Monday, March 31, 2014

Gravitational Lensing of a Super-Luminous Galaxy in the Young Cosmos

Far behind this nearby cluster of galaxies (Abell 773, seen here in the optical) lies a distant hyper-luminous galaxy seen as it was only about 800 million years after the big bang. The cluster, acting as a giant gravitational lens, has enable astronomers to study in detail the workings of this young giant. Credit: ALFOSC, the Nordic Optical Telescope

About fifteen years ago astronomers, using improved submillimeter wavelength telescopes, discovered a new class of very distant galaxies: submillimeter galaxies (SMGs). These objects are among the most luminous, rapidly star-forming galaxies known, and can shine brighter than a trillion Suns (about one hundred times more luminous than the Milky Way), but they are undetected in the visible. Their ultraviolet and optical light is absorbed by dust in the galaxies which is warmed and then emits in the submillimeter. SMGs are typically so distant that their light has been traveling for over ten billion years, more than 70% of the lifetime of the universe. Their power source is thought to be star formation, with some having rates as high as one thousand stars per year (in the Milky Way, the rate is more like a few stars per year), although the cause of such dramatic bursts is not understood.

Atomic and molecular lines are particularly important diagnostics of star formation, black hole activity, and interstellar gas properties. Furthermore, the shapes of the emission lines provide direct insights into the dynamics of the system. The observed far-infrared and submillimeter spectra of SMGs is dominated by such emission lines because the gas in their molecular clouds, as well as the dust, is exposed to ultraviolet flux from nearby young stars that stimulates the gas to glow.

A team of scientists including CfA astronomers Shane Bussmann, Mark Gurwell, and Giovanni Fazio wanted to study the energetics in the most distant SMGs possible in order to learn whether the processes at work during early times in the universe were similar to those currently dominant. They used the Submillimeter Array (and another facility) to measure the spectra of carbon, nitrogen, carbon monoxide, and water in a galaxy seen a mere 800 million years after the big bang. This object is so far away that even though it is among the most luminous SMGs known its light would normally be too faint to detect with the SMA. However, it was selected in part because it lies directly behind a massive foreground cluster of galaxies (only a few billion light-years away) whose gravity acts like a humongous lens to magnify the more distant galaxy.

The team not only detected these lines, but were able to identify at least three distinct components within them, revealing what appear to be two merging galaxies, one of them with two regions of star formation near its nucleus. The analysis indicates that surprisingly, although extraordinarily luminous, this merging system appears to have star formation activity that in character (if not in quantity) closely resembles that in normal star formation in the local universe. The results are another step in our understanding of the early universe, as well as a demonstration of the remarkable power of gravitationally lensed systems.

Reference(s): 
"[C II] and 12CO(1–0) Emission Maps in HLSJ091828.6+514223: A Strongly Lensed Interacting System at z = 5.24," T. D. Rawle, E. Egami, R. S. Bussmann, M. Gurwell, R. J. Ivison, F. Boone, F. Combes, A. L. R. Danielson, M. Rex, J. Richard, I. Smail, A. M. Swinbank, B. Altieri, A. W. Blain, B. Clement, M. Dessauges-Zavadsky, A. C. Edge, G. G. Fazio, T. Jones, J.-P. Kneib, A. Omont, P. G. Perez-Gonzalez, D. Schaerer, I. Valtchanov, P. P. van der Werf, G. Walth, M. Zamojski, and M. Zemcov, ApJ 783, 59, 2014.


Spitzer Sees the Galactic Dawn with 'Frontier Fields'

Credit: NASA/JPL-Caltech/P. Capak (Caltech)

About this image: J0717 isn't just a large cluster of galaxies; astronomers are using it like a giant telephoto lens attachment to study the very distant, very faint universe. This new infrared view from NASA's Spitzer Space Telescope will be used in tandem with observations from other major NASA observatories to glimpse the universe's very first galaxies. Called Frontier Fields, the project is a collaboration with the Hubble Space Telescope and the Chandra X-ray Observatory. 

The faintness of the earliest, most distant galaxies makes studying them a challenge, even with long, deep exposures. Frontier Fields, however, can spot these primordial galaxies courtesy of foreground clusters of galaxies, whose gargantuan mass and gravity form cosmic "zoom lenses."

The clusters warp space around them, magnifying background galaxies. The cluster in this image, known as J0717, is the grouping of bright objects near the center of the field, while examples of the very distant background galaxies appear as distorted arcs at the center of the two circular call-outs.

NASA's Spitzer Space Telescope, in tandem with other major NASA observatories, has recently embarked on a major new mission to glimpse the universe's very first galaxies. Called Frontier Fields, the project is a collaboration with the Hubble Space Telescope and the Chandra X-ray Observatory. All three telescopes, collectively known as NASA's Great Observatories, are playing indispensable roles in this quest.  

The faintness of the earliest, most distant galaxies makes studying them a challenge. Frontier Fields, however, can spot these primordial galaxies courtesy of foreground clusters of galaxies, whose gargantuan mass and gravity form cosmic "zoom lenses." Peering through these gravitational lenses is giving astronomers an unprecedented view of the galactic dawn. 

"Our overall science goal with the Frontier Fields is to understand how the first galaxies in the universe assembled," said Peter Capak, a research scientist with the NASA/JPL Spitzer Science Center at the California Institute of Technology and the Spitzer lead for the Frontier Fields. "This pursuit is made possible by how massive galaxy clusters warp space around them, kind of like when you look through the bottom of a wine glass."

Although astronomers have relied on this cosmic lensing for many years now to turn up distant galactic quarry, Frontier Fields takes the practice to a new level. The project has selected the most massive and distant clusters on record, thus offering the highest magnification and deepest probe of the early universe available. 

Plus, Frontier Fields will further characterize the foreground clusters to better gauge the lenses' magnifying, as well as distorting, effects. On average, the gravitational warping of space by foreground clusters magnifies background galaxies four to ten times. But some galaxies studied via Frontier Fields will be magnified on the order of a hundred times.

NASA's Great Observatories will view the cluster galaxies and background galaxies in different wavelengths of light, each of which carries important scientific information. Spitzer observes in longer wavelength, infrared light; Hubble, in shorter infrared and optical light; and Chandra in high-energy X-rays.  

The infrared light captured by Spitzer serves two key purposes. Firstly, infrared light is an indicator of the number of stars in a galaxy, which speaks to the galaxy's overall mass. In the case of extremely distant galaxies, the optical light from their stars has been stretched out, or "redshifted," into infrared wavelengths as a result of the expansion of the universe. "Spitzer basically measures the mass of galaxies," said Capak. "Because of the wavelengths it works in, Spitzer is the only instrument capable of making mass measurements of galaxies this far away." 

Secondly, Spitzer can help determine if certain galaxies also observed by Hubble are in fact the far-off, early galaxies of interest or just nearby galaxies. "Spitzer and Hubble can tell if galaxies discovered in the Frontier Fields are really at the edge of the universe or not," said Capak. 

Hubble and Spitzer scientists envisioned this sort of synergy when the Frontier Fields were conceived in 2012. "This program exemplifies the combined strength of NASA's Great Observatories when it comes to digging deep into the distant universe," said Jennifer Lotz from the Space Telescope Science Institute, which manages Hubble for NASA.

Chandra's role in Frontier Fields, meanwhile, is to provide a detailed map of the hot, X-ray-emitting gas in the galaxy clusters. Doing so will help to further pin down their masses. Spitzer will be integral to this aspect of the project as well by presenting astronomers with an overview of the stars in the clusters' galaxies.
Observations of the first Frontier Field cluster, Abell 2744, have been completed. Work is now underway on another cluster and two more are slated for summer. The Abell 2744 effort has already resulted in the discovery of one of the most distant galaxies ever seen, dubbed Abell 2744 Y1. This tiny, infant galaxy was witnessed at a time when the 13.8 billion-year-old universe was a mere 650 million years old. Frontier Fields is expected to reveal many other similarly primeval galaxies in the critical galaxy-forming epoch shortly after the Big Bang.  

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colo. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

Friday, March 28, 2014

Magnifying the distant Universe

Credit: ESA/Hubble & NASA
Acknowledgement: Nick Rose

Galaxy clusters are some of the most massive structures that can be found in the Universe — large groups of galaxies bound together by gravity. This image from the NASA/ESA Hubble Space Telescope reveals one of these clusters, known as MACS J0454.1-0300. Each of the bright spots seen here is a galaxy, and each is home to many millions, or even billions, of stars.

Astronomers have determined the mass of MACS J0454.1-0300 to be around 180 trillion times the mass of the Sun. Clusters like this are so massive that their gravity can even change the behaviour of space around them, bending the path of light as it travels through them, sometimes amplifying it and acting like a cosmic magnifying glass. Thanks to this effect, it is possible to see objects that are so far away from us that they would otherwise be too faint to be detected.

In this case, several objects appear to be dramatically elongated and are seen as sweeping arcs to the left of this image. These are galaxies located at vast distances behind the cluster — their image has been amplified, but also distorted, as their light passes through MACS J0454.1-0300. This process, known as gravitational lensing, is an extremely valuable tool for astronomers as they peer at very distant objects.

This effect will be put to good use with the start of Hubble's Frontier Fields program over the next few years, which aims to explore very distant objects located behind lensing clusters, similar to MACS J0454.1-0300, to investigate how stars and galaxies formed and evolved in the early Universe.

A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.





Thursday, March 27, 2014

Hubble Sees Mars-Bound Comet Sprout Multiple Jets

C/2013 A1 Siding Spring
Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)

Comet Siding Spring is plunging toward the Sun along a roughly 1-million-year orbit. The comet, discovered in 2013, was within the radius of Jupiter's orbit when the Hubble Space Telescope photographed it on March 11, 2014. Hubble resolves two jets of dust coming from the solid icy nucleus. These persistent jets were first seen in Hubble pictures taken on Oct. 29, 2013. The feature should allow astronomers to measure the direction of the nucleus's pole, and hence, rotation axis. The comet will make its closest approach to our Sun on Oct. 25, 2014, at a distance of 130 million miles, well outside Earth's orbit. On its inbound leg, Comet Siding Spring will pass within 84,000 miles of Mars on Oct. 19, 2014, which is less than half the Moon's distance from Earth. The comet is not expected to become bright enough to be seen by the naked eye.

About this Image:
 
[Left] This is a Hubble Space Telescope picture of comet C/2013 A1 Siding Spring as observed on March 11, 2014. At that time the comet was 353 million miles from Earth. The solid icy nucleus is too small to be resolved by Hubble, but it lies at the center of a dust cloud, called a coma, that is roughly 12,000 miles across in this image.


[Right] When the glow of the coma is subtracted through image processing, which incorporates a smooth model of the coma's light distribution, Hubble resolves what appear to be two jets of dust coming off the nucleus in opposite directions. This means that only portions of the surface of the nucleus are presently active as they are warmed by sunlight, say researchers. These jets were first seen in Hubble pictures taken on Oct. 29, 2013. The feature should allow astronomers to measure the direction of the nucleus's pole, and hence, rotation axis.

Discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory in New South Wales, Australia, the comet is falling toward the Sun along a roughly 1-million-year orbit and is now within the radius of Jupiter's orbit. The comet will make its closest approach to our Sun on Oct. 25, at a distance of 130 million miles — well outside Earth's orbit. On its inbound leg, Comet Siding Spring will pass within 84,000 miles of Mars on Oct. 19, 2014 (less than half the Moon's distance from Earth). The comet is not expected to become bright enough to be seen by the naked eye.

An earlier Hubble observation made on Jan. 21, 2014, caught the comet as Earth was crossing the comet's orbital plane. This special geometry allows astronomers to better determine the speed of the dust coming off the nucleus. "This is critical information that we need to determine how likely and how much the dust grains in the coma will impact Mars and Mars spacecraft," said Jian-Yang Li of the Planetary Science Institute in Tucson, Ariz. 

This visible-light image was taken with Hubble's Wide Field Camera 3.

Source: HubbleSite


The Search for Seeds of Black Holes

The galaxy NGC 4395 is shown here in infrared light, captured by NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech.  ›Full image and caption

How do you grow a supermassive black hole that is a million to a billion times the mass of our sun? Astronomers do not know the answer, but a new study using data from NASA's Wide-field Infrared Survey Explorer, or WISE, has turned up what might be the cosmic seeds from which a black hole will sprout. The results are helping scientists piece together the evolution of supermassive black holes -- powerful objects that dominate the hearts of all galaxies.

Growing a black hole is not as easy as planting a seed in soil and adding water. The massive objects are dense collections of matter that are literally bottomless pits; anything that falls in will never come out. They come in a range of sizes. The smallest, only a few times greater in mass than our sun, form from exploding stars. The biggest of these dark beasts, billions of times the mass of our sun, grow together with their host galaxies over time, deep in the interiors. But how this process works is an ongoing mystery.

Researchers using WISE addressed this question by looking for black holes in smaller, "dwarf" galaxies. These galaxies have not undergone much change, so they are more pristine than their heavier counterparts. In some ways, they resemble the types of galaxies that might have existed when the universe was young, and thus they offer a glimpse into the nurseries of supermassive black holes.

In this new study, using data of the entire sky taken by WISE in infrared light, up to hundreds of dwarf galaxies have been discovered in which buried black holes may be lurking. Infrared light, the kind that WISE collects, can see through dust, unlike visible light, so it's better able to find the dusty, hidden black holes. The researchers found that the dwarf galaxies' black holes may be about 1,000 to 10,000 times the mass of our sun -- larger than expected for these small galaxies.

"Our findings suggest the original seeds of supermassive black holes are quite massive themselves," said Shobita Satyapal of George Mason University, Fairfax, Va. Satyapal is lead author of a paper published in the March issue of Astrophysical Journal.

Daniel Stern, an astronomer specializing in black holes at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who was not a part of the new study, says the research demonstrates the power of an all-sky survey like WISE to find the rarest black holes. "Though it will take more research to confirm whether the dwarf galaxies are indeed dominated by actively feeding black holes, this is exactly what WISE was designed to do: find interesting objects that stand out from the pack."

The new observations argue against one popular theory of black hole growth, which holds that the objects bulk up in size through galaxy collisions. When our universe was young, galaxies were more likely to crash into others and merge. It is possible the galaxies' black holes merged too, accumulating more mass. In this scenario, supermassive black holes grow in size through a series of galaxy mergers.

The discovery of dwarf galaxy black holes that are bigger than expected suggests that galaxy mergers are not necessary to create big black holes. Dwarf galaxies don't have a history of galactic smash-ups, and yet their black holes are already relatively big.

Instead, supermassive black holes might form very early in the history of the universe. Or, they might grow harmoniously with their host galaxies, feeding off surrounding gas. 

"We still don't know how the monstrous black holes that reside in galaxy centers formed," said Satyapal. "But finding big black holes in tiny galaxies shows us that big black holes must somehow have been created in the early universe, before galaxies collided with other galaxies." 

Other authors of the study include: N.J. Secrest, W. McAlpine and J.L. Rosenberg of George Mason University; S.L. Ellison of the University of Victoria, Canada; and J. Fischer of the Naval Research Laboratory, Washington.

WISE was put into hibernation upon completing its primary mission in 2011. In September 2013, it was reactivated, renamed NEOWISE and assigned a new mission to assist NASA's efforts to identify the population of potentially hazardous near-Earth objects. NEOWISE will also characterize previously known asteroids and comets to better understand their sizes and compositions.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages and operates the NEOWISE mission for NASA's Science Mission Directorate. The WISE mission was selected competitively under NASA's Explorers Program managed by the agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

More information on WISE and NEOWISE can be found online at: http://www.nasa.gov/wise, http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise


Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov

Wednesday, March 26, 2014

First Ring System Around Asteroid

Artist’s impression of the rings around Chariklo

PR Image eso1410b
Artist’s impression close-up of the rings around Chariklo

 
Artist’s impression of the view from inside the rings around Chariklo

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Videos

ESOcast 64: First Ring System Around Asteroid
ESOcast 64: First Ring System Around Asteroid

Artist's impression of ring system around asteroid Chariklo
Artist's impression of ring system around asteroid Chariklo

Artist's impression of ring system around asteroid Chariklo
Artist's impression of ring system around asteroid Chariklo

Artist's impression of ring system around asteroid Chariklo
Artist's impression of ring system around asteroid Chariklo

Observations of the occultation of asteroid Chariklo
Observations of the occultation of asteroid Chariklo

Artist's impression of ring system around asteroid Chariklo
Artist's impression of ring system around asteroid Chariklo

Animation of the outer Solar System and orbits of Centaurs
Animation of the outer Solar System and orbits of Centaurs 

Chariklo found to have two rings

Observations at many sites in South America, including ESO’s La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris. The new results are published online in the journal Nature on 26 March 2014.

The rings of Saturn are one of the most spectacular sights in the sky, and less prominent rings have also been found around the other giant planets. Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System. Now observations of the distant minor planet [1] (10199) Chariklo [2] as it passed in front of a star have shown that this object too is surrounded by two fine rings.

"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!" says Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil) who planned the observation campaign and is lead author on the new paper.

Chariklo is the largest member of a class known as the Centaurs [3] and it orbits between Saturn and Uranus in the outer Solar System. Predictions had shown that it would pass in front of the star UCAC4 248-108672 on 3 June 2013, as seen from South America [4]. Astronomers using telescopes at seven different locations, including the 1.54-metre Danish and TRAPPIST telescopes at ESO’s La Silla Observatory in Chile [5], were able to watch the star apparently vanish for a few seconds as its light was blocked by Chariklo — an occultation [6].

But they found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation there were two further very short dips in the star’s apparent brightness [7]. Something around Chariklo was blocking the light! By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.

The team found that the ring system consists of two sharply confined rings only seven and three kilometres wide, separated by a clear gap of nine kilometres — around a small 250-kilometre diameter object orbiting beyond Saturn.

"For me, it was quite amazing to realise that we were able not only to detect a ring system, but also pinpoint that it consists of two clearly distinct rings," adds Uffe Gråe Jørgensen (Niels Bohr Institute, University of Copenhagen, Denmark), one of the team. "I try to imagine how it would be to stand on the surface of this icy object — small enough that a fast sports car could reach escape velocity and drive off into space — and stare up at a 20-kilometre wide ring system 1000 times closer than the Moon." [8]

Although many questions remain unanswered, astronomers think that this sort of ring is likely to be formed from debris left over after a collision. It must be confined into the two narrow rings by the presence of small putative satellites.

"So, as well as the rings, it’s likely that Chariklo has at least one small moon still waiting to be discovered," adds Felipe Braga Ribas.

The rings may prove to be a phenomenon that might in turn later lead to the formation of a small moon. Such a sequence of events, on a much larger scale, may explain the birth of our own Moon in the early days of the Solar System, as well as the origin of many other satellites around planets and asteroids.

The leaders of this project are provisionally calling the rings by the nicknames Oiapoque and Chuí, two rivers near the northern and southern extremes of Brazil [9].

Notes

[1] All objects that orbit the Sun, which are too small (not massive enough) for their own gravity to pull them into a nearly spherical shape are now defined by the IAU as being small solar system bodies. This class currently includes most of the Solar System asteroids, near-Earth objects (NEOs), Mars and Jupiter Trojan asteroids, most Centaurs, most Trans-Neptunian objects (TNOs), and comets. In informal usage the words asteroid and minor planet are often used to mean the same thing. 

[2] The IAU Minor Planet Center is the nerve centre for the detection of small bodies in the Solar System. The names assigned are in two parts, a number — originally the order of discovery but now the order in which orbits are well-determined — and a name.

[3] Centaurs are small bodies with unstable orbits in the outer Solar System that cross the orbits of the giant planets. Because their orbits are frequently perturbed they are expected to only remain in such orbits for millions of years. Centaurs are distinct from the much more numerous main belt asteroids between the orbits of Mars and Jupiter and may have come from the Kuiper Belt region. They got their name because — like the mythical centaurs — they share some characteristics of two different things, in this case comets and asteroids. Chariklo itself seems to be more like an asteroid and has not been found to display cometary activity.

[4] The event was predicted following a systematic search conducted with the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory and recently published.

[5] Besides the Danish 1.54-metre and TRAPPIST telescopes at ESO's La Silla Observatory, event observations were also performed by the following observatories: Universidad Católica Observatory (UCO) Santa Martina operated by the Pontifícia Universidad Católica de Chile (PUC); PROMPT telescopes, owned and operated by the University of North Carolina at Chapel Hill; Pico dos Dias Observatory from the National Laboratory of Astrophysics (OPD/LNA) - Brazil; Southern Astrophysical Research (SOAR) telescope; Caisey Harlingten's 20-inch Planewave telescope, which is part of the Searchlight Observatory Network; R. Sandness's telescope at San Pedro de Atacama Celestial Explorations; Universidade Estadual de Ponta Grossa Observatory; Observatorio Astronomico Los Molinos (OALM) — Uruguay; Observatorio Astronomico, Estacion Astrofisica de Bosque Alegre, Universidad Nacional de Cordoba, Argentina; Polo Astronômico Casimiro Montenegro Filho Observatory and Observatorio El Catalejo, Santa Rosa, La Pampa, Argentina.

[6] This is the only way to pin down the precise size and shape of such a remote body — Chariklo is only about 250 kilometres in diameter and is more than a billion kilometres from Earth. Even in the best telescopic views such a small and distant object just appears as a faint point of light.

[7] The rings of Uranus, and the ring arcs around Neptune, were found in a similar way during occultations in 1977 and 1984, respectively. ESO telescopes were also involved with the Neptune ring discovery.

[8] Strictly speaking the car would have to be rather fast — something like a Bugatti Veyron 16.4 or McLaren F1 — as the escape velocity is around 350 km/hour!

[9] These names are only for informal use, the official names will be allocated later by the IAU, following pre-established rules.

More information

This research was presented in a paper entitled “A ring system detected around the Centaur (10199) Chariklo”, by F. Braga-Ribas et al., to appear online in the journal Nature on 26 March 2014.

The team is composed of F. Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), B. Sicardy (LESIA, Observatoire de Paris, Paris, France [LESIA]), J. L. Ortiz (Instituto de Astrofísica de Andalucía, Granada, Spain), C. Snodgrass (Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany), F. Roques (LESIA), R. Vieira- Martins (Observatório Nacional/MCTI, Rio de Janeiro, Brazil; Observatório do Valongo, Rio de Janeiro, Brazil; Observatoire de Paris, France), J. I. B. Camargo (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), M. Assafin (Observatório do Valongo/UFRJ, Rio de Janeiro, Brazil), R. Duffard (Instituto de Astrofísica de Andalucía, Granada, Spain), E. Jehin (Institut d’Astrophysique de l’Université de Liege, Liege, Belgium), J. Pollock (Appalachian State University, Boone, North Carolina, USA), R. Leiva (Pontificia Universidad Católica de Chile, Santiago, Chile), M. Emilio (Universidade Estadual de Ponta Grossa, Ponta Grossa, Brazil), D. I. Machado (Polo Astronomico Casimiro Montenegro Filho/FPTI-BR, Foz do Iguaçu, Brazil; Universidade Estadual do Oeste do Paraná (Unioeste), Foz do Iguaçu, Brazil), C. Colazo (Ministerio de Educación de la Provincia de Córdoba, Córdoba, Argentina; Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba, Argentina), E. Lellouch (LESIA), J. Skottfelt (Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; Centre for Star and Planet Formation, Geological Museum, Copenhagen, Denmark), M. Gillon (Institut d’Astrophysique de l’Université de Liege, Liege, Belgium), N. Ligier (LESIA), L. Maquet (LESIA), G. Benedetti-Rossi (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), A. Ramos Gomes Jr (Observatório do Valongo, Rio de Janeiro, Brazil, P. Kervella (LESIA), H. Monteiro (Instituto de Física e Química, Itajubá, Brazil), R. Sfair (UNESP -– Univ Estadual Paulista, Guaratinguetá, Brazil), M. El Moutamid (LESIA; Observatoire de Paris, Paris, France), G. Tancredi (Observatorio Astronomico Los Molinos, DICYT, MEC, Montevideo, Uruguay; Dpto. Astronomia, Facultad Ciencias, Uruguay), J. Spagnotto (Observatorio El Catalejo, Santa Rosa, La Pampa, Argentina), A. Maury (San Pedro de Atacama Celestial Explorations, San Pedro de Atacama, Chile), N. Morales (Instituto de Astrofísica de Andalucía, Granada, Spain), R. Gil-Hutton (Complejo Astronomico El Leoncito (CASLEO) and San Juan National University, San Juan, Argentina), S. Roland (Observatorio Astronomico Los Molinos, DICYT, MEC, Montevideo, Uruguay), A. Ceretta (Dpto. Astronomia, Facultad Ciencias, Uruguay; Observatorio del IPA, Ensenanza Secundaria, Uruguay), S.-h. Gu (National Astronomical Observatories/Yunnan Observatory; Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming, China), X.-b. Wang (National Astronomical Observatories/Yunnan Observatory; Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming, China), K. Harpsøe (Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; Centre for Star and Planet Formation, Geological Museum, Copenhagen, Denmark), M. Rabus (Pontificia Universidad Católica de Chile, Santiago, Chile; Max Planck Institute for Astronomy, Heidelberg, Germany), J. Manfroid (Institut d’Astrophysique de l’Université de Liege, Liege, Belgium), C. Opitom (Institut d’Astrophysique de l’Université de Liege, Liege, Belgium), L. Vanzi (Pontificia Universidad Católica de Chile, Santiago, Chile), L. Mehret (Universidade Estadual de Ponta Grossa, Ponta Grossa, Brazil), L. Lorenzini (Polo Astronomico Casimiro Montenegro Filho/FPTI-BR, Foz do Iguaçu, Brazil), E. M. Schneiter (Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina; Instituto de Astronomía Teórica y Experimental IATE–CONICET, Córdoba, Argentina; Universidad Nacional de Córdoba, Córdoba, Argentina), R. Melia (Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba, Argentina), J. Lecacheux (LESIA), F. Colas (Observatoire de Paris, Paris, France), F. Vachier (Observatoire de Paris, Paris, France), T. Widemann (LESIA), L. Almenares (Observatorio Astronomico Los Molinos, DICYT, MEC, Montevideo, Uruguay; Dpto. Astronomia, Facultad Ciencias, Uruguay), R. G. Sandness (San Pedro de Atacama Celestial Explorations, San Pedro de Atacama, Chile), F. Char (Universidad de Antofagasta, Antofagasta, Chile), V. Perez (Observatorio Astronomico Los Molinos, DICYT, MEC, Montevideo, Uruguay; Dpto. Astronomia, Facultad Ciencias, Uruguay), P. Lemos (Dpto. Astronomia, Facultad Ciencias, Uruguay), N. Martinez (Observatorio Astronomico Los Molinos, DICYT, MEC, Montevideo, Uruguay; Dpto. Astronomia, Facultad Ciencias, Uruguay), U. G. Jørgensen (Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; Centre for Star and Planet Formation, Geological Museum, Copenhagen, Denmark), M. Dominik (University of St Andrews, St Andrews, United Kingdom) F. Roig (Observatório Nacional/MCTI, Rio de Janeiro, Brazil), D. E. Reichart (University of North Carolina – Chapel Hill, North Carolina [UNC]), A. P. LaCluyze (UNC), J. B. Haislip (UNC), K. M. Ivarsen (UNC), J. P. Moore (UNC), N. R. Frank (UNC) and D. G. Lambas (Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba, Argentina; Instituto de Astronomía Teórica y Experimental IATE–CONICET, Córdoba, Argentina).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contacts

Felipe Braga-Ribas
Observatório Nacional/MCTI
Rio de Janeiro, Brazil
Tel: +33 (0) 785944776 (until 28.3) and +55 (21) 3504-9252
Cell: +55 (21) 983803879 (after 28.3)
Email:
ribas@on.br

Bruno Sicardy
LESIA, Observatoire de Paris, CNRS
Paris, France
Tel: +33 (0) 1 45 07 71 15
Cell: +33 (0) 6 19 41 26 15
Email:
bruno.sicardy@obspm.fr

José Luis Ortiz
Instituto de Astrofísica de Andalucía, CSIC
Granada, Spain
Tel: +34 958 121 311
Email:
ortiz@iaa.es

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


 Source: ESO


Scientists solve riddle of celestial archaeology

Artist’s impression of debris around a white dwarf star. Credit: NASA, ESA, STScI, and G. Bacon (STScI).
 
Artist’s impression of a massive asteroid belt in orbit around a star. The new work shows that similar rubble around many white dwarfs contaminates these stars with rocky material and water. Credit: NASA-JPL / Caltech / T. Pyle (SSC)

A decades old space mystery has been solved by an international team of astronomers led by Professor Martin Barstow of the University of Leicester and President-elect of the Royal Astronomical Society. The team put forward a new theory for how collapsed stars become polluted – that points to the ominous fate that awaits planet Earth.

Scientists from the University of Leicester and University of Arizona investigated hot, young, white dwarfs — the super-dense remains of Sun-like stars that ran out of fuel and collapsed to about the size of the Earth. Their research is featured in the journal Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

It has been known that many hot white dwarfs’ atmospheres, essentially of pure hydrogen or pure helium, are contaminated by other elements – like carbon, silicon and iron.  What was not known, however, was the origins of these elements, known in astronomical terms as metals.

“The precise origin of the metals has remained a mystery and extreme differences in their abundance between stars could not be explained,” said Professor Barstow, a Pro-Vice-Chancellor at the University of Leicester whose research was assisted by his daughter Jo, a co-author of the paper,  during a summer work placement in Leicester. She has now gone on to be an astronomer working in Oxford on extra-solar planets.

“It was believed that this material was “levitated” by the intense radiation from deeper layers in the star,” said Professor Barstow.

Now the researchers have discovered that many of the stars show signs of contamination by rocky material, the leftovers from a planetary system.

The researchers surveyed 89 white dwarfs, using the orbiting Far Ultraviolet Spectroscopic Explorer telescope to obtain their spectra (dispersing the light by colour) in which the “fingerprints” of carbon, silicon, phosphorous and sulphur can be seen, when these elements are present in the atmosphere.

“We found that in stars with polluted atmospheres the ratio of silicon to carbon matched that seen in rocky material, much higher than found in stars or interstellar gas.  

‘The new work indicates that at around a one-third of all hot white dwarfs are contaminated in this way, with the debris most likely in the form of rocky minor planet analogues. This implies that a similar proportion of stars like our Sun, as well as stars that are a little more massive like Vega and Fomalhaut, build systems containing terrestrial planets.  This work is a form of celestial archaeology where we are studying the 'ruins' of rocky planets and/or their building blocks, following the demise of the main star.

‘The mystery of the composition of these stars is a problem we have been trying to solve for more than 20 years. It is exciting to realise that they are swallowing up the leftovers from planetary systems, perhaps like our own, with the prospect that more detailed follow-up work will be able to tell us about the composition of rocky planets orbiting other stars”, said Professor Barstow.

The study also points to the ultimate fate of the Earth billions of years from now - ending up as merely contamination within the white dwarf remnant of our Sun.


Science contact

Professor Martin Barstow (available from Wednesday 26 March)
University of Leicester
Tel: +44 (0)116 252 3492
mab@le.ac.uk


Media contacts

Ellen Rudge
News and Events Officer
University of Leicester
Tel: +44 (0)116 229 7467
er134@le.ac.uk

Peter Thorley
Corporate News Officer
University of Leicester
Tel: +44 (0)116 252 2415
pt91@le.ac.uk

Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 / 4582
Mob: +44 (0)794 124 8035
rm@ras.org.uk


Images and captions

Image 1
Artist’s impression of debris around a white dwarf star. Credit: NASA, ESA, STScI, and G. Bacon (STScI)

Artist’s impression of a massive asteroid belt in orbit around a star. The new work shows that similar rubble around many white dwarfs contaminates these stars with rocky material and water. Credit: NASA-JPL / Caltech / T. Pyle (SSC)


Further information

The new work appears in “Evidence for an external origin of heavy elements in hot DA white dwarfs”, M. A. Barstow, J. K. Barstow, S. L. Casewell, J. B. Holberg and I. Hubeny, Monthly Notices of the Royal Astronomical Society, Oxford University Press, in press.


Notes for editors

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Tuesday, March 25, 2014

Star-forming region ON2

Star-forming region ON2
Copyright: L.M. Oskinova, R.A. Gruendl, Spitzer Space Telescope, JPL, NASA & ESA

Massive stars are born in tumultuous clouds of gas and dust. They lead a brief but intense life, blowing powerful winds of particles and radiation that strike their surroundings, before their explosive demise as supernovas
.
The interplay between massive stars and their environment is revealed in this image of the star-forming region ON2. It combines X-ray coverage from ESA’s XMM-Newton X-ray observatory with an infrared view from NASA’s Spitzer Space Telescope.

This stellar cradle is associated with the open cluster of stars named Berkeley 87, some 4000 light-years from Earth. The cluster is home to over 2000 stars, most of which are low-mass stars like our Sun or smaller, but some – a few dozen – are stellar monsters weighing 10–80 times more.

Two glowing clouds of gas and dust – the raw material from which stars form – dominate the centre of the image and are shown in red. Scattered across the image are a multitude of protostars – seeds of future stellar generations; these are shown in green. The bright yellow star in the upper part of the image is BC Cygni, a massive star that has puffed up enormously and will eventually explode as a supernova.

Shown in blue is XMM-Newton’s X-ray view of ON2: it reveals individual sources – young, massive stars as well as protostars – and more diffuse regions of X-rays. Two ‘bubbles’ of X-rays can be seen in the upper and lower clouds, respectively, pink against the red background. These two bubbles conceal the cumulative emissions from many protostars, but also light radiated by very energetic particles – a signature of shockwaves triggered by massive stars and their winds.

The image combines observations performed in the X-ray energy range of 0.25–12 keV (blue) and at infrared wavelengths of 3.6 microns (green) and 8 microns (red). It spans about 15 arcminutes on each side; north is up and east is to the left.

This image was first published in the paper “Hard X-Ray Emission in the Star-Forming Region ON 2: Discovery with XMM-Newton” by Oskinova et al. in April 2010.

 Source: ESA


Monday, March 24, 2014

Transition Disks Around Young Stars

An image of the dark cloud in Lupus forming young stars. One of the invisible, embedded young objects here has a circumstellar disk of material whose infrared and submillimeter emission indicate it is intermediate in age between a very new star and one that is old enough to have formed a planetary system and disbursed the disk. Credit: ESO 

A star is typically born with a disk of gas and dust encircling it, the spinning remnant of the much larger cloud of natal material. As the star begins to shine, planets develop from the dust grains in the disk as they stick together and grow. Although the vast majority of very young stars show indirect evidence for such circumstellar disks, in only a few cases have disks been imaged directly or studied in any detail because their sizes on the sky are small (much smaller than the atmospherically blurred sizes of the stars themselves), and in most situations they are fainter than their parent stars. The discovery of ubiquitous planets (“exoplanets”) around other stars lends further credence to the ideas about disks, and adds to the need for an improved understanding of the details of disk formation, structure, and evolution.

Young disks are known to emit at infrared wavelengths because they are warmed by the star to temperatures above the cold, ambient interstellar dust. Astronomers use the particular colors of the star and disk system to characterize the young disk’s properties. After about five million years, however, nearly all stars lack evidence of warm circumstellar dust, suggesting that most disks (or at least around stars roughly the size of the Sun) have disappeared by this time: the disk material has been accreted onto the star or converted into planets or sub-planet-sized bodies, or else dispersed via ultraviolet evaporation or winds. So-called transition disks bridge the gap between the end points of disk evolution: They have not yet been disbursed, but although they are present they emit only slightly in the infrared, at characteristically cooler temperatures.

CfA astronomers Sean Andrews and David Wilner, along with a large team of collaborators, have used the Submillimeter Array (SMA) to probe the transition disk around Sz91, a young star about half the mass of the Sun, located about 600 light-years away. The color of its infrared emission is characteristic of a transition disk, and the scientists wanted to try to use the capabilities of the SMA to obtain an image of the disk that seemed to be nearing the end of its lifetime.

They succeeded. The team has directly imaged the disk, and find that it is more like a ring than a disk, with the dust having an inner radius of 65 AU (astronomical units, the average distance of the Earth from the Sun), and an outer radius is 170 AU; rotating gas is seen out to 420 AU. The mass of the disk is comparatively large, about the same as the mass of Jupiter. They find that the infrared emission also has a hot component, about 180 degrees kelvin, consistent with it coming from a thin ring inside the disk gap and only 2.3 AU from the star, or perhaps from a hot planet inside the gap. The results confirm previous models of the object but extend them, and allow the astronomers to conclude that this star probably in a stage of nearly completing its planet formation.

Reference(s): 
"High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk Around Sz 91," Takashi Tsukagoshi et al., ApJ 783, 90, 2014.


Friday, March 21, 2014

Secrets at the heart of NGC 5793

Credit: NASA, ESA, and E. Perlman (Florida Institute of Technology)
Acknowledgement: Judy Schmidt

This new Hubble image is centred on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright centre — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe.

NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centres that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the Sun — that pull in and devour gas and dust from their surroundings.

This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation [1]. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the Sun.

A version of this image was submitted to the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

Notes:

[1] This name originates from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum.


Thursday, March 20, 2014

NASA's Spitzer Telescope Brings 360-Degree View of Galaxy to Our Fingertips

A new panorama from NASA's Spitzer Space Telescope shows us our galaxy's plane all the way around us in infrared light. Image Credit: NASA/JPL-Caltech/University of Wisconsin. Full image and caption 
Touring the Milky Way now is as easy as clicking a button with NASA's new zoomable, 360-degree mosaic presented Thursday at the TEDActive 2014 Conference in Vancouver, Canada.
The star-studded panorama of our galaxy is constructed from more than 2 million infrared snapshots taken over the past 10 years by NASA's Spitzer Space Telescope.

"If we actually printed this out, we'd need a billboard as big as the Rose Bowl Stadium to display it," said Robert Hurt, an imaging specialist at NASA's Spitzer Space Science Center in Pasadena, Calif. "Instead we’ve created a digital viewer that anyone, even astronomers, can use."

The 20-gigapixel mosaic uses Microsoft’s WorldWide Telescope visualization platform. It captures about three percent of our sky, but because it focuses on a band around Earth where the plane of the Milky Way lies, it shows more than half of all the galaxy's stars.

The image, derived primarily from the Galactic Legacy Mid-Plane Survey Extraordinaire project, or GLIMPSE360, is online at: http://www.spitzer.caltech.edu/glimpse360

Spitzer, launched into space in 2003, has spent more than 10 years studying everything from asteroids in our solar system to the most remote galaxies at the edge of the observable universe. In this time, it has spent a total of 4,142 hours (172 days) taking pictures of the disk, or plane, of our Milky Way galaxy in infrared light. This is the first time those images have been stitched together into a single expansive view.

Our galaxy is a flat spiral disk; our solar system sits in the outer one-third of the Milky Way, in one of its spiral arms. When we look toward the center of our galaxy, we see a crowded, dusty region jam-packed with stars. Visible-light telescopes cannot look as far into this region because the amount of dust increases with distance, blocking visible starlight. Infrared light, however, travels through the dust and allows Spitzer to view past the galaxy's center.

"Spitzer is helping us determine where the edge of the galaxy lies," said Ed Churchwell, co-leader of the GLIMPSE team at the University of Wisconsin-Madison. "We are mapping the placement of the spiral arms and tracing the shape of the galaxy."

Using GLIMPSE data, astronomers have created the most accurate map of the large central bar of stars that marks the center of the galaxy, revealing the bar to be slightly larger than previously thought. GLIMPSE images have also shown a galaxy riddled with bubbles. These bubble structures are cavities around massive stars, which blast wind and radiation into their surroundings.

All together, the data allow scientists to build a more global model of stars, and star formation in the galaxy -- what some call the "pulse" of the Milky Way. Spitzer can see faint stars in the "backcountry" of our galaxy -- the outer, darker regions that went largely unexplored before.

"There are a whole lot more lower-mass stars seen now with Spitzer on a large scale, allowing for a grand study," said Barbara Whitney of the University of Wisconsin, Madison, co-leader of the GLIMPSE team. "Spitzer is sensitive enough to pick these up and light up the entire 'countryside' with star formation."

The Spitzer team previously released an image compilation showing 130 degrees of our galaxy, focused on its hub. The new 360-degree view will guide NASA's upcoming James Webb Space Telescope to the most interesting sites of star-formation, where it will make even more detailed infrared observations.

Some sections of the GLIMPSE mosaic include longer-wavelength data from NASA's Wide-field Infrared Survey Explorer, or WISE, which scanned the whole sky in infrared light.

The GLIMPSE data are also part of a citizen science project, where users can help catalog bubbles and other objects in our Milky Way galaxy. To participate, visit: http://www.milkywayproject.org

More information about Spitzer is online at: http://www.nasa.gov/spitzer

Contact:

J.D. Harrington
Headquarters, Washington
202-358-5241

j.d.harrington@nasa.gov

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673

whitney.clavin@jpl.nasa.gov

DEM L241: Hardy Star Survives Supernova Blast

DEM241 (Labeled)
Credit: X-ray: NASA/CXC/SAO/F.Seward et al; 
Optical: NOAO/CTIO/MCELS, DSS 
 


Tour of DEM L241

animation



When a massive star runs out fuel, it collapses and explodes as a supernova. Although these explosions are extremely powerful, it is possible for a companion star to endure the blast. A team of astronomers using NASA's Chandra X-ray Observatory and other telescopes has found evidence for one of these survivors.

This hardy star is in a stellar explosion's debris field - also called its supernova remnant - located in an HII region called DEM L241. An HII (pronounced "H-two") region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms (HI) to form clouds of ionized hydrogen (HII). This HII region is located in the Large Magellanic Cloud, a small companion galaxy to the Milky Way.

A new composite image of DEM L241 contains Chandra data (purple) that outlines the supernova remnant. The remnant remains hot and therefore X-ray bright for thousands of years after the original explosion occurred. Also included in this image are optical data from the Magellanic Cloud Emission Line Survey (MCELS) taken from ground-based telescopes in Chile (yellow and cyan), which trace the HII emission produced by DEM L241. Additional optical data from the Digitized Sky Survey (white) are also included, showing stars in the field.

R. Davies, K. Elliott, and J. Meaburn, whose last initials were combined to give the object the first half of its name, first mapped DEM L241 in 1976. The recent data from Chandra revealed the presence of a point-like X-ray source at the same location as a young massive star within DEM L241's supernova remnant. (Mouse over the image to see the location of the survivor companion star.)

Astronomers can look at the details of the Chandra data to glean important clues about the nature of X-ray sources. For example, how bright the X-rays are, how they change over time, and how they are distributed across the range of energy that Chandra observes.

In this case, the data suggest that the point-like source is one component of a binary star system. In such a celestial pair, either a neutron star or black hole (formed when the star went supernova) is in orbit with a star much larger than our Sun. As they orbit one another, the dense neutron star or black hole pulls material away its companion star through the wind of particles that flows away from its surface. If this result is confirmed, DEM L241 would be only the third binary containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova.

Chandra's X-ray data also show that the inside of the supernova remnant is enriched in oxygen, neon and magnesium. This enrichment and the presence of the massive star imply that the star that exploded had a mass greater than 25 times, to perhaps up to 40 times, that of the Sun.

Optical observations with the South African Astronomical Observatory's 1.9-meter telescope show the velocity of the massive star is changing and that it orbits around the neutron star or black hole with a period of tens of days. A detailed measurement of the velocity variation of the massive companion star should provide a definitive test of whether or not the binary contains a black hole.

Indirect evidence already exists that other supernova remnants were formed by the collapse of a star to form a black hole. However, if the collapsed star in DEM L241 turns out to be a black hole, it would provide the strongest evidence yet for such a catastrophic event.

What does the future hold for this system? If the latest thinking is correct, the surviving massive star will be destroyed in a supernova explosion some millions of years from now. When it does, it may form a binary system containing two neutron stars or a neutron star and a black hole, or even a system with two black holes.

A paper describing these results is available online and was published in the November 10, 2012 issue of The Astrophysical Journal. The authors are Fred Seward of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA; P. Charles from University of Southampton, UK; D. Foster from the South African Astronomical Observatory in Cape Town, South Africa; J. Dickel and P. Romero from University of New Mexico in Albuquerque, NM; Z. Edwards, M. Perry and R. Williams from Columbus State University in Columbus, GA.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations. Source: NASA’s Chandra X-ray Observatory

Fast Facts for DEM L241:  

Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS 
Scale: Image is 24 arcmin across (1100 light years) 
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 05h 36m 00.00s | Dec -67º 35' 09.00" 
Constellation: Dorado
Observation Date: 2 pointings on Feb 7 and Feb 8, 2011 
Observation Time: 12 hours 47 min 
Obs. ID: 12675, 13226  
Instrument: ACIS
References: Seward, F. et al, 2012, ApJ, 759, 123; arXiv:1208.1453
Color Code: X-ray (Magenta); Optical (Red, Green, Blue) 
Distance Estimate: About 160,000 light years 



Wednesday, March 19, 2014

Herschell completes largest survey of cosmic dust in local Universe

Collage of galaxies in the Herschel Reference Survey at infrared/submillimetre wavelengths by Herschel (left) and at visible wavelengths from the Sloan Digital Sky Survey (SDSS, right). The Herschel image is coloured with blue representing cold dust and red representing warm dust; the SDSS image shows young stars in blue and old stars in red. Together, the observations plot young, dust-rich spiral/irregular galaxies in the top left, with giant dust-poor elliptical galaxies in the bottom right. Copyright: ESA/Herschel/HRS-SAG2 and HeViCS Key Programmes/Sloan Digital Sky Survey/ L. Cortese (Swinburne University)

Collage of galaxies included in the Herschel Reference Survey, the largest census of cosmic dust in the local Universe. The galaxies are presented in false-colour to highlight different dust temperatures, with blue and red representing colder and warmer regions respectively. The collage is presented with dust-rich, spiral and irregular galaxies in the top left, and giant, dust-poor elliptical galaxies in the bottom-right. The images were composed from PACS and SPIRE observations at 100, 160 and 250 microns. Copyright ESA/Herschel/HRS-SAG2 and HeViCS Key Programmes/L. Cortese (Swinburne University)
.
Collage of galaxies included in the Herschel Reference Survey as seen at visible wavelengths in images obtained by the Sloan Digital Sky Survey. The colour distribution highlights different stellar ages, with red and blue indicating older and younger stars, respectively. Copyright: Sloan Digital Sky Survey/L. Cortese (Swinburne University)

The largest census of dust in local galaxies has been completed using data from ESA’s Herschel space observatory, providing a huge legacy to the scientific community. 

Cosmic dust grains are a minor but fundamental ingredient in the recipe of gas and dust for creating stars and planets. But despite its importance, there is an incomplete picture of the dust properties in galaxies beyond our own Milky Way. 

Key questions include how the dust varies with the type of galaxy, and how it might affect our understanding of how galaxies evolve. 

Before concluding its observations in April 2013, Herschel provided the largest survey of cosmic dust, spanning a wide range of nearby galaxies located 50–80 million light-years from Earth. 

The catalogue contains 323 galaxies with varying star formation activity and different chemical compositions, observed by Herschel’s instruments across far-infrared and submillimetre wavelengths. 

A sample of these galaxies is displayed in a collage, arranged from dust-rich in the top left to dust-poor in the bottom right. 

The dust-rich galaxies are typically spiral or irregular, whereas the dust-poor ones are usually elliptical. Blue and red colours represent cooler and warmer regions of dust, respectively. 

Dust is gently heated across a range of temperatures by the combined light of all of the stars in each galaxy, with the warmest dust being concentrated in regions where stars are being born. 

For comparison, the galaxies are also shown in visible light images obtained by the Sloan Digital Sky Survey. 

Here, blue corresponds to young stars – hot, massive stars that burn through their fuel very quickly and are therefore short-lived. 

Conversely, red stars are older population – they are less massive and cooler, and therefore live for longer. 

The Herschel observations allow astronomers to determine how much light is emitted by the dust as a function of wavelength, providing a means to study the physical properties of the dust. 

For example, a galaxy forming stars at a faster rate should have more massive, hot stars in it, and thus the dust in the galaxy should also be warmer. In turn, that means that more of the light emitted by the dust should come out at shorter wavelengths. 

However, the data show greater variations than expected from one galaxy to another based on their star formation rates alone, implying that other properties, such as its chemical enrichment, also play an important role. 

By allowing astronomers to investigate these correlations and dependences, the survey provides a much-needed local benchmark for quantifying the role played by dust in galaxy evolution throughout the history of the Universe. 

The data will complement observations being made by other telescopes, such as the ground-based Atacama Large Millimeter Array in Chile, which will allow astronomers to look at dust in galaxies to the very edge of the observable Universe.

More information:

“PACS photometry of the Herschel Reference Survey – far-infrared/sub-millimeter colours as tracers of dust properties in nearby galaxies,” by L. Cortese et al., is published in the Monthly Notices of the Royal Astronomical Society, 18 March 2014.


For further information, please contact:
 
Markus Bauer


ESA Science and Robotic Exploration Communication Officer



Tel: +31 71 565 6799



Mob: +31 61 594 3954



Email:
markus.bauer@esa.int

Luca Cortese
Swinburne University of Technology, Australia
Email:
lcortese@swin.edu.su

Göran Pilbratt
ESA Herschel Project Scientist
Tel: +31 71 565 3621

Email:
gpilbratt@rssd.esa.int

Source: ESA/Herschel