Sunday, April 29, 2018

What Uranus Cloud Tops Have in Common With Rotten Eggs

Arriving at Uranus in 1986, Voyager 2 observed a bluish orb with extremely subtle features. A haze layer hid most of the planet's cloud features from view. Credit: NASA/JPL-Caltech.  › Full image and caption

Even after decades of observations and a visit by NASA's Voyager 2 spacecraft, Uranus held on to one critical secret -- the composition of its clouds. Now, one of the key components of the planet's clouds has finally been verified.

A global research team that includes Glenn Orton of NASA's Jet Propulsion Laboratory in Pasadena, California, has spectroscopically dissected the infrared light from Uranus captured by the 26.25-foot (8-meter) Gemini North telescope on Hawaii's Mauna Kea. They found hydrogen sulfide, the odiferous gas that most people avoid, in Uranus' cloud tops. The long-sought evidence was published in the April 23rd issue of the journal Nature Astronomy.

The detection of hydrogen sulfide high in Uranus' cloud deck (and presumably Neptune's) is a striking difference from the gas giant planets located closer to the Sun -- Jupiter and Saturn -- where ammonia is observed above the clouds, but no hydrogen sulfide. These differences in atmospheric composition shed light on questions about the planets' formation and history.

"We've strongly suspected that hydrogen sulfide gas was influencing the millimeter and radio spectrum of Uranus for some time, but we were unable to attribute the absorption needed to identify it positively. Now, that part of the puzzle is falling into place as well," Orton said.

The Gemini data, obtained with the Near-Infrared Integral Field Spectrometer (NIFS), sampled reflected sunlight from a region immediately above the main visible cloud layer in Uranus' atmosphere.

"While the lines we were trying to detect were just barely there, we were able to detect them unambiguously thanks to the sensitivity of NIFS on Gemini, combined with the exquisite conditions on Mauna Kea," said lead author Patrick Irwin of the University of Oxford, U.K.

No worries, though, that the odor of hydrogen sulfide would overtake human senses. According to Irwin, "Suffocation and exposure in the negative 200 degrees Celsius [392 degrees Fahrenheit] atmosphere made of mostly hydrogen, helium and methane would take its toll long before the smell."
Read more on the news of Uranus' atmosphere from Gemini Observatory here.

Caltech in Pasadena, California, manages JPL for NASA.


News Media Contact

Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-6215
Gretchen.p.mccartney@jpl.nasa.gov

JoAnna Wendel
NASA Headquarters, Washington
202-358-1003
joanna.r.wendel@nasa.gov

Peter Michaud
Gemini Observatory, Hilo, Hawaii
808-974-2510
pmichaud@gemini.edu



Saturday, April 28, 2018

Stuck in the middle

NGC 2655
Credit: ESA/Hubble & NASA, A. Fillipenko


This pretty, cloud-like object may not look much like a galaxy — it lacks the well-defined arms of a spiral galaxy, or the reddish bulge of an elliptical — but it is in fact something known as a lenticular galaxy. Lenticular galaxies sit somewhere between the spiral and elliptical types; they are disc-shaped, like spirals, but they no longer form large numbers of new stars and thus contain only ageing populations of stars, like ellipticals. 

NGC 2655’s core is extremely luminous, resulting in its additional classification as a Seyfert galaxy: a type of active galaxy with strong and characteristic emission lines. This luminosity is thought to be produced as matter is dragged onto the accretion disc of a supermassive black hole sitting at the centre of NGC 2655. The structure of NGC 2655’s outer disc, on the other hand, appears calmer, but it is oddly-shaped. The complex dynamics of the gas in the galaxy suggest that it may have had a turbulent past, including mergers and interactions with other galaxies.

NGC 2655 is located about 80 million light-years from Earth in the constellation of Camelopardalis (The Giraffe). Camelopardalis contains many other interesting deep-sky objects, including the open cluster NGC 1502, the elegant Kemble’s Cascade asterism, and the starburst galaxy NGC 2146.



Friday, April 27, 2018

Stellar Thief Is the Surviving Companion to a Supernova

Seventeen years ago, astronomers witnessed supernova 2001ig go off 40 million light-years away in the galaxy NGC 7424, in the southern constellation Grus, the Crane. Shortly after, scientists photographed the supernova with the European Southern Observatory’s Very Large Telescope (VLT) in 2002. Two years later, they followed up with the Gemini South Observatory, which hinted at the presence of a surviving binary companion. As the supernova’s glow faded, scientists focused Hubble on that location in 2016. They pinpointed and photographed the surviving companion, which was possible only due to Hubble’s exquisite resolution and ultraviolet sensitivity. Hubble observations of SN 2001ig provide the best evidence yet that some supernovas originate in double-star systems. Credits: NASA, ESA, S. Ryder (Australian Astronomical Observatory), and O. Fox (STScI). Hi-res image


Seventeen years ago, astronomers witnessed a supernova go off 40 million light-years away in the galaxy called NGC 7424, located in the southern constellation Grus, the Crane. Now, in the fading afterglow of that explosion, NASA's Hubble Space Telescope has captured the first image of a surviving companion to a supernova. This picture is the most compelling evidence that some supernovas originate in double-star systems.

“We know that the majority of massive stars are in binary pairs,” said Stuart Ryder from the Australian Astronomical Observatory (AAO) in Sydney, Australia, and lead author of the study. “Many of these binary pairs will interact and transfer gas from one star to the other when their orbits bring them close together.”

The companion to the supernova’s progenitor star was no innocent bystander to the explosion. It siphoned off almost all of the hydrogen from the doomed star’s stellar envelope, the region that transports energy from the star’s core to its atmosphere. Millions of years before the primary star went supernova, the companion’s thievery created an instability in the primary star, causing it to episodically blow off a cocoon and shells of hydrogen gas before the catastrophe.

The supernova, called SN 2001ig, is categorized as a Type IIb stripped-envelope supernova. This type of supernova is unusual because most, but not all, of the hydrogen is gone prior to the explosion. This type of exploding star was first identified in 1987 by team member Alex Filippenko of the University of California, Berkeley.

How stripped-envelope supernovas lose that outer envelope is not entirely clear. They were originally thought to come from single stars with very fast winds that pushed off the outer envelopes. The problem was that when astronomers started looking for the primary stars from which supernovas were spawned, they couldn’t find them for many stripped-envelope supernovas.

“That was especially bizarre, because astronomers expected that they would be the most massive and the brightest progenitor stars,” explained team member Ori Fox of the Space Telescope Science Institute in Baltimore. “Also, the sheer number of stripped-envelope supernovas is greater than predicted.” That fact led scientists to theorize that many of the primary stars were in lower-mass binary systems, and they set out to prove it.

Looking for a binary companion after a supernova explosion is no easy task. First, it has to be at a relatively close distance to Earth for Hubble to see such a faint star. SN 2001ig and its companion are about at that limit. Within that distance range, not many supernovas go off. Even more importantly, astronomers have to know the exact position through very precise measurements.

In 2002, shortly after SN 2001ig exploded, scientists pinpointed the precise location of the supernova with the European Southern Observatory’s Very Large Telescope (VLT) in Cerro Paranal, Chile. In 2004, they then followed up with the Gemini South Observatory in Cerro Pachón, Chile. This observation first hinted at the presence of a surviving binary companion.

Knowing the exact coordinates, Ryder and his team were able to focus Hubble on that location 12 years later, as the supernova’s glow faded. With Hubble’s exquisite resolution and ultraviolet capability, they were able to find and photograph the surviving companion—something only Hubble could do.

Prior to the supernova explosion, the orbit of the two stars around each other took about a year.
When the primary star exploded, it had far less impact on the surviving companion than might be thought. Imagine an avocado pit—representing the dense core of the companion star—embedded in a gelatin dessert—representing the star’s gaseous envelope. As a shock wave passes through, the gelatin might temporarily stretch and wobble, but the avocado pit would remain intact.

In 2014, Fox and his team used Hubble to detect the companion of another Type IIb supernova, SN 1993J. However, they captured a spectrum, not an image. The case of SN 2001ig is the first time a surviving companion has been photographed. “We were finally able to catch the stellar thief, confirming our suspicions that one had to be there,” said Filippenko.

Perhaps as many as half of all stripped-envelope supernovas have companions—the other half lose their outer envelopes via stellar winds. Ryder and his team have the ultimate goal of precisely determining how many supernovas with stripped envelopes have companions.

Their next endeavor is to look at completely stripped-envelope supernovas, as opposed to SN 2001ig and SN 1993J, which were only about 90 percent stripped. These completely stripped-envelope supernovas don’t have much shock interaction with gas in the surrounding stellar environment, since their outer envelopes were lost long before the explosion. Without shock interaction, they fade much faster. This means that the team will only have to wait two or three years to look for surviving companions.

In the future, they also hope to use the James Webb Space Telescope to continue their search.

The paper on this team’s current work was published on March 28, 2018, in the Astrophysical Journal.

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 in Washington, D.C.


For NASA's Hubble webpage, visit: www.nasa.gov/hubble

For more images and information, visit: http://hubblesite.org/news_release/news/2018-20

For the science paper, visit: https://media.stsci.edu/preview/file/science_paper/file_attachment/321/Ryder_published_ApJ_paper.pdf


Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514 

jenkins@stsci.edu / villard@stsci.edu

Ori Fox
Space Telescope Science Institute, Baltimore, Maryland
410-338-6768 

ofox@stsci.edu

Stuart Ryder
Australian Astronomical Observatory, Sydney, Australia
011-61-2-93724843
011-61-419-970834 (cell) 

sdr@aao.gov.au

Alex Filippenko
University of California, Berkeley, California 

afilippenko@berkeley.edu



Ancient Galaxy Megamergers

Artist’s impression of ancient galaxy megamerger
 
Images of a galaxy protocluster from SPT, APEX and ALMA



Videos

ESOcast 157 Light: Ancient Galaxy Pileups (4K UHD)
ESOcast 157 Light: Ancient Galaxy Pileups (4K UHD)

Artist’s impression of ancient galaxy megamerger
Artist’s impression of ancient galaxy megamerger


ALMA and APEX discover massive conglomerations of forming galaxies in early Universe

The ALMA and APEX telescopes have peered deep into space — back to the time when the Universe was one tenth of its current age — and witnessed the beginnings of gargantuan cosmic pileups: the impending collisions of young, starburst galaxies. Astronomers thought that these events occurred around three billion years after the Big Bang, so they were surprised when the new observations revealed them happening when the Universe was only half that age! These ancient systems of galaxies are thought to be building the most massive structures in the known Universe: galaxy clusters.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX), two international teams of scientists led by Tim Miller from Dalhousie University in Canada and Yale University in the US and Iván Oteo from the University of Edinburgh, United Kingdom, have uncovered startlingly dense concentrations of galaxies that are poised to merge, forming the cores of what will eventually become colossal galaxy clusters.

Peering 90% of the way across the observable Universe, the Miller team observed a galaxy protocluster named SPT2349-56. The light from this object began travelling to us when the Universe was about a tenth of its current age.

The individual galaxies in this dense cosmic pileup are starburst galaxies and the concentration of vigorous star formation in such a compact region makes this by far the most active region ever observed in the young Universe. Thousands of stars are born there every year, compared to just one in our own Milky Way.

The Oteo team discovered a similar megamerger formed by ten dusty star-forming galaxies, nicknamed a “dusty red core” because of its very red colour, by combining observations from ALMA and the APEX.

Iván Oteo explains why these objects are unexpected: “The lifetime of dusty starbursts is thought to be relatively short, because they consume their gas at an extraordinary rate. At any time, in any corner of the Universe, these galaxies are usually in the minority. So, finding numerous dusty starbursts shining at the same time like this is very puzzling, and something that we still need to understand.”

These forming galaxy clusters were first spotted as faint smudges of light, using the South Pole Telescope and the Herschel Space Observatory. Subsequent ALMA and APEX observations showed that they had unusual structure and confirmed that their light originated much earlier than expected — only 1.5 billion years after the Big Bang.

The new high-resolution ALMA observations finally revealed that the two faint glows are not single objects, but are actually composed of fourteen and ten individual massive galaxies respectively, each within a radius comparable to the distance between the Milky Way and the neighbouring Magellanic Clouds.

"These discoveries by ALMA are only the tip of the iceberg. Additional observations with the APEX telescope show that the real number of star-forming galaxies is likely even three times higher. Ongoing observations with the MUSE instrument on ESO’s VLT are also identifying additional galaxies,” comments Carlos De Breuck, ESO astronomer.

Current theoretical and computer models suggest that protoclusters as massive as these should have taken much longer to evolve. By using data from ALMA, with its superior resolution and sensitivity, as input to sophisticated computer simulations, the researchers are able to study cluster formation less than 1.5 billion years after the Big Bang.

"How this assembly of galaxies got so big so fast is a mystery. It wasn’t built up gradually over billions of years, as astronomers might expect. This discovery provides a great opportunity to study how massive galaxies came together to build enormous galaxy clusters," says Tim Miller, a PhD candidate at Yale University and lead author of one of the papers.




More Information

This research was presented in two papers, “The Formation of a Massive Galaxy Cluster Core at z = 4.3”, by T. Miller et al., to appear in the journal Nature, and “An Extreme Proto-cluster of Luminous Dusty Starbursts in the Early Universe”, by I. Oteo et al., which appeared in the Astrophysical Journal.


The Miller team is composed of: T. B. Miller (Dalhousie University, Halifax, Canada; Yale University, New Haven, Connecticut, USA), S. C. Chapman (Dalhousie University, Halifax, Canada; Institute of Astronomy, Cambridge, UK), M. Aravena (Universidad Diego Portales, Santiago, Chile), M. L. N. Ashby (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), C. C. Hayward (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA; Center for Computational Astrophysics, Flatiron Institute, New York, New York, USA), J. D. Vieira (University of Illinois, Urbana, Illinois, USA), A. Weiß (Max-Planck-Institut für Radioastronomie, Bonn, Germany), A. Babul (University of Victoria, Victoria, Canada) , M. Béthermin (Aix-Marseille Université, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France), C. M. Bradford (California Institute of Technology, Pasadena, California, USA; Jet Propulsion Laboratory, Pasadena, California, USA), M. Brodwin (University of Missouri, Kansas City, Missouri, USA), J. E. Carlstrom (University of Chicago, Chicago, Illinois USA), Chian-Chou Chen (ESO, Garching, Germany), D. J. M. Cunningham (Dalhousie University, Halifax, Canada; Saint Mary’s University, Halifax, Nova Scotia, Canada), C. De Breuck (ESO, Garching, Germany), A. H. Gonzalez (University of Florida, Gainesville, Florida, USA), T. R. Greve (University College London, Gower Street, London, UK), Y. Hezaveh (Stanford University, Stanford, California, USA), K. Lacaille (Dalhousie University, Halifax, Canada; McMaster University, Hamilton, Canada), K. C. Litke (Steward Observatory, University of Arizona, Tucson, Arizona, USA), J. Ma (University of Florida, Gainesville, Florida, USA), M. Malkan (University of California, Los Angeles, California, USA) , D. P. Marrone (Steward Observatory, University of Arizona, Tucson, Arizona, USA), W. Morningstar (Stanford University, Stanford, California, USA), E. J. Murphy (National Radio Astronomy Observatory, Charlottesville, Virginia, USA), D. Narayanan (University of Florida, Gainesville, Florida, USA), E. Pass (Dalhousie University, Halifax, Canada), University of Waterloo, Waterloo, Canada), R. Perry (Dalhousie University, Halifax, Canada), K. A. Phadke (University of Illinois, Urbana, Illinois, USA), K. M. Rotermund (Dalhousie University, Halifax, Canada), J. Simpson (University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh; Durham University, Durham, UK), J. S. Spilker (Steward Observatory, University of Arizona, Tucson, Arizona, USA), J. Sreevani (University of Illinois, Urbana, Illinois, USA), A. A. Stark (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), M. L. Strandet (Max-Planck-Institut für Radioastronomie, Bonn, Germany) and A. L. Strom (Observatories of The Carnegie Institution for Science, Pasadena, California, USA).


The Oteo team is composed of: I. Oteo (Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK; ESO, Garching, Germany), R. J. Ivison (ESO, Garching, Germany; Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK), L. Dunne (Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK; Cardiff University, Cardiff, UK), A. Manilla-Robles (ESO, Garching, Germany; University of Canterbury, Christchurch, New Zealand), S. Maddox (Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK; Cardiff University, Cardiff, UK), A. J. R. Lewis (Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK), G. de Zotti (INAF-Osservatorio Astronomico di Padova, Padova, Italy), M. Bremer (University of Bristol, Tyndall Avenue, Bristol, UK), D. L. Clements (Imperial College, London, UK), A. Cooray (University of California, Irvine, California, USA), H. Dannerbauer (Instituto de Astrofíısica de Canarias, La Laguna, Tenerife, Spain; Universidad de La Laguna, Dpto. Astrofísica, La Laguna, Tenerife, Spain), S. Eales (Cardiff University, Cardiff, UK), J. Greenslade (Imperial College, London, UK), A. Omont (CNRS, Institut d’Astrophysique de Paris, Paris, France; UPMC Univ. Paris 06, Paris, France), I. Perez–Fournón (University of California, Irvine, California, USA; Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain), D. Riechers (Cornell University, Space Sciences Building, Ithaca, New York, USA), D. Scott (University of British Columbia, Vancouver, Canada), P. van der Werf (Leiden Observatory, Leiden University, Leiden, The Netherlands), A. Weiß (Max-Planck-Institut für Radioastronomie, Bonn, Germany) and Z-Y. Zhang (Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK; ESO, Garching, Germany).


ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 15 Member States: Austria, Belgium, 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 and with Australia as a strategic partner. 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



Contact:

Axel Weiss
Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 273
Email: aweiss@mpifr-bonn.mpg.de

Carlos de Breuck
ESO
Garching, Germany
Tel: +49 89 3200 6613
Email: cdebreuc@eso.org

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/News

Thursday, April 26, 2018

Gaia creates richest star map of our Galaxy and beyond

Gaia’s sky in colour
Copyright ESA/Gaia/DPAC

ESA’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.

A multitude of discoveries are on the horizon after this much awaited release, which is based on 22 months of charting the sky. The new data includes positions, distance indicators and motions of more than one billion stars, along with high-precision measurements of asteroids within our Solar System and stars beyond our own Milky Way Galaxy.

Preliminary analysis of this phenomenal data reveals fine details about the make-up of the Milky Way’s stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

The Galactic census takes shape
Copyright: ESA/Gaia/DPAC

“Gaia is an ambitious mission that relies on a huge human collaboration to make sense of a large volume of highly complex data. It demonstrates the need for long-term projects to guarantee progress in space science and technology and to implement even more daring scientific missions of the coming decades.” 

Gaia was launched in December 2013 and started science operations the following year. The first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars. 

The new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision. For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.  

With these accurate measurements it is possible to separate the parallax of stars – an apparent shift on the sky caused by Earth’s yearly orbit around the Sun – from their true movements through the Galaxy.

The new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars. From the most accurate parallax measurements, about ten per cent of the total, astronomers can directly estimate distances to individual stars.

“The second Gaia data release represents a huge leap forward with respect to ESA’s Hipparcos satellite, Gaia’s predecessor and the first space mission for astrometry, which surveyed some 118 000 stars almost thirty years ago,” says Anthony Brown of Leiden University, The Netherlands.

Anthony is the chair of the Gaia Data Processing and Analysis Consortium Executive, overseeing the large collaboration of about 450 scientists and software engineers entrusted with the task of creating the Gaia catalogue from the satellite data.


Gaia’s first and second data releases
Copyright: ESA/Gaia/DPAC
Access the video

“The sheer number of stars alone, with their positions and motions, would make Gaia’s new catalogue already quite astonishing,” adds Anthony. 

“But there is more: this unique scientific catalogue includes many other data types, with information about the properties of the stars and other celestial objects, making this release truly exceptional.”




Asteroid survey
Copyright: ESA/Gaia/DPAC   
 
Something for everyone

The comprehensive dataset provides a wide range of topics for the astronomy community.

As well as positions, the data include brightness information of all surveyed stars and colour measurements of nearly all, plus information on how the brightness and colour of half a million variable stars change over time. It also contains the velocities along the line of sight of a subset of seven million stars, the surface temperatures of about a hundred million and the effect of interstellar dust on 87 million.

Gaia also observes objects in our Solar System: the second data release comprises the positions of more than 14 000 known asteroids, which allows precise determination of their orbits. A much larger asteroid sample will be compiled in Gaia’s future releases.

Further afield, Gaia closed in on the positions of half a million distant quasars, bright galaxies powered by the activity of the supermassive black holes at their cores. These sources are used to define a reference frame for the celestial coordinates of all objects in the Gaia catalogue, something that is routinely done in radio waves but now for the first time is also available at optical wavelengths.

Cosmic scales covered by Gaia 
Copyright: ESA, CC BY-SA 3.0 IGO

Major discoveries are expected to come once scientists start exploring Gaia’s new release. An initial examination performed by the data consortium to validate the quality of the catalogue has already unveiled some promising surprises – including new insights on the evolution of stars.



Gaia’s Hertzsprung-Russell diagram
Copyright ESA/Gaia/DPAC

Galactic archaeology

“The new Gaia data are so powerful that exciting results are just jumping at us,” says Antonella Vallenari from the Istituto Nazionale di Astrofisica (INAF) and the Astronomical Observatory of Padua, Italy, deputy chair of the data processing consortium executive board.

“For example, we have built the most detailed Hertzsprung-Russell diagram of stars ever made on the full sky and we can already spot some interesting trends. It feels like we are inaugurating a new era of Galactic archaeology.”

Named after the two astronomers who devised it in the early twentieth century, the Hertzsprung-Russell diagram compares the intrinsic brightness of stars with their colour and is a fundamental tool to study populations of stars and their evolution.

A new version of this diagram, based on four million stars within five thousand light-years from the Sun selected from the Gaia catalogue, reveals many fine details for the first time. This includes the signature of different types of white dwarfs – the dead remnants of stars like our Sun – such that a differentiation can be made between those with hydrogen-rich cores and those dominated by helium.

Combined with Gaia measurements of star velocities, the diagram enables astronomers to distinguish between various populations of stars of different ages that are located in different regions of the Milky Way, such as the disc and the halo, and that formed in different ways. Further scrutiny suggests that the fast-moving stars thought to belong to the halo encompass two stellar populations that originated via two different formation scenarios, calling for more detailed investigations.

“Gaia will greatly advance our understanding of the Universe on all cosmic scales,” says Timo Prusti, Gaia project scientist at ESA.

“Even in the neighbourhood of the Sun, which is the region we thought we understood best, Gaia is revealing new and exciting features.”



Rotation of the Large Magellanic Cloud
Copyright: ESA/Gaia/DPAC 

Galaxy in 3D

For a subset of stars within a few thousand light-years of the Sun, Gaia has measured the velocity in all three dimensions, revealing patterns in the motions of stars that are orbiting the Galaxy at similar speeds.

Future studies will confirm whether these patterns are linked to perturbations produced by the Galactic bar, a denser concentration of stars with an elongated shape at the centre of the Galaxy, by the spiral arm architecture of the Milky Way, or by the interaction with smaller galaxies that merged with it billions of years ago.

At Gaia’s precision, it is also possible to see the motions of stars within some globular clusters – ancient systems of stars bound together by gravity and found in the halo of the Milky Way – and within our neighbouring galaxies, the Small and Large Magellanic Clouds.


 Globular cluster and dwarf galaxy orbits
Copyright: ESA/Gaia/DPAC  

Gaia data were used to derive the orbits of 75 globular clusters and 12 dwarf galaxies that revolve around the Milky Way, providing all-important information to study the past evolution of our Galaxy and its environment, the gravitational forces that are at play, and the distribution of the elusive dark matter that permeates galaxies.

“Gaia is astronomy at its finest,” says Fred Jansen, Gaia mission manager at ESA.

“Scientists will be busy with this data for many years, and we are ready to be surprised by the avalanche of discoveries that will unlock the secrets of our Galaxy.”


Parallax and proper motion on the sky
Copyright: ESA/Gaia/DPAC 
Access the video



Notes for Editors

The data from Gaia’s first release can be accessed at http://archives.esac.esa.int/gaia

The content of the second Gaia release was presented today during a media briefing at the ILA Berlin Air and Space Show in Germany.

A series of scientific papers describing the data contained in the release and their validation process will appear in a special issue of Astronomy & Astrophysics.

A series of 360-degree videos and other Virtual Reality visualisation resources are available at http://sci.esa.int/gaia-vr

Gaia is an ESA mission to survey more than one billion stars in our Galaxy and its local neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its structure, origin and evolution.

A large pan-European team of expert scientists and software developers, the Data Processing and Analysis Consortium, located in and funded by many ESA member states, is responsible for the processing and validation of Gaia’s data, with the final objective of producing the Gaia Catalogue. Scientific exploitation of the data will only take place once they are openly released to the community.

More data releases will be issued in future years, with the final Gaia catalogue to be published in the 2020s. This will be the definitive stellar catalogue for the foreseeable future, playing a central role in a wide range of fields in astronomy.

Gaia was originally planned for a five-year mission, operating until mid-2019. ESA has already approved an indicative extension until the end of 2020, which is up for confirmation at the end of this year.



For further information, please contact:

Markus Bauer
Head of the Joint Communication Office
European Space Agency

Tel: +31 71 565 6799

Mob: +31 61 594 3 954

Email: markus.bauer@esa.int

Anthony Brown
Leiden Observatory, Leiden University
Leiden, The Netherlands

Antonella Vallenari
INAF, Astronomical Observatory of Padua
Italy

Timo Prusti
Gaia Project Scientist
European Space Agency

Fred Jansen
Gaia mission manager
European Space Agency

Source: ESA/GAIA

Wednesday, April 25, 2018

NASA’s James Webb Space Telescope Could Potentially Detect the First Stars and Black Holes

Galaxy clusters like Abell 2744 can act as a natural cosmic lens, magnifying light from more distant, background objects through gravity. NASA’s James Webb Space Telescope may be able to detect light from the first stars in the universe if they are gravitationally lensed by such clusters.Credits: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI). Hi-res image

This diagram illustrates how rays of light from a distant galaxy or star can be bent by the gravity of an intervening galaxy cluster. As a result, an observer on Earth sees the distant object appear brighter than it would look if it weren’t gravitationally lensed.Credits: NASA, ESA, and A. Feild and F. Summers (STScI). Hi-res image



The first stars in the universe blazed to life about 200 to 400 million years after the big bang. Observing those very first individual stars across such vast distances of space normally would be a feat beyond any space science telescope. However, new theoretical work suggests that under the right circumstances, and with a little luck, NASA’s upcoming James Webb Space Telescope will be able to capture light from single stars within that first generation of stars.

“Looking for the first stars and black holes has long been a goal of astronomy. They will tell us about the actual properties of the very early universe, things we’ve only modeled on our computers until now,” said Rogier Windhorst of Arizona State University, Tempe. Windhorst is lead author of the paper that appeared in the Astrophysical Journal Supplement.

“We want to answer questions about the early universe such as, were binary stars common or were most stars single? How many heavy chemical elements were produced, cooked up by the very first stars, and how did those first stars effect star formation?” added co-author Frank Timmes of Arizona State University.

The key will be to look for a star that has been gravitationally lensed, its light bent and magnified by the gravity of an intervening galaxy cluster. But not just any gravitational lensing will do. Typical gravitational lensing can magnify light by a factor of 10 to 20 times, not enough to make a first-generation star visible to Webb.

But if the distant star and closer galaxy cluster line up just right, the star’s light can be amplified 10,000 times or more, bringing it within the realm of detectability. This could be done via so-called cluster caustic transits, where the light from a first star candidate could be enormously magnified for a few months due to the motion of the galaxy cluster across the sky.

The chances of such a precise alignment are small, but not zero. Astronomers recently announced that Hubble spotted a super-magnified star known as “Icarus.” Although it was the farthest single star ever seen, it was much closer than the stars Webb might locate. With Webb, the team hopes to find a lensed example of a star that formed from the primordial mix of hydrogen and helium that suffused the early universe, which astronomers call Population III stars.

In addition to the first stars, Windhorst and his colleagues investigated the possibility of seeing accretion disks surrounding the first black holes. Such a black hole, formed by the cataclysmic death of a massive star, could shine brightly if it pulled gas from a companion star.

The longer an object shines, the more likely it will drift into alignment with a gravitational lens. First-generation stars are expected to have been both massive and short-lived, lasting for just a few million years before exploding as supernovae. In contrast, a black hole stripping a companion star could shine for 10 times longer, feeding from a steady stream of gas. As a result, Webb might detect more black hole accretion disks than early stars.

The team calculates that an observing program that targets several galaxy clusters a couple of times a year for the lifetime of Webb could succeed in finding a lensed first star or black hole accretion disk. They have already selected some of the best target clusters, including the Hubble Frontier Fields clusters and the cluster known as “El Gordo."


“We just have to get lucky and observe these clusters long enough,” said Windhorst. “The astronomical community would need to continue to monitor these clusters during Webb’s lifetime.”

The James Webb Space Telescope will be the world's premier space science observatory. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).



Related Links:




Contacts:


Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland
410-338-4366
cpulliam@stsci.edu

Rogier Windhorst
Arizona State University, Tempe, Arizona
480-540-0816
rogier.windhorst@asu.edu


Tuesday, April 24, 2018

A New Method for Galaxy Density Wave Analysis

NGC 3433 (image from SDSS). Superposed: MUSE field (red square); GHaFaS field (yellow square); projected corotation circle for the bar (solid green line); and the other measured corotation radii (dashed green lines). Large format: [ JPEG ]. 


Astronomers from the Instituto de Astrofísica de Canarias (IAC) have produced a complex velocity analysis of the spiral galaxy NGC 3433 with surprisingly precise results. They compared observations using the 2D Fabry-Perot spectrometer GHaFaS on the William Herschel Telescope (WHT) with those of the same object taken with the IFU spectrograph MUSE on the Very Large Telescope (VLT) in Chile. 

Font and Beckman (IAC) have developed a technique (FB) for finding the corotation radii in galaxies, i.e. the radii at which the spiral density waves propagate at the same angular speed as the stars and the gas. Simple theory suggests that the bar of a galaxy should stimulate a density wave outside it, which in turn stimulates and maintains the spiral arms. Using FB, the IAC researchers had shown previously in a large sample of galaxies that normally more than a single corotation is found in a galaxy, but that only one of them is related to the bar, while the others are found in the spiral arms, at increasing radii, or associated with a smaller, nuclear bar or oval distortion at small radii. 

While MUSE has a 1 arcmin × 1 arcmin field and offers spectral coverage of both stellar and gas components with a resolution of some 50 km/s in velocity, GHaFaS has a larger field of view, 3.4 arcmin × 3.4 arcmin field, gives a resolution in velocity of 6 km/sec, but it can observe only the ionised interstellar gas. 

Now with NGC 3433 they have put all of their previous work on a firmer basis by comparing it with a classical, and quite different, technique for finding corotation radii, developed by Tremaine and Weinberg (TW). They applied both methods to the velocity fields of both the stars and the insterstellar gas, using the observations of both GHaFaS and MUSE. They found four corotation radii. 

The innermost one, in the circumnuclear zone, could be detected only using FB, but was found clearly in both MUSE and GHaFaS data for the gas with a difference of 7% in the values. The second one, corresponding to the main bar, and the most intense, was measured in six different ways: using FB on the gas with GHaFaS, FB on the gas with MUSE, FB on the stars with MUSE, TW on the gas with GHaFaS, TW on the gas with MUSE, and TW on the stars with MUSE. The uncertainty in the corotation found by using all 6 values was only 4%. 

A third corotation was found using FB on gas for both GHaFaS and MUSE, and a fourth corotation, beyond the limits of the field of MUSE, was measured using FB and TW on the gas with GHaFaS. The values for the corotation radii in both cases, gave excellent agreement between the two methods used. Measured this way the corotation radii are among the most accurately determined parameters of the galaxy, compared with, for example, the bar length.

Panel (a): velocity map of NGC 3433 using the first moment map of Hα emission in the FP data cube from GHaFaS. The box in black shows the size of the MUSE data. Panel (b): velocity map of Hα emission from the central square arcmin from the MUSE data cube. Panel (c): velocity map of the stellar component from the MUSE data. Large format: [ JPEG ]. 
 
Although this study deals with only a single galaxy, its results are powerful because they verify FB as a method, and it is considerably easier than TW to apply to large numbers of objects, demanding less observing time. Measuring the principal corotation radius allows us to measure the pattern speed of the bar, and this allows us to perform a whole range of tests on the evolution of galaxies, including measuring the braking effects of dark matter halos. "For the time being we are confined to low redshifts, but as our techniques advance we have hopes of reaching intermediate redshift objects in the fairly near future", said John Beckman. Isaac Newton Group of Telescopes



More Information


Beckman, John E.; Font, Joan; Borlaff, Alejandro; García-Lorenzo, Begoña, 2018, "Precision Determination of Corotation Radii in Galaxy Disks: Tremaine-Weinberg versus Font-Beckman for NGC 3433", ApJ, 854, 182 [ ADS ].
 
"The Galaxies "tune up their musical instruments", IAC press release, 9th April 2018. 

"New Light on Dark Matter Halos", ING web news release, 13th February 2017.



Contact:
 
Javier Méndez  
(Public Relations Officer)


Monday, April 23, 2018

Reaching New Heights at the ESO Supernova

"Reaching New Heights" poster



On Friday 4 May, a live planetarium show — Reaching New Heights — will be presented at the ESO Supernova Planetarium & Visitor Centre. This show will take the audience on a journey around ESO’s state-of-the-art facilities, immersing them in Chile’s stunning scenery and wonderful dark skies.

As the world’s leading ground-based astronomy organisation, the European Southern Observatory (ESO) builds and operates some of the best telescopes in the world, enabling exciting astronomical discoveries and the further understanding of our fascinating Universe. Reaching New Heights provides an overview of ESO, including amazing footage of the telescopes in the Atacama Desert, scientific simulations of discoveries made with these facilities, and a peek into the future as ESO sets out to build the world’s largest optical telescope, the Extremely Large Telescope (ELT).

The event is free of charge and is aimed at the general public including children over 8 years old. The show will be presented in German by ESO Supernova coordinator Tania Johnston, who will also present an English version on 15 June. More information about the show, as well as the link to book tickets for both the German and the English screenings, can be found here. Seats should be reserved before arrival.

The ESO Supernova Planetarium & Visitor Centre will open its doors to the public on 28 April 2018. To see the full range of activities on offer and to book a place at any forthcoming events, please use the following link.



More  Information


The ESO Supernova Planetarium & Visitor Centre

The ESO Supernova Planetarium & Visitor Centre is a cooperation between the European Southern Observatory (ESO) and the Heidelberg Institute for Theoretical Studies (HITS). The building is a donation from the Klaus Tschira Stiftung (KTS), a German foundation, and ESO runs the facility.



Links
 


Contacts

Tania Johnston
ESO Supernova Coordinator
Garching bei München, Germany
Tel: +49 89 320 061 30
Email:
tjohnsto@eso.org 

Oana Sandu
Community Coordinator & Communication Strategy Officer
ePOD
Tel: +49 89 320 069 65
Email:
osandu@partner.eso.org


Friday, April 20, 2018

Approaching the Universe’s origins

Credit:ESA/Hubble & NASA, RELICS


This intriguing image from the NASA/ESA Hubble Space Telescope shows a massive galaxy cluster called PSZ2 G138.61-10.84, about six billion light-years away. Galaxies are not randomly distributed in space, but rather aggregated in groups, clusters and superclusters. The latter span over hundreds of millions of light-years and contain billions of galaxies.

Our own galaxy, for example, is part of the Local Group, which in turn is part of the giant Laniakea Supercluster. It was thanks to Hubble that we were able to study massive galactic superstructures such as the Hercules-Corona Borealis Great Wall; a giant galaxy cluster that contains billions of galaxies and extends 10 billion light-years across — making it the biggest known structure in the Universe.

This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Source: ESA/Hubble/Potw

Thursday, April 19, 2018

Hubble celebrates 28th anniversary with a trip through the Lagoon Nebula

Hubble's 28th birthday picture: The Lagoon Nebula

Infrared view of the Lagoon Nebula
Infrared view of the Lagoon Nebula



Videos

Hubblecast 109: Diving into the Lagoon Nebula
Hubblecast 109: Diving into the Lagoon Nebula

The centre of the Lagoon Nebula over time
The centre of the Lagoon Nebula over time

Diving into the Lagoon Nebula
Diving into the Lagoon Nebula

Swimming across the Lagoon Nebula
Swimming across the Lagoon Nebula

Fulldome view of the Lagoon Nebula
Fulldome view of the Lagoon Nebula

Lagoon Nebula in visible and infrared light
Lagoon Nebula in visible and infrared light



Image Comparisons

Comparison image of the Lagoon Nebula in optical and infrared




This colourful cloud of glowing interstellar gas is just a tiny part of the Lagoon Nebula, a vast stellar nursery. This nebula is a region full of intense activity, with fierce winds from hot stars, swirling chimneys of gas, and energetic star formation all embedded within a hazy labyrinth of gas and dust. Hubble used both its optical and infrared instruments to study the nebula, which was observed to celebrate Hubble’s 28th anniversary.

Since its launch on 24 April 1990, the NASA/ESA Hubble Space Telescope has revolutionised almost every area of observational astronomy. It has offered a new view of the Universe and has reached and surpassed all expectations for a remarkable 28 years. To celebrate Hubble’s legacy and the long international partnership that makes it possible, each year ESA and NASA celebrate the telescope’s birthday with a spectacular new image. This year’s anniversary image features an object that has already been observed several times in the past: the Lagoon Nebula.

The Lagoon Nebula is a colossal object 55 light-year wide and 20 light-years tall. Even though it is about 4000 light-years away from Earth, it is three times larger in the sky than the full Moon. It is even visible to the naked eye in clear, dark skies. Since it is relatively huge on the night sky, Hubble is only able to capture a small fraction of the total nebula. This image is only about four light-years across, but it shows stunning details.

The inspiration for this nebula’s name may not be immediately obvious in this image. It becomes clearer only in a wider field of view, when the broad, lagoon-shaped dust lane that crosses the glowing gas of the nebula can be made out. This new image, however, depicts a scene at the very heart of the nebula.

Like many stellar nurseries, the nebula boasts many large, hot stars. Their ultraviolet radiation ionises the surrounding gas, causing it to shine brightly and sculpting it into ghostly and other-worldly shapes. The bright star embedded in dark clouds at the centre of the image is Herschel 36. Its radiation sculpts the surrounding cloud by blowing some of the gas away, creating dense and less dense regions.

Among the sculptures created by Herschel 36 are two interstellar twisters — eerie, rope-like structures that each measure half a light-year in length. These features are quite similar to their namesakes on Earth — they are thought to be wrapped into their funnel-like shapes by temperature differences between the hot surfaces and cold interiors of the clouds. At some point in the future, these clouds will collapse under their own weight and give birth to a new generation of stars.

Hubble observed the Lagoon Nebula not only in visible light but also at infrared wavelengths. While the observations in the optical allow astronomers to study the gas in full detail, the infrared light cuts through the obscuring patches of dust and gas, revealing the more intricate structures underneath and the young stars hiding within it. Only by combining optical and infrared data can astronomers paint a complete picture of the ongoing processes in the nebula.



More Information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA, STScI



Links



Contacts

Mathias Jäger
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500


Source: ESA/Hubble/News

Wednesday, April 18, 2018

Where is the Universe's missing matter?

Copyright: ESA/XMM-Newton; J-T. Li (University of Michigan, USA); 
Sloan Digital Sky Survey (SDSS)  


Astronomers using ESA’s XMM-Newton space observatory have probed the gas-filled haloes around galaxies in a quest to find ‘missing’ matter thought to reside there, but have come up empty-handed – so where is it? 

All the matter in the Universe exists in the form of ‘normal’ matter or the notoriously elusive and invisible dark matter, with the latter around six times more prolific. 

Curiously, scientists studying nearby galaxies in recent years have found them to contain three times less normal matter than expected, with our own Milky Way Galaxy containing less than half the expected amount. 

“This has long been a mystery, and scientists have spent a lot of effort searching for this missing matter,” says Jiangtao Li of the University of Michigan, USA, and lead author of a new paper.  

“Why is it not in galaxies — or is it there, but we are just not seeing it? If it’s not there, where is it? It is important we solve this puzzle, as it is one of the most uncertain parts of our models of both the early Universe and of how galaxies form.”

Rather than lying within the main bulk of the galaxy, the part can be observed optically, researchers thought it may instead lie within a region of hot gas that stretches further out into space to form a galaxy’s halo. 

These hot, spherical haloes have been detected before, but the region is so faint that it is difficult to observe in detail – its X-ray emission can become lost and indistinguishable from background radiation. Often, scientists observe a small distance into this region and extrapolate their findings but this can result in unclear and varying results. 

Jiangtao and colleagues wanted to measure the hot gas out to larger distances using ESA’s XMM-Newton X-ray space observatory. They looked at six similar spiral galaxies and combined the data to create one galaxy with their average properties. 

“By doing this, the galaxy’s signal becomes stronger and the X-ray background becomes better behaved,” adds co-author Joel Bregman, also of the University of Michigan. 

“We were then able to see the X-ray emission to about three times further out than if observing a single galaxy, which made our extrapolation more accurate and reliable.” 

Massive and isolated spiral galaxies offer the best chance to search for missing matter. They are massive enough to heat gas to temperatures of millions of degrees so that they emit X-rays, and have largely avoided being contaminated by other material through star formation or interactions with other galaxies.

Still missing

The team’s results showed that the halo surrounding galaxies like the ones observed cannot contain all of the missing matter after all. Despite extrapolating out to almost 30 times the radius of the Milky Way, nearly three-quarters of the expected material was still missing.

There are two main alternative theories as to where it could be: either it is stored in another gas phase that is poorly observed – perhaps either a hotter and more tenuous phase or a cooler and denser one – or within a patch of space that is not covered by our current observations or emits X-rays too faintly to be detected.

Either way, since the galaxies do not contain enough missing matter they may have ejected it out into space, perhaps driven by injections of energy from exploding stars or by supermassive black holes.

“This work is important to help create more realistic galaxy models, and in turn help us better understand how our own Galaxy formed and evolved,” says Norbert Schartel, ESA XMM-Newton project scientist. “This kind of finding is simply not possible without the incredible sensitivity of XMM-Newton.”

“In the future, scientists can add even more galaxies to our study samples and use XMM-Newton in collaboration with other high-energy observatories, such as ESA’s upcoming Advanced Telescope for High-ENergy Astrophysics, Athena, to probe the extended, low-density parts of a galaxy’s outer edges, as we continue to unravel the mystery of the Universe’s missing matter.”



Notes for Editors


“Baryon budget of the hot circumgalactic medium of massive spiral galaxies,” by J-T Li et al. (2018) is published in The Astrophysical Journal Letters. DOI: 10.3847/2041-8213/aab2af.



For further information, please contact:

Jiangtao Li
University of Michigan, USA
Email: jiangtal@umich.edu
Tel: 734-383-2089 

Joel Bregman
University of Michigan, USA
Email: jbregman@umich.edu
Tel: 734-764-2667 

Norbert Schartel
XMM-Newton Project Scientist
European Space Agency
Email: norbert.schartel@esa.int