May 28, 2017

Supercell and Lightning over Nebraska

Supercell and Lightning over Nebraska

Broken Bow, Nebraska, USA
May 25, 2013

Image Credit & Copyright: Vanessa Neufeld

Helix Nebula

Helix Nebula

Named for its resemblance to a coiling spiral seen face on, the Helix Nebula (NGC 7293) is a challenging stargazing target that has a more complex three-dimensional structure than expected. Now, the nebula has a new portrait, created by the penetrating infrared gaze of NASA's Spitzer Space Telescope, which was released at the 207th meeting of the American Astronomical Society on Jan. 9, 2006.

The nebula, which is composed of gaseous shells and disks puffed out by a dying sunlike star, exhibits complex structure on even the smallest visible scales.

This image is a composite of infrared data from Spitzer and visible-light data from NASA's Hubble Space Telescope.

Image Credit: NASA/ESA/JPL-Caltech/J. Hora (CfA) and C.R. O'Dell (Vanderbilt)
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_486.html

Spiral Galaxy Messier 106

Spiral Galaxy Messier 106

Using a quartet of space observatories, University of Maryland astronomers may have cracked a 45-year mystery surrounding two ghostly spiral arms in the galaxy M106.

The Maryland team, led by Yuxuan Yang, took advantage of the unique capabilities of NASA's Chandra X-ray Observatory, NASA's Spitzer Space Telescope, the European Space Agency's XMM-Newton X-ray observatory, and data obtained almost a decade ago with NASA's Hubble Space Telescope.

M106 (also known as NGC 4258) is a stately spiral galaxy 23.5 million light-years away in the constellation Canes Venatici. In visible-light images, two prominent arms emanate from the bright nucleus and spiral outward. These arms are dominated by young, bright stars, which light up the gas within the arms. "But in radio and X-ray images, two additional spiral arms dominate the picture, appearing as ghostly apparitions between the main arms," says team member Andrew Wilson of the University of Maryland. These so-called "anomalous arms" consist mostly of gas.

"The nature of these anomalous arms is a long-standing puzzle in astronomy," says Yang. "They have been a mystery since they were first discovered in the early 1960s."

By analyzing data from XMM-Newton, Spitzer, and Chandra, Yang, Bo Li, Wilson, and Christopher Reynolds, all at the University of Maryland at College Park, have confirmed earlier suspicions that the ghostly arms represent regions of gas that are being violently heated by shock waves.

Previously, some astronomers had suggested that the anomalous arms are jets of particles being ejected by a supermassive black hole in M106's nucleus. But radio observations by the National Radio Astronomy Observatory's Very Long Baseline Array, and the Very Large Array in New Mexico, later identified another pair of jets originating in the core. "It is highly unlikely that an active galactic nucleus could have more than one pair of jets," says Yang.

In 2001, Wilson, Yang, and Gerald Cecil, of the University of North Carolina, Chapel Hill, noted that the two jets are tipped 30 degrees with respect to the galaxy disk. But if one could vertically project the jets onto the disk, they would line up almost perfectly with the anomalous arms. Figuring that this alignment was not strictly a matter of chance, Wilson, Yang, and Cecil proposed that the jets heat the gas in their line of travel, forming an expanding cocoon. Because the jets lie close to M106's disk, the cocoon heats gas in the disk and generates shock waves, heating the gas to millions of degrees and causing it to radiate brightly in X-rays and other wavelengths.

To test this idea, Yang and his colleagues looked at archival spectral observations from XMM-Newton. With XMM-Newton's superb sensitivity, the team could measure the gas temperature in the anomalous arms and also see how strongly X-rays from the gas are absorbed en route by intervening material.

"One of the predictions of this scenario is that the anomalous arms will gradually be pushed out of the galactic disk plane by jet-heated gas," says Yang. The XMM-Newton spectra show that X-rays are more strongly absorbed in the direction of the northwest arm than in the southeast arm. The results strongly suggest that the southeast arm is partly on the near side of M106's disk, and the northwest arm is partly on the far side.

The scientists noted that these observations show clear consistency with their scenario. Confirmation of this interpretation has recently come from archival observations from NASA's Spitzer Space Telescope, whose infrared view shows clear signs that X-ray emission from the northwest arm is being absorbed by warm gas and dust in the galaxy's disk. Moreover, Chandra's superior imaging resolution gives clear indications of gas shocked by interactions with the two jets.

Besides addressing the mystery of the anomalous arms, these observations allowed the team to estimate the energy in the jets and gauge their relationship to M106's central black hole.

Image Credit: X-ray: NASA/CXC/Univ. of Maryland/A.S. Wilson et al.; Optical: Palomar Observatory. DSS; IR:NASA/JPL-Caltech; VLA: NRAO/AUI/NSF
Explanation from: http://www.spitzer.caltech.edu/news/253-ssc2007-06-Mystery-Spiral-Arms-Explained-

Aurora over Alaska

Aurora over Alaska

Alaska, USA

Image Credit: Noppawat Tom Charoensinphon/Getty Images

Exoplanet GJ1214b

Exoplanet GJ1214b

Astronomers have discovered the second super-Earth exoplanet for which they have determined the mass and radius, giving vital clues about its structure. It is also the first super-Earth where an atmosphere has been found. The exoplanet, orbiting a small star only 40 light-years away from us, opens up dramatic new perspectives in the quest for habitable worlds. The planet, GJ1214b, has a mass about six times that of Earth and its interior is likely to be mostly made of water ice. Its surface appears to be fairly hot and the planet is surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.

In this week’s issue of Nature, astronomers announce the discovery of a planet around the nearby, low-mass star GJ1214. It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b. A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star. The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune.

Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron.

GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. “Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid,” says David Charbonneau, lead author of the paper reporting the discovery.

When the astronomers compared the measured radius of GJ1214b with theoretical models of planets, they found that the observed radius exceeds the models’ predictions: there is something more than the planet’s solid surface blocking the star’s light — a surrounding atmosphere, 200 km thick. “This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it,” says Charbonneau, “but these conditions are still very interesting, as they could allow for some complex chemistry to take place.”

“Because the planet is too hot to have kept an atmosphere for long, GJ1214b represents the first opportunity to study a newly formed atmosphere enshrouding a world orbiting another star,” adds team member Xavier Bonfils. “Because the planet is so close to us, it will be possible to study its atmosphere even with current facilities.”

The planet was first discovered as a transiting object within the MEarth project, which follows about 2000 low-mass stars to look for transits by exoplanets. To confirm the planetary nature of GJ1214b and to obtain its mass (using the so-called Doppler method), the astronomers needed the full precision of the HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla. An instrument with unrivalled stability and great precision, HARPS is the world’s most successful hunter for small exoplanets.

“This is the second super-Earth exoplanet for which the mass and radius could be obtained, allowing us to determine the density and to infer the inner structure,” adds co-author Stephane Udry. “In both cases, data from HARPS was essential to characterise the planet.”

“The differences in composition between these two planets are relevant to the quest for habitable worlds,” concludes Charbonneau. If super-Earth planets in general are surrounded by an atmosphere similar to that of GJ1214b, they may well be inhospitable to the development of life as we know it on our own planet.

Image Credit: ESO/L. Calçada
Explanation from: https://www.eso.org/public/news/eso0950/

Saturn's moon Enceladus

Saturn's moon Enceladus

NASA's Cassini spacecraft captured this view as it neared icy Enceladus for its closest-ever dive past the moon's active south polar region. The view shows heavily cratered northern latitudes at top, transitioning to fractured, wrinkled terrain in the middle and southern latitudes. The wavy boundary of the moon's active south polar region -- Cassini's destination for this flyby -- is visible at bottom, where it disappears into wintry darkness.

This view looks towards the Saturn-facing side of Enceladus. North on Enceladus is up and rotated 23 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on October 28, 2015.

The view was acquired at a distance of approximately 60,000 miles (96,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 45 degrees. Image scale is 1,896 feet (578 meters) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA17202

May 27, 2017

Cygnus X

Cygnus X

Cygnus X hosts many young stellar groupings. The combined outflows and ultraviolet radiation from the region's numerous massive stars have heated and pushed gas away from the clusters, producing cavities of hot, lower-density gas.

In this 8-micron infrared image, ridges of denser gas mark the boundaries of the cavities. Bright spots within these ridges show where stars are forming today.

Image Credit: NASA/IPAC/MSX
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_2119.html

Veil Nebula

Veil Nebula

The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop (radio source W78, or Sharpless 103), a large but relatively faint supernova remnant. The source supernova exploded circa 3,000 BC to 6,000 BC, and the remnants have since expanded to cover an area roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). The distance to the nebula is not precisely known, but Far Ultraviolet Spectroscopic Explorer (FUSE) data supports a distance of about 1,470 light-years.

Image Credit & Copyright: T. A. Rector (U. Alaska), NOAO, AURA, NSF
Explanation from: https://en.wikipedia.org/wiki/Veil_Nebula

Jupiter's Aurora

Jupiter's Aurora

This ultraviolet image of Jupiter was taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on 26 November 1998 and gives a good impression of the observations that Hubble will make in the weeks to come. The bright emissions above the dark blue background are auroral lights, similar to those seen above the Earth's polar regions. The aurorae are curtains of light resulting from high energy electrons following the planet's magnetic field into the upper atmosphere, where collisions with atmospheric atoms and molecules produce the observed light. On Jupiter one can normally see three different types of auroral emissions:

a) a main oval, centred on the magnetic north pole

b) a pattern of more diffuse emissions inside the polar cap and

c) a unique auroral feature showing the 'magnetic footprints' of three of Jupiter's satellites. These 'footprints' can be seen in this image: from Io (along the left-hand limb), from Ganymede (near the centre just below the reference oval) and from Europa (just below and to the right of Ganymede's auroral footprint). These emissions are unlike anything seen on Earth and are produced by electric currents generated at the satellites that then flow along Jupiter's magnetic field, weaving in and out of its upper atmosphere.

This incredibly detailed image was taken on November 26 1998 when Jupiter was at a distance of 700 million km from Earth. The image was taken in UV light at 140 nm.

Image Credit: NASA, ESA & John T. Clarke (Univ. of Michigan)
Explanation from: https://www.spacetelescope.org/images/heic0009a/

Exoplanet HD 189733b

Exoplanet HD 189733b

HD 189733 b is an extrasolar planet approximately 63 light-years away from the Solar System in the constellation of Vulpecula. The planet was discovered orbiting the star HD 189733 A on October 5, 2005, when astronomers in France observed the planet transiting across the face of the star. With a mass 13% higher than that of Jupiter, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.5 kilometres per second (341,000 mph), making it a hot Jupiter with poor prospects for extraterrestrial life. Being the closest transiting hot Jupiter to Earth, HD 189733 b is a subject for extensive atmospheric examination. HD 189733 b was the first extrasolar planet for which a thermal map was constructed, to be detected through polarimetry, to have its overall color determined (deep blue), to have a transit detected in X-ray spectrum and to have carbon dioxide detected in its atmosphere.

In July, 2014, NASA announced finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b, WASP-12b) orbiting Sun-like stars.

Image Credit: NASA
Explanation from: https://en.wikipedia.org/wiki/HD_189733_b

Spiral Galaxy Messier 81

Spiral Galaxy Messier 81

This beautiful galaxy is tilted at an oblique angle on to our line of sight, giving a "birds-eye view" of the spiral structure. The galaxy is similar to our Milky Way, but our favorable view provides a better picture of the typical architecture of spiral galaxies.

M81 may be undergoing a surge of star formation along the spiral arms due to a close encounter it may have had with its nearby spiral galaxy NGC 3077 and a nearby starburst galaxy (M82) about 300 million years ago.

M81 is one of the brightest galaxies that can be seen from the Earth. It is high in the northern sky in the circumpolar constellation Ursa Major, the Great Bear. At an apparent magnitude of 6.8 it is just at the limit of naked-eye visibility. The galaxy's angular size is about the same as that of the Full Moon.

This image combines data from the Hubble Space Telescope, the Spitzer Space Telescope, and the Galaxy Evolution Explorer (GALEX) missions. The GALEX ultraviolet data were from the far-UV portion of the spectrum (135 to 175 nanometers). The Spitzer infrared data were taken with the IRAC channel 4 detector (8 microns). The Hubble data were taken at the blue portion of the spectrum.

Image Credit: Hubble data: NASA, ESA
Explanation from: http://www.spitzer.caltech.edu/images/2126-sig07-009-Multiwavelength-M81

Planetary Nebula NGC 6210

Planetary Nebula NGC 6210

The NASA/ESA Hubble Space Telescope has taken a striking high resolution image of the curious planetary nebula NGC 6210. Located about 6500 light-years away, in the constellation of Hercules, NGC 6210 was discovered in 1825 by the German astronomer Friedrich Georg Wilhelm Struve. Although in a small telescope it appears only as a tiny disc, it is fairly bright.

NGC 6210 is the last gasp of a star slightly less massive than our Sun at the final stage of its life cycle. The multiple shells of material ejected by the dying star form a superposition of structures with different degrees of symmetry, giving NGC 6210 its odd shape. This sharp image shows the inner region of this planetary nebula in unprecedented detail, where the central star is surrounded by a thin, bluish bubble that reveals a delicate filamentary structure. This bubble is superposed onto an asymmetric, reddish gas formation where holes, filaments and pillars are clearly visible.

The life of a star ends when the fuel available to its thermonuclear engine runs out. The estimated lifetime for a Sun-like star is some ten billion years. When the star is about to expire, it becomes unstable and ejects its outer layers, forming a planetary nebula and leaving behind a tiny, but very hot, remnant, known as white dwarf. This compact object, here visible at the centre of the image, cools down and fades very slowly. Stellar evolution theory predicts that our Sun will experience the same fate as NGC 6210 in about five billion years.

This picture was created from images taken with Hubble’s Wide Field Planetary Camera 2 through three filters: the broadband filter F555W (yellow) and the narrowband filters F656N (ionised hydrogen), F658N (ionised nitrogen) and F502N (ionised oxygen). The exposure times were 80 s, 140 s, 800 s and 700 s respectively and the field of view is only about 28 arcseconds across.

Image Credit: ESA/Hubble and NASA
Explanation from: https://www.spacetelescope.org/images/potw1026a/

May 26, 2017

Lightning over Lake Maracaibo

Lightning over Lake Maracaibo

Lake Maracaibo, Venezuela
October 2, 2013

Image Credit & Copyright: Ruzhugo27 via wikipedia.org

Star-Forming Regions

Star-Forming Regions

This image from NASA's Wide-field Infrared Survey Explorer, or WISE, highlights several star-forming regions. There are five distinct centers of star birth in this one image alone. Star-forming nebulae (called HII regions by astronomers) are clouds of gas and dust that have been heated up by nearby stars recently formed from the same cloud.

The largest, brightest cloud, in the upper right is known as Gum 22. It's named after Colin Gum, an Australian astronomer who surveyed the southern hemisphere sky in the early 1950's looking for star-forming regions like these. He catalogued 85 new such regions, named Gum 1 to85 (Gum Crater on the moon was also named in his honor).

Going counter-clockwise from Gum 22, the other catalogued nebulae in the image are Gum 23 (part of same cloud as 22), IRAS 09002-4732 (orange cloud near center), Bran 226 (upper cloud of the two at lower left), and finally Gum 25 at far lower left. There are also several smaller and/or more distant regions scattered throughout the image that have yet to be catalogued. Most of the regions are thought to be part of our local Orion spiral arm spur in the Milky Way galaxy. Their distances range from about 4,000 to 10,000 light-years away.

Notice the very bright green star near the lower right portion of the image. You can tell it's a star because it appears to have 'spikes' sticking out of it (diffraction spikes like these are an optical effect caused by the structure of the telescope). Bright stars in WISE images are typically blue, so you know this one is special. Known as IRAS 08535-4724, it's a unique type of stellar giant called a carbon star. Carbon stars are similar to red giants stars, which are much larger than the sun, glow brightly in longer wavelengths, and are in the late stages of their lives. But they have unusually high amounts of carbon in their outer atmospheres. Astronomers think this carbon comes either from convection currents deep within a star's core, or from a nearby neighboring star, from which it is siphoned. Recent evidence suggests that a carbon star like this one will end its life in an extremely powerful explosion called a gamma-ray burst, briefly outshining the sun a million trillion times.

The colors used in this image represent specific wavelengths of infrared light. Blue and cyan (blue-green) represent light emitted at wavelengths of 3.4 and 4.6 microns, which is predominantly from stars. Green and red represent light of 12 and 22 microns, respectively, which is mostly emitted by dust.

Image Credit: NASA/JPL-Caltech/UCLA
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA14105

Orion Nebula

Orion Nebula

This image shows smaller, particularly interesting areas of the Orion Nebula. It shows the delicate tracery created at the so-called Bright Bar, as the intense UV-light and strong winds from the hot Trapezium stars eat their way into the surrounding molecular cloud. Also visible are a number of very young red objects partly hidden in the cloud, waiting to be revealed as new members of the Trapezium Cluster.

Image Credit: ESO/M.McCaughrean et al. (AIP)
Explanation from: https://www.eso.org/public/images/eso0104c/

Six views of the Moon

Six views of the MoonSix views of the MoonSix views of the MoonSix views of the MoonSix views of the MoonSix views of the Moon

Six orthographic views of the Moon created from the new WAC global mosaic. From upper left to lower right the central longitude is 0°, 60°, 120°, 180°, 240°, 300°

Image Credit: NASA/GSFC/ Arizona State University

Jupiter's Southern Lights

Jupiter's Southern Lights

The complexity and richness of Jupiter's "southern lights" (also known as auroras) are on display in this animation of false-color maps from NASA's Juno spacecraft. Auroras result when energetic electrons from the magnetosphere crash into the molecular hydrogen in the Jovian upper atmosphere. The data for this animation were obtained by Juno's Ultraviolet Spectrograph.

The images are centered on the south pole and extend to latitudes of 50 degrees south. Each frame of the animation includes data from 30 consecutive Juno spins (about 15 minutes), just after the spacecraft's fifth close approach to Jupiter on February 2, 2017. The eight frames of the animation cover the period from 13:40 to 15:40 UTC at Juno. During that time, the spacecraft was receding from 35,000 miles to 153,900 miles (56,300 kilometers to 247,600 kilometers) above the aurora; this large change in distance accounts for the increasing fuzziness of the features.

Jupiter's prime meridian is toward the bottom, and longitudes increase counterclockwise from there. The sun was located near the bottom at the start of the animation, but was off to the right by the end of the two-hour period.

The red coloring of some of the features indicates that those emissions came from deeper in Jupiter's atmosphere; green and white indicate emissions from higher up in the atmosphere.

Image Credit: NASA/JPL-Caltech/SwRI
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21643

Spiral Galaxy IC 342

Spiral Galaxy IC 342

Looking like a spiders web swirled into a spiral, the galaxy IC 342 presents its delicate pattern of dust in this image from NASAs Spitzer Space Telescope. Seen in infrared light, the faint starlight gives way to the glowing bright patterns of dust found throughout the galaxys disk.

At a distance of about 10 million light-years, IC 342 is relatively close by galaxy standards, however our vantage point places it directly behind the disk of our own Milky Way. The intervening dust makes it difficult to see in visible light, but infrared light penetrates this veil easily. It belongs to the same group as its even more obscured galaxy neighbor, Maffei 2.

IC 342 is nearly face-on to our view giving a clear, top-down view of the structure of its disk. It has a low surface brightness compared to other spirals, indicating a lower density of stars (seen here in blue). Its dust structures show up much more vividly (yellow-green).

New stars are forming in the disk at a healthy clip. Glowing like gems trapped in the web, regions of heavy star formation appear as yellow-red dots due to the glow of warm dust. The very center glows especially brightly in the infrared, highlighting an enormous burst of star formation occurring in this tiny region. To either side of the center, a small bar of dust and gas is helping to fuel this central star formation.

Data from Spitzers infrared array camera (IRAC) are shown in blue (3.6 and 4.5 microns) and green (5.8 and 8.0 microns) while the multiband imaging photometer (MIPS) observation is red (24 microns).

Image Credit: NASA/JPL-Caltech/J. Turner (UCLA)
Explanation from: http://www.spitzer.caltech.edu/images/3669-sig11-009-A-Twisted-Star-Forming-Web-in-the-Galaxy-IC-342

May 23, 2017

Catatumbo Lightning

Catatumbo Lightning

Catatumbo lightning is an atmospheric phenomenon in Venezuela. It occurs only over the mouth of the Catatumbo River where it empties into Lake Maracaibo.

It originates from a mass of storm clouds at a height of more than 1 km, and occurs during 260 nights a year, 10 hours per day and up to 280 times per hour. It occurs over and around Lake Maracaibo, typically over the bog area formed where the Catatumbo River flows into the lake.

Catatumbo lightning changes its frequency throughout the year, and it is different from year to year. For example, it ceased from January to March 2010, apparently due to drought, temporarily raising fears that it might have been extinguished permanently.

Lake Maracaibo, Venezuela
November 1, 2015

Image Credit & Copyright: Fernando Flores
Explanation from: https://en.wikipedia.org/wiki/Catatumbo_lightning

Spiral Galaxy NGC 7714

Spiral Galaxy NGC 7714

NGC 7714 is a spiral galaxy 100 million light-years from Earth — a relatively close neighbour in cosmic terms.

The galaxy has witnessed some violent and dramatic events in its recent past. Tell-tale signs of this brutality can be seen in NGC 7714's strangely shaped arms, and in the smoky golden haze that stretches out from the galactic centre — caused by an ongoing merger with its smaller galactic companion NGC 7715, which is out of the frame of this image.

Image Credit: ESA, NASA
Explanation from: https://www.spacetelescope.org/images/heic1503a/

Open Star Cluster NGC 3572

Open Star Cluster NGC 3572

The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has captured the best image so far of the star cluster NGC 3572, a gathering of young stars, and its spectacular surroundings. This new image shows how the clouds of gas and dust around the cluster have been sculpted into whimsical bubbles, arcs and the odd features known as elephant trunks by the stellar winds flowing from the bright stars. The brightest of these cluster stars are heavier than the Sun and will end their short lives as supernova explosions.

Image Credit: ESO/G. Beccari
Explanation from: https://www.eso.org/public/images/eso1347a/

Colima Volcano Eruption

Colima Volcano Eruption

Colima, Mexico
2015

Image Credit: Hernando Rivera Cervantes/SWNS

Emission Nebula Sh2-308

Emission Nebula Sh2-308

The NASA/ESA Hubble Space Telescope still has a few tricks up its sleeve in its task of exploring the Universe. For one, it is able to image two adjacent parts of the sky simultaneously. It does this using two different cameras — one camera can be trained on the target object itself, and the other on a nearby patch of sky so that new and potentially interesting regions of the cosmos can be observed at the same time (these latter observations are known as parallel fields).

This image shows part of a bubble-like cloud of gas — a nebula named Sh2-308 — surrounding a massive and violent star named EZ Canis Majoris. It uses observations from Hubble’s Advanced Camera for Surveys, and is the parallel field associated with another view of the nebula produced by Hubble’s Wide Field Camera 3.

EZ Canis Majoris is something known as a Wolf-Rayet star, and is one of the brightest known stars of its kind. Its outer shell of hydrogen gas has been used up, revealing inner layers of heavier elements that burn at ferocious temperatures. The intense radiation pouring out from EZ Canis Majoris forms thick stellar winds that whip up nearby material, sculpting and blowing it outwards.

These processes have moulded the surrounding gas into a vast bubble. A bubble nebula produced by a Wolf-Rayet star is made of ionised hydrogen (HII), which is often found in interstellar space. In this case, it is the outer hydrogen layers of EZ Canis Majoris — the bubble — that are being inflated by the deluge of radiation — the air — coming from the central star. The fringes of these bubbles are nebulous and wispy, as can be seen in this image.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1721a/

Saturn

Saturn

The projection of Saturn's shadow on the rings grows shorter as Saturn's season advances toward northern summer, thanks to the planet's permanent tilt as it orbits the Sun. This will continue until Saturn's solstice in May 2017. At that point in time, the shadow will extend only as far as the innermost A ring, leaving the middle and outer A ring completely free of the planet's shadow.

Over the course of NASA's Cassini mission, the shadow of Saturn first lengthened steadily until equinox in August 2009. Since then, the shadow has been shrinking. These changes can be seen by comparing the shadow in the above view to its appearance as Cassini approached Saturn in 2004, equinox in 2009, and two years ago, in 2015.

This view looks toward the sunlit side of the rings from about 10 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Feb. 3, 2017.

The view was acquired at a distance of approximately 760,000 miles (1.2 million kilometers) from Saturn. Image scale is 46 miles (73 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21328

May 21, 2017

Storm seen from plane above Venezuela

Storm seen from plane above Venezuela

Plane above Caracas, Venezuela
Sepember 12, 2015

Image Credit & Copyright: Santiago Borja

Supernova Remnant RCW 86

Supernova Remnant RCW 86

This image combines data from four different space telescopes to create a multi-wavelength view of all that remains of the oldest documented example of a supernova, called RCW 86. The Chinese witnessed the event in 185 A.D., documenting a mysterious "guest star" that remained in the sky for eight months. X-ray images from the European Space Agency's XMM-Newton Observatory and NASA's Chandra X-ray Observatory are combined to form the blue and green colors in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova.

Infrared data from NASA's Spitzer Space Telescope, as well as NASA's Wide-Field Infrared Survey Explorer (WISE) are shown in yellow and red, and reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy.

By studying the X-ray and infrared data together, astronomers were able to determine that the cause of the explosion witnessed nearly 2,000 years ago was a Type Ia supernova, in which an otherwise-stable white dwarf, or dead star, was pushed beyond the brink of stability when a companion star dumped material onto it. Furthermore, scientists used the data to solve another mystery surrounding the remnant -- how it got to be so large in such a short amount of time. By blowing a wind prior to exploding, the white dwarf was able to clear out a huge "cavity," a region of very low-density surrounding the system. The explosion into this cavity was able to expand much faster than it otherwise would have.

This is the first time that this type of cavity has been seen around a white dwarf system prior to explosion. Scientists say the results may have significant implications for theories of white-dwarf binary systems and Type Ia supernovae.

RCW 86 is approximately 8,000 light-years away. At about 85 light-years in diameter, it occupies a region of the sky in the southern constellation of Circinus that is slightly larger than the full moon.

Image Credit: NASA/JPL-Caltech/B. Williams (NCSU)
Explanation from: http://www.spitzer.caltech.edu/images/4777-sig11-019-All-Eyes-on-Oldest-Recorded-Supernova

Spiral Galaxy NGC 2841

Spiral Galaxy NGC 2841

Star formation is one of the most important processes in shaping the Universe; it plays a pivotal role in the evolution of galaxies and it is also in the earliest stages of star formation that planetary systems first appear.

Yet there is still much that astronomers don’t understand, such as how do the properties of stellar nurseries vary according to the composition and density of gas present, and what triggers star formation in the first place? The driving force behind star formation is particularly unclear for a type of galaxy called a flocculent spiral, such as NGC 2841 shown here, which features short spiral arms rather than prominent and well-defined galactic limbs.

Image Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Explanation from: https://www.spacetelescope.org/images/heic1104a/

Lightning seen from plane above Colombia

Lightning seen from plane above Colombia

Plane above Colombia
February 17, 2017

Image Credit & Copyright: Santiago Borja

Star-Forming Region S106

Star-Forming Region S106

This image shows Sh 2-106, or S106 for short. This is a compact star forming region in the constellation Cygnus (The Swan). A newly-formed star called S106 IR is shrouded in dust at the centre of the image, and is responsible for the surrounding gas cloud’s hourglass-like shape and the turbulence visible within. Light from glowing hydrogen is coloured blue in this image.

The image combines observations from the Hubble Space Telescope (in the centre) with images from the National Astronomical Observatory of Japan’s Subaru Telescope to extend the field of view around the edges of the image.

Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and NAOJ
Explanation from: https://www.spacetelescope.org/images/heic1118b/

Globular Cluster NGC 6388

Globular Cluster NGC 6388

This image from the NASA/ESA Hubble Space Telescope shows NGC 6388, a dynamically middle-aged globular cluster in the Milky Way. While the cluster formed in the distant past (like all globular clusters, it is over ten billion years old), a study of the distribution of bright blue stars within the cluster shows that it has aged at a moderate speed, and its heaviest stars are in the process of migrating to the centre.

A new study using Hubble data has discovered that globular clusters of the same age can have dramatically different distributions of blue straggler stars within them, suggesting that clusters can age at substantially different rates.

Image Credit: NASA, ESA, F. Ferraro (University of Bologna)
Explanation from: https://www.spacetelescope.org/images/heic1221a/

May 20, 2017

Eyjafjallajökull Volcano Eruption

Eyjafjallajökull Volcano Eruption

Suðurland, Iceland

Image Credit: Árni Sæberg

Galaxy Cluster MACS J0717.5+3745

Galaxy Cluster MACS J0717.5+3745

This is a NASA/ESA Hubble Space Telescope image of the galaxy cluster MACS J0717.5+3745. Shown in blue on the image is a map of the dark matter found within the cluster. This cluster was part of a study of 72 galaxy cluster collisions which determined that dark matter interacts with other dark matter even less than previously thought.

Image Credit: NASA, ESA
Explanation from: http://spacetelescope.org/images/heic1506f/

Cassiopeia A

Cassiopeia A

Astronomers using NASA's infrared Spitzer Space Telescope have discovered that an exploded star, named Cassiopeia A, blew up in a somewhat orderly fashion, retaining much of its original onion-like layering.

"Spitzer has essentially found key missing pieces of the Cassiopeia A puzzle," said Jessica Ennis of the University of Minnesota, Minneapolis.

"We've found new bits of the 'onion' layers that had not been seen before," said Dr. Lawrence Rudnick, also of the University of Minnesota, and principal investigator of the research. "This tells us that the star's explosion was not chaotic enough to stir its remains into one big pile of mush."

Cassiopeia A, or Cas A for short, is what is known as a supernova remnant. The original star, about 15 to 20 times more massive than our sun, died in a cataclysmic "supernova" explosion relatively recently in our own Milky Way galaxy. Like all mature massive stars, the Cas A star was once neat and tidy, consisting of concentric shells made up of various elements. The star's outer skin consisted of lighter elements, such as hydrogen; its middle layers were lined with heavier elements like neon; and its core was stacked with the heaviest elements, such as iron.

Until now, scientists were not exactly sure what happened to the Cas A star when it ripped apart. One possibility is that the star exploded in a more or less uniform fashion, flinging its layers out in successive order. If this were the case, then those layers should be preserved in the expanding debris. Previous observations revealed portions of some of these layers, but there were mysterious gaps.

Spitzer was able to solve the riddle. It turns out that parts of the Cas A star had not been shot out as fast as others when the star exploded. Imagine an onion blasting apart with some layered chunks cracking off and zooming away, and other chunks from a different part of the onion shooting off at slightly slower speeds.

"Now we can better reconstruct how the star exploded," said Dr. William Reach of NASA's Spitzer Science Center, Pasadena, Calif. "It seems that most of the star's original layers flew outward in successive order, but at different average speeds depending on where they started."

How did Spitzer find the missing puzzle pieces? As the star's layers whiz outward, they are ramming, one by one, into a shock wave from the explosion and heating up. Material that hit the shock wave sooner has had more time to heat up to temperatures that radiate X-ray and visible light. Material that is just now hitting the shock wave is cooler and glowing with infrared light. Consequently, previous X-ray and visible-light observations identified hot, deep-layer material that had been flung out quickly, but not the cooler missing chunks that lagged behind. Spitzer's infrared detectors were able to find the missing chunks -- gas and dust consisting of the middle-layer elements neon, oxygen and aluminum.

Cassiopeia A is the ideal target for studying the anatomy of a supernova explosion. Because it is young and relatively close to our solar system, it is undergoing its final death throes right in front of the watchful eyes of various telescopes. In a few hundred years or so, Cas A's scattered remains will have completely mixed together, forever erasing important clues about how the star lived and died.

Image Credit: NASA/JPL-Caltech/L. Rudnick (University of Minnesota)
Explanation from: http://www.spitzer.caltech.edu/news/245-ssc2006-19-NASA-s-Spitzer-Peels-Back-Layers-of-Star-s-Explosion

Ara Ararauna

Ara Ararauna

The blue-and-yellow macaw (Ara ararauna), also known as the blue-and-gold macaw, is a large South American parrot with blue top parts and yellow under parts. It is a member of the large group of neotropical parrots known as macaws. It inhabits forest (especially varzea, but also in open sections of terra firme or unflooded forest) and woodland of tropical South America. They are popular in aviculture because of their striking color, ability to talk, ready availability in the marketplace, and close bonding to humans.

These birds can reach a length of 76–86 cm (30–34 in) and weigh 0.900–1.5 kg (2–3 lb), making them some of the larger members of their family. They are vivid in appearance with blue wings and tail, dark-blue chin, golden under parts, and a green forehead. Their beaks are black. The naked face is white, turning pink in excited birds, and lined with small, black feathers. Blue-and-yellow macaws live from 30 to 35 years in the wild.

Little variation in plumage is seen across the range. Some birds have a more orange or "butterscotch" underside color, particularly on the breast. This was often seen in Trinidad birds and others of the Caribbean area. The blue-and-yellow macaw uses its powerful beak for breaking nutshells, and for climbing up and hanging from trees.

This species occurs in Venezuela, Peru, Brazil, Bolivia, and Paraguay. The range extends slightly into Central America, where it is restricted to Panama. The species' range formerly included Trinidad, but it became extinct there by 1970 as a result of human activities. Between 1999 and 2003, wild-caught blue-and-gold macaws were translocated from Guyana to Trinidad, in an attempt to re-establish the species in a protected area around Nariva swamp. A small breeding population descended from introduced birds is found in Puerto Rico, and another has inhabited Miami-Dade County, Florida, since the mid-1980s.

Explanation from: https://en.wikipedia.org/wiki/Blue-and-yellow_macaw

Two Solar Prominences

Two Solar Prominences

At the edge of the Sun, a large prominence and a small prominence began to shift, turn and fall apart in less than one day (May 8-9, 2017). Prominences are notoriously unstable. Competing magnetic forces pulled the plasma back and forth until they dissipated. The images were taken in a wavelength of extreme ultraviolet light.

Image Credit: NASA/GSFC/Solar Dynamics Observatory
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21634

Exoplanet HD 189733b

Exoplanet HD 189733b

This illustration shows HD 189733b, a huge gas giant that orbits very close to its host star HD 189733. The planet's atmosphere is scorching with a temperature of over 1000 degrees Celsius, and it rains glass, sideways, in howling 7000 kilometre-per-hour winds.

At a distance of 63 light-years from us, this turbulent alien world is one of the nearest exoplanets to Earth that can be seen crossing the face of its star. By observing this planet before, during, and after it disappeared behind its host star during orbit, astronomers were able to deduce that HD 189733b is a deep, azure blue — reminiscent of Earth's colour as seen from space.

Image Credit: NASA, ESA, M. Kornmesser
Explanation from: https://www.spacetelescope.org/images/heic1312a/

May 19, 2017

Mount Tavurvur Volcano Eruption

Mount Tavurvur Volcano Eruption

Rabaul, New Britain, Papua New Guinea
August 29, 2014

Image Credit: Oliver Bluett/AFP/Getty Images

Andromeda Galaxy

Andromeda Galaxy

This mosaic of the Andromeda spiral galaxy highlights explosive stars in its interior, and cooler, dusty stars forming in its many rings. The image is a combination of observations from the Herschel Space Observatory taken in infrared light (seen in orange hues), and the XMM-Newton telescope captured in X-rays (seen in blues). NASA plays a role in both of these European Space Agency-led missions.

Herschel provides a detailed look at the cool clouds of star birth that line the galaxy's five concentric rings. Massive young stars are heating blankets of dust that surround them, causing them to glow in the longer-wavelength infrared light, known as far-infrared, that Herschel sees.

In contrast, XMM-Newton is capturing what happens at the end of the lives of massive stars. It shows the high-energy X-rays that come from, among other objects, supernova explosions and massive dead stars rotating around companions. These X-ray sources are clustered in the center of the galaxy, where the most massive stars tend to form.

Andromeda is our Milky Way galaxy's nearest large neighbor. It is located about 2.5 million light-years away and holds up to an estimated trillion stars. Our Milky Way is thought to contain about 200 billion to 400 billion stars.

Image Credit: ESA/Herschel/PACS/SPIRE/J. Fritz, U. Gent; X-ray: ESA/XMM Newton/EPIC/W. Pietsch, MPE
Explanation from: https://www.nasa.gov/mission_pages/herschel/pia13771.html

Eta Carinae Nebula

Eta Carinae Nebula

Eta Carinae is one of the most massive and brightest stars in the Milky Way. Compared to our own Sun, it is about 100 times as massive and a million times as bright. This famed variable hypergiant star (upper center) is surrounded by the Carina Nebula. In this composite image spanning the visible and infrared parts of the spectrum, areas that appear blue are not obscured by dust, while areas that appear red are hidden behind dark clouds of dust in visible light. A study combining X-ray and Infrared observations has revealed a new population of massive stars lurking in regions of the nebula that are highly obscured by dust. Adding these new massive stars to the known massive stars suggests that the Carina Nebula will produce twice as many supernova explosions as previously supposed.

Visible light in the blue part of the spectrum from the Digital Sky Survey is represented as blue, near infrared light with a wavelength of 2.2 microns from the Two Micron All Sky Survey (2MASS) is green, and infrared observations from the Infrared Array Camera on NASA's Spitzer Space telescope at 3.6 microns is red.

Image Credit: NASA/JPL-Caltech/M. Povich (Penn State Univ.)
Explanation from: http://www.spitzer.caltech.edu/images/3599-sig11-006-New-View-of-the-Great-Nebula-in-Carina

May 18, 2017

Puyehue-Cordón Caulle Volcano Eruption

Puyehue-Cordón Caulle Volcano Eruption 

Osorno, Los Lagos, Chile

Image Credit & Copyright: Francisco Negroni

Jupiter's Little Red Spot

Jupiter's Little Red Spot

This view of Jupiter, taken by the JunoCam imager of NASA's Juno spacecraft, highlights Oval BA -- a massive storm known as the Little Red Spot. Despite its unofficial name, the Little Red Spot is about as wide as Earth. The storm reached its current size when three smaller spots collided and merged in the year 2000. The Great Red Spot, which is about twice as wide as the Little Red Spot, may have formed from the same process centuries ago.

Juno acquired this image on February 2, 2017, at 6:13 a.m. PDT (9:13 a.m. EDT), as the spacecraft performed a close flyby of Jupiter. When the image was taken, the spacecraft was about 9,000 miles (14,500 kilometers) from the planet.

Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Bjorn Jonsson
Explanation from: https://photojournal.jpl.nasa.gov/catalog/PIA21391

Star IRAS 13481-6124

Star IRAS 13481-6124

This star-forming region, captured by NASA's Spitzer Space Telescope, is dominated by the bright, young star IRAS 13481-6124 (upper left), which is about twenty times the mass of our Sun and five times its radius, and is surrounded by its pre-natal cocoon. It is the first massive baby star for which astronomers could obtain a detailed look at the dusty disk closely encircling it. The research provides direct evidence that massive stars do form in the same way as their smaller brethren.

From this archival Spitzer image, as well as from observations done with the APEX 12-metre sub-millimetre telescope, astronomers discovered the presence of a jet, hinting at the presence of a disk. This was then confirmed by observations made with the European Southern Observatory Very Large Telescope Interferometer.

This picture was taken with Spitzer's infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red. Dust appears red-orange and most stars are blue, though ones deeply embedded within dust (like IRAS 13481-6124) take on greenish-yellow tints.

Image Credit: ESO/NASA/JPL-Caltech/S. Kraus
Explanation from: http://www.spitzer.caltech.edu/images/3206-sig10-011-A-Massive-Star-and-Its-Cradle

May 17, 2017

Copahue Volcano Eruption

Copahue Volcano Eruption

Caviahue, Neuquen Province, Argentina
December 22, 2012

Image Credit: AFP/Getty Images

Super Star Cluster Westerlund 1

Super Star Cluster Westerlund 1

This new picture from the VLT Survey Telescope (VST) at ESO's Paranal Observatory shows the remarkable super star cluster Westerlund 1. This exceptionally bright cluster lies about 16 000 light-years from Earth in the southern constellation of Ara (The Altar). It contains hundreds of very massive and brilliant stars, all of which are just a few million years old — babies by stellar standards. But our view of this cluster is hampered by gas and dust that prevents most of the visible light from the cluster's stars from getting to Earth.

Now, astronomers studying images of Westerlund 1 from a new survey of the southern skies have spotted something unexpected in this cluster. Around one of the stars — known as W26, a red supergiant and possibly the biggest star known— they have discovered clouds of glowing hydrogen gas, shown as green features in this new image.

Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star. W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionising radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.

W26 will eventually explode as a supernova. The nebula that surrounds it is very similar to the nebula surrounding SN1987A, the remnants of a star that went supernova in 1987. SN1987A was the closest observed supernova to Earth since 1604, and as such it gave astronomers a chance to explore the properties of these explosions. Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise.

Image Credit: ESO/VPHAS+ Survey/N. Wright
Explanation from: https://www.eso.org/public/images/potw1341a/

The Tarantula Nebula

Tarantula Nebula

This composite of 30 Doradus, aka the Tarantula Nebula, contains data from Chandra (blue), Hubble (green), and Spitzer (red). Located in the Large Magellanic Cloud, the Tarantula Nebula is one of the largest star-forming regions close to the Milky Way. Chandra's X-rays detect gas that has been heated to millions of degrees by stellar winds and supernovas. This high-energy stellar activity creates shock fronts, which are similar to sonic booms. Hubble reveals the light from massive stars at various stages of star birth, while Spitzer shows where the relatively cooler gas and dust lie.

Image Credit: X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.
Explanation from: http://www.spitzer.caltech.edu/images/5130-sig12-004-A-New-View-of-the-Tarantula-Nebula