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The VLT Survey Telescope (VST), the latest addition to ESO’s Paranal Observatory, has made its first release of impressive images of the southern sky. The VST is a state-of-the-art 2.6-metre telescope, with the huge 268-megapixel camera OmegaCAM at its heart, which is designed to map the sky both quickly and with very fine image quality. It is a visible-light telescope that perfectly complements ESO’s VISTA infrared survey telescope. New images of the Omega Nebula and the globular cluster Omega Centauri demonstrate the VST’s power.

A New Telescope and Camera

The VLT Survey Telescope (VST) is the latest telescope to be added to ESO’s Paranal Observatory in the Atacama Desert of northern Chile. It is housed in an enclosure immediately adjacent to the four VLT Unit Telescopes on the summit of Cerro Paranal under the pristine skies of one of the best observing sites on Earth. The VST is a wide-field survey telescope with a field of view twice as broad as the full Moon. It is the largest telescope in the world designed to exclusively survey the sky in visible light. Over the next few years the VST and its camera OmegaCAM will make several very detailed surveys of the southern sky. All survey data will be made public.

“I am very pleased to see the impressive first images from the VST and OmegaCAM. The unique combination of the VST and the VISTA infrared survey telescope will allow many interesting objects to be identified for more detailed follow-up observations with the powerful telescopes of the VLT,” says Tim de Zeeuw, the ESO Director General.

“The VST project has overcome many difficulties but it is now repaying, with its excellent image quality, the expectations of the astronomical community and the efforts of the many people at INAF involved in its construction. I am very pleased to see the VST in operation,” adds Tommaso Maccacaro, the President of the Italian National Institute for Astrophysics (INAF).

The VST programme is a joint venture between the INAF–Osservatorio Astronomico di Capodimonte, Naples, Italy and ESO. INAF has designed and built the telescope with the collaboration of leading Italian industries and ESO is responsible for the enclosure and the civil engineering works at the site. OmegaCAM, the VST’s camera, was designed and built by a consortium including institutes in the Netherlands, Germany and Italy with major contributions from ESO. The new facility will be operated by ESO, which will also archive and distribute data from the telescope.

The VST is a state-of-the-art 2.6-metre aperture telescope with an active optics system to keep the mirrors perfectly positioned at all times. At its core, behind large lenses that ensure the best possible image quality, lies the 770 kg OmegaCAM camera, built around 32 CCD detectors, sealed in vacuum, that together create 268-megapixel images.

The First Images

Both the telescope and the camera have been designed to fully exploit the high quality skies at Paranal.

“The superb images now coming from VST and OmegaCAM are a tribute to the hard work of many groups around Europe over many years. We are now looking forward to a rich harvest of science and unexpected discoveries from the VST surveys,” adds Massimo Capaccioli, principal investigator of the VST project.

The first released image shows the spectacular star-forming region Messier 17, also known as the Omega Nebula or the Swan Nebula, as it has never been seen before. This dramatic region of gas, dust and hot young stars lies in the heart of the Milky Way in the constellation of Sagittarius (The Archer). The VST field of view is so large that the entire nebula, including its fainter outer parts, is captured — and retains its superb sharpness across the entire image.

The second released image may be the best portrait of the globular star cluster Omega Centauri ever made. This is the largest globular cluster in the sky, but the very wide field of view of VST and OmegaCAM can encompass even the faint outer regions of this spectacular object. This view, which includes about 300 000 stars, demonstrates the excellent resolution of VST.

The Surveys

The VST will make three public surveys over the next five years. The KIDS survey will image several regions of the sky away from the Milky Way. It will further the study of dark matter, dark energy and galaxy evolution, and find many new galaxy clusters and high-redshift quasars. The VST ATLAS survey will cover a larger area of sky and focus on understanding dark energy and supporting more detailed studies using the VLT and other telescopes. The third survey, VPHAS+, will image the central plane of the Milky Way to map the structure of the Galactic disc and its star formation history. VPHAS+ will yield a catalogue of around 500 million objects and will discover many new examples of unusual stars at all stages of their evolution.

The data volume produced by OmegaCAM will be large. About 30 terabytes of raw data will be produced per year and will flow back into data centres in Europe for processing. A novel and sophisticated software system has been developed at Groningen and Naples to handle the very large data flow. The end products from the processing will be huge lists of the objects found, as well as images, and these will be made available to astronomers worldwide for scientific analysis.

“The combination of large field of view, excellent image quality, and the very efficient operations scheme of the VST will produce an enormous wealth of information that will advance many fields of astrophysics,” concludes Konrad Kuijken, head of the OmegaCAM consortium.

Science astronomy, eso

An international team of astronomers has used ESO’s Very Large Telescope to carefully study the star VFTS 682 in the Large Magellanic Cloud, a small neighbouring galaxy to the Milky Way. By analysing the star’s light, using the FLAMES instrument on the VLT, they have found that it is about 150 times the mass of the Sun. Stars like these have so far only been found in the crowded centres of star clusters, but VFTS 682 lies on its own.

“We were very surprised to find such a massive star on its own, and not in a rich star cluster,” notes Joachim Bestenlehner, the lead author of the new study and a student at Armagh Observatory in Northern Ireland. “Its origin is mysterious.”

This star was spotted earlier in a survey of the most brilliant stars in and around the Tarantula Nebula in the Large Magellanic Cloud. It lies in a stellar nursery: a huge region of gas, dust and young stars that is the most active star-forming region in the Local Group of galaxies. At first glance VFTS 682 was thought to be hot, young and bright, but unremarkable. But the new study using the VLT has found that much of the star’s energy is being absorbed and scattered by dust clouds before it gets to Earth — it is actually more luminous than previously thought and among the brightest stars known.

Red and infrared light emitted by the star can get through the dust, but the shorter-wavelength blue and green light is scattered more and lost. As a result the star appears reddish, although if the view were unobstructed it would shine a brilliant blue-white.

As well as being very bright, VFTS 682 is also very hot, with a surface temperature of about 50 000 degrees Celsius. Stars with these unusual properties may end their short lives not just as a supernova, as is normal for high-mass stars, but just possibly as an even more dramatic long-duration gamma-ray burst, the brightest explosions in the Universe.

Although VFTS 682 seems to now be alone it is not very far away from the very rich star cluster RMC 136 (often called just R 136), which contains several similar “superstars” (eso1030).

“The new results show that VFTS 682 is a near identical twin of one of the brightest superstars at the heart of the R 136 star cluster,” adds Paco Najarro, another member of the team from CAB (INTA-CSIC, Spain).

Is it possible that VFTS 682 formed there and was ejected? Such “runaway stars” are known, but all are much smaller than VFTS 682 and it would be interesting to see how such a heavy star could be thrown from the cluster by gravitational interactions.

“It seems to be easier to form the biggest and brightest stars in rich star clusters,” adds Jorick Vink, another member of the team. “And although it may be possible, it is harder to understand how these brilliant beacons could form on their own. This makes VFTS 682 a really fascinating object.”

Science astronomy, eso

The spiral galaxy NGC 247 is one of the closest spiral galaxies of the southern sky. In this new view from the Wide Field Imager on the MPG/ESO 2.2-metre telescope in Chile large numbers of the galaxy’s component stars are clearly resolved and many glowing pink clouds of hydrogen, marking regions of active star formation, can be made out in the loose and ragged spiral arms.

NGC 247 is part of the Sculptor Group, a collection of galaxies associated with the Sculptor Galaxy (NGC 253, also shown in eso0902 and eso1025). This is the nearest group of galaxies to our Local Group, which includes the Milky Way, but putting a precise value on such celestial distances is inherently difficult.

To measure the distance from the Earth to a nearby galaxy, astronomers have to rely on a type of variable star called a Cepheid to act as a distance marker. Cepheids are very luminous stars, whose brightness varies at regular intervals. The time taken for the star to brighten and fade can be plugged into a simple mathematical relation that gives its intrinsic brightness. When compared with the measured brightness this gives the distance. However, this method isn’t foolproof, as astronomers think this period–luminosity relationship depends on the composition of the Cepheid.

Another problem arises from the fact that some of the light from a Cepheid may be absorbed by dust en route to Earth, making it appear fainter, and therefore further away than it really is. This is a particular problem for NGC 247 with its highly inclined orientation, as the line of sight to the Cepheids passes through the galaxy’s dusty disc.

However, a team of astronomers is currently looking into the factors that influence these celestial distance markers in a study called the Araucaria Project. The team has already reported that NGC 247 is more than a million light-years closer to the Milky Way than was previously thought, bringing its distance down to just over 11 million light-years.

Apart from the main galaxy itself, this view also reveals numerous galaxies shining far beyond NGC 247. In the upper right of the picture three prominent spirals form a line and still further out, far behind them, many more galaxies can be seen, some shining right through the disc of NGC 247.

This colour image was created from a large number of monochrome exposures taken through blue, yellow/green and red filters taken over many years. In addition exposures through a filter that isolates the glow from hydrogen gas have also been included and coloured red. The total exposure times per filter were 20 hours, 19 hours, 25 minutes and 35 minutes, respectively.

Science astronomy, eso

Using ESO’s Very Large Telescope an international team of astronomers has been able to study the short-lived disc of material around a young star that is in the early stages of making a planetary system. For the first time a smaller companion could be detected that may be the cause of the large gap found in the disc. Future observations will determine whether this companion is a planet or a brown dwarf.

Planets form from the discs of material around young stars, but the transition from dust disc to planetary system is rapid and few objects are caught during this phase . One such object is T Chamaeleontis (T Cha), a faint star in the small southern constellation of Chamaeleon that is comparable to the Sun, but very near the beginning of its life. T Cha lies about 350 light-years from the Earth and is only about seven million years old. Up to now no forming planets have been found in these transitional discs, although planets in more mature discs have been seen before.

“Earlier studies had shown that T Cha was an excellent target for studying how planetary systems form,” notes Johan Olofsson (Max Planck Institute for Astronomy, Heidelberg, Germany), one of the lead authors of two papers in the journal Astronomy & Astrophysics that describe the new work. “But this star is quite distant and the full power of the Very Large Telescope Interferometer (VLTI) was needed to resolve very fine details and see what is going on in the dust disc.”

The astronomers first observed T Cha using the AMBER instrument and the VLT Interferometer (VLTI). They found that some of the disc material formed a narrow dusty ring only about 20 million kilometres from the star. Beyond this inner disc, they found a region devoid of dust with the outer part of the disc stretching out into regions beyond about 1.1 billion kilometres from the star.

Nuria Huélamo (Centro de Astrobiología, ESAC, Spain), the lead author of the second paper takes up the story: “For us the gap in the dust disc around T Cha was a smoking gun, and we asked ourselves: could we be witnessing a companion digging a gap inside its protoplanetary disc?”

However, finding a faint companion so close to a bright star is a huge challenge and the team had to use the VLT instrument NACO in a novel and powerful way, called sparse aperture masking, to reach their goal. After careful analysis they found the clear signature of an object located within the gap in the dust disc, about one billion kilometres from the star — slightly further out than Jupiter is within our Solar System and close to the outer edge of the gap. This is the first detection of an object much smaller than a star within a gap in the planet-forming dust disc around a young star. The evidence suggests that the companion object cannot be a normal star but it could be either a brown dwarf surrounded by dust or, most excitingly, a recently formed planet.

Huélamo concludes: “This is a remarkable joint study that combines two different state-of-the-art instruments at ESO’s Paranal Observatory. Future observations will allow us to find out more about the companion and the disc, and also understand what fuels the inner dusty disc.”

Science astronomy, eso

NGC 3621 is a spiral galaxy about 22 million light-years away in the constellation of Hydra (The Sea Snake). It is comparatively bright and can be seen well in moderate-sized telescopes. This picture was taken using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. The data were selected from the ESO archive by Joe DePasquale as part of the Hidden Treasures competition. Joe’s picture of NGC 3621 was ranked fourth in the competition.

This galaxy has a flat pancake shape, indicating that it hasn’t yet come face to face with another galaxy as such a galactic collision would have disturbed the thin disc of stars, creating a small bulge in its centre. Most astronomers think that galaxies grow by merging with other galaxies, in a process called hierarchical galaxy formation. Over time, this should create large bulges in the centres of spirals. Recent research, however, has suggested that bulgeless, or pure-disc, spiral galaxies like NGC 3621 are actually fairly common.

This galaxy is of further interest to astronomers because its relative proximity allows them to study a wide range of astronomical objects within it, including stellar nurseries, dust clouds, and pulsating stars called Cepheid variables, which astronomers use as distance markers in the Universe. In the late 1990s, NGC 3621 was one of 18 galaxies selected for a Key Project of the Hubble Space Telescope: to observe Cepheid variables and measure the rate of expansion of the Universe to a higher accuracy than had been possible before. In the successful project, 69 Cepheid variables were observed in this galaxy alone.

Multiple monochrome images taken through four different colour filters were combined to make this picture. Images taken through a blue filter have been coloured blue in the final picture, images through a yellow-green filter are shown as green and images through a red filter as dark orange. In addition images taken through a filter that isolates the glow of hydrogen gas have been coloured red. The total exposure times per filter were 30, 40, 40 and 40 minutes respectively.

This zoom sequence starts with a view of the southern parts of the Milky Way. As we zoom in we can see the spiral galaxy NGC 3621, lying about 22 million light-years from us. The final detailed view shows a new image from the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. The data used to make this image were selected from the ESO archive by Joe DePasquale as part of the Hidden Treasures competition.

Credit:

ESO/S. Brunier and Joe DePasquale. Music:John Dyson (from the album “Moonwind”)

via : A Picture-perfect Pure-disc Galaxy

Science astronomy, eso

The Orion Nebula, also known as Messier 42, is one of the most easily recognisable and best-studied celestial objects. It is a huge complex of gas and dust where massive stars are forming and is the closest such region to the Earth. The glowing gas is so bright that it can be seen with the unaided eye and is a fascinating sight through a telescope. Despite its familiarity and closeness there is still much to learn about this stellar nursery. It was only in 2007, for instance, that the nebula was shown to be closer to us than previously thought: 1350 light-years, rather than about 1500 light-years.

Astronomers have used the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile to observe the stars within Messier 42. They found that the faint red dwarfs in the star cluster associated with the glowing gas radiate much more light than had previously been thought, giving us further insights into this famous object and the stars that it hosts. The data collected for this science project, with no original intention to make a colour image, have now been reused to create the richly detailed picture of Messier 42 shown here.

The image is a composite of several exposures taken through a total of five different filters. Light that passed through a red filter as well as light from a filter that shows the glowing hydrogen gas, were coloured red. Light in the yellow–green part of the spectrum is coloured green, blue light is coloured blue and light that passed through an ultraviolet filter has been coloured purple. The exposure times were about 52 minutes through each filter.

via : The Orion Nebula: Still Full of Surprises

Science astronomy, eso

Today seems to be astronomy day, as we have three posts for you. In the first of these, the European Southern Observatory (ESO) have captured a truly gorgeous image of the Lagoon Nebula using the Visible and Infrared Survey Telescope for Astronomy (VISTA). The Lagoon Nebula is an emission nebula. An emission nebula is simply one that is being heated up from stars within its interior, and emitting light in various colors. The Lagoon Nebula is located approximately 4,000 light years away in the constellation of Sagittarius (the Archer). If you looked at this nebula with your eye, it would appear grey. A time exposure image of the nebula would make it appear pink. However, this image appears blue because it is being imaged by VISTA in the near-infrared wavelengths.

This zoom sequence starts with a wide view of the spectacular central regions of the Milky Way. As we zoom in the prominent red patch of the Lagoon Nebula becomes apparent. First we see a detailed visible-light view from the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla in Chile and then finally the new infrared view from the VISTA telescope at Paranal.

Credit:

ESO/VVV/S. Brunier/S. Guisard
Music: John Dyson (from the album “Darklight”)
Acknowledgment: Cambridge Astronomical Survey Unit

via : VISTA Stares Deeply into the Blue Lagoon

Another video is after the break:

Read more…

Science astronomy, eso

Hubble has recently imaged an expanding shock wave from a supernova that exploded 400 years ago. This supernova, called SNR B0509-67.5, is located approximately 160,000 light years from earth. When it exploded, the supernova would have been visible from the southern hemisphere. SNR B0509-67.5 has been imaged by the Chandra X-ray observatory as well.

Hubble has spotted a festive bauble of gas in our neighbouring galaxy, the Large Magellanic Cloud. Formed in the aftermath of a supernova explosion that took place four centuries ago, this sphere of gas has been snapped in a series of observations made between 2006 and 2010.

The delicate shell, photographed by the NASA/ESA Hubble Space Telescope, appears to float serenely in the depths of space, but this apparent calm hides an inner turmoil. The gaseous envelope formed as the expanding blast wave and ejected material from a supernova tore through the nearby interstellar medium. Called SNR B0509-67.5 (or SNR 0509 for short), the bubble is the visible remnant of a powerful stellar explosion in the Large Magellanic Cloud (LMC), a small galaxy about 160 000 light-years from Earth.

Ripples seen in the shell’s surface may be caused either by subtle variations in the density of the ambient interstellar gas, or possibly be driven from the interior by fragments from the initial explosion. The bubble-shaped shroud of gas is 23 light-years across and is expanding at more than 18 million km/h.

Astronomers have concluded that the explosion was an example of an especially energetic and bright variety of supernova. Known as Type Ia, such supernova events are thought to result when a white dwarf star in a binary system robs its partner of material, taking on more mass than it is able to handle, so that it eventually explodes.

Hubble’s Advanced Camera for Surveys observed the supernova remnant on 28 October 2006 with a filter that isolates light from the glowing hydrogen seen in the expanding shell. These observations were then combined with visible-light images of the surrounding star field that were imaged with Hubble’s Wide Field Camera 3 on 4 November 2010.

With an age of about 400 years, the supernova might have been visible to southern hemisphere observers around the year 1600, although there are no known records of a “new star” in the direction of the LMC near that time. A much more recent supernova in the LMC, SN 1987A, did catch the eye of Earth viewers and continues to be studied with ground- and space-based telescopes, including Hubble.
Notes

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Acknowledgement: J. Hughes (Rutgers University)

via : Hubble spots a celestial bauble

Science astronomy, eso, hubble, nasa

Back in 2004, ESO astronomers using the ISAAC near-infrared instrument on ESO’s Very Large Telescope (VLT) claimed that they had found a galaxy with a redshift of 10, equating to a time of when the universe was just 470 million years old. It turns out that no one else could find the galaxy.

Today, ESO astronomers using the VLT have claimed that they have found a galaxy with a redshift of 8.6, equating to a time of when the universe was just 600 million years old. This claim has been verified by observations from the Hubble Space Telescope. If the current theory of how the Universe was formed is true, then at this early time the Universe was still filled with a hydrogen fog that rendered it opaque to light. If the Universe was opaque at that time, how can we see the light of this galaxy? Although not yet found, there are probably other nearby galaxies that helped to clear out the local area of the hydrogen fog to allow this light to shine through.

Astronomers using ESO’s Very Large Telescope (VLT) have measured the distance to the most remote galaxy so far, UDFy-38135539, which we see as it was when the Universe was only about 600 million years old (a redshift of 8.6). This video uses images from the Hubble Ultra-Deep Field to visualise a zoom towards UDFy-38135539.

Credit: A. M. Swinbank and S. Zieleniewski, Music: movetwo

via : Clearing the Cosmic Fog

Science astronomy, eso

A new image taken with the powerful HAWK-I camera on ESO’s Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth.

NGC 1365 is one of the best known and most studied barred spiral galaxies and is sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form, with the straight bar and two very prominent outer spiral arms. Closer to the centre there is also a second spiral structure and the whole galaxy is laced with delicate dust lanes.

This galaxy is an excellent laboratory for astronomers to study how spiral galaxies form and evolve. The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light (potw1037a) and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very centre of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

NGC 1365, including its two huge outer spiral arms, spreads over around 200 000 light-years. Different parts of the galaxy take different times to make a full rotation around the core of the galaxy, with the outer parts of the bar completing one circuit in about 350 million years. NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that the Milky Way could also be a barred spiral galaxy. Such galaxies are quite common — two thirds of spiral galaxies are barred according to recent estimates, and studying others can help astronomers understand our own galactic home.

via : An Elegant Galaxy in an Unusual Light

Science astronomy, eso