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Saturday, February 4, 2017

Emission Nebulae NGC 6334 and NGC 6357

Emission Nebulae NGC 6334 and NGC 6357
Click on the image for full resolution (4.3 MB)

This spectacular image from the VLT Survey Telescope shows the Cat’s Paw Nebula (NGC 6334, upper right) and the Lobster Nebula (NGC 6357, lower left). These dramatic objects are regions of active star formation where the hot young stars are causing the surrounding hydrogen gas to glow red. The very rich field of view also includes dark clouds of dust. With around two billion pixels this is one of the largest images ever released by ESO. A zoomable version of this giant image is available here. Note that the circular features in the image around bright stars are not real, they are due to reflections within the optics of the telescope and camera.
Image Credit: ESO
Image enhancement: Jean-Baptiste Faure

Tuesday, January 31, 2017

Planetary Nebula OH 231.8+04.2

Planetary Nebula OH 231.8+04.2
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The Calabash Nebula, pictured here – which has the technical name OH 231.8+04.2 – is a spectacular example of the death of a low-mass star like the Sun. This image taken by the Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed – the gas shown in yellow is moving close to a million kilometers an hour. Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye – in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully fledged planetary nebula. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg – but luckily, it resides over 5000 light-years away in the constellation of Puppis (The Poop deck).
Image Credit: ESA/Hubble and NASA
Acknowledgement: Judy Schmidt
Image enhancement: Jean-Baptiste Faure

Saturday, January 28, 2017

Dwarf Spiral Galaxy NGC 4707

Dwarf Spiral Galaxy NGC 4707
Click on the image for full resolution (4.0 MB)

On a clear evening in April of 1789, the renowned astronomer William Herschel continued his unrelenting survey of the night sky, hunting for new cosmic objects – and found cause to celebrate! Lengthening his impressive list of cosmic discoveries yet again, the astronomer spotted this bright spiral galaxy, named NGC 4707, lurking in the constellation of Canes Venatici (The Hunting Dog). NGC 4707 lies roughly 22 million light-years from Earth. Over two centuries later, the Hubble Space Telescope is able to view the same galaxy in far greater detail than Herschel could, allowing us to appreciate the intricacies and characteristics of NGC 4707 as never before. This striking image comprises observations from Hubble's Advanced Camera for Surveys (ACS), one of a handful of high-resolution instruments currently aboard the space telescope. Herschel himself reportedly described NGC 4707 as a "small, stellar" galaxy; while it is classified as a spiral (type Sm), its overall shape, centre, and spiral arms are very loose and undefined, and its central bulge is either very small or non-existent. It instead appears as a rough sprinkling of stars and bright flashes of blue on a dark canvas, as if a pointillist painter had dotted the cosmos with small pinpricks of bright paint. The blue smudges seen across the frame highlight regions of recent or ongoing star formation, with newborn stars glowing in bright, intense shades of cyan and turquoise.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure

Monday, December 12, 2016

Barred Spiral Galaxy IC 5201

Barred Spiral Galaxy IC 5201
Click on the image for full resolution (7.6 MB)

In 1900, astronomer Joseph Lunt made a discovery: Peering through a telescope at Cape Town Observatory, the British–South African scientist spotted this beautiful sight in the southern constellation of Grus: a barred spiral galaxy now named IC 5201. Over a century later, the galaxy is still of interest to astronomers. For this image, the Hubble Space Telescope used its Advanced Camera for Surveys (ACS) to produce a beautiful and intricate image of the galaxy. Hubble's ACS can resolve individual stars within other galaxies, making it an invaluable tool to explore how various populations of stars have sprung to life, evolved, and died throughout the cosmos. IC 5201 sits over 40 million light-years away from us. As with two thirds of all the spirals we see in the Universe – including the Milky Way, the galaxy has a bar of stars slicing through its center.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure

Sunday, December 11, 2016

Globular Cluster Terzan 5

Globular Cluster Terzan 5
Click on the image for full resolution (4.0 MB)

Peering through the thick dust clouds of the galactic bulge an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way. Observations were made with the Wide Field Camera 3 (WFC3) on board the Hubble, the Multi-conjugate Adaptive Optics Demonstrator (MAD) instrument on ESO's Very Large Telescope and the second generation Near Infrared Camera at the Keck Telescope.
Terzan 5, 19 000 light-years from Earth, has been classified as a globular cluster for the forty-odd years since its detection. Now, an Italian-led team of astronomers have discovered that Terzan 5 is like no other globular cluster known. The team scoured data from the Advanced Camera for Surveys and the Wide Field Camera 3 on board Hubble, as well as from a suite of other ground-based telescopes. They found compelling evidence that there are two distinct kinds of stars in Terzan 5 which not only differ in the elements they contain, but have an age-gap of roughly 7 billion years. The ages of the two populations indicate that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation. Its unusual properties make Terzan 5 the ideal candidate for a living fossil from the early days of the Milky Way. Current theories on galaxy formation assume that vast clumps of gas and stars interacted to form the primordial bulge of the Milky Way, merging and dissolving in the process.
Image Credit: NASA/ESA/Hubble/F. Ferraro
Image enhancement: Jean-Baptiste Faure

Elliptical Galaxy NGC 4696

Elliptical Galaxy NGC 4696
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This picture, taken by Hubble's Wide Field Camera 3 (WFC3), shows NGC 4696, the largest galaxy in the Centaurus Cluster. The new images taken with Hubble show the dusty filaments surrounding the center of this huge galaxy in greater detail than ever before. These filaments loop and curl inwards in an intriguing spiral shape, swirling around the supermassive black hole at such a distance that they are dragged into and eventually consumed by the black hole itself. NGC 4696 is a member of the Centaurus galaxy cluster, a swarm of hundreds of galaxies all sitting together, bound together by gravity, about 150 million light-years from Earth and located in the constellation of Centaurus. Despite the cluster's size, NGC 4696 still manages to stand out from its companions – it is the cluster's brightest member, known for obvious reasons as the Brightest Cluster Galaxy. This puts it in the same category as some of the biggest and brightest galaxies known in the Universe. Even if NGC 4696 keeps impressive company, it has a further distinction: the galaxy's unique structure.
Previous observations have revealed curling filaments that stretch out from its main body and carve out a cosmic question mark in the sky, the dark tendrils encircling a brightly glowing center. An international team of scientists, led by astronomers from the University of Cambridge, UK, have now used new observations from the Hubble Space Telescope to explore this thread-like structure in more detail. They found that each of the dusty filaments has a width of about 200 light-years, and a density some 10 times greater than the surrounding gas. These filaments knit together and spiral inwards towards the center of NGC 4696, connecting the galaxy's constituent gas to its core. In fact, it seems that the galaxy's core is actually responsible for the shape and positioning of the filaments themselves. At the center of NGC 4696 lurks an active supermassive black hole. This floods the galaxy's inner regions with energy, heating the gas there and sending streams of heated material outwards. It appears that these hot streams of gas bubble outwards, dragging the filamentary material with them as they go. The galaxy's magnetic field is also swept out with this bubbling motion, constraining and sculpting the material within the filaments. At the very center of the galaxy, the filaments loop and curl inwards in an intriguing spiral shape, swirling around the supermassive black hole at such a distance that they are dragged into and eventually consumed by the black hole itself. Understanding more about filamentary galaxies such as NGC 4696 may help us to better understand why so many massive galaxies near to us in the Universe appear to be dead; rather than forming newborn stars from their vast reserves of gas and dust, they instead sit quietly, and are mostly populated with old and aging stars. This is the case with NGC 4696. It may be that the magnetic structure flowing throughout the galaxy stops the gas from creating new stars.
Image Credit: NASA, ESA/Hubble, A. Fabian
Image enhancement: Jean-Baptiste Faure

Saturday, December 10, 2016

Spiral Galaxy NGC 4388

Spiral Galaxy NGC 4388
Click on the image for full resolution (2.9 MB)

The constellation of Virgo is especially rich in galaxies, due in part to the presence of a massive and gravitationally-bound collection of over 1300 galaxies called the Virgo Cluster. One particular member of this cosmic community, NGC 4388, is captured in this image, as seen by the Hubble Space Telescope's Wide Field Camera 3 (WFC3). Located some 60 million light-years away, NGC 4388 is experiencing some of the less desirable effects that come with belonging to such a massive galaxy cluster. It is undergoing a transformation, and has taken on a somewhat confused identity. While the galaxy's outskirts appear smooth and featureless, a classic feature of an elliptical galaxy, its centre displays remarkable dust lanes constrained within two symmetric spiral arms, which emerge from the galaxy's glowing core – one of the obvious features of a spiral galaxy. Within the arms, speckles of bright blue mark the locations of young stars, indicating that NGC 4388 has hosted recent bursts of star formation. Despite the mixed messages, NGC 4388 is classified as a spiral galaxy. Its unusual combination of features are thought to have been caused by interactions between NGC 4388 and the Virgo Cluster. Gravitational interactions – from glancing blows to head-on collisions, tidal influencing, mergers, and galactic cannibalism – can be devastating to galaxies. While some may be lucky enough to simply suffer a distorted spiral arm or newly-triggered wave of star formation, others see their structure and contents completely and irrevocably altered.
Image Credit: ESA/Hubble and NASA
Image enhancement: Jean-Baptiste Faure