July 23, 2016

Earth and Moon seen by MESSENGER spacecraft from 183 million kilometers away

Earth and Moon from Mercury

Looking back from its orbit around Mercury, MESSENGER captured this view of Earth and the Moon on May 6, 2010. The spacecraft was 183 million kilometers (114 million miles) from Earth at the time, farther than our average distance from the Sun (150 million kilometers, or 93 million miles) because Mercury and Earth were at different places in their orbits around the Sun. The image was taken by the spacecraft's Wide Angle Camera (WAC) on the Mercury Dual Imaging System (MDIS).

The view was a happy coincidence for the MESSENGER science team, as the probe was looking for vulcanoids, small rocky objects that have been postulated to exist in orbits between Mercury and the Sun. From the spacecraft’s view, Earth and the Moon are located near the boundary of the constellations Libra and Scorpius.

MESSENGER is the first spacecraft to fly by Mercury since Mariner 10 in 1974-75. It is not, however, the first to get a long-distance shot of Earth. In 2003, the Mars Global Surveyor spied Earth and its Moon in the same frame, while the Spirit Rover on Mars snapped the first shot of our planet as viewed from the surface of another planet. In 2006, Cassini sent back snapshots from 1.5 billion kilometers (930 million miles) from Earth as the spacecraft orbited Saturn. And the operators of the venerable Voyager 1 spacecraft pieced together a family portrait of the entire solar system in 1990, spying Earth from more than 6.4 billion kilometers (4 billion miles) away.

Image Credit: NASA
Explanation from: http://earthobservatory.nasa.gov/IOTD/view.php?id=45710

Pillars around Westerlund 2

Pillars around Westerlund 2

This image shows an example of the pillars that surround the star cluster Westerlund 2.

These pillars are composed of dense gas and dust are a few light-years tall and point to the central cluster. They are thought to be incubators for new stars. Besides sculpting the gaseous terrain, intense radiation from the most brilliant of the cluster stars is creating a successive generation of baby stars.

Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team
Explanation from: https://www.spacetelescope.org/images/heic1509e/

Supernova Remnant 1E 0102.2-7219

Supernova Remnant 1E 0102.2-7219

In the nearby galaxy known as the Small Magellanic Cloud, a massive star has exploded as a supernova and begun to dissipate its interior into a spectacular display of colorful filaments, reminiscent of fireworks display.

The supernova remnant (SNR), known as "E0102" for short, is the greenish-blue shell of debris just below the center of this image from NASA's Hubble Space Telescope. This delicate structure, glowing a multitude of lavenders and peach hues, resides in the upper right of the image.

Determined to be only about 2,000 years old, E0102 is relatively young on astronomical scales and is just beginning its interactions with the nearby interstellar medium. Young supernova remnants like E0102 allow astronomers to examine material from the cores of massive stars directly. This in turn gives insight on how stars form, their composition, and the chemical enrichment of the surrounding area. As well, young remnants are a great learning tool to better understand the physics of supernova explosions.

The Small Magellanic Cloud is a nearby dwarf galaxy to our own Milky Way. It is visible in the Southern Hemisphere, in the direction of the constellation Tucana, and lies roughly 210,000 light-years distant.

Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA) and J. Green
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_684.html

July 22, 2016

Earth and Moon seen from Saturn by Cassini spacecraft from 900 million miles away

earth from saturnearth from saturnEarth seen from SaturnEarth seen from SaturnEarth and Moon seen from SaturnEarth and Moon seen from Saturn

In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its Moon in the same frame. It is only one footprint in a mosaic of 33 footprints covering the entire Saturn ring system (including Saturn itself). At each footprint, images were taken in different spectral filters for a total of 323 images: some were taken for scientific purposes and some to produce a natural color mosaic. This is the only wide-angle footprint that has the Earth-moon system in it.

The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are clearly seen; the limb of Saturn and the F ring are overexposed. The "breaks" in the brightness of Saturn's limb are due to the shadows of the rings on the globe of Saturn, preventing sunlight from shining through the atmosphere in those regions. The E and G rings have been brightened for better visibility.

Earth, which is 898 million miles (1.44 billion kilometers) away in this image, appears as a blue dot at center right; the Moon can be seen as a fainter protrusion off its right side. An arrow indicates their location in the annotated version. The other bright dots nearby are stars.

This is only the third time ever that Earth has been imaged from the outer Solar System. The acquisition of this image, along with the accompanying composite narrow- and wide-angle image of Earth and the Moon and the full mosaic from which both are taken, marked the first time that inhabitants of Earth knew in advance that their planet was being imaged. That opportunity allowed people around the world to join together in social events to celebrate the occasion.

This view looks toward the unilluminated side of the rings from about 20 degrees below the ring plane.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were obtained with the Cassini spacecraft wide-angle camera on July 19, 2013 at a distance of approximately 753,000 miles (1.212 million kilometers) from Saturn, and approximately 898.414 million miles (1.445858 billion kilometers) from Earth. Image scale on Saturn is 43 miles (69 kilometers) per pixel; image scale on the Earth is 53,820 miles (86,620 kilometers) per pixel. The illuminated areas of neither Earth nor the Moon are resolved here. Consequently, the size of each "dot" is the same size that a point of light of comparable brightness would have in the wide-angle camera.

Image Credit: NASA/JPL-Caltech/Space Science Institute
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA17171

Planetary Nebula Hen 2-437

Planetary Nebula Hen 2-437

In this picture, the spectacularly symmetrical wings of Hen 2-437 show up in a magnificent icy blue hue. Hen 2-437 is a planetary nebula, one of around 3000 such objects known to reside within the Milky Way.

Located within the faint northern constellation of Vulpecula (The Fox), Hen 2-437 was first identified in 1946 byRudolph Minkowski, who later also discovered the famous and equally beautiful M2-9 (otherwise known as theTwin Jet Nebula). Hen 2-437 was added to a catalogue of planetary nebula over two decades later by astronomer and NASA astronaut Karl Gordon Henize.

Planetary nebulae such as Hen 2-437 form when an aging low-mass star — such as the Sun — reaches the final stages of life. The star swells to become a red giant, before casting off its gaseous outer layers into space. The star itself then slowly shrinks to form a white dwarf, while the expelled gas is slowly compressed and pushed outwards by stellar winds. As shown by its remarkably beautiful appearance, Hen 2-437 is a bipolar nebula — the material ejected by the dying star has streamed out into space to create the two icy blue lobes pictured here.

Image Credit: ESA/Hubble, NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1606a/

Hubble image of galaxy cluster MACS J0717

Hubble image of galaxy cluster MACS J0717

This enormous image shows Hubble’s view of massive galaxy cluster MACS J0717.5+3745. The large field of view is a combination of 18 separate Hubble images.

Studying the distorting effects of gravity on light from background galaxies, a team of astronomers has uncovered the presence of a filament of dark matter extending from the core of the cluster. This is one of the first positive detections of a filament, and the most precise to date.

Using additional observations from ground-based telescopes, the team were able to map the filament’s structure in three dimensions, the first time this has ever been done.

Image Credit: NASA, ESA, Harald Ebeling, Jean-Paul Kneib (LAM)
Explanation from: https://www.spacetelescope.org/images/heic1215b/

July 21, 2016

Earth seen from Mars by Mars Exploration Rover Spirit

Earth from MarsEarth from Mars

This is the first image ever taken of Earth from the surface of a planet beyond the Moon. It was taken by the Mars Exploration Rover Spirit one hour before sunrise on the 63rd martian day, or sol, of its mission. The image is a mosaic of images taken by the rover's navigation camera showing a broad view of the sky, and an image taken by the rover's panoramic camera of Earth. The contrast in the panoramic camera image was increased two times to make Earth easier to see.

The inset shows a combination of four panoramic camera images zoomed in on Earth. The arrow points to Earth. Earth was too faint to be detected in images taken with the panoramic camera's color filters.

Image Credit: NASA/JPL/Cornell/Texas A&M
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA05547

Reflection Nebula NGC 1333

Reflection Nebula NGC 1333

Located 1,000 light years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born. Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed. With NASA's Spitzer Space Telescope, scientists can detect the infrared light from these objects, allowing a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives. The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups. One group is the nebula shown as red in the image. The other group lies where the features shown in yellow and green abound in the densest part of the natal gas cloud. By looking for differences in the disk properties between the two subgroups, scientists hope to find hints of the star and planet formation history of this region.

The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are plowing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented, leading scientists to believe that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333. In contrast, the upper portion of the image is dominated by the infrared light from warm dust, shown as red.

Image Credit: NASA/JPL-Caltech/R. A. Gutermuth (Harvard-Smithsonian CfA)
Explanation from: https://www.nasa.gov/multimedia/imagegallery/image_feature_450.html

Planetary Nebula NGC 6153

Planetary Nebula NGC 6153

This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the Sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionised by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula.

NGC 6153 is a planetary nebula that is elliptical in shape, with an extremely rich network of loops and filaments, shown clearly in this Hubble image. However, this is not what makes this planetary nebula so interesting for astronomers.

Measurements show that NGC 6153 contains large amounts of neon, argon, oxygen, carbon and chlorine — up to three times more than can be found in the Solar System. The nebula contains a whopping five times more nitrogen than the Sun! Although it may be that the star developed higher levels of these elements as it grew and evolved, it is more likely that the star originally formed from a cloud of material that already contained lots more of these elements.

Image Credit: ESA/Hubble, NASA, Matej Novak
Explanation from: https://www.spacetelescope.org/images/potw1525a/

Wide-field image of the Bubble Nebula

Bubble Nebula

This ground-based image shows the Bubble Nebula and its surroundings, including the interstellar cloud which is illuminated by stellar winds from the central star within the Bubble Nebula.

Image Credit: NASA, ESA, Digitized Sky Survey 2, Davide De Martin
Explanation from: https://www.spacetelescope.org/images/heic1608b/

July 20, 2016

H II Region NGC 604

H II Region NGC 604

This festively colorful nebula, called NGC 604, is one of the largest known seething cauldrons of star birth in a nearby galaxy. NGC 604 is similar to familiar star-birth regions inour Milky Way galaxy, such as the Orion Nebula, but it is vastlylarger in extent and contains many more recently formed stars.

This monstrous star-birth region contains more than 200 brilliant blue stars within a cloud of glowing gases some 1,300 light-year sacross, nearly 100 times the size of the Orion Nebula. By contrast,the Orion Nebula contains just four bright central stars. The bright stars in NGC 604 are extremely young by astronomical standards, having formed a mere 3 million years ago.

Image Credit: NASA/ESA and The Hubble Heritage Team (AURA/STScI)
Explanation from: https://www.spacetelescope.org/images/opo0330a/

Planetary Nebula NGC 6818

Planetary Nebula NGC 6818

This colourful bubble is a planetary nebula called NGC 6818, also known as the Little Gem Nebula. It is located in the constellation of Sagittarius (The Archer), roughly 6000 light-years away from us. The rich glow of the cloud is just over half a light-year across — humongous compared to its tiny central star — but still a little gem on a cosmic scale.

When stars like the Sun enter retirement, they shed their outer layers into space to create glowing clouds of gas called planetary nebulae. This ejection of mass is uneven, and planetary nebulae can have very complex shapes. NGC 6818 shows knotty filament-like structures and distinct layers of material, with a bright and enclosed central bubble surrounded by a larger, more diffuse cloud.

Scientists believe that the stellar wind from the central star propels the outflowing material, sculpting the elongated shape of NGC 6818. As this fast wind smashes through the slower-moving cloud it creates particularly bright blowouts at the bubble’s outer layers.

Hubble previously imaged this nebula back in 1997 with its Wide Field Planetary Camera 2, using a mix of filters that highlighted emission from ionised oxygen and hydrogen. This image, while from the same camera, uses different filters to reveal a different view of the nebula.

Image Credit: ESA/Hubble, NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1531a/

Supermassive Black Hole

Supermassive Black Hole

In this artist's rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole.

Image Credit: NASA/Swift/Aurore Simonnet, Sonoma State Univ.
Explanation from: https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=12265

July 19, 2016

A Giant Galaxy Centaurus A

A Giant Galaxy Centaurus A

Centaurus A is our nearest giant galaxy, at a distance of about 13 million light-years in the southern constellation of Centaurus, and as such, it is one of the most extensively studied objects in the southern sky. It is an elliptical galaxy, currently merging with a companion spiral galaxy, resulting in areas of intense star formation and making it one of the most spectacular objects in the sky. Centaurus A hosts a very active and highly luminous central region, caused by the presence of a supermassive black hole with a mass of about 100 million solar masses, and is the source of strong radio and X-ray emission. Thick dust layers almost completely obscure the galaxy's centre. This image is based on data acquired with the 1.5-metre Danish telescope at ESO’s La Silla Observatory in Chile, through three filters (B, V, R).

Image Credit: ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen & S. Guisard
Explanation from: http://www.eso.org/public/images/cena/

Globular Cluster Messier 5

Globular Cluster Messier 5

This sparkling jumble is Messier 5 — a globular cluster consisting of hundreds of thousands of stars bound together by their collective gravity.

But Messier 5 is no normal globular cluster. At 13 billion years old it is incredibly old, dating back to close to the beginning of the Universe, which is some 13.8 billion years of age. It is also one of the biggest clusters known, and at only 24 500 light-years away, it is no wonder that Messier 5 is a popular site for astronomers to train their telescopes on.

Messier 5 also presents a puzzle. Stars in globular clusters grow old and wise together. So Messier 5 should, by now, consist of old, low-mass red giants and other ancient stars. But it is actually teeming with young blue stars known as blue stragglers. These incongruous stars spring to life when stars collide, or rip material from one another.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1416a/

The North America Nebula in Infrared

The North America Nebula in Infrared

This swirling landscape of stars is known as the North America nebula. In visible light, the region resembles North America, but in this infrared view from NASA's Spitzer Space Telescope, the continent disappears.

Where did the continent go? The reason you don't see it in Spitzer's view has to do, in part, with the fact that infrared light can penetrate dust whereas visible light cannot. Dusty, dark clouds in the visible image become transparent in Spitzer's view. In addition, Spitzer's infrared detectors pick up the glow of dusty cocoons enveloping baby stars.

Clusters of young stars (about one million years old) can be found throughout the image. Slightly older but still very young stars (about three to five million years) are also liberally scattered across the complex, with concentrations near the "head" region of the Pelican nebula, which is located to the right of the North America nebula (upper right portion of this image).

Some areas of this nebula are still very thick with dust and appear dark even in Spitzer's view. For example, the dark "river" in the lower left-center of the image -- in the Gulf of Mexico region -- are likely to be the youngest stars in the complex (less than a million years old).

This image contains data taken by Spitzer's infrared array camera at wavelengths of 3.6 (blue), 4.5 (green), 5.8 and 8.0 (red) microns.

Image Credit: NASA/JPL-Caltech/L. Rebull (SSC/Caltech)
Explanation from: http://www.spitzer.caltech.edu/images/3514-ssc2011-03a2-The-Case-of-the-Disappearing-Continent

July 18, 2016

Colubrine Sea Krait

Colubrine Sea Krait

Laticauda colubrina, commonly known as the banded sea krait, colubrine sea krait, or yellow-lipped sea krait, is a species of venomous sea snake found in tropical Indo-Pacific oceanic waters. Although it has potent venom, the banded sea krait is not aggressive and only rarely bites humans. The snake has distinctive black stripes and a yellow snout, and feeds on eels and small fish.

The banded sea krait is widespread throught the eastern Indian Ocean and Western Pacific. It can be found from the eastern coast of India, along the coast of the Bay of Bengal in Bangladesh, Myanmar and other parts of Southeast Asia, to the Malay Archipelago and to some parts of southern China, Taiwan, and the Ryukyu Islands of Japan. The species is also common on Fiji and other Pacific islands within its range. Vagrant individuals have been recorded in Australia, New Caledonia, and New Zealand.

Banded sea kraits spend time both on land and in water. When hunting, sea kraits frequently head into deep water far away from land, but return to small islands in order to digest, shed skin, and reproduce. Individual kraits return to their specific home islands, exhibiting philopatry. A study found that when sea kraits on Fijian islands were relocated to different islands 5.3 km away, all recaptured individuals were found on their home islands in an average of 30.7 days.

Banded sea kraits often hunt alone, but have also been recorded in large numbers in the company of hunting parties of giant trevally and goatfish. This cooperative hunting technique is similar to that of the moray eel, with the kraits flushing out prey from narrow crevices and holes, and the trevally and goatfish feeding on fleeing prey.

While probing crevices with their head, sea kraits are unable to observe approaching predators and could be vulnerable. The snakes can deter predators by fooling them that their tail is the head, because the color and movement of the tail is similar to that of the snake's head. For example, the lateral aspect of tail corresponds to the dorsal view of the head.

Kraits primarily feed on varieties of eels, but also eat small fish. Male and female kraits exhibit sexual dimorphism in hunting behavior, as adult females, which are significantly larger than males, prefer to hunt larger conger eels, while adult males hunt smaller moray eels. In addition, females hunt for only one prey item per foraging bout, while males often hunt for multiple items. After hunting, the kraits return to land in order to digest their prey.

Image Credit: Craig D via en.wikipedia.org
Explanation from: https://en.wikipedia.org/wiki/Laticauda_colubrina

Blue Compact Dwarf Galaxy NGC 5253

Blue Compact Dwarf Galaxy NGC 5253

The NASA/ESA Hubble Space Telescope provides us this week with an impressive image of the irregular galaxy NGC 5253.

NGC 5253 is one of the nearest of the known Blue Compact Dwarf (BCD) galaxies, and is located at a distance of about 12 million light-years from Earth in the southern constellation of Centaurus. The most characteristic signature of these galaxies is that they harbour very active star-formation regions. This is in spite of their low dust content and comparative lack of elements heavier than hydrogen and helium, which are usually the basic ingredients for star formation.

These galaxies contain molecular clouds that are quite similar to the pristine clouds that formed the first stars in the early Universe, which were devoid of dust and heavier elements. Hence, astronomers consider the BCD galaxies to be an ideal testbed for better understanding the primordial star-forming process.

NGC 5253 does contain some dust and heavier elements, but significantly less than the Milky Way galaxy. Its central regions are dominated by an intense star forming region that is embedded in an elliptical main body, which appears red in Hubble’s image. The central starburst zone consists of a rich environment of hot, young stars concentrated in star clusters, which glow in blue in the image. Traces of the starburst itself can be seen as a faint and diffuse glow produced by the ionised oxygen gas.

The true nature of BCD galaxies has puzzled astronomers for a long time. Numerical simulations following the current leading cosmological theory of galaxy formation, known as the Lambda Cold Dark Matter model, predict that there should be far more satellite dwarf galaxies orbiting big galaxies like the Milky Way. Astronomers refer to this discrepancy as the Dwarf Galaxy Problem.

This galaxy is considered part of the Centaurus A/Messier 83 group of galaxies, which includes the famous radio galaxy Centaurus A and the spiral galaxy Messier 83. Astronomers have pointed out the possibility that the peculiar nature of NGC 5253 could result from a close encounter with Messier 83, its closer neighbour.

This image was taken with the Hubble’s Advanced Camera for Surveys, combining visible and infrared exposures. The field of view in this image is approximately 3.4 by 3.4 arcminutes.

Image Credit: ESA/Hubble, NASA, N. Sulzenauer
Explanation from: https://www.spacetelescope.org/images/potw1248a/

Earth and the far side of the Moon seen by DSCOVR Observatory

DSCOVR, 1 million miles from Earth
July 5, 2016

Image Credit: NASA/NOAA

July 17, 2016

Earth seen by Voyager 1 spacecraft from 4 billion miles away

Earth from Space

This narrow-angle color image of the Earth, dubbed 'Pale Blue Dot', is a part of the first ever 'portrait' of the Solar System taken by Voyager 1. The spacecraft acquired a total of 60 frames for a mosaic of the Solar System from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic. From Voyager's great distance Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size. Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the Sun. This blown-up image of the Earth was taken through three color filters -- violet, blue and green -- and recombined to produce the color image. The background features in the image are artifacts resulting from the magnification.

Image Credit: NASA/JPL
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA00452

Victoria Crater, Mars

Victoria Crater, Mars

Victoria is an impact crater on Mars located at 2.05°S, 5.50°W in the Meridiani Planum extraterrestrial plain, lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. This crater was first visited by the Mars Exploration Rover Opportunity. It is roughly 730 metres wide, nearly eight times the size of the crater Endurance, visited by Opportunity from sols 951 to 1630. It is informally named after Victoria – one of the five ships of Ferdinand Magellan and the first ship to circumnavigate the globe – and formally named after Victoria, Seychelles. Along the edges of the crater are many outcrops within recessed alcoves and promontories, named for bays and capes that Magellan discovered.

Image Credit: NASA/JPL-Caltech
Explanation from:https://en.wikipedia.org/wiki/Victoria_(crater)

The Veil Nebula

Veil Nebula

This image shows a beautiful portion of the Veil Nebula - the shattered remains of a supernova that exploded some 5-10 000 years ago. The intertwined rope-like filaments of gas result from the enormous amounts of energy released as the fast-moving debris from the explosion ploughs into its surroundings and creates shock fronts.

The image displays two characteristic features: sharp filaments and diffuse emission. These correspond to two different viewing geometries: sharp filaments correspond to an edge-on view of a shock front, and diffuse emission corresponds to a face-on view of it.

This image is a small portion of the Veil located in the western part of the Veil (to the left in the overview image). The entire structure spans about 3 degrees, corresponding to about 6 full moons.

The image was taken with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope. The colour is produced by composite of three different images. The different colours indicate emission from different kinds of atoms excited by the shock: blue shows oxygen, green shows sulphur, and red shows hydrogen.

Image Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Explanation from: https://www.spacetelescope.org/images/heic0712c/