown in black, are strewn about the universe like spider webs, while the relatively rare clumps of familiar baryonic matter are colored orange. These simulations are good statistical matches to astronomical observations. In what is perhaps a scarier turn of events, dark matter -- although quite strange and in an unknown form -- is no longer thought to be the strangest source of gravity in the universe. That honor now falls to dark energy, a more uniform source of repulsive gravity that seems to now dominate the expansion of the entire universe.
Ghost Aurora over CanadaOctober 31, 2016
What does this aurora look like to you? While braving the cold to watch the skies above northern Canada early one morning in 2013, a most unusual aurora appeared. The aurora definitely appeared to be shaped like something , but what? Two ghostly possibilities recorded by the astrophotographer were "witch" and "goddess of dawn", but please feel free to suggest your own Halloween-enhanced impressions. Regardless of fantastical pareidolic interpretations, the pictured aurora had a typical green color and was surely caused by the scientifically commonplace action of high energy particles from space interacting with oxygen in Earth's upper atmosphere. In the image foreground, at the bottom, is a frozen Alexandra Falls, while evergreen trees cross the middle.
Haunting the Cepheus FlareOctober 28, 2016
Spooky shapes seem to haunt this jeweled expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds faintly visible in dimly reflected starlight. Far from your own neighborhood on planet Earth, they lurk along the plane of the Milky Way at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across and brighter than the other ghostly apparitions, vdB 141 or Sh2-136 is also known as the Ghost Nebula, seen at the right of the starry field of view. Within the nebula are the telltale signs of dense cores collapsing in the early stages of star formation.
Ghosts and Star TrailsOctober 31, 2015
Don't be scared. Stars won't fall from the sky and ghosts won't really haunt your neighborhood tonight. But it looks like they might be doing just that in this eerie picture of an eccentric old abandoned house in moonlight. A treat for the eye the image is a trick of stacked multiple exposures, 60 frames exposed for 25 seconds each. While the digital frames were recorded with a camera fixed to a tripod stars traced concentric arcs about the north celestial pole, only a reflection of planet Earth's rotation on its axis. Conveniently marked by bright star Polaris, the pole could be positioned above the peaks of the deserted dwelling. Wrapped in a blanket to stay warm, the photographer's own movements during the exposures were blended into the ghostly apparitions. Of course, the grinning Jack-o-Lantern is there to wish you a safe and Happy Halloween!
The Witch Head NebulaOctober 30, 2015
Double, double toil and trouble; Fire burn, and cauldron bubble .... maybe Macbeth should have consulted the Witch Head Nebula. A suggestively shaped reflection nebula, this cosmic crone is about 800 light-years away though. Its frightening visage seems to glare toward nearby bright star Rigel in Orion, just off the right edge of this frame. More formally known as IC 2118, the interstellar cloud of dust and gas is nearly 70 light-years across, its dust grains reflecting Rigel's starlight. In this composite portrait, the nebula's color is caused not only by the star's intense bluish light but because the dust grains scatter blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in planet Earth's atmosphere are molecules of nitrogen and oxygen.
The Day After MarsNovember 1, 2014
Explanation: October 31, 1938 was the day after Martians encountered planet Earth, and everything was calm. Reports of the invasion were revealed to be part of a Halloween radio drama, the now famous broadcast based on H.G. Wells' scifi novel War of the Worlds. On Mars October 20, 2014 was calm too, the day after its close encounter with Comet Siding Spring. Not a hoax, this comet really did come within 86,700 miles or so of Mars, about 1/3 the Earth-Moon distance. Earth's spacecraft and rovers in Mars orbit and on the surface reported no ill effects though, and had a ringside seat as a visitor from the outer solar system passed by. Spanning over 2 degrees against stars of the constellation Ophiuchus, this colorful telescopic snapshot captures our view of Mars on the day after. Bluish star 51 Ophiuchi is at the upper right and the comet is just emerging from the Red Planet's bright glare.
A Spectre in the Eastern VeilOctober 30, 2014
Explanation: Frightening forms and scary faces are a mark of the Halloween season. They also haunt this cosmic close-up of the eastern Veil Nebula. The Veil Nebula itself is a large supernova remnant, the expanding debris cloud from the death explosion of a massive star. While the Veil is roughly circular in shape and covers nearly 3 degrees on the sky in the constellation Cygnus, this portion of the eastern Veil spans only 1/2 degree, about the apparent size of the Moon. That translates to 12 light-years at the Veil's estimated distance, a reassuring 1,400 light-years from planet Earth. In the composite of image data recorded through broad and narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen atoms in blue-green hues. Of course, in the western part of the Veil lies another seasonal apparition, the Witch's Broom.
Night on a Spooky PlanetOctober 31, 2013
Explanation: What spooky planet is this? Planet Earth of course, on the dark and stormy night of September 12 at Hverir, a geothermally active area along the volcanic landscape in northeastern Iceland. Geomagnetic storms produced the auroral display in the starry night sky while ghostly towers of steam and gas venting from fumaroles danced against the eerie greenish light. Tonight, there is still a chance for geomagnetic storms triggered by recent solar activity, so high-latitude skygazers should beware. And ghostly shapes may dance in your neighborhood, too. Have a safe and Happy Halloween!
VdB 152: A Ghost in CepheusOctober 31, 2012
Explanation: Described as a "dusty curtain" or "ghostly apparition", mysterious reflection nebula VdB 152 really is very faint. Far from your neighborhood on this Halloween Night, the cosmic phantom is nearly 1,400 light-years away. Also catalogued as Ced 201, it lies along the northern Milky Way in the royal constellation Cepheus. Near the edge of a large molecular cloud, pockets of interstellar dust in the region block light from background stars or scatter light from the embedded bright star 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 space is very different from the cloud's velocity. This deep telescopic image of the region spans about 7 light-years.
Ghost of the Cepheus FlareOctober 31, 2011
Explanation: Spooky shapes seem to haunt this starry expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds faintly visible in dimly reflected starlight. Far from your own neighborhood on planet Earth, they lurk at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across the ghostly nebula and relatively isolated Bok globule, also known as vdB 141 or Sh2-136, is near the center of the field. The core of the dark cloud on the right is collapsing and is likely a binary star system in the early stages of formation. Even so, if the spooky shapes could talk, they might well wish you a happy Halloween.
Halloween and the Ghost Head NebulaOctober 31, 2010
Explanation: Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With a modern calendar, however, the real cross-quarter day will occur next week. Another cross-quarter day is Groundhog's Day. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead. Perhaps a fitting tribute to this ancient holiday is this view of the Ghost Head Nebula taken with the Hubble Space Telescope. Similar to the icon of a fictional ghost, NGC 2080 is actually a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy. The Ghost Head Nebula spans about 50 light-years and is shown in representative colors.
Star Trails and the Captain's GhostOctober 29, 2010
Explanation: Look closely at this surreal nightscape. In the dreamlike scene, star trails arc over an old ship run aground on a beach near Gytheio, Peloponnesus in southern Greece. Could that be the captain's ghost haunting the beach, gazing forlornly at the decaying wreck, hovering over starlight reflected in still water? Actually, the ephemeral shape is the photographer. Instead of a single long exposure to record the motion of the stars as the Earth rotates on its axis, the picture is composed of 90 consecutive images, each exposure 90 seconds long. Digitally stacking the individual exposures then reconstructs the star trails. It also creates a ghostly, semi-transparent figure of the photographer who was captured standing on the beach in only one of the exposures.
Halloween's MoonNovember 5, 2009
Explanation: Illuminating the landscape all through the night of November 2nd, this week's bright Full Moon was known in the northern hemisphere as a Hunter's Moon. But this dramatic view of the shining lunar orb, from Sobreda, Portugal, was captured just a few nights earlier, on Halloween. In the spirit of the season, the image plays a little trick. The picture is actually two digital photos - one short and one long exposure. They were combined to bring out the details of the bright lunar surface and the fainter features in the dark, surrounding clouds, in a single image. Of course, you may recognize some of the spookier shapes in the clouds as having visited your neighborhood last week, along with Halloween's Moon.
A Witch by StarlightOctober 31, 2008
Explanation: By starlight this eerie visage shines in the dark, a crooked profile evoking its popular name, the Witch Head Nebula. In fact, this entrancing telescopic portrait gives the impression the witch has fixed her gaze on Orion's bright supergiant star Rigel. Spanning over 50 light-years, the dusty cosmic cloud strongly reflects nearby Rigel's blue light, giving it the characteristic color of a reflection nebula. Cataloged as IC 2118, the Witch Head Nebula is about 1,000 light-years away. Of course, you might see a witch this scary tonight, but don't panic. Have a safe and Happy Halloween!
SH2 136: A Spooky NebulaOctober 31, 2006
Explanation: The dark nebula SH2-136 appears to be celebrating Halloween all of the time. The complex process of star formation create dust clouds of many shapes and sizes -- it is human perception that might identify a ghoulish creature, on the right of the above image, chasing humans. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With our modern calendar, however, the real cross-quarter day will occur next week. Other cross-quarter markers include Groundhog Day and Walpurgis Night.
Martian HalloweenOctober 31, 2005
Explanation: From sunset to sunrise, an unusually bright yellowish orb will hang in the sky this Halloween: Mars. Yesterday, Earth passed Mars as they orbited the Sun, bringing Mars closer than it will be for the next thirteen years. Tonight though, Mars will be nearly as bright as last night, a beacon of extraterrestrial spookiness. Opposite the Sun, Mars will rise just when the Sun sets, set just when the Sun rises, and be visible the entire night. Mars will not always be the brightest object in tonight's sky, though. Brighter than even Mars, almost spooky Venus will light up the western horizon for a brief time just after sunset. Please have a safe and happy All Hallows Eve.
Pumpkin MoonOctober 31, 2004
Explanation: Does this look familiar? Red and orange hues haunting the face of the Moon should remind you of the October 27th total lunar eclipse. Created from exposures taken at intervals of 8.5 minutes during the total eclipse phase, the midpoint of the eclipse corresponds to the central exposure. The play of light across the lunar surface nicely demonstrates that the Earth's shadow is not uniformly dark as it extends into space. In fact, lunar maria and montes are still visible in the dimmed, reddened sunlight scattered into the cone-shaped shadow region, or umbra, by the atmosphere. Still, while processing the pictures into this composite image, astronomer Sebastien Gauthier was reminded of another haunting orange face. Have a safe and happy Halloween!
A Dark and Stormy NightOctober 31, 2003
Explanation: It was a dark and stormy night. But on August 29th the red planet Mars, near its closest approach to Earth in almost 60,000 years, shone brightly in the sky against a background of stars in the constellation Aquarius. In the foreground of this scary view, huge thunder clouds are lit by lightning strokes from within. Mars, of course, has nothing to do with storms on Earth, though both have the power to excite the imagination and wonder of Earthdwellers. And who knows what luminous sights you might see if you go out tonight? Have a safe and Happy Halloween!
Aurora HalloweenOctober 31, 2002
Explanation: For much of the month of October, traveling shock waves from the Sun and solar wind gusts have buffeted planet Earth's magnetosphere. As a result, skywatchers at high latitudes in the northern hemisphere were treated to many displays of the aurora borealis or northern lights. For example, on the first of October this particularly ghostly apparition was photographed looming above the horizon near the town of Inari in northern Finnish Lapland. But the solar wind is dying down for now. So if you just happen to be out tonight and you see such a specter haunting your skies ... it may not be an aurora. Have a safe and happy Halloween!
Perseus Cluster's X-Ray SkullOctober 31, 2000
Explanation: This haunting image from the orbiting Chandra Observatory reveals the Perseus Cluster of Galaxies in x-rays, photons with a thousand or more times the energy of visible light. Three hundred twenty million light-years distant, the Perseus Cluster contains thousands of galaxies, but none of them are seen here. Instead of mere galaxies, a fifty million degree cloud of intracluster gas, itself more massive than all the cluster's galaxies combined, dominates the x-ray view. From this angle, voids and bright knots in the x-ray hot gas cloud lend it a very suggestive appearance. Like eyes in a skull, two dark bubbles flank a bright central source of x-ray emission. A third elongated bubble (at about 5 o'clock) forms a toothless mouth. The bright x-ray source is likely a supermassive black hole at the cluster center with the bubbles blown by explosions of energetic particles ejected from the black hole and expanding into the immense gas cloud. Fittingly, the dark spot forming the skull's "nose" is an x-ray shadow ... the shadow of a large galaxy inexorably falling into the cluster center. Over a hundred thousand light-years across, the Perseus Cluster's x-ray skull is a bit larger than skulls you may see tonight. Have a safe and happy Halloween!
The Cat's Eye NebulaOctober 31, 1999
Explanation: Three thousand light-years away, a dying star throws off shells of glowing gas. This image from the Hubble Space Telescope reveals The Cat's Eye Nebula to be one of the most complex planetary nebulae known. In fact, the features seen in the Cat's Eye are so complex that astronomers suspect the bright central object may actually be a binary star system. The term planetary nebula, used to describe this general class of objects, is misleading. Although these objects may appear round and planet-like in small telescopes, high resolution images reveal them to be stars surrounded by cocoons of gas blown off in the late stages of stellar evolution. On planet Earth, of course, cats and other creatures may be on the prowl tonight. Keep your eyes peeled and have a safe and happy Halloween!
Bats And The Barren MoonOctober 31, 1998
Explanation: This picture, taken as the Apollo 17 astronauts orbited the Moon in 1972, depicts the stark lunar surface around the Eratosthenes and Copernicus craters. Images of a Moon devoid of life are familiar to denizens of the space age. Contrary to this modern perception, life on the Moon was reported in August of 1835 in a series of sensational stories first published by the New York Sun - apparently intended to improve the paper's circulation. These descriptions of lunar life received broad credence and became one of the most spectacular hoaxes in history. Supposedly based on telescopic observations, the stories featured full, lavish accounts of a Moon with oceans and beaches, teeming with plant and animal life and climaxing with reported sightings of winged, furry, human-like creatures resembling bats ! Within a month the trick had been revealed but the newspaper continued to enjoy an increased readership. For now ... have a safe and happy Halloween !
Haunting MarsOctober 31, 1997
Explanation: This Halloween, the news about Mars is good news - Mars Global Surveyor will resume aerobraking into a mapping orbit around the haunting red planet. Wide angle cameras onboard the spacecraft recently recorded this shadowy image of Olympus Mons, the Solar System's largest volcano, from an altitude of over 100 miles. The summit depression or caldera of Olympus Mons is about 40 miles across and 15 miles above the Martian surface. On Halloween Night in 1938, Mars also made the news when Orson Welles' radio theatre adaptation of H.G. Wells' "War of the Worlds" - a fictional account of invaders from Mars - was dramatized as a live news report. The performance was so convincing it tricked some listeners, but most who heard the broadcast felt it was a treat. Have a happy and safe Halloween!
A Halloween Invasion from MarsNASA - October 31, 1995
Explanation: Orson Welles became an instant legend on Halloween in 1938 for his radio dramatization of H.G. Wells' "War of the Worlds". Some listeners who did not realize it was a theatrical production were driven to near panic by this fictional account of invaders from Mars. In the story, as in the above Hubble Space Telescope image, Mars was at "opposition", its point of closest approach to the Earth, a distance of some 65 million miles. For the Martians, it was imagined that this was a good time to invade. For astronomers, opposition is a good time to study the red planet and this HST image, represents the clearest view of Mars ever for an Earth telescope. The icy north polar cap is visible at the top of the picture as well as a veil of white clouds along the planet's left edge. The dark markings represent areas where the reddish tinged dust characteristic of the surface has been blown away by the Martian winds.
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