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.


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Panoramic view of the Mezcala Bridge on Highway 95 in Mexico


Chukchi Sea

Regardless of the amount of winter ice cover, the waters off of the Alaskan coast usually come alive each spring with blooms of phytoplankton. These blooms can form striking patterns of blue and green seawater, such as those visible in this image of the Chukchi Sea acquired on June 18, 2018, by the Operational Land Imager (OLI) on Landsat 8.

Blooms are a common occurrence this time of year. But the regularity of the blooms and their simple beauty belie the complexity of this ecosystem.

Two main water masses flow from the Bering Strait and enter the southern Chukchi. One type, known as “Bering Sea Water,” is cool, salty, and rich in nutrients. This water fuels most of the phytoplankton growth, primarily diatoms, which are likely the main reason for the colorful green waters pictured here. (Sediments could also be contributing to the bright green areas.)

The second mass of seawater is known as “Alaskan Coastal Water,” which is warmer, less salty, and nutrient-poor. Diatom growth is usually lower in these waters, but coccolithophores can do well here. Some areas pictured here could contain this type of plankton, known to impart a milky turquoise hue to the water with their plates of calcium carbonate armor.

While experts expect blooms to consistently show up in these waters from year to year, the size is less consistent, and the reason is not clear.

Image Credit: NASA/U. S. Geological Survey/Norman Kuring/Kathryn Hansen


Source: www.nasa.gov

What's that spot next to the Moon? Venus. Two days ago, the crescent Moon slowly drifted past Venus, appearing within just two degrees 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.


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Two SBB RABDe 500 "ICN" tilting trains on the Jura foot railway line, at Twann, with Lake Biel in the back


Infrared View of NGC 4993

Launched nearly 15 years ago on August 25, 2003, the Spitzer Space Telescope is the final mission in NASA's Great Observatories Program - a family of four space-based observatories, each observing the universe in a different kind of light. The other missions in the program include the visible-light Hubble Space Telescope, Compton Gamma-Ray Observatory, and the Chandra X-Ray Observatory.

Over the years, Spitzer, which makes observations in the infrared spectrum, has made a plethora of discoveries, including this detection of the faint afterglow of the explosive merger of two neutron stars in the galaxy NGC 4993 on September 29, 2017. The event, labeled GW170817, was initially detected nearly simultaneously in gravitational waves and gamma rays, but subsequent observations by many dozens of telescopes have monitored its afterglow across the entire spectrum of light. Spitzer's observation came late in the game, just over six weeks after the event was first seen, but this played an important role in helping astronomers understand how many of the heaviest elements in the periodic table are created in explosive neutron star mergers.

The telescope was named after Lyman Spitzer, Jr. (1914-1997), one of the 20th century's great astrophysicists, who made major contributions in the areas of stellar dynamics, plasma physics, thermonuclear fusion, and space astronomy. He was laos the first person to propose the idea of placing a large telescope in space and was instrumental in the development of the Hubble Space Telescope.

Image Credit: NASA/JPL-Caltech


Source: www.nasa.gov

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, 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.


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Mute swans (Cygnus olor) and their cygnets in Oxfordshire. Today sees the first day of Royal Swan Upping on the River Thames when swans are ringed. Ownership of swans in the Thames is shared by The Crown, the Vintners' Company and the Dyers' Company.



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.

Open Science: Browse 1,700+ codes in the Astrophysics Source Code Library

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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.


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Goalie Brice Samba and an incoming ball at the 2013 Valais Cup


Mars

This image from NASA's Mars Reconnaissance Orbiter, acquired May 13, 2018 during winter at the South Pole of Mars, shows a carbon dioxide ice cap covering the region and as the sun returns in the spring, "spiders" begin to emerge from the landscape.

But these aren't actual spiders. Called "araneiform terrain," describes the spider-like radiating mounds that form when carbon dioxide ice below the surface heats up and releases. This is an active seasonal process not seen on Earth. Like dry ice on Earth, the carbon dioxide ice on Mars sublimates as it warms (changes from solid to gas) and the gas becomes trapped below the surface.

Over time the trapped carbon dioxide gas builds in pressure and is eventually strong enough to break through the ice as a jet that erupts dust. The gas is released into the atmosphere and darker dust may be deposited around the vent or transported by winds to produce streaks. The loss of the sublimated carbon dioxide leaves behind these spider-like features etched into the surface.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. 

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Source: www.nasa.gov

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.


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Arches in the interior of the church of Holy Mother of God Narthex within the Sanahin Monastery complex, Lori Province, Armenia. Sanahin literally translates from Armenian as "this one is older than that one", presumably representing a claim to having an older monastery than the neighbouring Haghpat Monastery. The Armenian Apostolic monastery was built in the 10th century in Armenian style and has become a tourist magnet.


The Eagle Nebula, also known as Messier 16.

The Eagle Nebula, also known as Messier 16, contains the young star cluster NGC 6611. It also the site of the spectacular star-forming region known as the Pillars of Creation, which is located in the southern portion of the Eagle Nebula.

This new composite image shows the region around the Pillars, which are about 5,700 light years from Earth. The image combines X-ray data from NASA’s Chandra X-ray Observatory and Hubble Space Telescope optical data. The optical image, taken with filters to emphasize the interstellar gas and dust, shows dusty brown nebula immersed in a blue-green haze, and a few stars that appear as pink dots in the image. The Chandra data reveal X-rays from hot outer atmospheres from stars. In this image, low, medium, and high-energy X-rays detected by Chandra have been colored red, green, and blue. 

Using Chandra, researchers detected over 1,700 individual sources of X-rays in the Eagle Nebula (only a fraction are seen in this small field of view). Optical and infrared identifications with stars were used to sort out chance interlopers in the foreground or background, and to determine that more than two-thirds of the sources are likely young stars that are members of the NGC 6611 cluster.

Chandra’s unique ability to resolve and locate X-ray sources made it possible to identify hundreds of very young stars, and those still in the process of forming (known as “protostars”). Infrared observations from NASA’s Spitzer Space Telescope and the European Southern Observatory indicate that 219 of the X-ray sources in the Eagle Nebula are young stars surrounded by disks of dust and gas and 964 are young stars without these disks.

Combined with the Chandra observations, the data show that X-ray activity in young stars with disks is, on average, a few times less intense that in young stars without disks. This behavior is likely due to the interaction of the disk with the magnetic field of the host star. Much of the matter in the disks around these protostars will eventually be blown away by radiation from their host stars, but, in certain cases, some of it may form into planets. 

In the image, some of the X-ray sources appear to be located in the Pillars.

However, an analysis of the absorption of X-rays from these sources indicates that almost all of these sources belong to the larger Eagle Nebula rather than being immersed in the Pillars.

Three X-ray sources appear to lie near the tip of the largest Pillar. Infrared observations show a protostar containing four or five times the mass of the Sun is located near one of these sources – the blue one near the tip of the Pillar. This source exhibits strong absorption of low-energy X-rays, consistent with a location inside the Pillar. Similar arguments show that one of these sources is associated with a disk-less star outside the Pillar, and one is a foreground object.

A paper by Mario Guarcello, currently at the National Institute for Astronomy in Italy, and colleagues describing these results appeared in The Astrophysical Journal, and is available online.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read more from NASA's Chandra X-ray Observatory.

For more Chandra images, multimedia and related materials, visit:

http://www.nasa.gov/chandra


Source: www.nasa.gov

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.



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.


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Sony Alpha A77 with 16-50mm f/2.8 SSM lens.


Overhead view of river estuary

As the International Space Station flew overhead, NASA astronaut Ricky Arnold captured this photograph of a changing landscape in the heart of Madagascar, observing drainage into the sea in the Betsiboka Estuary due to decimation of rainforests and coastal mangroves. 

Image Credit: NASA


Source: www.nasa.gov

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.