July 1, 2017

Hekla Volcano Eruption

Hekla Volcano Eruption

Hekla, Iceland

Image Credit: Vilhelm Gunnarsson

The map of the Milky Way Galaxy

The map of the Milky Way Galaxy

Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA's Spitzer Space Telescope, scientists have discovered that the Milky Way's elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms.

This annotated artist's concept illustrates the new view of the Milky Way, along with other findings presented at the 212th American Astronomical Society meeting in St. Louis, Mo. The galaxy's two major arms (Scutum-Centaurus and Perseus) can be seen attached to the ends of a thick central bar, while the two now-demoted minor arms (Norma and Sagittarius) are less distinct and located between the major arms. The major arms consist of the highest densities of both young and old stars; the minor arms are primarily filled with gas and pockets of star-forming activity.

The artist's concept also includes a new spiral arm, called the "Far-3 kiloparsec arm," discovered via a radio-telescope survey of gas in the Milky Way. This arm is shorter than the two major arms and lies along the bar of the galaxy.

Our Sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.

Image Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
Explanation from: http://www.spitzer.caltech.edu/images/1925-ssc2008-10b-A-Roadmap-to-the-Milky-Way-Annotated-

Jupiter seen by Juno spacecraft in Near Infrared

Jupiter seen by Juno spacecraft in Near Infrared

This composite infrared image of Jupiter reveals haze particles over a range of altitudes, as seen in reflected sunlight. It was taken using the Gemini North Telescope's Near-InfraRed Imager (NIRI) on May 18, 2017, in collaboration with the investigation of Jupiter by NASA's Juno mission. Juno completed its sixth close approach to Jupiter a few hours after this observation.

The multiple filters corresponding to each color used in the image cover wavelengths between 1.69 microns and 2.275 microns. Jupiter's Great Red Spot (GRS) appears as the brightest (white) region at these wavelengths, which are primarily sensitive to high-altitude clouds and hazes near and above the top of Jupiter's convective region.

The GRS is one of the highest-altitude features in Jupiter's atmosphere. Narrow spiral streaks that appear to lead into it or out of it from surrounding regions probably represent atmospheric features being stretched by the intense winds within the GRS, such as the hook-like structure on its western edge (left side). Some are being swept off its eastern edge (right side) and into an extensive wave-like flow pattern, and there is even a trace of flow from its northern edge.

Other features near the GRS include the dark block and dark oval to the south and the north of the eastern flow pattern, respectively, indicating a lower density of cloud and haze particles in those locations. Both are long-lived cyclonic circulations, rotating clockwise -- in the opposite direction as the counterclockwise rotation of the GRS.

A prominent wave pattern is evident north of the equator, along with two bright ovals, which are anticyclones that appeared in January 2017. Both the wave pattern and the ovals may be associated with an impressive upsurge in stormy activity that has been observed in these latitudes this year. Another bright anticyclonic oval is seen further north. The Juno spacecraft may pass over these ovals, as well as the Great Red Spot, during its close approach to Jupiter on July 10, 2017, Pacific Time (July 11, Universal Time).

High hazes are evident over both polar regions with much spatial structure not previously been seen quite so clearly in ground-based images

The filters used for observations combined into this image admit infrared light centered on the following infrared wavelengths (and presented here in these colors): 1.69 microns (blue), 2.045 microns (cyan), 2.169 microns (green), 2.124 microns (yellow), and 2.275 microns (red).

Image Credit: Gemini Observatory/AURA/NASA/JPL-Caltech
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21713

June 30, 2017

Earth, Aurora and the International Space Station

Earth, Aurora and the International Space Station

Expedition 52 Flight Engineer Jack Fischer of NASA photographed the glowing nighttime lights of an aurora from his vantage point in the International Space Station's cupola module on June 19, 2017. Part of the station's solar array is also visible.

ISS, Orbit of the Earth
June 19, 2017

Image Credit: NASA

Elliptical Galaxy 4C 73.08

Elliptical Galaxy 4C 73.08

Luminous galaxies glow like fireflies on a dark night in this image snapped by the NASA/ESA Hubble Space Telescope. The central galaxy in this image is a gigantic elliptical galaxy designated 4C 73.08. A prominent spiral galaxy seen from "above" shines in the lower part of the image, while examples of galaxies viewed edge-on also populate the cosmic landscape.

In the optical and near-infrared light captured to make this image, 4C 73.08 does not appear all that beastly. But when viewed in longer wavelengths the galaxy takes on a very different appearance. Dust-piercing radio waves reveal plumes emanating from the core, where a supermassive black hole spews out twin jets of material. 4C 73.08 is classified as a radio galaxy as a result of this characteristic activity in the radio part of the electromagnetic spectrum.

Astronomers must study objects such as 4C 73.08 in multiple wavelengths in order to learn their true natures, just as seeing a firefly’s glow would tell a scientist only so much about the insect. Observing 4C 73.08 in visible light with Hubble illuminates galactic structure as well as the ages of constituent stars, and therefore the age of the galaxy itself. 4C 73.08 is decidedly redder than the prominent, bluer spiral galaxy in this image. The elliptical galaxy’s redness comes from the presence of many older, crimson stars, which shows that 4C 73.08 is older than its spiral neighbour.

The image was taken using Hubble’s Wide Field Camera 3 through two filters: one which captures green light, and one which captures red and near-infrared light.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1246a/

IRAS 21078+5211

IRAS 21078+5211

This image shows an outflow of gas from a new star as it jets from a space object dubbed IRAS 21078+5211, among other designations. The reddish blob in its center, as picked up by Spitzer's 4.5 micron infrared band, contrasts nicely with the green PAHs that surround it. These telltale outflow features of young, hulking stars show up well even without the longer wavelengths available to the original GLIMPSE survey that ran during the "cold" segment of Spitzer's mission. These so-called shocked outflows ram into the hydrogen gas around them and make it glow - a bright beacon in the lonely outskirts of the Milky Way.

This image is a combination of data from Spitzer and the Two Micron All Sky Survey (2MASS). The Spitzer data was taken after Spitzer's liquid coolant ran dry in May 2009, marking the beginning of its "warm" mission. Light from Spitzer's remaining infrared channels at 3.6 and 4.5 microns has been represented in green and red, respectively. 2MASS 2.2 micron light is blue.

Image Credit: NASA/JPL-Caltech/2MASS/B. Whitney (SSI/University of Wisconsin)
Explanation from: http://www.spitzer.caltech.edu/images/3224-sig10-014-A-Shocking-Outflow

NASA Wallops Rocket Launch Lights up the Mid-Atlantic Coast

NASA Wallops Rocket Launch Lights up the Mid-Atlantic Coast

NASA Terrier-Improved Malemute sounding rocket was successfully launched at 4:25 a.m., Thursday, June 29, from the agency’s Wallops Flight Facility in Virginia.

During the 8-minute flight, 10 canisters about the size of a soft drink can were ejected in space, 6 to 12 miles away from the 670-pound main payload.

The canisters deployed blue-green and red vapor that formed artificial clouds visible from New York to North Carolina.

During an ionosphere or aurora science mission, these clouds, or vapor tracers, allow scientists on the ground to visually track particle motions in space.

The development of the multi-canister ampoule ejection system will allow scientists to gather information over a much larger area than previously possible when deploying the tracers just from the main payload.

The rocket, after being delayed multiple times over the last 30 days, flew to an altitude of about 118 miles.

Wallops received nearly 2,000 reports and photos of the cloud sightings from areas as far north as New York, south to North Carolina, and inland throughout Virginia, Maryland, Pennsylvania, and points in-between.

NASA's Wallops Flight Facility provides agile, low-cost flight and launch range services to meet government and commercial sector needs for accessing flight regimes worldwide from the Earth’s surface to the moon. Wallops' flight assets ranging from research aircraft, unmanned aerial systems and high-altitude balloons to suborbital and orbital rockets provide a full-range of capability, while operational launch range and airfield capabilities meet ongoing and emerging needs in the science, aerospace, defense, and commercial industries.

Image Credit: NASA
Explanation from: https://www.nasa.gov/feature/wallops/2017/nasa-wallops-rocket-launch-lights-up-the-mid-atlantic-coast

The Coma Galaxy Cluster

The Coma Galaxy Cluster

  • Long arms of hot gas been discovered in the Coma cluster of galaxies.
  • These arms were likely formed by hot gas being stripped and left behind smaller clusters of galaxies as they merged with Coma.
  • These arms span at least a half a million light years.
  • Galaxies clusters are the largest structures in the Universe held together by gravity.

A team of astronomers has discovered enormous arms of hot gas in the Coma cluster of galaxies by using NASA's Chandra X-ray Observatory and ESA's XMM-Newton. These features, which span at least half a million light years, provide insight into how the Coma cluster has grown through mergers of smaller groups and clusters of galaxies to become one of the largest structures in the Universe held together by gravity.

A new composite image, with Chandra data in pink and optical data from the Sloan Digital Sky Survey appearing in white and blue, features these spectacular arms (mouse over the image for their location). In this image, the Chandra data have been processed so extra detail can be seen.

The X-ray emission is from multimillion-degree gas and the optical data shows galaxies in the Coma Cluster, which contain only about 1/6 the mass in hot gas. Only the brightest X-ray emission is shown here, to emphasize the arms, but the hot gas is present over the entire field of view.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the cluster through the hot gas, in much the same way that the headwind created by a roller coaster blows the hats off riders.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its center. These two giant elliptical galaxies are probably the vestiges from each of the two largest clusters that merged with Coma in the past. The researchers also uncovered other signs of past collisions and mergers in the data.

From their length, and the speed of sound in the hot gas (~4 million km/hr), the newly discovered X-ray arms are estimated to be about 300 million years old, and they appear to have a rather smooth shape. This gives researchers some clues about the conditions of the hot gas in Coma. Most theoretical models expect that mergers between clusters like those in Coma will produce strong turbulence, like ocean water that has been churned by many passing ships. Instead, the smooth shape of these lengthy arms points to a rather calm setting for the hot gas in the Coma cluster, even after many mergers.

Large-scale magnetic fields are likely responsible for the small amount of turbulence that is present in Coma. Estimating the amount of turbulence in a galaxy cluster has been a challenging problem for astrophysicists. Researchers have found a range of answers, some of them conflicting, and so observations of other clusters are needed.

Two of the arms appear to be connected to a group of galaxies located about two million light years from the center of Coma. One or both of these arms connects to a larger structure seen in the XMM-Newton data, and spans a distance or at least 1.5 million light years. A very thin tail also appears behind one of the galaxies in Coma. This is probably evidence of gas being stripped from a single galaxy, in addition to the groups or clusters that have merged there.

Image Credit: X-ray: NASA/CXC/MPE/J.Sanders et al, Optical: SDSS
Explanation from: http://chandra.harvard.edu/photo/2013/coma/

Supernova Remnant G299.2-2.9

Supernova Remnant G299.2-2.9

  • G299.2-2.9 is a supernova remnant found about 16,000 light years from Earth in the Milky Way galaxy.
  • It is the remains of a Type Ia supernova, the class of explosions astronomers use to measure the accelerating Universe and dark energy.
  • High-mass stars are those that contain 8 times the Sun's mass or more.
  • Because it is older than most Type Ia remnants astronomers have found, G299.2-2.9 gives a look at how the remnants evolve over time.

G299.2-2.9 is an intriguing supernova remnant found about 16,000 light years away in the Milky Way galaxy . Evidence points to G299.2-2.9 being the remains of a Type Ia supernova, where a white dwarf has grown sufficiently massive to cause a thermonuclear explosion. Because it is older than most supernova remnants caused by these explosions, at an age of about 4500 years, G299.2-2.9 provides astronomers with an excellent opportunity to study how these objects evolve over time. It also provides a probe of the Type Ia supernova explosion that produced this structure.

This composite image shows G299.2-2.9 in X-ray light from Chandra, along with data from the ROSAT satellite (orange), that has been overlaid on an infrared image from the Two Micron All-Sky Survey (2MASS). The faint X-ray emission from the inner region reveals relatively large amounts of iron and silicon, as expected for a remnant of a Type Ia supernova. The outer shell of the remnant is complex, with at least a double shell structure. Typically, such a complex outer shell is associated with a star that has exploded into space where gas and dust are not uniformly distributed.

Since most theories to explain Type Ia supernovas assume they go off in a uniform environment, detailed studies of this complicated outer shell should help astronomers improve their understanding of the environments where these explosions occur. It is very important to understand the details of Type Ia explosions because astronomers use them as cosmic mile markers to measure the accelerated expansion of the universe and study dark energy. The discovery of this accelerated expansion in the late 1990s led to the recent award of the Nobel Prize in Physics.

Image Credit: X-ray: NASA/CXC/U. Texas at Arlington/S.Park et al, ROSAT; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
Explanation from: http://chandra.harvard.edu/photo/2011/g299/

June 28, 2017

Dwarf Galaxy UGC 8201

Dwarf Galaxy UGC 8201

The galaxy UGC 8201, captured here by the NASA/ESA Hubble Space Telescope, is a dwarf irregular galaxy, so called because of its small size and chaotic structure. It lies just under 15 million light-years away from us in the constellation of Draco (the Dragon). As with most dwarf galaxies it is a member of a larger group of galaxies. In this case UCG 8201 is part of the M81 galaxy group; this group is one of the closest neighbours to the Local Group of galaxies, which contains our galaxy, the Milky Way.

UGC 8201 is at an important phase in its evolution. It has recently finished a long period of star formation, which had significant impact on the whole galaxy. This episode lasted for several hundred million years and produced a high number of newborn bright stars. These stars can be seen in this image as the dominating light source within the galaxy. This process also changed the distribution and amount of dust and gas in between the stars in the galaxy.

Such large star formation events need extensive sources of energy to trigger them. However, compared to larger galaxies, dwarf galaxies lack such sources and they do not appear to have enough gas to produce as many new stars as they do. This raises an important unanswered question in galaxy evolution: How do relatively isolated, low-mass systems such as dwarf galaxies sustain star formation for extended periods of time?

Due to its relative proximity to Earth UGC 8201 is an excellent object for research and provides an opportunity to improve our understanding of how dwarf galaxies evolve and grow.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1510a/

Wide-field view of the sky around the young star HL Tauri

Wide-field view of the sky around the young star HL Tauri

This image shows the region in which HL Tauri is situated. HL Tauri is part of one of the closest star-forming regions to Earth and there are many young stars, as well as clouds of dust, in its vicinity. This picture was created from images forming part of the Digitized Sky Survey 2.

Explanation from: ESO/Digitized Sky Survey 2

Globular Cluster NGC 6752

Globular Cluster NGC 6752

Looking like a hoard of gems fit for an emperor’s collection, this deep sky object called NGC 6752 is in fact far more worthy of admiration. It is a globular cluster, and at over 10 billion years old is one the most ancient collections of stars known. It has been blazing for well over twice as long long as our Solar System has existed.

NGC 6752 contains a high number of “blue straggler” stars, some of which are visible in this image. These stars display characteristics of stars younger than their neighbours, despite models suggesting that most of the stars within globular clusters should have formed at approximately the same time. Their origin is therefore something of a mystery.

Studies of NGC 6752 may shed light on this situation. It appears that a very high number — up to 38% — of the stars within its core region are binary systems. Collisions between stars in this turbulent area could produce the blue stragglers that are so prevalent.

Lying 13 000 light-years distant, NGC 6752 is far beyond our reach, yet the clarity of Hubble’s images brings it tantalisingly close.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1205a/

Lightning and Wildfire

Lightning and Wildfire

A new NASA-funded study finds that lightning storms were the main driver of recent massive fire years in Alaska and northern Canada, and that these storms are likely to move farther north with climate warming, potentially altering northern landscapes.

The study, led by Vrije Universiteit Amsterdam and the University of California, Irvine, examined the cause of the fires, which have been increasing in number in recent years. There was a record number of lightning-ignited fires in the Canadian Northwest Territories in 2014 and in Alaska in 2015. The team found increases of between two and five percent a year in the number of lightning-ignited fires since 1975.

To study the fires, the team analyzed data from NASA’s Terra and Aqua satellites and from ground-based lightning networks.

Lead author Sander Veraverbeke of Vrije Universiteit Amsterdam, who conducted the work while at UC Irvine, said that while the drivers of large fire years in the high north are still poorly understood, the observed trends are consistent with climate change.

“We found that it is not just a matter of more burning with higher temperatures. The reality is more complex: higher temperatures also spur more thunderstorms. Lightning from these thunderstorms is what has been igniting many more fires in these recent extreme events,” Veraverbeke said.

Study co-author Brendan Rogers at Woods Hole Research Center in Falmouth, Massachusetts, said these trends are likely to continue. “We expect an increasing number of thunderstorms, and hence fires, across the high latitudes in the coming decades as a result of climate change.” This is confirmed in the study by different climate model outputs.

Study co-author Charles Miller of NASA’s Jet Propulsion Laboratory in Pasadena, California, said while data from the lightning networks were critical to this study, it is challenging to use these data for trend detection because of continuing network upgrades. “A spaceborne sensor that provides high northern latitude lightning data that can be linked with fire dynamics would be a major step forward,” he said.

The researchers found that the fires are creeping farther north, near the transition from boreal forests to Arctic tundra. “In these high-latitude ecosystems, permafrost soils store large amounts of carbon that become vulnerable after fires pass through,” said co-author James Randerson of the University of California, Irvine. “Exposed mineral soils after tundra fires also provide favorable seedbeds for trees migrating north under a warmer climate.”

“Taken together, we discovered a complex feedback loop between climate, lightning, fires, carbon and forests that may quickly alter northern landscapes,” Veraverbeke concluded. “A better understanding of these relationships is critical to better predict future influences from climate on fires, and from fires on climate.”

Explanation from: https://www.nasa.gov/feature/jpl/lightning-sparking-more-boreal-forest-fires/

Coils of Magnetic Field Lines

Coils of Magnetic Field Lines

A smallish solar filament looks like it collapsed into the Sun and set off a minor eruption that hurled plasma into space (June 20, 2017). Then, the disrupted magnetic field immediately began to reorganize itself, hence the bright series of spirals coiling up over that area. The magnetic field lines are made visible in extreme ultraviolet light as charged particles spin along them. Also of interest are the darker, cooler strands of plasma being pulled and twisted at the edge of the Sun just below the active region.

Image Credit: NASA/GSFC/Solar Dynamics Observatory
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21764

The 2XMM J143450.5+033843 Galaxy

The 2XMM J143450.5+033843 Galaxy

Not all galaxies have the luxury of possessing a simple moniker or quirky nickname. The subject of this NASA/ESA Hubble Space Telescope image was one of the unlucky ones, and goes by the rather unpoetic name of 2XMM J143450.5+033843.

Such a name may seem like a random jumble of numbers and letters, but like all galactic epithets it has a distinct meaning. This galaxy, for example, was detected and observed as part of the second X-ray sky survey performed by ESA’s XMM-Newton Observatory. Its celestial coordinates form the rest of the bulky name, following the “J”: a right ascension value of 14h 34m 50.5s (this can be likened to terrestrial longitude), and a declination of +03d 38m 43s (this can be likened to terrestrial latitude). The other fuzzy object in the frame was named in the same way — it is a bright galaxy named 2XMM J143448.3+033749.

2XMM J143450.5+033843 lies nearly 400 million light-years away from Earth. It is a Seyfert galaxy that is dominated by something known as an Active Galactic Nucleus — its core is thought to contain a supermassive black hole that is emitting huge amounts of radiation, pouring energetic X-rays out into the Universe.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1726a/

June 26, 2017



This orange blob shows the nearby star Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). This is the first time that ALMA has ever observed the surface of a star and this first attempt has resulted in the highest-resolution image of Betelgeuse available.

Betelgeuse is one of the largest stars currently known — with a radius around 1400 times larger than the Sun’s in the millimeter continuum. About 600 light-years away in the constellation of Orion (The Hunter), the red supergiant burns brightly, causing it to have only a short life expectancy. The star is just about eight million years old, but is already on the verge of becoming a supernova. When that happens, the resulting explosion will be visible from Earth, even in broad daylight.

The star has been observed in many other wavelengths, particularly in the visible, infrared, and ultraviolet. Using ESO’s Very Large Telescope astronomers discovered a vast plume of gas almost as large as our Solar System. Astronomers have also found a gigantic bubble that boils away on Betelgeuse’s surface. These features help to explain how the star is shedding gas and dust at tremendous rates. In this picture, ALMA observes the hot gas of the lower chromosphere of Betelgeuse at sub-millimeter wavelengths — where localised increased temperatures explain why it is not symmetric. Scientifically, ALMA can help us to understand the extended atmospheres of these hot, blazing stars.

Image Credit: ALMA (ESO/NAOJ/NRAO)/E. O’Gorman/P. Kervella
Explanation from: https://www.eso.org/public/images/potw1726a/

Colliding Galaxies Arp 299

Colliding Galaxies Arp 299

  • Arp 299 is a system where two galaxies are in the process of merging.
  • Chandra data has revealed 25 bright point-like X-ray sources in Arp 299, 14 of which are categorized as "ULXs".
  • These ULXs are likely binary systems where a black hole or neutron star is pulling material from a companion star.
  • Such a high concentration of ULXs is rare, but caused by a high rate of star formation triggered by the galactic merger.

What would happen if you took two galaxies and mixed them together over millions of years? A new image including data from NASA's Chandra X-ray Observatory reveals the cosmic culinary outcome.

Arp 299 is a system located about 140 million light years from Earth. It contains two galaxies that are merging, creating a partially blended mix of stars from each galaxy in the process.

However, this stellar mix is not the only ingredient. New data from Chandra reveals 25 bright X-ray sources sprinkled throughout the Arp 299 concoction. Fourteen of these sources are such strong emitters of X-rays that astronomers categorize them as "ultra-luminous X-ray sources," or ULXs.

These ULXs are found embedded in regions where stars are currently forming at a rapid rate. Most likely, the ULXs are binary systems where a neutron star or black hole is pulling matter away from a companion star that is much more massive than the Sun. These double star systems are called high-mass X-ray binaries.

Such a loaded buffet of high-mass X-ray binaries is rare, but Arp 299 is one of the most powerful star-forming galaxies in the nearby Universe. This is due at least in part to the merger of the two galaxies, which has triggered waves of star formation. The formation of high-mass X-ray binaries is a natural consequence of such blossoming star birth as some of the young massive stars, which often form in pairs, evolve into these systems.

This new composite image of Arp 299 contains X-ray data from Chandra (pink), higher-energy X-ray data from NuSTAR (purple), and optical data from the Hubble Space Telescope (white and faint brown). Arp 299 also emits copious amounts of infrared light that has been detected by observatories such as NASA's Spitzer Space Telescope, but those data are not included in this composite.

The infrared and X-ray emission of the galaxy is remarkably similar to that of galaxies found in the very distant Universe, offering an opportunity to study a relatively nearby analog of these distant objects. A higher rate of galaxy collisions occurred when the universe was young, but these objects are difficult to study directly because they are located at colossal distances.

The Chandra data also reveal diffuse X-ray emission from hot gas distributed throughout Arp 299. Scientists think the high rate of supernovas, another common trait of star-forming galaxies, has expelled much of this hot gas out of the center of the system.

Image Credit: X-ray: NASA/CXC/Univ of Crete/K. Anastasopoulou et al, NASA/NuSTAR/GSFC/A. Ptak et al; Optical: NASA/STScI
Explanation from: http://chandra.harvard.edu/photo/2017/arp299/



NASA's Cassini spacecraft peers toward a sliver of Saturn's sunlit atmosphere while the icy rings stretch across the foreground as a dark band.

This view looks toward the unilluminated side of the rings from about 7 degrees below the ring plane. The image was taken in green light with the Cassini spacecraft wide-angle camera on March 31, 2017.

The view was obtained at a distance of approximately 620,000 miles (1 million kilometers) from Saturn. Image scale is 38 miles (61 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21334

June 25, 2017

Andromeda Galaxy, Triangulum Galaxy and VLT Telescope

Andromeda Galaxy, Triangulum Galaxy and VLT Telescope

This stunning image of the clear Chilean sky shows a speckling of bright stars and distant galaxies across the frame, all suspended above one of the four Unit Telescopes (UTs) of the Very Large Telescope (VLT). This is the fourth UT and it is known as Yepun (Venus).

Two objects seen in this frame are more famous than their neighbours. In the left hand portion of the image is a fairly prominent galaxy that forms a streak across the sky — Messier 31, or the Andromeda Galaxy. Upwards and to the right of this smudge is a bright star, which in turn points upwards to a galaxy that lies roughly along the same extended line. This star is named Beta Andromedae — otherwise known as Mirach — and the second galaxy is Messier 33 (at the top of the frame). These two galaxies are thought to have interacted in the past, forming a bridge of hydrogen gas that spans the gap between them.

Image Credit: ESO/B. Tafreshi
Explanation from: https://www.eso.org/public/images/potw1342a/

Jupiter's Clouds

Jupiter's Clouds

This enhanced-color image of Jupiter's bands of light and dark clouds was created by citizen scientists Gerald Eichstädt and Seán Doran using data from the JunoCam imager on NASA's Juno spacecraft.

Three of the white oval storms known as the "String of Pearls" are visible near the top of the image. Each of the alternating light and dark atmospheric bands in this image is wider than Earth, and each rages around Jupiter at hundreds of miles (kilometers) per hour. The lighter areas are regions where gas is rising, and the darker bands are regions where gas is sinking.

Juno acquired the image on May 19, 2017, at 11:30 a.m. PST (2:30 p.m. EST) from an altitude of about 20,800 miles (33,400 kilometers) above Jupiter's cloud tops.

Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstadt/Sean Doran
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21393

Galaxy Cluster MACS J2129-0741

Galaxy Cluster MACS J2129-0741

This image is a wide-field view of the galaxy cluster MACS J2129-0741, located in the constellation Aquarius (the Water-Bearer). The massive galaxy cluster magnifies, brightens, and distorts the images of remote background galaxies, including the far-distant, dead disc galaxy MACS2129-1.

Image Credit: NASA, ESA, Marc Postman (STScI), and the CLASH team