• ESO/G.Hüdepohl

    Gerhard Hudepohl, a photographer at the European Southern Observatory in Chile, has captured a green flash from the moon, instead of the Sun. The photographs are very probably the best ever taken of the moon's green flash.

    See the moon's green flash

    By John Roach, Contributing Writer, NBC News

    Many a beach vacation cocktail hour is spent gazing at the sunset in hopes of catching the elusive green flash that occurs just before the last bit of sun disappears below the horizon. Now, a photographer at the European Southern Observatory has caught the green flash from the moon.

    The series of images was made by Gerhard Hüdepohl, a photo ambassador at the observatory in Chile's Atacama Desert. An image advisory describes them "as very probably the best ever taken of the moon's green flash."

    The effect is due to how the Earth's atmosphere bends, or refracts, light, an effect that is greater in the lower, denser layers of the atmosphere.

    ESO explains:

    "Shorter wavelengths of light are bent more than longer wavelengths, so that the green light from the Sun or moon appears to be coming from a slightly higher position than the orange and red light, from the point of view of an observer. When the conditions are just right, with an additional mirage effect due to the temperature gradient in the atmosphere, the elusive green flash is briefly visible at the upper edge of the solar or lunar disc when it is close to the horizon."

    For more details on the physics and history of the green flash, check out this explanation on the Hyperphysics website and then schedule a beach vacation, relax and look for it yourself.

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

     

     

     

  • NASA, ESA and the Hubble Heritage Team (STScI/AURA)

    This image of a pair of interacting galaxies called Arp 273 was released to celebrate the 21st anniversary of the launch of the Hubble Space Telescope. The distorted shape of the larger of the two galaxies shows signs of tidal interactions with the smaller of the two. It is thought that the smaller galaxy has actually passed through the larger one.

    A galactic rose for Hubble's anniversary

    By John Roach, Contributing Writer, NBC News

    After 21 years, the Hubble Space Telescope continues to wow the world with mind-bending views of the universe. In celebration of its anniversary, the wonder continues with this gift of a galactic rose formed by a group of interacting galaxies roughly 300 million light years away from Earth.

    In the group, known as Arp 273, the upper, larger of the spiral galaxies, UGC 1810, has a disc that is tidally distorted into a rose-like shape by the gravitational pull of the companion galaxy below it, known as UGC 1813, according to an image advisory.

    The uncommon spiral patterns in the large galaxy are a tell-tale sign of interaction between the two galaxies. For example, the large, outer arm appears partially as a ring, a feature that is seen when interacting galaxies pass through one another. This suggests that the smaller companion galaxy actually dived deeply, but off-center, through UGC 1810.

    Other notable features in the image include:

    • The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and combing back out the other side. How they connect isn't precisely known.
    • A possible mini spiral may be visible in the spiral arms of UGC 1810 to the upper right. Note how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars on one side, to clumpy and extremely blue on the other.
    • The swath of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars, which glow fiercely in ultraviolet light.
    • The smaller galaxy, viewed close to edge-on, shows signs of intense star formation in its nucleus that was perhaps triggered by the encounter with the companion galaxy.

    The larger galaxy in the UGC 1810-UGC 1813 pair has a mass that is about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of the companion galaxy produces the lopsided structure in the main spiral.

    The Hubble Space Telescope was launched from space shuttle Discovery on April 24, 1990. It circles the Earth once every 97 minutes. Though its digital postcards routinely wow the world, it hasn't always been smooth sailing, as noted in this photo trip through the telescope's highs and lows.

    NASA astronauts successfully performed a final servicing of the telescope in 2009 that should keep it sending back images for years to come. Meanwhile, the space agency is preparing Hubble's replacement, the James Webb Space Telescope, currently scheduled for launch in 2014. For now, though, let's wish Hubble a happy anniversary and thank it for the galactic rose.

    More stunners from Hubble:

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • Plasmons harnessed for holograms

    Science / AAAS

    Reconstruction of a red apple with a green leaf in three dimensions using surface plasmon holograms

    By John Roach, Contributing Writer, NBC News

    A new technique to produce full-color holograms that stay the same when viewed from any angle could usher in a day when we plop down on the couch and watch 3-D TV without optical illusions.

    Current methods for creating 3-D images are based on producing a separate image for the left and right eyes. "Inside the brain we reconstruct the 3-D, so it is sort of an illusion," optical physicist Satoshi Kawata of Osaka University of Japan explains in a video made available to reporters.

    He and colleagues instead made 3-D color holograms that can be viewed with the naked eye and don't change color no matter what angle they are viewed from. They did this by harnessing so-called surface plasmons, which Kawata describes as "the collective electron oscillations traveling on a very thin metal film."

    The researchers coat the metal film onto a light sensitive material called photoresist that contains a hologram made with red, green, and blue lasers. The photoresist hologram rests on a thin glass plate. A corrugated layer of silver is laid on top of the photoresist to help guide the holograph's light waves.

    The surface plasmons in the metal film are excited using white light. The angle of the incoming light determines which plasmons are excited and diffracted by the hologram, reconstructing the light waves reaching the viewers eyes so that the 3-D image appears.

    "No one has thought to use plasmons for display applications, so it was fun for me," Kawata told Wired Science. "I just wanted to demonstrate that this could be done. But I hope people would be interested in thinking seriously to use this technology for larger-scale 3-D display."

    Before it goes big time, however, the technology needs to be scaled up — the current images are a few centimeters across. In addition, the images are static, not moving picture such as film or TV.

    A paper describing the research appears in the April 8 issue of Science.

    Update for 6:20 p.m. ET: Check out videos of a hologram demonstration and an interview with Kawata, available via EurekAlert.

    Tip o' the Log to Lisa Grossman at Wired Science

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • Supernova emits X-ray stripes

    Chandra X-ray Observatory

    This image comes from a very deep Chandra observation of the Tycho supernova remnant, produced by the explosion of a white dwarf star in our Galaxy. Low-energy X-rays (red) in the image show expanding debris from the supernova explosion and high energy X-rays (blue) show the blast wave, a shell of extremely energetic electrons.

    By John Roach, Contributing Writer, NBC News

    Scientists have discovered X-ray stripes in the remains of a supernova that may be the first direct evidence that these exploded stars can accelerate particles to energies a hundred times higher than those achieved with the Large Hadron Collider, the most powerful particle accelerator on Earth.

    The striking 3-D-esque image of the Tycho supernova remnant was made from a long observation with NASA's Chandra X-ray Observatory. It could explain how some of the extremely energetic particles bombarding the Earth, called cosmic rays, are produced.

    Since cosmic rays are composed of charged particles, like protons and electrons, their direction of motion changes when they encounter magnetic fields throughout the galaxy. As a result, the origin of individual cosmic rays detected on Earth cannot be determined, though supernova remnants have long been considered a good candidate for producing the most energetic cosmic rays in our galaxy.

    The X-ray stripes observed in Tycho provide support for a theory about how magnetic fields can be dramatically amplified in supernova blast waves, producing cosmic rays. According to this theory, the magnetic fields become a tangled mess and the motions of the particles very turbulent near the expanding shock wave at the edge of the supernova. High energy charged particles can bounce back and forth across the shock wave repeatedly, gaining energy with each crossing.

    Theoretical models of the motion of the most energetic particles — which are mostly protons — are predicted to leave a messy network of holes and dense walls corresponding to weak and strong regions of the magnetic field.

    Chandra X-ray Observatory

    The X-ray stripes are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field lines.

    The X-ray stripes discovered by the Chandra researchers are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas, and may be the walls predicted by the theory. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field.

    That said, the regular and almost periodic pattern of the X-ray stripes (image at right) was not predicted by the theory and caught the researchers by surprise. "It could mean that the theory is incomplete, or that there's something else we don’t' understand," Jack Hughes, a professor of physics and astronomy at Rutgers University, said in a statement.

    The size of the holes, or spacing, between the X-ray stripes is thought to correspond to the radius of the spiraling motion of the highest energy protons in the supernova remnant, the researchers say. If so, the spacing corresponds to energies about 100 times higher than reached in the Large Hadron Collider and equal the highest energies of cosmic rays thought to be produced in our galaxy.

    The Tycho supernova remnant is named for the famous Danish astronomer Tycho Brahe, who reported observing the supernova in 1572. It is located in the Milky Way, about 13,000 light years from Earth. Because of its proximity and intrinsic brightness, the supernova was so bright that it could be seen during the daytime with the naked eye.

    The results were published in the Feb. 20. 2011 issue of the Astrophysical Journal Letters.

    More on cosmic rays:

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • NASA JPL, Ed Olsen / Henry Kline

    This collection of images of Ireland positioned in the shape of a clover include visible (left), infrared (center) and microwave (right). They were captured from the AIRS instrument onboard NASA's Aqua satellite on March 3, and revealed a land surface temperature near 50 degrees Fahrenheit.

    Catch a 'three-leaf clover' view of Ireland

    By John Roach, Contributing Writer, NBC News

    In a St. Patrick's Day special, NASA has released a three leaf clover view of Ireland taken by an instrument on its Aqua satellite that sees in near-infrared/visible, infrared, and microwave light.

    The Atmospheric Infrared Sounder measures the temperatures of land, sea, and air to provide a better understanding of what is happening in those environments, the space agency says.

    On March 3, when this trio of images was made, temperatures near the surface of the Emerald Isle were "near normal" for this time of year. In March, the Ireland's average daytime high is 49 degrees F and nighttime lows are 38 degrees F.

    NASA's Aqua satellite circles Earth pole-to-pole 15 times a day in a sun-synchronous orbit to provide data and images to researchers in the Earth, ocean, and atmospheric sciences.

    Cloud top temperatures, for example, provide clues to scientists about the power of the thunderstorms. The colder the clouds are, the higher they are, and the more powerful the thunderstorms, NASA says. When AIRS measures cloud temperatures as cold as or colder than minus 63 degrees F, that indicates high cloud tops, strong convection and the likelihood of powerful thunderstorms.

    For more information on what the three-leaf clover image of Ireland reveals, check out this press release from NASA.

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • Hinode / XRT

    An X-ray image of the sun shows gaping holes in the corona. Plasma escapes to space through these coronal holes.

    Satellite spots the sun's latest leaks

    By John Roach, Contributing Writer, NBC News

    A Japanese-led satellite mission that's studying the sun in extreme ultraviolet and X-ray wavelengths has revealed gaping holes in the solar corona through which plasma can easily escape into space. The so-called coronal holes are the darker areas in this X-ray image — one at the top center and another capping the solar south pole, about where Antarctica is on Earth.

    Scientists believe the sun's magnetic field traps jets of plasma from the sun's surface, heating up the solar atmosphere, or corona, to millions of degrees. Coronal holes represent gaps in the magnetic field, allowing the plasma to stream straight out into space. The lack of trapped plasma also means the holes are relatively cool in temperature, compared to the active regions nearby.

    The Hinode satellite, which made this image, is part of a swarm of scientific instruments dedicated to monitoring the sun to help scientists improve forecasts of space weather. Coronal holes are thought to be the start of the space weather chain that can wreak havoc on Earth by knocking out communications satellites and power grids.

    SpaceWeather.com is one of the best places on the Web to keep yourself up to date on the solar outlook. Today's highlights include the passage of an active sunspot around the sun's far side, plus an amazing Hubble flare and a beautiful recap of last week's northern lights.

    More stories on sun and space weather:

    Tip o' the Log to Ian O'Neill at Discovery News.

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • ESO

    The distant galaxy NGC 157 boasts a central sweep of stars resembling a giant "S", reminiscent of Superman's symbol. This celestial spiral is a super example of how new technology is helping us to learn more about the cosmos.

    A galaxy fit for Superman

    By John Roach, Contributing Writer, NBC News

    It may not be able to leap tall buildings in a single bound, but from the looks of it, galaxy NGC 157 appears to have the stamp that belongs to the one and only Superman – a giant sweep of stars that resemble the letter "S".

    Whether the galaxy itself harbors the superhero remains unknown, but the image was made with some mighty powerful technology: the High Acuity Wide-field K-band Imager (HAWK-I) on the European Southern Observatory's Very Large Telescope in Chile, which sees in infrared light.

    Using the imager, astronomers are able to peer through the gas and dust that normally obscures the view of the distant galaxy. This technology enhances the ability to study dense areas of star formation, which is a step towards understanding our own origins.

    "The same processes that are coalescing material in NGC 157 and creating stars there took place 4.5 billion years ago in the Milky Way to form our own star, the sun," the ESO notes in an image advisory.

    Tip o' the Log to Nancy Atkinson and Universe Today.

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

  • It's a Saturnian moonapalooza!

    NASA / JPL / Space Science Institute

    The Saturnian moon Rhea stars in an image captured by the Cassini orbiter during a flyby on Tuesday, but several other moons play supporting roles, along with Saturn's nearly edge-on rings. The moon Dione is just below Rhea and just above the rings. Tethys is to the right of Rhea, below the ring plane. Epimetheus appears as a speck in space between Rhea and Tethys. And the shepherd moon Prometheus is barely visible as a bump in the rings, just to the right of Dione.

    By John Roach, Contributing Writer, NBC News

    Raw images of Saturn's icy moon Rhea captured by NASA's Cassini spacecraft during this week's flyby are delighting space enthusiasts and scientists.

    In the image above, Rhea takes center stage, though Saturn's rings and three other moons make a cameo appearance. Below Rhea, just above the rings, is Dione. The moon Tethys is the larger circle in the lower right, while Epimetheus is the smaller dot to the right of Rhea and Dione. If you look closely, Prometheus is barely distinguishable as a speck embedded in the rings to the right of Dione.

    Other images from the flyby show Rhea's cratered and fractured surface up close, which will allow scientists studying the images to understand just how often meteoroids bombard Rhea:

    The Cassini orbiter's wide-angle camera took this image of Rhea as it flew past at a distance of about 120 miles (200 kilometers) from the Saturnian moon's surface.

    In addition, NASA noted in an image advisory, scientists using fields and particles instruments are looking through their data to see if they gleaned any more information about Rhea's thin oxygen-and-carbon-dioxide atmosphere and the interaction between Rhea and the particles within Saturn's magnetosphere.

    The scientific value of the data aside, the Planetary Society's Emily Lakdawalla, says the raw images left her "drooling." For more views of the icy moon, check out her post here.

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

     

  • NASA

    NASA's Voyager 1 spacecraft made this image of Earth -- the dot at center right -- when it was 4 billion miles away. The image was requested by Carl Sagan, who died on Dec. 20, 1996.

    Holiday calendar: Our pale blue dot

    By John Roach, Contributing Writer, NBC News

    On Feb. 14, 1990, NASA controllers instructed the Voyager 1 spacecraft to turn around and take one last look at its home planet as it pushed on to the fringe of our solar system. Look closely at the resulting image. That tiny pinpoint of light in the center-right is us – you, me, and everyone else that calls Earth home.

    The request came from the late, great astronomer Carl Sagan, one of the world's greatest advocates for advancing the general public's appreciation and understanding of science. He passed away 14 years ago today after a two-year battle with bone-marrow disease.

    The image, called "A Pale Blue Dot," was made when Voyager 1 was about 4 billion miles away. It inspired Sagan's 1994 book "Pale Blue Dot: A Vision of the Human Future in Space." An excerpt puts the image's significance into context:

    "It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. It underscores our responsibility to deal more kindly with one another, and to preserve and cherish the only home we've ever known, the pale blue dot."

    We leave you to reflect on Sagan's thoughts as we head into the final days of our Cosmic Log Space Advent Calendar. For more views of Earth from space, check out these past offerings. We've also included links to other online Advent calendars that have been serving up space images daily since the beginning of the month:

    Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).

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