Aurora seen from the International Space Station

This still shows a stunning aurora captured from the International Space Station. Auroras are a space weather phenomenon that occur when electrically-charged electrons and protons collide with neutral atoms in the upper atmosphere. The dancing lights of the aurora provide a spectacular show for those on the ground, but also capture the imaginations of scientists who study the aurora and the complex processes that create them.

Image Credit: NASA

The PGC 39058 Galaxy

Astronomers are used to encountering challenges in their work, but studying the prosaically-named galaxy PGC 39058 proves more difficult than usual. Due to a stroke of bad luck, a bright star happens to lie between the galaxy and the Earth, meaning our view is partly obscured by the glare of the star. The astounding image from the NASA/ESA Hubble Space Telescope shows the nearby star easily outshining the more distant galaxy PGC 39058. The galaxy is about 14 million light-years away and contains millions of stars — many of them not unlike the bright star in the foreground.

The bright foreground star seems to shine with incredible intensity due to the power of Hubble. Most Earth-bound observers would however consider the star to be quite faint. At magnitude 6.7, binoculars or a small telescope are needed to see it at all. That the image manages to capture both objects serves to further highlight Hubble’s excellent optics and sharp vision.

PGC 39058 is a dwarf galaxy, which explains its faintness despite its modest distance by galaxy standards. The sharp Hubble image easily resolves it completely into its component stars and also reveals many much more distant galaxies in the background.

This star and galaxy pair is located within the constellation of Draco (the Dragon). It is visible in the northern hemisphere, appearing to slither over a large portion of the sky around the north celestial pole. The ancient Greeks claimed that Draco represented Ladon, the dragon with 100 heads. One of Hercules' twelve near-impossible tasks was to steal golden apples guarded by Ladon. The difficulty of this challenge is perhaps on a par with observing such a faint galaxy obscured by a bright star.

This picture was created from images taken using the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Images through yellow (F606W, shown as blue) and near infrared (F814W, shown as red) were combined. The exposure times were 20 minutes and 15 minutes respectively and the field of view is 2 × 1.6 arcminutes.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1021a/

Wide Field Image of Cygnus X-1

Cygnus X-1 is a black hole about 15 times the mass of the Sun in orbit with a massive blue companion star. Using optical observations of the companion star and its motion around its unseen companion, the team made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

Image Credit: DSS
Explanation from: http://chandra.si.edu/photo/2011/cygx1/more.html

Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way

This artist’s impression shows stars orbiting the supermassive black hole at the centre of the Milky Way. In 2018 one of these stars, S2, will pass very close to the black hole and this event will be the best opportunity to study the effects of very strong gravity and test the predictions of Einstein’s general relativity in the near future.

The GRAVITY instrument on the ESO Very Large Telescope Interferometer is the most powerful tool for measuring the positions of these stars in existence and it was successfully tested on the S2 star in the summer of 2016. The orbit of S2 is shown in red and the position of the central black hole is marked with a red cross.

Image Credit: ESO/L. Calçada
Explanation from: http://www.eso.org/public/images/eso1622a/

Auroras in Jupiter's Atmosphere

This composite video illustrates the auroras on Jupiter relative to their position on the giant planet. As on Earth, auroras are produced by the interaction of a planet's magnetic field with its atmosphere. The Jupiter auroras observed by NASA's Hubble Space Telescope are some of the most active and brightest ever caught by Hubble, reaching intensities over a thousand times brighter than those seen on Earth. Hubble's sensitivity to ultraviolet light captures the glow of the auroras above Jupiter's cloud top.

The auroras were photographed on May 19, 2016, during a series of far-ultraviolet-light observations taking place as NASA's Juno spacecraft approaches and enters into orbit around Jupiter. The aim of the program is to determine how Jupiter's auroras respond to changing conditions in the solar wind, a stream of charged particles emitted from the sun.

The full-color disk of Jupiter in this video was separately photographed at a different time by Hubble's Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble project that annually captures global maps of the outer planets.

Auroras are formed when charged particles in the space surrounding the planet are accelerated to high energies along the planet's magnetic field. When the particles hit the atmosphere near the magnetic poles, they cause it to glow like gases in a fluorescent light fixture. Jupiter's magnetosphere is 20,000 times stronger than Earth's. These observations will reveal how the solar system's largest and most powerful magnetosphere behaves.

Video Credit: NASA, ESA, J. Nichols, G. Bacon (STScI), A. Simon (GSFC) and the OPAL team
Explanation from: http://hubblesite.org/newscenter/archive/releases/2016/24/video/c/

Banff National Park

Banff National Park is Canada's oldest national park, established in 1885 in the Rocky Mountains. The park, located 110–180 kilometres (68–112 mi) west of Calgary in the province of Alberta, encompasses 6,641 square kilometres (2,564 sq mi) of mountainous terrain, with numerous glaciers and ice fields, dense coniferous forest, and alpine landscapes. The Icefields Parkway extends from Lake Louise, connecting to Jasper National Park in the north. Provincial forests and Yoho National Park are neighbours to the west, while Kootenay National Park is located to the south and Kananaskis Country to the southeast. The main commercial centre of the park is the town of Banff, in the Bow River valley.

The Canadian Pacific Railway was instrumental in Banff's early years, building the Banff Springs Hotel and Lake Louise Chalet, and attracting tourists through extensive advertising. In the early 20th century, roads were built in Banff, at times by war internees from World War I, and through Great Depression-era public works projects. Since the 1960s, park accommodations have been open all year, with annual tourism visits to Banff increasing to over 5 million in the 1990s. Millions more pass through the park on the Trans-Canada Highway. As Banff has over three million visitors annually, the health of its ecosystem has been threatened. In the mid-1990s, Parks Canada responded by initiating a two-year study, which resulted in management recommendations, and new policies that aim to preserve ecological integrity.

Banff National Park has a subarctic climate with three ecoregions, including montane, subalpine, and alpine. The forests are dominated by Lodgepole pine at lower elevations and Engelmann spruce in higher ones below the treeline, above which is primarily rocks and ice. Mammal species such as the grizzly, cougar, wolverine, elk, bighorn sheep and moose are found, along with hundreds of bird species. Reptiles and amphibians are also found but only a limited number of species have been recorded. The mountains are formed from sedimentary rocks which were pushed east and over newer rock strata between 80 and 55 million years ago. Over the past few million years, glaciers have at times covered most of the park, but today are found only on the mountain slopes though they include the Columbia Icefield, the largest uninterrupted glacial mass in the Rockies. Erosion from water and ice have carved the mountains into their current shapes.

Explanation from: https://en.wikipedia.org/wiki/Banff_National_Park

IC 2118: The Witch Head Nebula

IC 2118 (also known as Witch Head Nebula due to its shape), is an extremely faint reflection nebula believed to be an ancient supernova remnant or gas cloud illuminated by nearby supergiant star Rigel in Orion. It lies in the Eridanus constellation, about 900 light-years from Earth. The nature of the dust particles, reflecting blue light better than red, is a factor in giving the Witch Head its blue color. Radio observations show substantial carbon monoxide emission throughout parts of IC 2118 an indicator of the presence of molecular clouds and star formation in the nebula. In fact candidates for pre-main sequence stars and some classic T-Tauri stars have been found deep within the nebula.

The molecular clouds of IC 2118 are probably juxtaposed to the outer boundaries of the vast Orion-Eridanus bubble, a giant supershell of molecular hydrogen blown by the high mass stars of the Orion OB1 association. As the supershell expands into the interstellar medium, favorable circumstances for star formation occur. IC 2118 is located in one such area. The wind blown appearance and cometary shape of the bright reflection nebula is highly suggestive of a strong association with the high mass luminous stars of Orion OB1. The fact that the heads of the cometary clouds of IC2118 point northeast towards the association is strong support of that relationship.

Image Credit & Copyright: Jeff Signorelli
Explanation from: https://en.wikipedia.org/wiki/IC_2118

Messier 51

Nearly a million seconds of observing time with NASA’s Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way glittering with hundreds of X-ray points of light.

The galaxy is officially named Messier 51 (M51) or NGC 5194, but often goes by its nickname of the “Whirlpool Galaxy.” Like the Milky Way, the Whirlpool is a spiral galaxy with spectacular arms of stars and dust. M51 is located 30 million light years from Earth, and its face-on orientation to Earth gives us a perspective that we can never get of our own spiral galactic home.

By using Chandra, astronomers can peer into the Whirlpool to uncover things that can only be detected in X-rays. In this new composite image, Chandra data are shown in purple. Optical data from the Hubble Space Telescope are red, green and blue.

Most of the X-ray sources are X-ray binaries (XRBs). These systems consist of pairs of objects where a compact star, either a neutron star or, more rarely, a black hole, is capturing material from an orbiting companion star. The infalling material is accelerated by the intense gravitational field of the compact star and heated to millions of degrees, producing a luminous X-ray source. The Chandra observations reveal that at least ten of the XRBs in M51 are bright enough to contain black holes. In eight of these systems the black holes are likely capturing material from companion stars that are much more massive than the sun.

Because astronomers have been observing M51 for about a decade with Chandra, they have critical information about how X-ray sources containing black holes behave over time. The black holes with massive stellar companions are consistently bright over the ten years of Chandra observations. These results suggest that the high-mass stars in these X-ray sources also have strong winds that allow for a steady stream of material to flow onto the black hole.

A difference between the Milky Way and the Whirlpool galaxy is that M51 is in the midst of merging with a smaller companion galaxy seen in the upper left of the image. Scientists think this galactic interaction is triggering waves of star formation. The most massive of the newly formed stars will race through their evolution in a few million years and collapse to form neutron stars or black holes. Most of the XRBs containing black holes in M51 are located close to regions where stars are forming, showing their connection to the oncoming galactic collision.

Previous studies of the Whirlpool Galaxy with Chandra revealed just over 100 X-ray sources. The new dataset, equivalent to about 900,000 seconds of Chandra observing time, reveals nearly 500 X-ray sources. About 400 of these sources are thought to be within M51, with the remaining either being in front of or behind the galaxy itself.

Much of the diffuse, or fuzzy, X-ray emission in M51 comes from gas that has been superheated by supernova explosions of massive stars.

Image Credit: X-ray: NASA/CXC/Wesleyan Univ./R.Kilgard, et al; Optical: NASA/STScI
Explanation from: http://www.nasa.gov/mission_pages/chandra/multimedia/sparkling-m51.html

Auroras on Jupiter

Astronomers are using NASA's Hubble Space Telescope to study auroras — stunning light shows in a planet's atmosphere — on the poles of the largest planet in the Solar System, Jupiter. This observation program is supported by measurements made by NASA's Juno spacecraft, currently on its way to Jupiter.

Jupiter, the largest planet in the Solar System, is best known for its colorful storms, the most famous being the Great Red Spot. Now astronomers have focused on another beautiful feature of the planet, using the ultraviolet capabilities of NASA's Hubble Space Telescope.

The extraordinary vivid glows shown in the new observations are known as auroras. They are created when high-energy particles enter a planet's atmosphere near its magnetic poles and collide with atoms of gas. As well as producing beautiful images, this program aims to determine how various components of Jupiter's auroras respond to different conditions in the solar wind, a stream of charged particles ejected from the Sun.

This observation program is perfectly timed as NASA's Juno spacecraft is currently in the solar wind near Jupiter and will enter the orbit of the planet in early July 2016. While Hubble is observing and measuring the auroras on Jupiter, Juno is measuring the properties of the solar wind itself — a perfect collaboration between a telescope and a space probe.

"These auroras are very dramatic and among the most active I have ever seen," said Jonathan Nichols from the University of Leicester, UK, and principal investigator of the study. "It almost seems as if Jupiter is throwing a fireworks party for the imminent arrival of Juno."

To highlight changes in the auroras, Hubble is observing Jupiter almost daily for several months. Using this series of far-ultraviolet images from Hubble's Space Telescope Imaging Spectrograph, it is possible for scientists to create videos that demonstrate the movement of the vivid auroras, which cover areas bigger than the Earth.

Not only are the auroras huge in size, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. While on Earth the most intense auroras are caused by solar storms — when charged particles rain down on the upper atmosphere, excite gases, and cause them to glow red, green, and purple — Jupiter has an additional source for its auroras.

The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind, but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanos.

The new observations and measurements made with Hubble and Juno will help to better understand how the Sun and other sources influence auroras. While the observations with Hubble are still ongoing and the analysis of the data will take several more months, the first images and videos are already available and show the auroras on Jupiter's north pole in their full beauty. In support of the Juno mission, Hubble will continue to monitor Jupiter auroras several times a month for the duration of the Juno mission.

Image Credit: NASA, ESA, and J. Nichols
Explanation from: http://hubblesite.org/newscenter/archive/releases/2016/24/full/

Coronal Mass Ejection

This LASCO C2 image, taken 8 January 2002, shows a widely spreading coronal mass ejection (CME) as it blasts more than a billion tons of matter out into space at millions of kilometers per hour. The C2 image was turned 90 degrees so that the blast seems to be pointing down. An EIT 304 Angstrom image from a different day was enlarged and superimposed on the C2 image so that it filled the occulting disk for effect.

Image Credit: ESA/NASA/SOHO

Star Cluster NGC 281

High-mass stars are important because they are responsible for much of the energy pumped into our galaxy over its lifetime. Unfortunately, these stars are poorly understood because they are often found relatively far away and can be obscured by gas and dust. The star cluster NGC 281 is an exception to this rule. It is located about 9,200 light years from Earth and, remarkably, almost 1,000 light years above the plane of the Galaxy, giving astronomers a nearly unfettered view of the star formation within it.

This composite image of NGC 281 contains X-ray data from Chandra (purple) with infrared observations from Spitzer (red, green, blue). The high-mass stars in NGC 281 drive many aspects of their galactic environment through powerful winds flowing from their surfaces and intense radiation that heats surrounding gas, "boiling it away" into interstellar space. This process results in the formation of large columns of gas and dust, as seen on the left side of the image. These structures likely contain newly forming stars. The eventual deaths of massive stars as supernovas will also seed the galaxy with material and energy.

Image Credit: X-ray: NASA/CXC/CfA/S.Wolk; IR: NASA/JPL/CfA/S.Wolk
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_2071.html

Artist’s impression of the Black Hole Flare

This diagram shows how a shifting feature, called a corona, can create a flare of X-rays around a black hole. The corona (feature represented in purplish colors) gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right). Astronomers don't know why the coronas shift, but they have learned that this process leads to a brightening of X-ray light that can be observed by telescopes.

Normally, before a black hole's corona shifts, there is already an effect at work called relativistic boosting. As X-ray light from the corona reflects off the black hole's surrounding disk of material -- which is traveling near half the speed of light -- the X-ray light becomes brightened, as seen on the left side of the illustration. This boosting occurs on the side of the disk where the material is traveling toward us. The opposite effect, a dimming of the X-ray light, occurs on the other side of the disk moving away from us.

Another form of relativistic boosting happens when the corona shoots away from the black hole, and later collapses. Its X-ray light is also brightened, as the corona travels toward us leading to X-ray flares.

In 2014, NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, and Swift space telescopes witnessed an X-flare from the supermassive black hole in a distant galaxy called Markarian 335. The observations allowed astronomers to link a shifting corona to an X-ray flare for the first time.

Image Credit: NASA/JPL-Caltech
Explanation from: https://www.nasa.gov/image-feature/jpl/pia20051/the-anatomy-of-a-black-hole-flare

New Zealand seen from the International Space Station

In this panorama taken from the International Space Station (ISS), the Sun’s glint point highlights the details of Cook Strait, between New Zealand’s North and South Islands. Astronauts looking west towards the setting Sun were able to see this high-contrast detail even though the center of the glint point was 1,000 kilometers (600 miles) away from the ISS.

The sunglint shows Wellington Bay—where the capital city is located—opening onto Cook Strait. Banks Peninsula, near the city of Christchurch, is the prominent cape whose characteristic shape is well known to ISS crews.

Clouds are approaching from the top left (west) in the image. New Zealand is seldom photographed from orbit because it is one of the cloudier parts of planet, and because crew sleep periods often occur when the ISS passes over the area.

Image Credit: NASA
Explanation from: http://earthobservatory.nasa.gov/IOTD/view.php?id=85332

The Snowflake Cluster and the Cone Nebula

Strange shapes and textures can be found in the neighborhood of the Cone Nebula. These patterns result from the tumultuous unrest that accompanies the formation of the open cluster of stars known as NGC 2264, the Snowflake Cluster. To better understand this process, a detailed image of this region was taken in two colors of infrared light by the orbiting Spitzer Space Telescope.

Bright stars from the Snowflake Cluster dot the field. These stars soon heat up and destroy the gas and dust mountains in which they formed. One such dust mountain is the famous Cone Nebula, visible in the above image on the left, pointing toward a bright star near the center of the field. The entire NGC 2264 region is located about 2,500 light years away toward the constellation of the Unicorn (Monoceros).

Image Credit: NASA
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_822.html

The NGC 3021 Galaxy

This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 3021 which lies about 100 million light-years away in the constellation of Leo Minor (The Little Lion).

Among many other types of stars, this galaxy contains Cepheid variable stars, which can be used work out the distance to the galaxy. These stars pulsate at a rate that is closely related to their intrinsic brightness, so measurements of their rate of pulsation and their observed brightness give astronomers enough information to calculate the distance to the galaxy itself.

Cepheids are also used to calibrate an even brighter distance marker, that can be used over greater distances: Type Ia supernovae. One of these bright exploding stars was observed in NGC 3021, back in 1995.

In addition, the supernova in NGC 3021 was also used to refine the measurement of what is known as the Hubble constant. The value of this constant defines how fast the Universe is expanding and the more accurately we know it the more we can understand about the evolution of the Universe in the past as well as in the future. So, there is much more to this galaxy than just a pretty spiral.

Image Credit: NASA, ESA, A. Riess (STScI)
Explanation from: https://www.spacetelescope.org/images/potw1513a/

Hubble Confirms New Dark Spot on Neptune

New images obtained on May 16, 2016, by NASA's Hubble Space Telescope confirm the presence of a dark vortex in the atmosphere of Neptune. Though similar features were seen during the Voyager 2 flyby of Neptune in 1989 and by the Hubble Space Telescope in 1994, this vortex is the first one observed on Neptune in the 21st century.

The discovery was announced on May 17, 2016, in a Central Bureau for Astronomical Telegrams (CBAT) electronic telegram by University of California at Berkeley research astronomer Mike Wong, who led the team that analyzed the Hubble data.

Neptune's dark vortices are high-pressure systems and are usually accompanied by bright "companion clouds," which are also now visible on the distant planet. The bright clouds form when the flow of ambient air is perturbed and diverted upward over the dark vortex, causing gases to likely freeze into methane ice crystals. "Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains," Wong said. "And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth."

Beginning in July 2015, bright clouds were again seen on Neptune by several observers, from amateurs to astronomers at the W. M. Keck Observatory in Hawaii. Astronomers suspected that these clouds might be bright companion clouds following an unseen dark vortex. Neptune's dark vortices are typically only seen at blue wavelengths, and only Hubble has the high resolution required for seeing them on distant Neptune.

In September 2015, the Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble Space Telescope project that annually captures global maps of the outer planets, revealed a dark spot close to the location of the bright clouds, which had been tracked from the ground. By viewing the vortex a second time, the new Hubble images confirm that OPAL really detected a long-lived feature. The new data enabled the team to create a higher-quality map of the vortex and its surroundings.

Neptune's dark vortices have exhibited surprising diversity over the years, in terms of size, shape, and stability (they meander in latitude, and sometimes speed up or slow down). They also come and go on much shorter timescales compared to similar anticyclones seen on Jupiter; large storms on Jupiter evolve over decades.

Planetary astronomers hope to better understand how dark vortices originate, what controls their drifts and oscillations, how they interact with the environment, and how they eventually dissipate, according to UC Berkeley doctoral student Joshua Tollefson, who was recently awarded a prestigious NASA Earth and Space Science Fellowship to study Neptune's atmosphere. Measuring the evolution of the new dark vortex will extend knowledge of both the dark vortices themselves, as well as the structure and dynamics of the surrounding atmosphere.

Image Credit: NASA, ESA, and M.H. Wong and J. Tollefson (UC Berkeley)
Explanation from: http://hubblesite.org/newscenter/archive/releases/2016/22/full/

The Spider Nebula

Located in the constellation Auriga, IC 417 lies about 10,000 light-years away. It is in the outer part of the Milky Way, almost exactly in the opposite direction from the galactic center.

A cluster of young stars called "Stock 8" can be seen at center right. The light from this cluster carves out a bowl in the nearby dust clouds, seen here as green fluff. Along the sinuous tail in the center and to the left, groupings of red point sources are also young stars.

In this image, infrared wavelengths, which are invisible to the unaided eye, have been assigned visible colors. Light with a wavelength of 1.2 microns, detected by 2MASS, is shown in blue. The Spitzer wavelengths of 3.6 and 4.5 microns are green and red, respectively.

Image Credit: NASA/JPL-Caltech/2MASS
Explanation from: http://www.nasa.gov/image-feature/jpl/pia20357/the-spider-nebula

Artist’s impression of the Shifting Coronas Around Black Holes

A supermassive black hole is depicted in this artist's concept, surrounded by a swirling disk of material falling onto it. The purplish ball of light above the black hole, a feature called the corona, contains highly energetic particles that generate X-ray light. If you could view the corona with your eyes, it would appear nearly invisible since we can't see its X-ray light.

Figure 1 shows how a shifting corona can create a flare of X-rays around a black hole. The corona gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right). Astronomers don't know why the coronas shift, but they have learned that this process leads to a brightening of X-ray light that can be observed by telescopes.

Normally, before a black hole's corona shifts, there is already an effect at work called relativistic boosting. As X-ray light from the corona reflects off the black hole's surrounding disk of material -- which is traveling near half the speed of light -- the X-ray light becomes brightened, as seen on the left side of the illustration. This boosting occurs on the side of the disk where the material is traveling toward us. The opposite effect, a dimming of the X-ray light, occurs on the other side of the disk moving away from us.

Another form of relativistic boosting happens when the corona shoots away from the black hole, and later collapses. Its X-ray light is also brightened as the corona travels toward us at very fast speeds, leading to X-ray flares.

In 2014, NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, and Swift space telescopes witnessed an X-flare from the supermassive black hole in a distant galaxy called Markarian 335. The observations allowed astronomers to link a shifting corona to an X-ray flare for the first time.

Image Credit: NASA/JPL-Caltech
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA20051

Jupiter imaged using the VISIR instrument on the VLT

In preparation for the imminent arrival of NASA’s Juno spacecraft in July 2016, astronomers used ESO’s Very Large Telescope to obtain spectacular new infrared images of Jupiter using the VISIR instrument. They are part of a campaign to create high-resolution maps of the giant planet to inform the work to be undertaken by Juno over the following months, helping astronomers to better understand the gas giant.

This image was created by selecting and combining the best images obtained from many short VISIR exposures at a wavelength of 5 micrometres.

Image Credit: ESO/L. Fletcher
Explanation from: https://www.eso.org/public/images/eso1623a/

Shedding Light on Dark Gamma Ray Bursts

Gamma-ray bursts are the universe's biggest explosions, capable of producing so much light that ground-based telescopes easily detect it billions of light-years away. Yet, for more than a decade, astronomers have puzzled over the nature of so-called dark bursts, which produce gamma rays and X-rays but little or no visible light. They make up roughly half of the bursts detected by NASA's Swift satellite since its 2004 launch.

Using one of the world's largest optical telescopes, the Keck I in Hawaii, researchers looked for unknown galaxies at the locations of 14 Swift-discovered dark bursts.

In this artist's concept, dense knots of dust in otherwise normal galaxies dim the light of a dark gamma-ray burst (center). The dust absorbs most or all of a burst's visible light but not higher-energy X-rays and gamma rays.

Image Credit: NASA/Swift/Aurore Simonnet
Explanation from: http://www.nasa.gov/multimedia/imagegallery/image_feature_1388.html

The Tarantula Nebula (30 Doradus)

Turning its 2.4-metre eye to the Tarantula Nebula, the NASA/ESA Hubble Space Telescope has taken this close-up of the outskirts of the main cloud of the Nebula.

The bright wispy structures are the signature of an environment rich in ionised hydrogen gas, called H II by astronomers. In reality these appear red, but the choice of filters and colours of this image, which includes exposures both in visible and infrared light, make the gas appear green.

These regions contain recently formed stars, which emit powerful ultraviolet radiation that ionises the gas around them. These clouds are ephemeral as eventually the stellar winds from the newborn stars and the ionisation process will blow away the clouds, leaving stellar clusters like the Pleiades.

Located in the Large Magellanic Cloud, one of our neighbouring galaxies, and situated at a distance of 170 000 light-years away from Earth, the Tarantula Nebula is the brightest known nebula in the Local Group of galaxies. It is also the largest (around 650 light-years across) and most active star-forming region known in our group of galaxies, containing numerous clouds of dust and gas and two bright star clusters. A recent Hubble image shows a large part of the nebula immediately adjacent to this field of view.

The cluster at the Tarantula nebula’s centre is relatively young and very bright. While it is outside the field of view of this image, the energy from it is responsible for most of the brightness of the Nebula, including the part we see here. The nebula is in fact so luminous that if it were located within 1000 light-years from Earth, it would cast shadows on our planet.

The Tarantula Nebula was host to the closest supernova ever detected since the invention of the telescope,supernova 1987A, which was visible to the naked eye.

Image Credit: ESA/Hubble, NASA, Judy Schmid
Explanation from: https://www.spacetelescope.org/images/potw1232a/

Artist’s impression of the disc around the young star TW Hydrae

This artist’s impression shows the closest known protoplanetary disc, around the star TW Hydrae in the huge constellation of Hydra (The Female Watersnake). The organic molecule methyl alcohol (methanol) has been found by the Atacama Large Millimeter/Submillimeter Array (ALMA) in this disc. This is the first such detection of the compound in a young planet-forming disc.

Image Credit: ESO/M. Kornmesser

Tungurahua Volcano Eruption

Runtun, Ecuador

December 4, 2011

Image Credit: Pablo Cozzaglio

Infrared view of the Cat’s Paw Nebula

Infrared view of the Cat’s Paw Nebula (NGC 6334) taken by VISTA. NGC 6334 is a vast region of star formation about 5500 light-years from Earth in the constellation of Scorpius. The whole gas cloud is about 50 light-years across. NGC 6334 is one of the most active nurseries of young massive stars in our galaxy, some nearly ten times the mass of our Sun and most born in the last few million years. The images were taken through Y, J and Ks filters (shown as blue, green and red respectively) and the exposure time was five minutes per filter. The field of view is about one degree across.

Image Credit: ESO/J. Emerson/VISTA
Explanation from: https://www.eso.org/public/images/eso1017a/