Saturday, June 24, 2017

A stormy stellar nursery

A stormy stellar nursery
Copyright: ESA/Hubble & NASA; CC BY 4.0


This shot from the NASA/ESA Hubble Space Telescope shows a maelstrom of glowing gas and dark dust within one of the Milky Way’s satellite galaxies, the Large Magellanic Cloud.

The stormy scene shows a stellar nursery known as N159, measuring over 150 light-years across. It is known as a HII region, meaning it is rich in ionised hydrogen. Indeed, it contains many hot young stars that are emitting intense ultraviolet light, which causes nearby hydrogen gas to glow. Torrential stellar winds are also carving out ridges, arcs and filaments from the surrounding material.

At the heart of this cosmic cloud lies the Papillon Nebula, a butterfly-shaped region of nebulosity dominating the left of the scene. This compact nebula likely contains massive stars in the very early stages of formation. Its shape earned it the name (papillon being French for butterfly) and was first resolved by Hubble in 1999.

N159 is located over 160 000 light-years away. It resides just south of the Tarantula Nebula, another massive star-forming complex within the Large Magellanic Cloud.

This image was first released as a Hubble picture of the week on 5 September 2016.



Friday, June 23, 2017

Surveying the cosmos

Credit:  ESA/Hubble & NASA


The object in the middle of this image, sitting alone within a star-studded cosmos, is a galaxy known as ESO 486-21. ESO 486-21 is a spiral galaxy — albeit with a somewhat irregular and ill-defined structure — located some 30 million light-years from Earth.

The NASA/ESA Hubble Space Telescope observed this object while performing a survey — the Legacy ExtraGalactic UV Survey (LEGUS) — of 50 nearby star-forming galaxies. The LEGUS sample was selected to cover a diverse range of galactic morphologies, star formation rates, galaxy masses, and more. Astronomers use such data to understand how stars form and evolve within clusters, and how these processes affect both their home galaxy and the wider Universe. ESO 486-21 is an ideal candidate for inclusion in such a survey as it is known to be in the process of forming new stars, which are created when large clouds of gas and dust (seen here in pink) within the galaxy crumple inwards upon themselves.

LEGUS made use of Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS). The WFC3 obtained detailed observations of the target objects while the ACS obtained what are known as parallel fields — instead of leaving ACS idle, it was instead trained on a small patch of sky just offset from the target field itself, allowing it to gather additional valuable information while the primary target was being observed by WFC3. Parallel fields played an important role in Hubble’s Frontier Fields programme, which used the magnifying power of large galaxy clusters (via a phenomenon known as gravitational lensing) to explore objects in the distant Universe.



Thursday, June 22, 2017

Hubble Captures Massive Dead Disk Galaxy that Challenges Theories of Galaxy Evolution

Galaxy Cluster MACS J2129-0741 and Lensed Galaxy MACS2129-1
Credits: Science: NASA, ESA, and S. Toft (University of Copenhagen)
Acknowledgment: NASA, ESA, M. Postman (STScI), and the CLASH team




Young, Dead, Compact, Disk Galaxy Surprises Astronomers, Offers New Clues to How Modern-Day Elliptical Galaxies Formed


By combining the power of a "natural lens" in space with the capability of NASA's Hubble Space Telescope, astronomers made a surprising discovery—the first example of a compact yet massive, fast-spinning, disk-shaped galaxy that stopped making stars only a few billion years after the big bang.

Finding such a galaxy early in the history of the universe challenges the current understanding of how massive galaxies form and evolve, say researchers.

When Hubble photographed the galaxy, astronomers expected to see a chaotic ball of stars formed through galaxies merging together. Instead, they saw evidence that the stars were born in a pancake-shaped disk.

This is the first direct observational evidence that at least some of the earliest so-called "dead" galaxies — where star formation stopped — somehow evolve from a Milky Way-shaped disk into the giant elliptical galaxies we see today.

This is a surprise because elliptical galaxies contain older stars, while spiral galaxies typically contain younger blue stars. At least some of these early "dead" disk galaxies must have gone through major makeovers. They not only changed their structure, but also the motions of their stars to make a shape of an elliptical galaxy.

"This new insight may force us to rethink the whole cosmological context of how galaxies burn out early on and evolve into local elliptical-shaped galaxies," said study leader Sune Toft of the Dark Cosmology Center at the Niels Bohr Institute, University of Copenhagen, Denmark. "Perhaps we have been blind to the fact that early "dead" galaxies could in fact be disks, simply because we haven't been able to resolve them."

Previous studies of distant dead galaxies have assumed that their structure is similar to the local elliptical galaxies they will evolve into. Confirming this assumption in principle requires more powerful space telescopes than are currently available. However, through the phenomenon known as "gravitational lensing," a massive, foreground cluster of galaxies acts as a natural "zoom lens" in space by magnifying and stretching images of far more distant background galaxies. By joining this natural lens with the resolving power of Hubble, scientists were able to see into the center of the dead galaxy.

The remote galaxy is three times as massive as the Milky Way but only half the size. Rotational velocity measurements made with the European Southern Observatory's Very Large Telescope (VLT) showed that the disk galaxy is spinning more than twice as fast as the Milky Way.

Using archival data from the Cluster Lensing And Supernova survey with Hubble (CLASH), Toft and his team were able to determine the stellar mass, star-formation rate, and the ages of the stars.

Why this galaxy stopped forming stars is still unknown. It may be the result of an active galactic nucleus, where energy is gushing from a supermassive black hole. This energy inhibits star formation by heating the gas or expelling it from the galaxy. Or it may be the result of the cold gas streaming onto the galaxy being rapidly compressed and heated up, preventing it from cooling down into star-forming clouds in the galaxy's center.

But how do these young, massive, compact disks evolve into the elliptical galaxies we see in the present-day universe? "Probably through mergers," Toft said. "If these galaxies grow through merging with minor companions, and these minor companions come in large numbers and from all sorts of different angles onto the galaxy, this would eventually randomize the orbits of stars in the galaxies. You could also imagine major mergers. This would definitely also destroy the ordered motion of the stars."

The findings are published in the June 22 issue of the journal Nature. Toft and his team hope to use NASA's upcoming James Webb Space Telescope to look for a larger sample of such galaxies.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

The Very Large Telescope is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of Northern Chile.



Related Links

This site is not responsible for content found on external links



Contacts

Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514
jenkins@stsci.edu / villard@stsci.edu

Sune Toft
Dark Cosmology Center, Niels Bohr Institute,
University of Copenhagen, Copenhagen, Denmark
sune@dark-cosmology.dk


Source: HubbleSit

Wednesday, June 21, 2017

Star’s Birth May Have Triggered Another Star Birth, Astronomers Say

Fig 1. Protostar FIR 3 (HOPS 370) with outflow that may have triggered the formation of younger protostar FIR 4 (HOPS 108, location marked with red dot), in the Orion star-forming region. (au = astronomical unit, the distance from the Earth to the Sun, about 93 million miles.) Credit: Osorio et al., NRAO/AUI/NSF.
 
Fig 2. Protostar FIR 3 (HOPS 370) with outflow that may have triggered the formation of younger protostar FIR 4 (HOPS 108), in the Orion star-forming region. Pullouts are individual VLA images of each protostar. (au = astronomical unit, the distance from the Earth to the Sun, about 93 million miles.) Credit: Osorio et al., NRAO/AUI/NSF.


Astronomers using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have found new evidence suggesting that a jet of fast-moving material ejected from one young star may have triggered the formation of another, younger protostar.

“The orientation of the jet, the speed of its material, and the distance all are right for this scenario,” said Mayra Osorio, of the Astrophysical Institute of Andalucia (IAA-CSIC) in Spain. Osorio is the lead author of a paper reporting the findings in the Astrophysical Journal.

The scientists studied a giant cloud of gas some 1,400 light-years from Earth in the constellation Orion, where numerous new stars are being formed. The region has been studied before, but Osorio and her colleagues carried out a series of VLA observations at different radio frequencies that revealed new details.

Images of the pair show that the younger protostar, called HOPS (Herschel Orion Protostar Survey) 108, lies in the path of the outflow from the older, called HOPS 370. This alignment led Yoshito Shimajiri and collaborators to suggest in 2008 that the shock of the fast-moving material hitting a clump of gas had triggered the clump’s collapse into a protostar.

“We found knots of material within this outflow and were able to measure their speeds,” said Ana K. Diaz-Rodriguez also of IAA-CSIC.

The new measurements gave important support to the idea that the older star’s outflow had triggered the younger’s star’s formation process.

The scientists suggest that the jet from HOPS 370 (also known as FIR 3) began to hit the clump of gas about 100,000 years ago, starting the process of collapse that eventually led to the formation of HOPS 108 (also known as FIR 4). Four other young stars in the region also could be the result of similar interactions, but the researchers found evidence for shocks only in the case of HOPS 108.
While the evidence for this triggering scenario is strong, one fact appears to contradict it. The younger star seems to be moving rapidly in a way that indicates it should have been formed elsewhere, apart from the region impacted by the older star’s outflow.

“This motion, however, might be an illusion possibly created by an outflow from the newer star itself,” explained Osorio. “We want to continue to observe it over a period of time to resolve this question,” she added.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302

dfinley@nrao.edu



Tuesday, June 20, 2017

NASA Releases Kepler Survey Catalog with Hundreds of New Planet Candidates

NASA’s Kepler space telescope team has identified 219 new planet candidates, 10 of which are near-Earth size and in the habitable zone of their star.Credits: NASA/JPL-Caltech


NASA’s Kepler space telescope team has released a mission catalog of planet candidates that introduces 219 new planet candidates, 10 of which are near-Earth size and orbiting in their star's habitable zone, which is the range of distance from a star where liquid water could pool on the surface of a rocky planet.

This is the most comprehensive and detailed catalog release of candidate exoplanets, which are planets outside our solar system, from Kepler’s first four years of data. It’s also the final catalog from the spacecraft’s view of the patch of sky in the Cygnus constellation.

With the release of this catalog, derived from data publicly available on the NASA Exoplanet Archive, there are now 4,034 planet candidates identified by Kepler. Of which, 2,335 have been verified as exoplanets. Of roughly 50 near-Earth size habitable zone candidates detected by Kepler, more than 30 have been verified.

Additionally, results using Kepler data suggest two distinct size groupings of small planets. Both results have significant implications for the search for life. The final Kepler catalog will serve as the foundation for more study to determine the prevalence and demographics of planets in the galaxy, while the discovery of the two distinct planetary populations shows that about half the planets we know of in the galaxy either have no surface, or lie beneath a deep, crushing atmosphere – an environment unlikely to host life.

The findings were presented at a news conference Monday at NASA's Ames Research Center in California's Silicon Valley.

“The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs – planets with roughly the same size and orbit as Earth,” said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate. “Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”

The Kepler space telescope hunts for planets by detecting the minuscule drop in a star’s brightness that occurs when a planet crosses in front of it, called a transit.

This is the eighth release of the Kepler candidate catalog, gathered by reprocessing the entire set of data from Kepler’s observations during the first four years of its primary mission. This data will enable scientists to determine what planetary populations – from rocky bodies the size of Earth, to gas giants the size of Jupiter – make up the galaxy’s planetary demographics.

To ensure a lot of planets weren't missed, the team introduced their own simulated planet transit signals into the data set and determined how many were correctly identified as planets. Then, they added data that appear to come from a planet, but were actually false signals, and checked how often the analysis mistook these for planet candidates. This work told them which types of planets were overcounted and which were undercounted by the Kepler team’s data processing methods.

“This carefully-measured catalog is the foundation for directly answering one of astronomy’s most compelling questions – how many planets like our Earth are in the galaxy?” said Susan Thompson, Kepler research scientist for the SETI Institute in Mountain View, California, and lead author of the catalog study.

One research group took advantage of the Kepler data to make precise measurements of thousands of planets, revealing two distinct groups of small planets. The team found a clean division in the sizes of rocky, Earth-size planets and gaseous planets smaller than Neptune. Few planets were found between those groupings.

Using the W. M. Keck Observatory in Hawaii, the group measured the sizes of 1,300 stars in the Kepler field of view to determine the radii of 2,000 Kepler planets with exquisite precision.

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals,” said Benjamin Fulton, doctoral candidate at the University of Hawaii in Manoa, and lead author of the second study. “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

It seems that nature commonly makes rocky planets up to about 75 percent bigger than Earth. For reasons scientists don't yet understand, about half of those planets take on a small amount of hydrogen and helium that dramatically swells their size, allowing them to "jump the gap" and join the population closer to Neptune’s size.

The Kepler spacecraft continues to make observations in new patches of sky in its extended mission, searching for planets and studying a variety of interesting astronomical objects, from distant star clusters to objects such as the TRAPPIST-1 system of seven Earth-size planets, closer to home.

Ames manages the Kepler missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.


For more information about the Kepler mission, visit:  https://www.nasa.gov/kepler


Felicia Chou
Headquarters, Washington
202-358-0257

felicia.chou@nasa.gov

Michele Johnson
Ames Research Center, California’s Silicon Valley
650-604-6882

michele.johnson@nasa.gov

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425

elizabeth.landau@jpl.nasa.gov


Editor: Karen Northon


Monday, June 19, 2017

A most detailed view into distant stellar nurseries

This composition out of six images shows far distant galaxies. Depicted in green are the visually visible and near-infrared regimes. Only at radio wavelengths (red) the hidden activities of the central black holes deep within the galaxies are unveiled via highly energetic emission processes on spatial scales far beyond the host galaxy. The radio waves also map the birth places of stars as the example of a relatively nearby galaxy shows (lower left). A bright reddish ring of radio emission indicates that star formation proceeds over virtually the entire extent oft he host galaxy. [less] Image credit: Dr. Eleni Vardoulaki and Eric Faustino Jimenez-Andrade (Argelander-Institute)/VLA-COSMOS Team



Press release of the University of Bonn with participation of MPIA regarding the VLA-COSMOS 3 GHz project

Just like in human civilizations the birth rate in the Universe fluctuated over time. When the Universe had reached 2.5 Billion years of its current age of approximately 13.8 Billion years, galaxies produced the majority of all stars ever formed. An international team of astronomers including reasearcher from the Argelander-Institute for Astronomy at the University of Bonn and the Max-Planck-Institute for Astronomy Heidelberg has now vastly improved on previous estimates. The Karl G. Jansky Very Large Array Telescope in New Mexico (USA) allowed to undertake a survey of distant galaxies that produced unprecendentedly detailed and deep radio views over a very large celestial area. The results will now be published in a special edition of the journal „Astronomy & Astrophysics“.

The international team observed almost 11,000 galaxies over an area equivalent to about nine full moons on the sky. Thanks to these unique data the life cycle of galaxies over the past 13 Billion years could be reconstructed. „The radio light from a galaxy can show us at least two very important things,” said the lead investigator of the project, Associate-Professor Vernesa Smolčić from the University of Zagreb. „Radio light helps us to see straight through dust clouds and so reveals new stars forming within galaxies. It can also show us highly energetic signatures of growing supermassive black holes.“

Contrary to visible light, radio-light is not blocked by the large clouds of interstellar dust that often reside in galaxies. This means that radio waves can be used to detect newborn stars within galaxies in a way usually not possible at other wavelengths.

The VLA-COSMOS project started with Dr. Eva Schinnerer at the Max-Planck Institute for Astronomy Heidelberg as principal investigator already back in 2004 with a first radio survey of a celestial area called „COSMOS“. The tremendous scientific success of this project motivated the team – now led by Prof. Smolčić who at that time was based as a researcher at the Argelander-Institute for Astronomy at the University of Bonn – to apply for a large follow-up survey. This effort only became possible thanks to a major technological upgrade the Karl G. Jansky Very Large Array (VLA) Telescope in New Mexico (USA) had undergone in the meanwhile.

The astronomers combined the new radio data with optical, infrared, and X-ray information from many of the world’s leading telescopes. „The synergy of sensitive, multi-wavelength data allowed us to investigate the properties of galaxies shining at radio wavelengths out to about 13 billion years into the universe’s past,” said Dr. Alexander Karim who is responsible for the VLA-COSMOS survey at the Argelander-Institute for Astronomy at the University of Bonn.

The team found that the rate of production of new stars within galaxies was the highest when the universe was about 2.5 billion years old – a fifth of its current age. During that period, about a quarter of all newborn stars were being created in massive galaxies. They also found that up to 20 percent more star formation was occurring in galaxies in the early universe, compared to what was previously thought.

Moreover, a very distant but vigurously star forming population of galaxies – so called submillimeter-galaxies – were found to be substantially larger than previously expected. The exact reasons for this have not been entirely clarified yet but they could be linked to collisions and gravitational interactions between galaxies.

The new radio survey has also provided a unique insight into galaxies containing actively growing supermassive black holes in their centers. These galaxies are called Active Galactic Nuclei, or AGN for short. Matter orbiting around and falling into the black hole can release huge amounts of energy. Using the new radio data, the astronomers discovered more than 1000 AGN. Only their radio emission signatures betray their hidden black hole activity. They are particularly interesting because of their influence on the fate of their host galaxies but even on their cosmic environment. The astronomers compared the AGN heating process assumed in cosmological simulations to what they detected in the new radio data. They found a strong similarity between the two. „Physical processes associated with emission from these supermassive black holes may heat the gas in and around the galaxy, preventing the formation of new stars and halting the runaway growth of galaxies”, says Dr. Schinnerer from the MPI for Astronomy in Heidelberg. Dr. Karim adds: „The VLA-COSMOS survey marks an important milestone on our way towards the next generation large area sky surveys.”


Original press release with additional images, videos and all contact persons:  

German press release of Bonn University at the Informationsdienst Wissenschaft (idw):  

English version of the press release of Bonn University at Informationsdienst Wissenschaft (idw):  

Scientific publications belonging to the project: The VLA-COSMOS 3 GHz Large Project, Astronomy & Astrophysics -  https://www.aanda.org/component/toc/?task=topic&id=752



Project funding:


  • ERC Starting Grant project (‘CoSMass’): Constraining Stellar Mass and Supermassive Black Hole Growth through Cosmic Times: Paving the way for the next generation sky surveys (European Union’s Seventh Framework program under grant agreement 337595)
  • CIG project (‘AGN feedback’): Constraining AGN feedback through cosmic times: Paving the way for the next generation radio facilities (European Union’s Seventh Framework program under grant agreement 333654)
  • Deutsche Foschungsgemeinschaft (DFG): grant BE 1837/13-1 (‘The Cosmic Evolution of Black Hole and Stellar Mass Growth Probed Through Radio Observations’) and Collaborative Research Council 956 (“Conditions and Impact of Star Formation”) sub-project A1.



Contact at MPIA:

Eva Schinnerer
Phone: (+49|0) 6221 528-293
Email: schinnerer@mpia.de
Links: Personal homepage

Media Contact:

Klaus Jäger
Scientific coordinator
Phone: (+49|0) 6221 528-379
Email: jaeger@mpia.de



Sunday, June 18, 2017

True shape of the Boomerang


Boomerang Nebula
Credit: ALMA (ESO/NAOJ/NRAO)/R. Sahai

This Picture of Week shows the Boomerang Nebula, a protoplanetary nebula,  as seen by the Atacama Large Millimeter/submillimeter Array (ALMA). The background purple structure, as seen in visible light with the NASA/ESA Hubble Space Telescope, shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in orange.

Since 2003 the nebula, located about 5000 light-years from Earth, has held the record for the coldest known object in the Universe. The nebula is thought to have formed from the envelope of a star in its later stages of life which engulfed a smaller, binary companion. It is possible that this is the cause of the ultra-cold outflows, which are illuminated by the light of the central, dying star.

ALMA looked at the nebula’s central dusty disc and the outflows further out, which span a distance of almost four light-years across the sky. These outflows are even colder than the cosmic microwave background, reaching temperatures below –270 °C. The outflows are also expanding at a speed of 590 000 kilometres per hour.



Links


Source: ESO/Potw

Saturday, June 17, 2017

Chaotically Magnetized Cloud Is No Place to Build a Star, or Is It?

Now, a team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has discovered a surprisingly weak and wildly disorganized magnetic field very near a newly emerging protostar. These observations suggest that the impact of a magnetic field on star formation is more complex than previously thought.

The researchers used ALMA to map the magnetic field surrounding the young protostar dubbed Ser-emb 8, which resides about 1,420 light-years away in the Serpens star-forming region. These new observations are the most sensitive ever made of the small-scale magnetic fields surrounding a young protostar. They also provide important insights into the formation of low-mass stars like our own sun.
Previous observations with other telescopes found that magnetic fields surrounding some young protostars form a classic "hourglass" shape – a hallmark of a strong magnetic field – that starts near the protostar and extends many light-years into the surrounding cloud of dust and gas.

"Before now, we didn’t know if all stars formed in regions that were controlled by strong magnetic fields. Using ALMA, we found our answer," said Charles L. H. "Chat" Hull, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and lead author on a paper appearing in the Astrophysical Journal Letters. "We can now study magnetic fields in star-forming clouds on the broadest of scales all the way down to the forming star itself. This is exciting because it may mean stars can emerge from a wider range of conditions than we once thought."

ALMA is able to study magnetic fields at the small scales inside star-forming clumps by mapping the polarization of light emitted by dust grains that have aligned themselves with magnetic fields.

By comparing the structure of the magnetic field in the observations with cutting-edge supercomputer simulations on multiple scales, the astronomers gained important insights into the earliest stages of magnetized star formation. The simulations – which extend from a relatively nearby 140 astronomical units from the protostar (about four times the distance from the sun to Pluto) to as far out as 15 light-years – were performed by CfA astronomers Philip Mocz and Blakesley Burkhart, who are co-authors on the paper.

In the case of Ser-emb 8, the astronomers believe they have captured the original magnetic field around the star "red handed," before outflowing material from the star could erase the pristine signature of the magnetic field in the surrounding molecular cloud, noted Mocz.

"Our observations show that the importance of the magnetic field in star formation can vary widely from star to star," concluded Hull. "This protostar formed in a weakly magnetized environment dominated by turbulence, while previous observations show sources that clearly formed in strongly magnetized environments. We need further research to understand how common each scenario is."

This research was presented in a paper titled "Unveiling the Role of the Magnetic Field at the Smallest Scales of Star Formation," by C. Hull et al., appearing in the Astrophysical Journal Letters.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

Megan Watzke
Harvard-Smithsonian Center for Astrophysics
+1 617-496-7998

mwatzke@cfa.harvard.edu

Charles Blue
National Radio Astronomy Observatory
434-296-0314

cblue@nrao.edu


Friday, June 16, 2017

Einstein revisited

Credit: NASA, ESA, and K. Sahu (STScI)


A century ago, Albert Einstein published his famous theory of relativity. He proposed that all objects physically warp the fabric of space, with larger masses producing a more pronounced effect, and very massive objects (such as the Sun) causing light to travel along curved paths through space. Such an effect was first observed during the 1919 solar eclipse by English astronomer Arthur Eddington.

Researchers had to wait a century, however, to get a telescope powerful enough to detect this gravitational microlensing caused by a star outside the Solar System. Even around objects with very large masses, such as stars, this effect is very slight, making such detections extremely challenging for ground-based telescopes. It is, however, within the capabilities of the NASA/ESA Hubble Space Telescope, which gathered the data comprising this Picture of the Week.

The bright star in the centre of the image is the nearby white dwarf Stein 2051B, only 17 light-years from Earth. The smaller star below is about 5000 light-years away. Astronomers observed Stein 2051B eight times within two years while the white dwarf travelled in front of of the distant background star. During the close alignment, the white dwarf’s gravity bent the light from the distant star, making it appear offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a 1€ coin from 2300 kilometres away.

Links


New Evidence That All Stars Are Born in Pairs

Almost certainly yes -- though not an identical twin. And so did every other Sun-like star in the universe, according to a new analysis by a theoretical physicist from the University of California, Berkeley, and a radio astronomer from the Smithsonian Astrophysical Observatory at Harvard University.

Many stars have companions, including our nearest neighbor, Alpha Centauri, a triplet system. Astronomers have long sought an explanation. Are binary and triplet star systems born that way? Did one star capture another? Do binary stars sometimes split up and become single stars?

Astronomers have even searched for a companion to our Sun, a star dubbed Nemesis because it was supposed to have kicked an asteroid into Earth’s orbit that collided with our planet and exterminated the dinosaurs. It has never been found.

The new assertion is based on a radio survey of a giant molecular cloud filled with recently formed stars in the constellation Perseus, and a mathematical model that can explain the Perseus observations only if all Sun-like stars are born with a companion.

"We are saying, yes, there probably was a Nemesis, a long time ago," said co-author Steven Stahler, a UC Berkeley research astronomer.

"We ran a series of statistical models to see if we could account for the relative populations of young single stars and binaries of all separations in the Perseus molecular cloud, and the only model that could reproduce the data was one in which all stars form initially as wide binaries. These systems then either shrink or break apart within a million years."

In this study, "wide" means that the two stars are separated by more than 500 astronomical units, or AU, where one astronomical unit is the average distance between the Sun and Earth (93 million miles). A wide binary companion to our Sun would have been 17 times farther from the Sun than its most distant planet today, Neptune.

Based on this model, the Sun's sibling most likely escaped and mixed with all the other stars in our region of the Milky Way galaxy, never to be seen again.

"The idea that many stars form with a companion has been suggested before, but the question is: how many?" said first author Sarah Sadavoy, a NASA Hubble fellow at the Smithsonian Astrophysical Observatory. "Based on our simple model, we say that nearly all stars form with a companion. The Perseus cloud is generally considered a typical low-mass star-forming region, but our model needs to be checked in other clouds."

The idea that all stars are born in a litter has implications beyond star formation, including the very origins of galaxies, Stahler said.

Stahler and Sadavoy posted their findings in April on the arXiv and is available online. Their paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

Stars Birthed in 'Dense Cores'

Astronomers have speculated about the origins of binary and multiple star systems for hundreds of years, and in recent years have created computer simulations of collapsing masses of gas to understand how they condense under gravity into stars. They have also simulated the interaction of many young stars recently freed from their gas clouds. Several years ago, one such computer simulation by Pavel Kroupa of the University of Bonn led him to conclude that all stars are born as binaries.

Yet direct evidence from observations has been scarce. As astronomers look at younger and younger stars, they find a greater proportion of binaries, but why is still a mystery.

"The key here is that no one looked before in a systematic way at the relation of real young stars to the clouds that spawn them," Stahler said. "Our work is a step forward in understanding both how binaries form and also the role that binaries play in early stellar evolution. We now believe that most stars, which are quite similar to our own Sun, form as binaries. I think we have the strongest evidence to date for such an assertion."

According to Stahler, astronomers have known for several decades that stars are born inside egg-shaped cocoons called dense cores, which are sprinkled throughout immense clouds of cold, molecular hydrogen that are the nurseries for young stars. Through an optical telescope, these clouds look like holes in the starry sky, because the dust accompanying the gas blocks light from both the stars forming inside and the stars behind. The clouds can, however, be probed by radio telescopes, since the cold dust grains in them emit at these radio wavelengths, and radio waves are not blocked by the dust.

The Perseus molecular cloud is one such stellar nursery, about 600 light-years from Earth and about 50 light-years long. Last year, a team of astronomers completed a survey that used the Very Large Array, a collection of radio dishes in New Mexico, to look at star formation inside the cloud. Called VANDAM, it was the first complete survey of all young stars in a molecular cloud, that is, stars less than about 4 million years old, including both single and multiple stars down to separations of about 15 astronomical units. This captured all multiple stars with a separation of more than about the radius of Uranus’ orbit -- 19 AU -- in our solar system.

Stahler heard about the survey after approaching Sadavoy, a member of the VANDAM team, and asking for her help in observing young stars inside dense cores. The VANDAM survey produced a census of all Class 0 stars -- those less than about 500,000 years old -- and Class I stars -- those between about 500,000 and 1 million years old. Both types of stars are so young that they are not yet burning hydrogen to produce energy.

Sadavoy took the results from VANDAM and combined them with additional observations that reveal the egg-shaped cocoons around the young stars. These additional observations come from the Gould Belt Survey with SCUBA-2 on the James Clerk Maxwell Telescope in Hawaii. By combining these two data sets, Sadavoy was able to produce a robust census of the binary and single-star populations in Perseus, turning up 55 young stars in 24 multiple-star systems, all but five of them binary, and 45 single-star systems.

Using these data, Sadavoy and Stahler discovered that all of the widely separated binary systems -- those with stars separated by more than 500 AU -- were very young systems, containing two Class 0 stars. These systems also tended to be aligned with the long axis of the egg-shaped dense core. The slightly older Class I binary stars were closer together, many separated by about 200 AU, and showed no tendency to align along the egg’s axis.

"This has not been seen before or tested, and is super interesting," Sadavoy said. "We don’t yet know quite what it means, but it isn't random and must say something about the way wide binaries form."

Egg-Shaped Cores Collapse into Two Centers

Stahler and Sadavoy mathematically modeled various scenarios to explain this distribution of stars, assuming typical formation, breakup and orbital shrinking times. They concluded that the only way to explain the observations is to assume that all stars of masses around that of the Sun start off as wide Class 0 binaries in egg-shaped dense cores, after which some 60 percent split up over time. The rest shrink to form tight binaries.

"As the egg contracts, the densest part of the egg will be toward the middle, and that forms two concentrations of density along the middle axis," he said. "These centers of higher density at some point collapse in on themselves because of their self-gravity to form Class 0 stars."

"Within our picture, single low-mass, Sun-like stars are not primordial," Stahler added. "They are the result of the breakup of binaries."

Their theory implies that each dense core, which typically comprises a few solar masses, converts twice as much material into stars as was previously thought.

Stahler said that he has been asking radio astronomers to compare dense cores with their embedded young stars for more than 20 years, in order to test theories of binary star formation. The new data and model are a start, he says, but more work needs to be done to understand the physics behind the rule.

Such studies may come along soon, because the capabilities of a now-upgraded VLA and the ALMA telescope in Chile, plus the SCUBA-2 survey in Hawaii, "are finally giving us the data and statistics we need. This is going to change our understanding of dense cores and the embedded stars within them," Sadavoy said.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

Robert Sanders
UC Berkeley Media Relations
+1 510-643-6998
rlsanders@berkeley.edu

Megan Watzke
Harvard-Smithsonian Center for Astrophysics
+1 617-496-7998
mwatzke@cfa.harvard.edu


Thursday, June 15, 2017

VST Captures Three-In-One

The VST captures three spectacular nebulae in one image

Highlights from huge VST nebula image

Nebulae on the borders of the constellations of Sagittarius and Serpens 
PR Image eso1719d
The VST captures three spectacular nebulae in one image (annotated)



Videos

ESOcast 111 Light: VST captures glowing celestial triplet
ESOcast 111 Light: VST captures glowing celestial triplet

Zooming in on a rich region of star formation
Zooming in on a rich region of star formation

Highlights from huge VST nebula image

The Omega Nebula region seen with the VST
The Omega Nebula region seen with the VST

The region of the Eagle Nebula seen with the VST
The region of the Eagle Nebula seen with the VST

The Sharpless 2-54 region seen with ESO's VST
The Sharpless 2-54 region seen with ESO's VST 



Two of the sky’s more famous residents share the stage with a lesser-known neighbour in this enormous new three gigapixel image from ESO’s VLT Survey Telescope (VST). On the right lies the faint, glowing cloud of gas called Sharpless 2-54, the iconic Eagle Nebula is in the centre, and the Omega Nebula to the left. This cosmic trio makes up just a portion of a vast complex of gas and dust within which new stars are springing to life and illuminating their surroundings.

Sharpless 2-54 and the Eagle and Omega Nebula are located roughly 7000 light-years away — the first two fall within the constellation of Serpens (The Serpent), while the latter lies within Sagittarius (The Archer). This region of the Milky Way houses a huge cloud of star-making material. The three nebulae indicate where regions of this cloud have clumped together and collapsed to form new stars; the energetic light from these stellar newborns has caused ambient gas to emit light of its own, which takes on the pinkish hue characteristic of areas rich in hydrogen.

Two of the objects in this image were discovered in a similar way. Astronomers first spotted bright star clusters in both Sharpless 2-54 and the Eagle Nebula, later identifying the vast, comparatively faint gas clouds swaddling the clusters. In the case of Sharpless 2-54, British astronomer William Herschel initially noticed its beaming star cluster in 1784. That cluster, catalogued as NGC 6604 (eso1218), appears in this image on the object’s left side. The associated very dim gas cloud remained unknown until the 1950s, when American astronomer Stewart Sharpless spotted it on photographs from the National Geographic Society–Palomar Observatory Sky Survey.

The Eagle Nebula did not have to wait so long for its full glory to be appreciated. Swiss astronomer Philippe Loys de Chéseaux first discovered its bright star cluster, NGC 6611, in 1745 or 1746 (eso0142). A couple of decades later, French astronomer Charles Messier observed this patch of sky and also documented the nebulosity present there, recording the object as Messier 16 in his influential catalogue (eso0926).

As for the Omega Nebula, de Chéseaux did manage to observe its more prominent glow and duly noted it as a nebula in 1745. However, because the Swiss astronomer’s catalogue never achieved wider renown, Messier’s re-discovery of the Omega Nebula in 1764 led to its becoming Messier 17, the seventeenth object in the Frenchman’s popular compendium (eso0925).

The observations from which this image was created were taken with ESO’s VLT Survey Telescope (VST), located at ESO’s Paranal Observatory in Chile. The huge final colour image was created by mosaicing dozens of pictures — each of 256 megapixels — from the telescope’s large-format OmegaCAM camera. The final result, which needed lengthy processing, totals 3.3 gigapixels, one of the largest images ever released by ESO.



More Information

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 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Links



Contacts

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591


Source: ESO

Wednesday, June 14, 2017

VLA Gives New Insight Into Galaxy Cluster’s Spectacular “Mini-Halo”


VLA image of radio-emitting mini-halo in the Perseus Cluster of galaxies. Radio emission in red; optical in white. Credit: Gendron-Marsolais et al.; NRAO/AUI/NSF; NASA; SDSS. Released images


Astronomers using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have discovered new details that are helping them decipher the mystery of how giant radio-emitting structures are formed at the center of a cluster of galaxies.

The scientists studied a cluster of thousands of galaxies more than 250 million light-years from Earth, named the Perseus Cluster after the constellation in which it appears. Embedded within the center, the Perseus Cluster hosts a pool of superfast particles that emit radio waves, creating a radio structure known as a “mini-halo.” Mini-haloes have been found in about 30 galaxy clusters, but the halo in the Perseus Cluster is the largest known, about 1.3 million light-years in diameter, or 10 times the size of our Milky Way Galaxy.

The sizes of the mini-haloes have presented a puzzle to astronomers. As the particles travel away from the cluster’s center, they should slow down and stop emitting radio waves long before they reach the distances observed, according to theory.

“At large distances from the central galaxy, we don’t expect to be able to see these haloes,” said Marie-Lou Gendron-Marsolais, of the University of Montreal. “However, we do see them and we want to know why,” she added.

The astronomers took advantage of the upgraded capabilities of the VLA to make new images of the Perseus Cluster that were both more sensitive to fainter radio emissions and provided higher resolution than previous radio observations.

“The new VLA images provided an unprecedented view of the mini-halo by revealing a multitude of new structures within it,” said Julie Hlavacek-Larrondo, also of the University of Montreal. “These structures tell us that the origin of the radio emission is not as simple as we thought,” she said.
The new details indicate that the halo’s radio emission is caused by complex mechanisms that vary throughout the cluster. As theorized before, some radio emission is caused by particles being reaccelerated when small groups of galaxies collide with the cluster and give the particles a gravitational shove. In addition, however, the scientists now think that the radio emission is also caused by the powerful jets of particles generated by the supermassive black hole at the core of the central galaxy that give an extra “kick” of energy to the particles.

“This would help explain the rich variety of complex structures that we see,” Gendron-Marsolais said.

“The high-quality images that the upgraded VLA can produce will be key to helping us gain new insights into these mini-haloes in our quest to understand their origin,” Hlavacek-Larrondo said. The VLA, built during the 1970s, was equipped with all-new electronics to bring it up to the technological state of the art by a decade-long project completed in 2012.

Gendron-Marsolais and Hlavacek-Larrondo, along with an international team of researchers, are reporting their findings in the Monthly Notices of the Royal Astronomical Society.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302

dfinley@nrao.edu


Tuesday, June 13, 2017

Gemini Discovered world is most like Jupiter

Figure 1. Discovery image of 51 Eri b with the Gemini Planet Imager taken in the near-infrared light on December 18, 2014. The bright central star has been mostly removed by a hardware and software mask to enable the detection of the exoplanet one million times fainter. Credits: J. Rameau (UdeM) and C. Marois (NRC Herzberg).  Full Resolution JPEG

Figure 2. An artistic conception of the Jupiter-like exoplanet, 51 Eri b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago. Credits: Danielle Futselaar & Franck Marchis, SETI Institute.  Full Resolution JPEG

The Gemini Planet Imager utilizes an integral field spectrograph, an instrument capable of taking images at multiple wavelengths – or colors – of infrared light simultaneously, in order to search for young self-luminous planets around nearby stars. The left side of the animation shows the GPI images of the nearby star 51 Eridani in order of increasing wavelength from 1.5 to 1.8 microns. The images have been processed to suppress the light from 51 Eridani, revealing the exoplanet 51 Eridani b (indicated) which is approximately a million times fainter than the parent star. The bright regions to the left and right of the masked star are artifacts from the image processing algorithm, and can be distinguished from real astrophysical signals based on their brightness and position as a function of wavelength. The spectrum of 51 Eridani b, on the right side of the animation, shows how the brightness of the planet varies as a function of wavelength. If the atmosphere was entirely transmissive, the brightness would be approximately constant as a function of wavelength. This is not the case for 51 Eridani b, the atmosphere of which contains both water (H2O) and methane (CH4). Over the spectral range of this GPI dataset, water absorbs photons between 1.5 and 1.6 microns, and methane absorbs between 1.6 and 1.8 microns. This leads to a strong peak in the brightness of the exoplanet at 1.6 microns, the wavelength at which absorption by both water and methane is weakest.Robert De Rosa (UC Berkeley), Christian Marois (NRC Herzberg, University of Victoria).


Gemini-Discovered world is most like Jupiter
The simulated fly-by of the 51 Eridani star and planet system begins with the view of the sky showing the location of the star near the constellation Orion visible in the northern hemisphere winter. The young star 51 Eridani is 100 light-years from the Sun and a Jupiter-like planet is directly imaged in the infrared in an orbit similar in size to the Sun-Saturn distance. The star also has indirect evidence of belts of rocky debris orbiting closer and farther to the the star than the new planet. The fly-by ends with a view back toward the Sun from the newly discovered planet. Credits: J. Patience & J. Cornelison (ASU).   Fly-by video in AVI (600MB)



Going beyond the discovery and imaging of a young Jupiter, astronomers using the Gemini Observatory's new Planet Imager (GPI) have probed a newly discovered world in unprecedented detail. What they found is a planet about two times the mass of Jupiter, and the most Solar System-like planet ever directly imaged around another star.

The planet, known as 51 Eridani b, orbits its host star at about 13 times the Earth-Sun distance (equivalent to being between Saturn and Uranus in our Solar System). The system is located about 100 light years away. The Gemini data also provide scientists with the strongest-ever spectroscopic detection of methane in the atmosphere of a planet outside of our Solar System, adding to its similarities to giant planets in our Solar System.

"Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars" said Bruce Macintosh, of Stanford University who led the construction of GPI and now leads the planet-hunting survey. "This one looks like a planet."

The research is published in the August 13, 2015 issue of the journal Science.

"This superb result is a clear demonstration of the remarkable imaging and spectroscopic capabilities of GPI," said Chris Davis, the US National Science Foundation (NSF) Astronomy Division program officer who oversees Gemini Observatory funding. "The exoplanet surveys now possible with Gemini will undoubtedly lead to a far better understanding of the numbers of gas giants orbiting neighboring stars, the characteristics of their atmospheres, and ultimately the way in which giant planets like Jupiter and Saturn are formed."

The discovery is part of the team's broader effort to find and characterize new planets called the GPI Exoplanet Survey (GPIES). The survey expects to explore over 600 stars that could host planetary systems; so far they've looked at almost a hundred stars. "This is exactly the kind of system we envisioned discovering when we designed GPI", says James Graham, professor at UC Berkeley and Project Scientist for GPI.

"GPI is capable of dissecting the light of exoplanets in unprecedented detail so we can now characterize other worlds like never before," says Christian Marois of the National Research Council of Canada (NRC). Marois, one of almost 90 researchers on the team, pioneered many of the observation strategies and data reduction techniques that played a critical role in the detection and analysis of the new planet. The light from the planet is very faint – a million times fainter than the star – but GPI can see it clearly. "The planet is so faint and located so close to its star, that it is also the first directly imaged exoplanet to be fully consistent with Solar System-like planet formation models," adds Marois.

The Gemini observations were also followed up by the W.M. Keck Observatory on Maunakea in Hawaii to verify the discovery.

GPI Instrument Scientist, Fredrik Rantakyro, added, "Since I was a child, I dreamed about planets around other stars and the possible lives that could be out there. As an astronomer, it's common to work with state-of-the-art telescopes but not to make your heart beat faster. This is exactly what happened with this dream-come-true discovery of this brother to Jupiter!"

51 Eridani is young – only 20 million years old – and this is exactly what made the direct detection of the planet possible. When planets coalesce, material falling into the planet releases energy and heats it up. Over the next hundred million years they radiate that energy away, mostly as infrared light, and gradually cool.

In addition to being what is likely the lowest-mass planet ever imaged, its atmosphere is also very cool – 430 degrees C (800 degrees Fahrenheit). It also features the strongest spectroscopic atmospheric methane signal, similar to the heavy methane dominated atmospheres of the gas giant planets in our Solar System.

GPI Exoplanet Survey (GPIES) is currently less than 20% through the 600 targets slated for observations during the 3-year campaign. The targets were selected because of their youth and relatively close proximity to our Solar System (within about 300 light years). The results of this survey will be remarkable, as it is probing a regime of exoplanet mass and separation that have never been properly surveyed before. It is expected to provide the first detailed census and demography of gas giant exoplanets, to find several multi-planet systems, and to perform detailed spectral characterization of many new exoplanets.

GPI was made possible with funding by the US National Science Foundation and Gemini partnership to support the work of an international team from the US and Canada. Lawrence Livermore National Laboratory constructed GPI's adaptive optics system and worked to match it to the Gemini telescope. Engineers with the National Research Council of Canada (NRC) designed and built GPI's optical-mechanical structure, and wrote the top level and mechanical control software. UCLA produced GPI's infrared spectrograph. The American Museum of Natural History developed starlight-blocking masks. JPL was responsible for a precision wavefront sensor. University of Montreal, the Space Telescope Science Institute, and other members of the GPI team produced the data analysis software.




Media Contact:

Peter Michaud Public Information and Outreach Manager
Gemini Observatory, Hilo, HI
Email: pmichaud@gemini.edu
Cell: (808) 936-6643
Desk: (808) 974-2510

Antonieta Garcia
Gemini Observatory, La Serena, Chile
Email: agarcia@gemini.edu
Cell: 9 - 69198294
Desk: +56 (51) 205628



Science Contacts:

Bruce Macintosh
Department of Physics, Stanford University
Email: bmacintosh@stanford.edu
Desk: (650) 725-4116

Franck Marchis
SETI Institute
Email: fmarchis@seti.edu
Desk: (650) 960-4236

Fredrik Rantakyro 
Gemini Observatory, La Serena, Chile
Email: frantaky@gemini.edu
Cell: 9 - 995097802 
Desk: 56-51- 2205665