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  • richardmitnick 10:33 am on November 19, 2014 Permalink | Reply
    Tags: , , , , , ESO La Silla,   

    From SPACE.com: “Asteroid Found with Rings! First-of-Its-Kind Discovery Stuns Astronomers (Video, Images)” 

    space-dot-com logo

    SPACE.com

    March 26, 2014
    Nola Taylor Redd

    Scientists have made a stunning discovery in the outer realm of the solar system — an asteroid with its own set of rings that orbits the sun between Saturn and Uranus. The space rock is the first non-planetary object ever found to have its own ring system, researchers say.

    The pair of space rock rings encircle the asteroid Chariklo. They were most likely formed after a collision scattered debris around the asteroid, according to a new study unveiled today (March 27). The asteroid rings also suggests the presence of a still-undiscovered moon around Chariklo that’s keeping them stable, researchers said.

    “We weren’t looking for a ring and didn’t think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise!” study leader Felipe Braga-Ribas, of the National Observatory in Brazil said in a statement today.

    Astronomers used seven telescopes, but just one revealed the pair of rings orbiting the rocky Chariklo. The asteroid’s 155-mile diameter (250 kilometers) is dwarfed by the giant gas planets, the only other bodies known to have rings.

    “This discovery shows that size is not important in order to have — or not have — rings,” Felipe Braga-Ribas, of the National Observatory in Brazil, told Space.com by email.

    An asteroid among giants

    On June 3, 2013, Braga-Ribas led a team of astronomers in observing Chariklo as it passed in front of a distant star — a process known as an occultation. As the asteroid traveled, it blocked light from the star, enabling scientists to learn more about it.

    The astronomers were surprised to discover that a few seconds before and after the main occultation, the light dimmed slightly, indicating that something circled the rocky asteroid. By comparing the data gathered from seven different telescopes, the team was able to identify the shape, size and orientation of the rings.

    The system consists of a dense, 4-mile-wide (7 km) ring near the planet, and a smaller 2-mile-wide (3 km) ring farther out.

    From the surface of the asteroid, “they would be two spectacular sharp and really bright rings, crossing all the sky,” Braga-Ribas said. “They would be noticeably close, as they are at about 1/1,000 of the moon’s distance from us,” he added.

    He went on to say that the larger, inner ring would block the view of the outer ring from the ground. The rings are similar to those around Saturn, in that both are very dense, bright and possibly formed by rock and water ice. But their scales are quite different.

    “The whole Chariklo system would fit about 12 times in the Cassini Division,” Braga-Ribas said, referring to the largest gap in Saturn’s rings.

    Particles orbiting Chariklo also travel more slowly — only tens of meters per second, compared with tens of kilometers per second in the rings of Saturn.

    While Saturn is the most well-known ringed body in the solar system, Jupiter, Neptune and Uranus also have their own, fainter rings. These gas giants significantly dwarf the smaller asteroid.

    Astronomers utilized seven telescopes, most of which were located in South America. Of them, only the European Southern Observatory’s La Silla telescope in Chile was able to capture the small gap between the rings.

    ESO LaSilla Long View
    ESO/LaSilla

    “This was possible due to the use of the ‘Lucky Imager,’ a fast and sensible camera that obtained a sequence of images like a video at a rate of 10 images per second,” Braga-Ribas said. “As the stellar occultation by both rings lasted for 0.6 seconds in total, it was able to ‘see’ the rings in detail.”

    The other telescopes had exposure times greater than 0.7 seconds, so they were only able to observe a single gap in the light.

    What’s so special about this asteroid to make it have rings?
    “Chariklo seems to be nothing special, otherwise,” Joseph Burns, of Cornell University, told Space.com by email. Burns was not a member of Braga-Ribas’ team, but he studies planetary rings and the small bodies of the solar system. He authored a perspective article that appeared alongside the new findings.

    Chariklo may not be the only nonplanetary body to have rings, Braga-Ribas said. “Rings may be a much more common property than we thought,” he said.

    The research and Burns’ accompanying article were published online today (March 26) in the journal Nature.

    Chariklo’s ‘toy ring’

    Chariklo is the largest of the centaurs, several bodies in the outer solar system whose orbits cross — and are changed by — the outer planets. The centaurs share characteristics with both asteroids and comets, and are thought to come from the Kuiper Belt region beyond Pluto. Rocky Chariklo appears to be more asteroid than comet in composition, according to the paper.

    kb
    Kuiper Belt

    This placement may help to explain the presence of Chariklo’s rings and their absence in the asteroid belt that lies between Mars and Jupiter. The rocky inner planets and the asteroid belt lie closer to the sun, and experience stronger forces from the solar wind, which can more efficiently blow small particles away from objects they might otherwise orbit, Braga-Ribas said.

    Collisions in the fast-moving asteroid belt are also violent processes due to their faster orbital speeds. Crashes between the nearby rocky bodies may wind up hurling any potential ring material away too quickly. The collision that likely created Chariklo’s rings would have had to have been a slow-moving impact. The asteroid’s small size means it has very little gravity, allowing fast-moving objects to easily escape from its orbit; the asteroid would only have been able to hold on to slower-traveling objects.

    The presence of a ring system answers questions about why the asteroid has brightened since observations in 2008. Originally viewed edge-on, the rings have become visible over the last five years as their inclination changed.

    Twice in its 29-year orbit, Saturn’s rings act the same way, appearing as a thin line to observers on Earth, Burns said. “This behavior confounded Galileo, as viewed through his crude telescope, on his discovery of Saturn’s rings,” Burns said. “It took many more observers and nearly 50 years before the rings’ nature was understood by Christiaan Huygens.”

    The age of the rings remains another mystery. Over the course of a few million years, the small pieces of a ring system should spread out. Because they are still contained as a ring, the authors concluded that either the system is very young, or the asteroid hosts a small moon that shepherds and confines the particles in their orbit. The moon would be about as massive as both rings combined, and would easily escape detection given Chariklo’s great distance.

    “Shepherds are the preferred — and basically only — explanation,” Burns said. “But Saturn’s and Uranus’ rings have many gaps where we should see shepherds and we don’t. Something is missing in our understanding. Maybe studying Chariklo’s toy rings will bring us ideas.”

    If a missing moon circles the asteroid, keeping the rings in line, then the system could have lasted since the dawn of the solar system, Braga-Ribas said, adding that the disturbance of the gas giant that moved Chariklo to its present-day orbit would require a very close pass to disturb the ring system, indicating that they could have survived the migration.

    Studying the stability of Chariklo’s rings can tell astronomers about the environment required to form and maintain them — a process that can be used to understand the dynamics of the early stages of the solar system.

    On a wider scale, the tiny ringed asteroid can also help scientists to understand more about how galaxies form.

    “The shepherd mechanism seems to be universal from the giant planets to the small minor planet,” Braga-Ribas said. “This mechanism may be acting in other kinds of debris discs, such as proto-planetary nebulae and galaxies.”

    See the full article, with other material, here.

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  • richardmitnick 1:30 pm on October 22, 2014 Permalink | Reply
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    From ESO: “Two Families of Comets Found Around Nearby Star” 


    European Southern Observatory

    22 October 2014
    Contacts

    Alain Lecavelier des Etangs
    Institut d’astrophysique de Paris (IAP)/CNRS/UPMC
    France
    Tel: +33-1-44-32-80-77
    Cell: +33 6 21 75 12 03
    Email: lecaveli@iap.fr

    Flavien Kiefer
    Institut d’astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
    France / Israel
    Tel: +972-502-838-163
    Email: kiefer@iap.fr

    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.

    ESO HARPS
    ESO HARPS at La Silla

    ESO LaSilla Long View
    La Silla

    comets

    Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

    Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”

    For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.

    To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

    ESO 3.6m telescope & HARPS at LaSilla
    ESO 3.6 metre telescope with HARPS

    The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.

    This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet [1], and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.

    The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris [2].

    The exocomets of the second family are much more active and are also on nearly identical orbits [3]. This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.

    Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”
    Notes

    [1] A giant planet, Beta Pictoris b, has also been discovered in orbit at about a billion kilometres from the star and studied using high resolution images obtained with adaptive optics.

    [2] Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star — close to where the planet Beta Pictoris b was discovered.

    [3] This makes them similar to the comets of the Kreutz family in the Solar System, or the fragments of Comet Shoemaker-Levy 9, which impacted Jupiter in July 1994.
    More information

    This research was presented in a paper entitled Two families of exocomets in the Beta Pictoris system which will be published in the journal Nature on 23 October 2014.

    The team is composed of F. Kiefer (Institut d’astrophysique de Paris [IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris, France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de radioastronomie millimétrique, Saint Martin d’Hères, France), A. Vidal-Madjar (IAP), H. Beust (Institut de planétologie et d’astrophysique de Grenoble [IPAG], CNRS, Université Joseph Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard (IAP) and R. Ferlet (IAP).

    See the full article here.

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  • richardmitnick 6:48 pm on October 6, 2014 Permalink | Reply
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    From ESO: “Brilliant Star in a Colourful Neighbourhood” 2010 


    European Southern Observatory

    28 July 2010
    Contacts

    Douglas Pierce-Price
    ESO
    Garching, Germany
    Tel: +49 89 3200 6759
    Email: dpiercep@eso.org

    Richard Hook
    ESO, Survey Telescopes PIO
    Garching Tel: +49 89 3200 6655
    Email: rhook@eso.org

    A spectacular new image from ESO’s Wide Field Imager at the La Silla Observatory in Chile shows the brilliant and unusual star WR 22 and its colourful surroundings. WR 22 is a very hot and bright star that is shedding its atmosphere into space at a rate many millions of times faster than the Sun. It lies in the outer part of the dramatic Carina Nebula from which it formed.

    WR22

    ESO Wide Field Imager 2.2m LaSilla
    ESO WFI onMPG/ESO 2.2m telescope at LaSilla

    ESO 2.2 meter telescope
    ESO 2.2 meter telescope interior
    ESO MPG/ESO 2.2m telescope

    ESO LaSilla Long View
    LaSilla

    Very massive stars live fast and die young. Some of these stellar beacons have such intense radiation passing through their thick atmospheres late in their lives that they shed material into space many millions of times more quickly than relatively sedate stars such as the Sun. These rare, very hot and massive objects are known as Wolf–Rayet stars [1], after the two French astronomers who first identified them in the mid-nineteenth century, and one of the most massive ones yet measured is known as WR 22. It appears at the centre of this picture, which was created from images taken through red, green and blue filters with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. WR 22 is a member of a double star system and has been measured to have a mass at least 70 times that of the Sun.

    WR 22 lies in the southern constellation of Carina, the keel of Jason’s ship Argo in Greek mythology. Although the star lies over 5000 light-years from the Earth it is so bright that it can just be faintly seen with the unaided eye under good conditions. WR 22 is one of many exceptionally brilliant stars associated with the beautiful Carina Nebula (also known as NGC 3372) and the outer part of this huge region of star formation in the southern Milky Way forms the colourful backdrop to this image.

    The subtle colours of the rich background tapestry are a result of the interactions between the intense ultraviolet radiation coming from hot massive stars, including WR 22, and the vast gas clouds, mostly hydrogen, from which they formed. The central part of this enormous complex of gas and dust lies off the left side of this picture as can be seen in image eso1031b. This area includes the remarkable star Eta Carinae and was featured in an earlier press release (eso0905).
    Notes

    [1] More information about Wolf–Rayet stars

    See the full article here.

    Another view, the Carina Nebula

    cn
    This broad panorama of the Carina Nebula, a region of massive star formation in the southern skies, was taken in infrared light using the HAWK-I camera on ESO’s Very Large Telescope. Many previously hidden features, scattered across a spectacular celestial landscape of gas, dust and young stars, have emerged. Some of these features have been annotated in Commons. Trumpler 16 (annotated) is an open cluster that contains the luminous, massive blue variable Eta Carinae, one of the brightest stars in the galaxy, possibly as much as 120 times the mass of the Sun, and emitting the light of 4,000,000 Suns. Eta Carinae is nearing the end of its life, and is surrounded by a huge nebula, cast off by numerous eruptions of the star over the last several centuries; it is expected to explode into a supernova at any time. Trumpler 14 (annotated) contains the huge double star HD 93129 A/B. The young O3 class star HD 93129 A is one of the brightest stars in the galaxy that is still on the main sequence, and with a luminosity equivalent to 3,000,000 Suns, is very nearly as bright as Eta Carinae, but this is not obvious in the photo due to obscuring nebulosities.

    ESO HAWK-I
    ESO HAWK I

    ESOVLTI
    ESO VLT

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  • richardmitnick 6:31 am on October 2, 2014 Permalink | Reply
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    From Daily Galaxy: “Did Our Solar System Originate in a Distant Star Cluster?” 

    Daily Galaxy
    The Daily Galaxy

    September 30, 2014
    NO Writer Credit

    Is it possible that our original home exists as a great collection of stars, a star cluster known as Messier 67, a gathering of suns and stellar remnants some 2,700 light-years distant that contains more than a hundred stars that bear a striking resemblance to the Sun. Astronomers have searched for star clusters in our galaxy whose members come close to matching the Sun’s elemental composition and age. This past January, astronomers using ESO’s HARPS planet hunter in Chile, along with other telescopes around the world, discovered three planets orbiting stars in the cluster Messier 67.

    m67
    Messier 67

    ESO HARPS
    ESO/HARPS

    Although more than one thousand planets outside the Solar System [exoplanets] are now confirmed, only a handful have been found in star clusters. Remarkably one of these new exoplanets is orbiting a star that is a rare solar twin — a star that is almost identical to the Sun in all respects.

    Planets orbiting stars outside the Solar System are now known to be very common. These exoplanets have been found orbiting stars of widely varied ages and chemical compositions and are scattered across the sky. But, up to now, very few planets have been found inside star clusters. This is particularly odd as it is known that most stars are born in such clusters. Astronomers have wondered if there might be something different about planet formation in star clusters to explain this strange paucity.

    Star clusters come in two main types. Open clusters are groups of stars that have formed together from a single cloud of gas and dust in the recent past. They are mostly found in the spiral arms of a galaxy like the Milky Way. On the other hand globular clusters are much bigger spherical collections of much older stars that orbit around the centre of a galaxy. Despite careful searches, no planets have been found in a globular cluster and less than six in open clusters. Exoplanets have also been found in the past two years in the clusters NGC 6811 and Messier 44, and even more recently one has also been detected in the bright and nearby Hyades cluster.

    Anna Brucalassi (Max Planck Institute for Extraterrestrial Physics, Garching, Germany), lead author of the new study, and her team wanted to find out more. “In the Messier 67 star cluster the stars are all about the same age and composition as the Sun. This makes it a perfect laboratory to study how many planets form in such a crowded environment, and whether they form mostly around more massive or less massive stars.”

    The team used the HARPS planet-finding instrument on ESO’s 3.6-metre telescope at the La Silla Observatory. These results were supplemented with observations from several other observatories around the world. They carefully monitored 88 selected stars in Messier 67 over a period of six years to look for the tiny telltale motions of the stars towards and away from Earth that reveal the presence of orbiting planets. Many of the cluster stars are fainter than those normally targeted for exoplanet searches and trying to detect the weak signal from possible planets pushed HARPS to the limit.

    ESO 3.6m telescope & HARPS at LaSilla
    ESO 3.6m telescope and HARPS

    ESO LaSilla Long View
    ESO LaSilla

    Three planets were discovered, two orbiting stars similar to the Sun and one orbiting a more massive and evolved red giant star. The first two planets both have about one third the mass of Jupiter and orbit their host stars in seven and five days respectively. The third planet takes 122 days to orbit its host and is more massive than Jupiter.

    The first of these planets proved to be orbiting a remarkable star — it is one of the most similar solar twins identified so far and is almost identical to the Sun. It is the first solar twin in a cluster that has been found to have a planet. Solar twins, solar analogues and solar-type stars are categories of stars according to their similarity to the Sun. Solar twins are the most similar to the Sun, as they have very similar masses, temperatures, and chemical abundances. Solar twins are very rare, but the other classes, where the similarity is less precise, are much more common.

    Two of the three planets are “hot Jupiters” — planets comparable to Jupiter in size, but much closer to their parent stars and hence much hotter. All three are closer to their host stars than the habitable zone where liquid water could exist.

    “These new results show that planets in open star clusters are about as common as they are around isolated stars — but they are not easy to detect,” adds Luca Pasquini (ESO, Garching, Germany), co-author of the new paper. “The new results are in contrast to earlier work that failed to find cluster planets, but agrees with some other more recent observations. We are continuing to observe this cluster to find how stars with and without planets differ in mass and chemical makeup.”

    To get back to our opening question of which stars could have shared our original region of the galaxy is limited by our precision in measuring such enormous distances and the specific motions of stars, as well as by the sheer number of objects to sift through. Recent computer simulations of the motions of stars in Messier 67 have examined the projected path that our solar system would have had to take if it were ejected from the star cluster and it appears that it would require a very rare alignment of no less than two or three massive stars in Messier 67 to provide the gravitational ejector seat to place our Solar System to its present location. Additionally, in the process of this ejection, gravitational tides would likely have ripped our nascent planetary system apart.

    However, Caleb Scharf, Caleb points out in his new book The Copernicus Complex, “this conclusion itself rests on assumptions about the configuration of the Milky Way’s great spiral arms of stellar objects. If these change more than we thought over billions of years, it’s possible that Messier 67 could have let the Sun go in a less dramatic, and more plausible, fashion. So the jury is still out on where our solar system originated, but the radioisotope clues and the events unfolding in other nebulae leave us in little doubt that, one way or the other, we have been orphaned.”

    See the full article here.

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  • richardmitnick 8:46 am on October 1, 2014 Permalink | Reply
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    From ESO: “Wild Ducks Take Flight in Open Cluster” 


    European Southern Observatory

    The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known — Messier 11, also known as NGC 6705 or the Wild Duck Cluster.

    m11

    ESO Wide Field Imager 2.2m LaSilla
    WFI

    ESO 2.2 meter telescope
    ESO 2.2 meter telescope interior
    2.2 meter telescope at LaSilla

    ESO LaSilla Long View
    ESO at LaSilla

    Messier 11 is an open cluster, sometimes referred to as a galactic cluster, located around 6000 light-years away in the constellation of Scutum (The Shield). It was first discovered by German astronomer Gottfried Kirch in 1681 at the Berlin Observatory, appearing as nothing more than a fuzzy blob through the telescope. It wasn’t until 1733 that the blob was first resolved into separate stars by the Reverend William Derham in England, and Charles Messier added it to his famous catalogue in 1764.

    Messier was a comet hunter and the catalogue came into being as he was frustrated by constantly observing fixed, diffuse objects that looked like comets (for example, objects that we now know to be clusters, galaxies and nebulae). He wanted a record in order to avoid accidentally observing them again and confusing them with possible new comets. This particular stellar cluster was noted down as the eleventh such object — hence the name of Messier 11.

    Open clusters are typically found lying in the arms of spiral galaxies or in the denser regions of irregular galaxies, where star formation is still common. Messier 11 is one of the most star-rich and compact of the open clusters, being almost 20 light-years across and home to close to 3000 stars. Open clusters are different to globular clusters, which tend to be very dense, tightly bound by gravity, and contain hundreds of thousands of very old stars — some of which are nearly as old as the Universe itself.

    Studying open clusters is great way to test theories of stellar evolution, as the stars form from the same initial cloud of gas and dust and are therefore very similar to one another — they all have roughly the same age, chemical composition, and are all the same distance away from Earth. However, each star in the cluster has a different mass, with the more massive stars evolving much faster than their lower mass counterparts as they use up all of their hydrogen much sooner.

    In this way, direct comparisons between the different evolutionary stages can be made within the same cluster: for example, does a 10 million year old star with the same mass as the Sun evolve in a different way to another star that is the same age, but half as massive? In this sense, open clusters are the closest thing astronomers have to “laboratory conditions”.

    Because the stars within open clusters are very loosely bound to one another, individuals are very susceptible to being ejected from the main group due to the effect of gravity from neighbouring celestial objects. NGC 6705 is already at least 250 million years old, so in a few more million years it is likely that this Wild Duck formation will disperse, and the cluster will break up and merge into its surroundings [1].

    Notes

    [1] The alternative and evocative name for NGC 6705, the Wild Duck Cluster, came about in the 19th century. When the cluster was seen through a small telescope it was noticed that the brightest stars formed an open triangle pattern on the sky that resembled ducks flying in formation.

    See the full article here.

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  • richardmitnick 5:44 am on September 3, 2014 Permalink | Reply
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    From ESO- “Cosmic Forecast: Dark Clouds Will Give Way to Sunshine 


    European Southern Observatory

    3 September 2014

    Contacts
    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Lupus 4, a spider-shaped blob of gas and dust, blots out background stars like a dark cloud on a moonless night in this intriguing new image. Although gloomy for now, dense pockets of material within clouds such as Lupus 4 are where new stars form and where they will later burst into radiant life. The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile captured this new picture.

    black

    ESO Wide Field Imager 2.2m LaSilla
    WFI
    ESO 2.2 meter telescope
    ESO 2.2 meter telescope interior
    ESO 2.2 meter telescope

    ESO LaSilla Long View
    ESO/LaSilla

    Lupus 4 is located about 400 light-years away from Earth, straddling the constellations of Lupus (The Wolf) and Norma (The Carpenter’s Square). The cloud is one of several affiliated dark clouds found in a loose star cluster called the Scorpius–Centaurus OB association. An OB association is a relatively young, yet widely dispersed grouping of stars [1]. The stars likely had a common origin in a gigantic cloud of material.

    Because the association, and its Lupus clouds, form the closest such grouping to the Sun, they are a prime target for studying how stars grow up together before going their separate ways. The Sun, along with most stars in our galaxy, is thought to have started out in a similar environment.

    American astronomer Edward Emerson Barnard is credited with the earliest descriptions of the Lupus dark clouds in the astronomical literature, back in 1927. Lupus 3, neighbour to Lupus 4, is the best studied, thanks to the presence of at least 40 fledgling stars formed over the last three million years, and which are on the cusp of igniting their fusion furnaces (eso1303). The main energy source in these adolescent stars, known as T Tauri stars, is the heat generated by their gravitational contraction. That is in contrast to the fusion of hydrogen and other elements which powers mature stars such as the Sun.

    Observations of the cold darkness of Lupus 4 have turned up only a few T Tauri stars. Yet promisingly for Lupus 4 in terms of future star formation is a dense, starless core of material in the cloud. Given a few million years, that core should develop into T Tauri stars. Comparing Lupus 3 and Lupus 4 in this way suggests that the former is older than the latter, because its contents have had more time to develop into stars.

    How many stars might eventually start to shine within Lupus 4? It is hard to say, as mass estimates for Lupus 4 vary. Two studies agree on a figure of around 250 times the mass of the Sun, though another, using a different method, arrives at a figure of around 1600 solar masses. Either way, the cloud contains ample material to give rise to plenty of bright new stars. Rather as earthly clouds make way for sunshine, so, too, shall this cosmic dark cloud eventually dissipate and give way to brilliant starlight.

    Notes
    [1] The “OB” refers to the hot, bright, short-lived stars of spectral types O and B that are still shining brilliantly within the widely dispersed cluster as it travels through the Milky Way galaxy.

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  • richardmitnick 10:08 am on August 31, 2014 Permalink | Reply
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    From ESO: “Possible Planetary System Photographed Around Nearby Star” 1987 A Good Piece of ESO History 


    European Southern Observatory

    5 January 1987
    Contacts
    Richard West
    ESO
    Garching, Germany
    Tel: +49 89 3200 6276
    Email: information@eso.org

    Based on observations obtained at the European Southern Observatory (ESO), astronomers at the Space Telescope Science Institute (STScI) have uncovered the strongest evidence yet for the presence of a giant planetary or protoplanetary system accompanying a nearby star [1].

    image

    Using special observational and image analysis techniques, Francesco Paresce and Christopher Burrows, of STScI and the European Space Agency (ESA), have made the first visible light images of a large disc of material closely bound to the star Beta Pictoris. The disc is at least 80.000 million kilometres across, or more than three times the diameter of our solar system.

    bp
    The red dot shows the location of Beta Pictoris.

    The observations were made at the ESO La Silla observatory in the Atacama desert in Chile. The astronomers will present their findings at the 169th meeting of the American Astronomical Society in Pasadena, California on January 5th.

    ESO LaSilla
    ESO/LaSilla

    An unusual excess of infrared radiation, indicative of circumstellar matter, was initially detected around Beta Pictoris by the Infrared Astronomy Satellite (IRAS) in 1983. Subsequent ground-based observations revealed the presence of a disc-like feature at near-infrared wavelengths.

    Caltech IRAS
    Caltech IRAS

    When Paresce and Burrows made detailed observations of the disc at several regions of the visible light spectrum, they found that the reflectivity of the disc material was neutral, or wavelength independent. This means that the colour and spectral characteristics of light reflected from the disc almost exactly matched the spectrum of light emitted from the star itself.

    This observation offers the strongest indications yet that the disc is made up of relatively large solid particles. If it were extremely fine dust, which is commonly found in interstellar space, it would scatter only the bluer wavelengths of starlight. The observational data alone cannot establish the true size of the reflecting particles but does set a lower limit of about 0.001 millimetre (1 micron). At this diametre or greater, the particles found around Beta Pictoris are at least ten times larger than material normally observed in interstellar space.

    “The observations show unequivocally that an agglomeration process is in an advanced state, where fine interstellar grains stuck together to form larger clumps”, reports Dr. Paresce. It is believed that as such a ‘snowballing’ process continues, the disc material may eventually accrete into planet-sized objects, if they have not done so already. Our solar system may have condensed or accreted out of thick dust grains which formed a circumstellar nebula that accompanied the birth of our sun, approximately 4600 million years ago.

    The presently available observational data cannot determine the composition of the particles, though they likely contain silicates, carbonaceous materials, and water ice – common elements abundant within our own solar system.

    The evidence for planetary formation is also supported by the fact that the large dust particles are arranged in a flattened disc. The disc likely formed out of an immense, protostellar nebula that contracted and collapsed into the feature seen today. Most of the nebula’s gas and dust concentrated at the centre of the disc to form the star Beta Pictoris. The remaining material now continues to orbit the star.

    At present it is not known if planets already formed within the disc or if it is still in a protoplanetary stage. “All that can be said for sure is that the disc has progressed from a ‘fine sand’ stage into at least a ‘pebble’ stage”, says Dr. Paresce.

    Beta Pictoris is a relatively young star estimated to be no older than 1000 million years, or about one fifth the age of our sun. Approximately 50 light years away, it is a socalled ‘main-sequence dwarf‘, like our sun.

    Paresce and Burrows made their observations of Beta Pictoris, which is visible as a fourth magnitude star in the southern hemisphere, with the ESO 2.2 metre telescope. Attaching a coronograph of their own design and fabrication, the researchers blocked out the brilliant image of the star, so that the faint circumstellar features could be photographed with a CCD (Charge Coupled Device) detector. To allow analysis of the disc at various wavelengths of light, a series of exposures were then taken through bandpass filters across the visible spectrum. These difficult observations were facilitated by the excellent atmospheric conditions at the ESO La Silla observatory.

    ESO 2.2 meter telescope
    2.2
    ESO/ 2.2 meter telescope

    As a control, an identical observing sequence was performed on the stars Delta Hydrus and Alpha Pictoris which are not expected to have prominent circumstellar disc features visible from Earth.

    Through special data analysis techniques developed by Paresce and Burrows, the two stellar images were corrected for known instrumental effects, precisely registered, and differences between the two images were evaluated. This was an especially challenging task since the researchers were probing the near vicinity of Beta Pictoris and had to contend with intense scattered light from the star itself. They also had to be sure that they were seeing reflected light from a true disc feature and not contamination produced by the instrument optics.

    Their resulting data yields the first true, photometrically accurate image of the Beta Pictoris disc, down to about four arcseconds from the star. Never before has such a relatively faint feature been photographed within such close proximity to such a bright star.

    The resulting images reveal a highly flattened disc which extends symmetrically outward from Beta Pictoris, into a northeast and southwest direction on the sky. The disc’s apparent angular width may indicate that it is slightly tilted to our line of sight. The disc dramatically increases in brightness toward its center, though its structure closer to Beta Pictoris is not visible due to the occulting finger which blocks out most of the light from the star.

    Astronomers are eager to find evidence of extrasolar planetary systems to learn whether our own solar system was created out of very unique conditions, or whether it is the result of common and fundamental processes that accompany stellar formation. These questions can not be satisfactorily answered until astronomers have carefully studied examples of planetary formation other than our own solar system.

    Paresce and Burrows have images of planetary or protoplanetary around other stars to analyze. They also plan to make detailed observations of Beta Pictoris with the NASA/ESA Hubble Space Telescope, which is now scheduled for launch in late 1988. With its significant increase in resolution over present ground-based instruments, the Space Telescope will have the capability to provide a far more detailed view of the disc’s structure, closer to the star. It will also have the potential for detecting the extremely faint glow of planets which may accompany the star. It is also expected that this fascinating area of astronomical research will greatly benefit from future, giant telescopes on the ground, such as the ESO 16 metre Very Large Telescope (VLT), now in the final planning stage.

    NASA Hubble Telescope
    NASA/ESA Hubble

    ESO VLT
    ESO VLT Interior
    ESO/VLT

    Notes

    [1] The text of this Press Release is published simultaneously by STScI and ESO. A B/W picture is available on request from both organisations.
    More information

    The Hubble Space Telescope is a project of international collaboration between NASA and ESA. The Space Telescope Science Institute is operated for NASA by the Association of Universities for Research in Astronomy (AURA). It is located on the Johns Hopkins University Campus in Baltimore, Maryland, U.S.A.

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  • richardmitnick 8:02 am on August 20, 2014 Permalink | Reply
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    From ESO: “A Spectacular Landscape of Star Formation” 


    European Southern Observatory

    20 August 2014
    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany

    Tel: +49 89 3200 6655
    Email: rhook@eso.org

    This image, captured by the Wide Field Imager at ESO’s La Silla Observatory [on the 2.2 meter telescope] in Chile, shows two dramatic star formation regions in the southern Milky Way. The first is of these, on the left, is dominated by the star cluster NGC 3603, located 20 000 light-years away, in the Carina–Sagittarius spiral arm of the Milky Way galaxy. The second object, on the right, is a collection of glowing gas clouds known as NGC 3576 that lies only about half as far from Earth.

    scene

    ngc3603
    NASA/ESA Hubble

    ngc3576
    NGC 3576

    ESO Wide Field Imager 2.2m LaSilla
    WFI at LaSilla

    ESO 2.2 meter telescope
    2.2 meter telescope

    ESO LaSilla
    LaSilla

    NGC 3603 is a very bright star cluster and is famed for having the highest concentration of massive stars that have been discovered in our galaxy so far. At the centre lies a Wolf–Rayet multiple star system, known as HD 97950. Wolf–Rayet stars are at an advanced stage of stellar evolution, and start off with around 20 times the mass of the Sun. But, despite this large mass, Wolf–Rayet stars shed a considerable amount of their matter due to intense stellar winds, which blast the star’s surface material off into space at several million kilometres per hour, a crash diet of cosmic proportions.

    NGC 3603 is in an area of very active star formation. Stars are born in dark and dusty regions of space, largely hidden from view. But as the very young stars gradually start to shine and clear away their surrounding cocoons of material they become visible and create glowing clouds in the surrounding material, known as HII regions. HII regions shine because of the interaction of ultraviolet radiation given off by the brilliant hot young stars with the hydrogen gas clouds. HII regions can measure several hundred light-years in diameter, and the one surrounding NGC 3603 has the distinction of being the most massive in our galaxy.

    The cluster was first observed by John Herschel on 14 March 1834 during his three-year expedition to systematically survey the southern skies from near Cape Town. He described it as a remarkable object and thought that it might be a globular star cluster. Future studies showed that it is not an old globular, but a young open cluster, one of the richest known.

    NGC 3576, on the right of the image, also lies in the Carina–Sagittarius spiral arm of the Milky Way. But it is located only about 9000 light-years from Earth — much closer than NGC 3603, but appearing next to it in the sky.

    >NGC 3576 is notable for two huge curved objects resembling the curled horns of a ram. These odd filaments are the result of stellar winds from the hot, young stars within the central regions of the nebula, which have blown the dust and gas outwards across a hundred light-years. Two dark silhouetted areas known as Bok globules are also visible in this vast complex of nebulae. These black clouds near the top of the nebula also offer potential sites for the future formation of new stars.

    NGC 3576 was also discovered by John Herschel in 1834, making it a particularly productive and visually rewarding year for the English astronomer.

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  • richardmitnick 7:41 am on July 23, 2014 Permalink | Reply
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    From ESO: “Lives and Deaths of Sibling Stars” 


    European Southern Observatory

    23 July 2014
    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany

    Tel: +49 89 3200 6655
    Email: rhook@eso.org

    In this striking new image from ESO’s La Silla Observatory in Chile young stars huddle together against a backdrop of clouds of glowing gas and lanes of dust. The star cluster, known as NGC 3293, would have been just a cloud of gas and dust itself about ten million years ago, but as stars began to form it became the bright group of stars we see here. Clusters like this are celestial laboratories that allow astronomers to learn more about how stars evolve.

    ngc3293

    ESO LaSilla
    LaSilla

    Star clusters like NGC 3293 contain stars that all formed at the same time, at the same distance from Earth and out of the same cloud of gas and dust, giving them the same chemical composition. As a result clusters like this are ideal objects for testing stellar evolution theory.

    Most of the stars seen here are very young, and the cluster itself is less than 10 million years old. Just babies on cosmic scales if you consider that the Sun is 4.6 billion years old and still only middle-aged. An abundance of these bright, blue, youthful stars is common in open clusters like NGC 3293, and, for example, in the better known Kappa Crucis cluster, otherwise known as the Jewel Box or NGC 4755.

    kcc
    The FORS1 instrument on the ESO Very Large Telescope (VLT) at ESO’s Paranal Observatory was used to take this exquisitely sharp close up view of the colourful Jewel Box cluster, NGC 4755. The telescope’s huge mirror allowed very short exposure times: just 2.6 seconds through a blue filter (B), 1.3 seconds through a yellow/green filter (V) and 1.3 seconds through a red filter (R).

    ESO FORS1
    FORS1 on VLT

    ESO VLT
    ESO VLT

    These open clusters each formed from a giant cloud of molecular gas and their stars are held together by their mutual gravitational attraction. But these forces are not enough to hold a cluster together against close encounters with other clusters and clouds of gas as the cluster’s own gas and dust dissipates. So, open clusters will only last a few hundred million years, unlike their big cousins, the globular clusters, which can survive for billions of years, and hold on to far more stars.

    Despite some evidence suggesting that there is still some ongoing star formation in NGC 3293, it is thought that most, if not all, of the nearly fifty stars in this cluster were born in one single event. But even though these stars are all the same age, they do not all have the dazzling appearance of a star in its infancy; some of them look positively elderly, giving astronomers the chance to explore how and why stars evolve at different speeds.

    Take the bright orange star at the bottom right of the cluster. This huge star, a red giant, would have been born as one of the biggest and most luminous of its litter, but bright stars burn out fast. As the star used up the fuel at its core its internal dynamics changed and it began to swell and cool, becoming the red giant we now observe. Red giants are reaching the end of their life cycle, but this red giant’s sister stars are still in what is known as the pre-main-sequence — the period before the long, stable, middle period in a star’s life. We see these stars in the prime of their life as hot, bright and white against the red and dusty background.

    This image was taken with the Wide Field Imager (WFI)ESO Wide Field Imager 2.2m LaSilla installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in northern Chile.

    ESO 2.2 meter telescope

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  • richardmitnick 6:22 am on July 2, 2014 Permalink | Reply
    Tags: , , , , ESO La Silla   

    From ESO: “A Stellar Womb Shaped and Destroyed by its Ungrateful Offspring” 


    European Southern Observatory

    2 July 2014
    Richard Hook
    ESO, Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    The little-known cloud of cosmic gas and dust called Gum 15 is the birthplace and home of hot young stars. Beautiful and deadly, these stars mould the appearance of their mother nebula and, as they progress into adulthood, will eventually also be the death of her.

    gum

    This image was taken as part of the ESO Cosmic Gems programme using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. It shows Gum 15, located in the constellation of Vela (The Sails), some 3000 light-years from Earth. This glowing cloud is a striking example of an HII region. Such clouds form some of the most spectacular astronomical objects we can see; for example the Eagle Nebula (which includes the feature nicknamed “The Pillars of Creation”), the great Orion Nebula, and this less famous example, Gum 15.

    ESO Wide Field Imager 2.2m LaSilla
    ESO’s WFI

    ESO 2.2 meter telescope
    >MPG/ESO 2.2-metre telescope at the La Silla Observatory

    pillars
    Pillars of Creation
    Star forming pillars in the Eagle Nebula, as seen by the Hubble Space Telescope’s WFPC2. The picture is composed of 32 different images from four separate cameras in this instrument. The photograph was made with light emitted by different elements in the cloud and appears as a different colour in the composite image: green for hydrogen, red for singly-ionized sulphur and blue for double-ionized oxygen atoms.

    The missing part at the top right is because one of the four cameras has a magnified view of its portion, which allows astronomers to see finer detail. The images from this camera were scaled down in size to match those from the other three cameras.

    Orion
    Orion Nebula
    In one of the most detailed astronomical images ever produced, NASA/ESA’s Hubble Space Telescope captured an unprecedented look at the Orion Nebula. … This extensive study took 105 Hubble orbits to complete. All imaging instruments aboard the telescope were used simultaneously to study Orion. The Advanced Camera mosaic covers approximately the apparent angular size of the full moon.

    Hydrogen (H) is the most common element in the Universe, and can be found in virtually every environment investigated by astronomers. HII regions are different because they contain substantial amounts of ionised hydrogen — hydrogen atoms that have been stripped of their electrons through high energy interactions with ultraviolet photons — particles of light. As the ionised hydrogen nuclei recapture electrons they release light at different characteristic wavelengths. It is one of these that gives nebulae such as Gum 15 their reddish glow — a glow which astronomers call hydrogen alpha (Hα).

    In HII regions the ionising photons come from the young hot stars within the region, and Gum 15 is no exception. At the centre of this image you can see one of the culprits: the star HD 74804, the brightest member of a cluster of stars known as Collinder 197.

    The clumpy, irregular appearance that enhances this nebula’s beauty is not unusual for a HII region and is again a result of the stars within. HII regions have diverse shapes because the distribution of stars and gas inside them is so irregular. Adding to Gum 15’s interesting shape are the forked dark patch of obscuring dust visible in the centre of this image and some dim blue reflection structures crossing it. This dust feature makes the nebula resemble a larger and fainter version of the better known Trifid Nebula (Messier 20), although in this case the name Bifid Nebula might be more apposite.

    m20
    The Trifid nebula (M20, NGC NGC 6514) in pseudocolor.
    Image taken with the Palomar 1.5-m telescope.
    Caltech Palomar Observatory
    Palomar at Caltech

    An HII region like this one might give birth to thousands of stars over a period of several million years. Some of these stars cause it to glow and sculpt its shape, and it is these stars that will eventually destroy it. Once the newly minted stars have passed through their infant stages, strong winds of particles will stream away from these large stars, sculpting and dispersing the gases around them, and when the most massive of these stars begin to die, Gum 15 will die with them. Some stars are so large that they will go out with a bang, exploding as supernovae and dispersing the regions last traces of HII, leaving behind just a cluster of infant stars.

    See the full article,with notes, here.

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