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Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
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2018 July 7

A Northern Summer's Night
Image Credit &
License: Ruslan Merzlyakov (RMS Photography)

Near a summer's midnight a mist haunts the river bank in this dreamlike skyscape taken on July 3rd from northern Denmark. Reddened light from the Sun a little below the horizon gives an eerie tint to low hanging clouds. Formed near the edge of space, the silvery apparitions above them are noctilucent or night shining clouds. The icy condensations on meteoric dust or volcanic ash are still in full sunlight at the extreme altitudes of the mesophere. Usually seen at high latitudes in summer months, wide spread displays of the noctilucent clouds are now being reported.
2018 July 8

The Extraordinary Spiral in LL Pegasi
Image Credit:
NASA, ESA, Hubble, HLA; Processing & Copyright: Domingo Pestana & Raul Villaverde

What created the strange spiral structure on the upper left? No one is sure, although it is likely related to a star in a binary star system entering the planetary nebula phase, when its outer atmosphere is ejected. The huge spiral spans about a third of a light year across and, winding four or five complete turns, has a regularity that is without precedent. Given the expansion rate of the spiral gas, a new layer must appear about every 800 years, a close match to the time it takes for the two stars to orbit each other. The star system that created it is most commonly known as LL Pegasi, but also AFGL 3068. The unusual structure itself has been cataloged as IRAS 23166+1655. The featured image was taken in near-infrared light by the Hubble Space Telescope. Why the spiral glows is itself a mystery, with a leading hypothesis being illumination by light reflected from nearby stars.
2018 July 9

Road to Mars
Image Credit & Copyright:
John Chumack

What's that light at the end of the road? Mars. This is a good month to point out Mars to your friends and family because our neighboring planet will not only be its brightest in 15 years, it will be visible for much of night. During this month, Mars will be about 180 degrees around from the Sun, and near the closest it ever gets to planet Earth. In terms of orbits, Mars is also nearing the closest point to the Sun in its elliptical orbit, just as Earth moves nearly between it and the Sun -- an alignment known as perihelic opposition. In terms of viewing, orange Mars will rise in the east just as the Sun sets in the west, on the opposite side of the sky. Mars will climb in the sky during the night, reach its highest near midnight, and then set in the west just as the Sun begins to rise in the east. The red planet was captured setting beyond a stretch of road in Arches National Park in mid-May near Moab, Utah, USA.
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2018 July 10

Noctilucent Clouds over Paris Fireworks
Video Credit & Copyright:
Jean-Luc Dauvergne (Ciel et Espace);

It's northern noctilucent cloud season -- perhaps a time to celebrate! Composed of small ice crystals forming only during specific conditions in the upper atmosphere, noctilucent clouds may become visible at sunset during late summer when illuminated by sunlight from below. Noctilucent clouds are the highest clouds known and now established to be polar mesospheric clouds observed from the ground. Although observed with NASA's AIM satellite since 2007, much about noctilucent clouds remains unknown and so a topic of active research. The featured time-lapse video shows expansive and rippled noctilucent clouds wafting over Paris, France, during a post-sunset fireworks celebration on Bastille Day in 2009 July. This year, several locations are already reporting especially vivid displays of noctilucent clouds.
2018 July 11

Symbiotic R Aquarii
Image Credit:
Hubble, NASA, ESA; Processing & License: Judy Schmidt

You can see it change in brightness with just binoculars over the course of a year. Variable star R Aquarii is actually an interacting binary star system, two stars that seem to have a close, symbiotic relationship. About 710 light years away, this intriguing system consists of a cool red giant star and hot, dense white dwarf star in mutual orbit around their common center of mass. The binary system's visible light is dominated by the red giant, itself a Mira-type long period variable star. But material in the cool giant star's extended envelope is pulled by gravity onto the surface of the smaller, denser white dwarf, eventually triggering a thermonuclear explosion and blasting material into space. The featured image from the Hubble Space Telescope shows the still-expanding ring of debris which spans less than a light year and originated from a blast that would have been seen in the early 1770s. The evolution of less understood energetic events producing high energy emission in the R Aquarii system has been monitored since 2000 using Chandra X-ray Observatory data.
2018 July 12

Centaurus A
Image Credit &
Copyright: CEDIC Team at Chilescope, Processing - Bernhard Hubl

Only 11 million light-years away, Centaurus A is the closest active galaxy to planet Earth. Spanning over 60,000 light-years, the peculiar elliptical galaxy also known as NGC 5128, is featured in this sharp telescopic view. Centaurus A is apparently the result of a collision of two otherwise normal galaxies resulting in a fantastic jumble of star clusters and imposing dark dust lanes. Near the galaxy's center, left over cosmic debris is steadily being consumed by a central black hole with a billion times the mass of the Sun. As in other active galaxies, that process likely generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A.
2018 July 13

Star Trails and the Bracewell Radio Sundial
Image Credit &
Copyright: Miles Lucas at NRAO

Sundials use the location of a shadow to measure the Earth's rotation and indicate the time of day. So it's fitting that this sundial, at the Very Large Array Radio Telescope Observatory in New Mexico, commemorates the history of radio astronomy and radio astronomy pioneer Ronald Bracewell. The radio sundial was constructed using pieces of a solar mapping radio telescope array that Bracewell orginaly built near the Stanford University campus. Bracewell's array was used to contribute data to plan the first Moon landing, its pillars signed by visiting scientists and radio astronomers, including two Nobel prize winners. As for most sundials the shadow cast by the central gnomon follows markers that show the solar time of day, along with solstices and equinoxes. But markers on the radio sundial are also laid out according to local sidereal time. They show the position of the invisible radio shadows of three bright radio sources in Earth's sky, supernova remnant Cassiopeia A, active galaxy Cygnus A, and active galaxy Centaurus A. Sidereal time is just star time, the Earth's rotation as measured with the stars and distant galaxies. That rotation is reflected in this composited hour-long exposure. Above the Bracewell Radio Sundial, the stars trace concentric trails around the north celestial pole.
2018 July 14

A Nibble on the Sun
Image Credit &
Copyright: Padraic Koen, Adelaide, South Australia

The smallest of the three partial solar eclipses during 2018 was just yesterday, Friday, July 13. It was mostly visible over the open ocean between Australia and Antarctica. Still, this video frame of a tiny nibble on the Sun was captured through a hydrogen-alpha filter from Port Elliott, South Australia, during the maximum eclipse visible from that location. There, the New Moon covered about 0.16 percent of the solar disk. The greatest eclipse, about one-third of the Sun's diameter blocked by the New Moon, could be seen from East Antarctica near Peterson Bank, where the local emperor penguin colony likely had the best view. During this prolific eclipse season, the coming Full Moon will bring a total lunar eclipse on July 27, followed by yet another partial solar eclipse at the next New Moon on August 11.
2018 July 15

Rings Around the Ring Nebula
Image Credit:
Hubble, Large Binocular Telescope, Subaru Telescope; Composition & Copyright: Robert Gendler

There is much more to the familiar Ring Nebula (M57), however, than can be seen through a small telescope. The easily visible central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from three different large telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. This remarkable composite image includes narrowband hydrogen image, visible light emission, and infrared light emission. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from a dying, sun-like star. The Ring Nebula is about 2,000 light-years away toward the musical constellation Lyra.
2018 July 16

Neutrino Associated with Distant Blazar Jet
Illustration Credit:
DESY, Science Communication Lab

With equipment frozen deep into ice beneath Earth's South Pole, humanity appears to have discovered a neutrino from far across the universe. If confirmed, this would mark the first clear detection of cosmologically-distant neutrinos and the dawn of an observed association between energetic neutrinos and cosmic rays created by powerful jets emanating from blazing quasars (blazars). Once the Antarctican IceCube detector measured an energetic neutrino in 2017 September, many of humanity's premier observatories sprang into action to try to identify a counterpart in light. And they did. An erupting counterpart was pinpointed by high energy observatories including AGILE, Fermi, HAWC, H.E.S.S., INTEGRAL, MAGIC, NuSTAR, Swift, and VERITAS, which found that gamma-ray blazar TXS 0506+056 was in the right direction and with gamma-rays from a flare arriving nearly coincidental in time with the neutrino. Even though this and other position and time coincidences are statistically strong, astronomers will await other similar neutrino - blazar light associations to be absolutely sure. Pictured here is an artist's drawing of a particle jet emanating from a black hole at the center of a blazar.
2018 July 17

Moon and Venus over Cannon Beach
Image Credit & Copyright:
James W. Young

What's that spot next to the Moon? Venus. Two days ago, the crescent Moon slowly drifted past Venus, appearing within just one degree at its closest. This conjunction, though, was just one of several photographic adventures for our Moon this month (moon-th), because, for one, a partial solar eclipse occurred just a few days before, on July 12. Currently, the Moon appears to be brightening, as seen from the Earth, as the fraction of its face illuminated by the Sun continues to increase. In a few days, the Moon will appear more than half full, and therefore be in its gibbous phase. Next week the face of the Moon that always faces the Earth will become, as viewed from the Earth, completely illuminated by the Sun. Even this full phase will bring an adventure, though, as a total eclipse of this Thunder Moon will occur on July 27. Don't worry about our Luna getting tired, though, because she'll be new again next month (moon-th) -- August 11 to be exact -- just as she causes another partial eclipse of the Sun. Pictured, Venus and the Moon were captured from Cannon Beach above a rock formation off the Oregon (USA) coast known as the Needles. About an hour after this image was taken, the spin of the Earth caused both Venus and the Moon to set.
2018 July 18

Dark Slope Streaks Split on Mars
Image Credit:
HiRISE, MRO, LPL (U. Arizona), NASA

What is creating these dark streaks on Mars? No one is sure. Candidates include dust avalanches, evaporating dry ice sleds, and liquid water flows. What is clear is that the streaks occur through light surface dust and expose a deeper dark layer. Similar streaks have been photographed on Mars for years and are one of the few surface features that change their appearance seasonally. Particularly interesting here is that larger streaks split into smaller streaks further down the slope. The featured image was taken by the HiRISE camera on board the Mars-orbiting Mars Reconnaissance Orbiter (MRO) several months ago. Currently, a global dust storm is encompassing much of Mars.
2018 July 19

Cerealia Facula
Image Credit:
NASA, JPL-Caltech, UCLA, MPS/DLR/IDA

Cerealia Facula, also known as the brightest spot on Ceres, is shown in this stunning mosaic close-up view. The high-resolution image data was recorded by the Dawn spacecraft, in a looping orbit, from altitudes as low as 34 kilometers (21 miles) above the dwarf planet's surface. Cerealia Facula is about 15 kilometers wide, found in the center of 90 kilometer diameter Occator crater. Like the other bright spots (faculae) scattered around Ceres, Cerealia Facula is not ice, but an exposed salty residue with a reflectivity like dirty snow. The residue is thought to be mostly sodium carbonate and ammonium chloride from a slushy brine within or below the dwarf planet's crust. Driven by advanced ion propulsion on an 11-year mission, Dawn explored main-belt asteriod Vesta before traveling on to Ceres. But sometime between this August and October, the interplanetary spacecraft is expected to finally run out of fuel for its hydrazine thrusters. The subsequent loss of control of its orientation will result in the loss of power and the ability to communicate with Earth. Meanwhile Dawn will continue to explore Ceres in unprecedented detail, and ultimately retire in its orbit around the small world.
2018 July 20

The Teapot and the Milky Way
Image Credit &
Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)

The recognizable stars of the Teapot asterism in the constellation Sagittarius posed with the Milky Way over Death Valley, planet Earth on this quiet, dark night. The surreal scene was appropriately captured from Teakettle Junction, marked by the wooden sign adorned with terrestrial teapots and kettles on the rugged road to Racetrack Playa. Shining against the luminous starlight of the central Milky Way is bright planet Saturn, just above the star at the celestial teapot's peak. But the brightest celestial beacon, high above the southern horizon, is an orange tinted Mars at upper left in the frame.
2018 July 21

Apollo 11 Landing Site Panorama
Image Credit:
Neil Armstrong, Apollo 11, NASA

Have you seen a panorama from another world lately? Assembled from high-resolution scans of the original film frames, this one sweeps across the magnificent desolation of the Apollo 11 landing site on the Moon's Sea of Tranquility. The images were taken by Neil Armstrong looking out his window of the Eagle Lunar Module shortly after the July 20, 1969 landing. The frame at the far left (AS11-37-5449) is the first picture taken by a person on another world. Toward the south, thruster nozzles can be seen in the foreground on the left, while at the right, the shadow of the Eagle is visible to the west. For scale, the large, shallow crater on the right has a diameter of about 12 meters. Frames taken from the Lunar Module windows about an hour and a half after landing, before walking on the lunar surface, were intended to initially document the landing site in case an early departure was necessary.
2018 July 22

Planck Maps the Microwave Background
Image Credit:
European Space Agency, Planck Collaboration

What is our universe made of? To help find out, ESA launched the Planck satellite from 2009 to 2013 to map, in unprecedented detail, slight temperature differences on the oldest optical surface known -- the background sky when our universe first became transparent to light. Visible in all directions, this cosmic microwave background is a complex tapestry that could only show the hot and cold patterns observed were the universe to be composed of specific types of energy that evolved in specific ways. The final results, reported last week, confirm again that most of our universe is mostly composed of mysterious and unfamiliar dark energy, and that even most of the remaining matter energy is strangely dark. Additionally, the "final" 2018 Planck data impressively peg the age of the universe at about 13.8 billion years and the local expansion rate -- called the Hubble constant -- at 67.4 (+/- 0.5) km/sec/Mpc. Oddly, this early-universe determined Hubble constant is slightly lower than that determined by other methods in the late-universe, creating a tension that is causing much discussion and speculation.
2018 July 23

Fermi Science Finals
Illustration Credit:
NASA, DOE, International Fermi LAT Collaboration, Jay Friedlander (Goddard Space Flight Center)

The Fermi Science Playoffs celebrate 10 years of the Fermi Gamma-ray Space Telescope's exploration of the high-energy universe. Surviving all early rounds of voting, these two finalists in the competition square off at last. Digital illustrations from a list of 16 of Fermi's top scientific discoveries, they represent the competition's two top seeds, defeating 12th seed New Clues to Dark Matter and 14th seed Starquakes in Magnetar Storm in the semifinal round. On the left are unprecedented, unpredicted, 25,000 light-year tall Gamma-ray Bubbles above and below the plane of our Milky Way galaxy. On the right, violently merging Neutron Stars Collide to create the first gamma-ray detected gravitational wave event. Pick one now and cast your vote here to crown the most popular science result from Fermi's first decade.
2018 July 24

Clouds of Earth and Sky
Image Credit & Copyright:
Angelo Perrone

If you go high enough, you may find yourself on a picturesque perch between the water clouds of the Earth and the star clouds of the Milky Way. Such was the case last month for one adventurous alpinist astrophotographer. Captured here in the foreground above white clouds are mountain peaks in the Dolomite range in northern Italy. This multi-exposure image was captured from Lagazuoi, one of the Dolomites. Hundreds of millions of years ago, the Dolomites were not mountains but islands an ancient sea that rose through colliding tectonic plates. The Dolomites divergent history accounts for its unusually contrasting features, which include jagged crests and ancient marine fossils. High above even the Dolomites, and far in the distance, dark dust lanes streak out from the central plane of our Milky Way Galaxy. The stars and dust are dotted with bright red clouds of glowing hydrogen gas -- such as the Lagoon Nebula just above and to the left of center.
2018 July 25

The Edge-On Spindle Galaxy
Image Credit &
Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona

What kind of celestial object is this? A relatively normal galaxy -- but seen from its edge. Many disk galaxies are actually just as thin as NGC 5866, pictured here, but are not seen edge-on from our vantage point. A perhaps more familiar galaxy seen edge-on is our own Milky Way Galaxy. Cataloged as M102 and NGC 5866, the Spindle galaxy has numerous and complex dust lanes appearing dark and red, while many of the bright stars in the disk give it a more blue underlying hue. The blue disk of young stars can be seen extending past the dust in the extremely thin galactic plane. There is evidence that the Spindle galaxy has cannibalized smaller galaxies over the past billion years or so, including multiple streams of faint stars, dark dust that extends away from the main galactic plane, and a surrounding group of galaxies (not shown). In general, many disk galaxies become thin because the gas that forms them collides with itself as it rotates about the gravitational center. The Spindle galaxy lies about 50 million light years distant toward the constellation of the Dragon (Draco).
2018 July 26

Barnard 228: The Dark Wolf Nebula in Lupus
Image Credit &
Copyright: Gabriel Rodrigues Santos

These dark markings on the sky can just be found in silhouette against a rich, luminous background of stars. Seen toward the southern constellation of Lupus the Wolf, the dusty, obscuring clouds are part of the Lupus Molecular Cloud some 500 light-years distant. Packs of low mass stars are forming within them, from collapsing cores only visible at long infrared wavelengths. Still, colorful stars in Lupus add to this pretty galactic skyscape. It spans about 8 degrees, not far from the central Milky Way.