mercredi 25 avril 2018

Ancient Galaxy Megamergers












ALMA - Atacama Large Millimeter/submillimeter Array logo.

25 April 2018

 Artist’s impression of ancient galaxy megamerger

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.

Images of a galaxy protocluster from SPT, APEX and ALMA

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.

Artist’s impression of ancient galaxy megamerger

"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:

ESOcast 157 Light: Ancient Galaxy Pileups: https://www.eso.org/public/videos/eso1812a/

Research paper (Miller et al.): http://www.eso.org/public/archives/releases/sciencepapers/eso1812/eso1812a.pdf

Research paper (Oteo et al.): http://www.eso.org/public/archives/releases/sciencepapers/eso1812/eso1812b.pdf

Photos of APEX: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Atacama%20Pathfinder%20Experiment

Photos of ALMA: http://www.eso.org/public/images/archive/search/?adv=&subject_name=Atacama%20Large%20Millimeter/submillimeter%20Array

Atacama Large Millimeter/submillimeter Array (ALMA): http://www.eso.org/public/teles-instr/alma/

Atacama Pathfinder Experiment (APEX): http://www.eso.org/public/teles-instr/apex/

South Pole Telescope: https://pole.uchicago.edu/

Herschel Space Observatory: http://sci.esa.int/herschel/

Images, Video, Text, Credits: ESO/M. Kornmesser/ALMA (ESO/NAOJ/NRAO)/Miller et al.

Greetings, Orbiter.ch

Seventh Sentinel satellite launched for Copernicus









ESA - Sentinel 3 Mission logo.

25 April 2018

Sentinel-3B liftoff

The second Sentinel-3 satellite, Copernicus Sentinel-3B, was launched today, joining its identical twin Sentinel-3A in orbit. This pairing of satellites increases coverage and data delivery for the European Union’s Copernicus environment programme.

The 1150 kg Sentinel-3B satellite was carried into orbit on a Rockot launcher from Plesetsk, Russia, at 17:57 GMT (19:57 CEST; 21:57 local time) on 25 April.

Sentinel-3B liftoff replay

Rockot’s upper stage delivered Sentinel-3B into its planned orbit.

Just 92 minutes after liftoff, Sentinel-3B sent its first signals to the Kiruna station in Sweden. Data links were quickly established by teams at ESA’s operations centre in Darmstadt, Germany, allowing them to assume control of the satellite.

During the three-day launch and the early orbit phase, controllers will check that all the satellite’s systems are working and begin calibrating the instruments to commission the satellite. The mission is expected to begin routine operations after five months.

“This is the seventh launch of a Sentinel satellite in the last four years. It is a clear demonstration of what European cooperation can achieve and it is another piece to operating the largest Earth observation programme in the world, together with our partners from the European Commission and Eumetsat,” said ESA Director General Jan Wörner.

Sentinel-3 in orbit

With this launch, the first set of Sentinel missions for the European Union’s Copernicus environmental monitoring network are in orbit, carrying a range of technologies to monitor Earth’s land, oceans and atmosphere.

ESA’s Director of Earth Observation Programmes, Josef Aschbacher, said, “With Sentinel-3B, Europe has put the first constellation of Sentinel missions into orbit – this is no small job and has required strong support by all involved. It allows us to get a very detailed picture of our planet on a daily basis and provides crucial information for policy makers.

“It also offers lots of opportunities for commercial companies to develop new innovative services. And, the free and open data policy allows every citizen to have updates for their own use.

“When we designed such a satellite constellation 20 years ago not everyone was convinced Europe could do that. I am glad to see this has become reality and that it is now a large European success story.”

Sentinel-3 scans Earth’s colour

Copernicus relies on the Sentinels and contributing missions to provide data for monitoring the environment and for supporting civil security activities. Sentinel-3 carries a series of cutting-edge sensors to do just that.

Over oceans, it measures the temperature, colour and height of the sea surface as well as the thickness of sea ice. These measurements are used, for example, to monitor changes in Earth’s climate and for more hands-on applications such as marine pollution.

Over land, this innovative mission monitors wildfires, maps the way land is used, checks vegetation health and measures the height of rivers and lakes.

Data from the Copernicus Programme are used worldwide and are free of charge.

Related links:

Sentinel-3: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-3

Sentinel data access: https://scihub.copernicus.eu/

Eurockot: http://www.eurockot.com/

Images, Video, Text, Credits: ESA/ATG medialab.

Best regards, Orbiter.ch

Space Gardening, Dragon Packing and Spacewalk Work Aboard Lab











ISS - Expedition 55 Mission patch.

April 25, 2018

The Expedition 55 crew is experimenting with space gardening today while packing research samples and cargo for return to Earth. The space residents are also breaking down gear brought in from last month’s spacewalk and getting ready for the next spacewalk.

Botany research aboard the International Space Station helps scientists and astronauts learn how to grow food off Earth to sustain future missions. Today’s space gardening work performed by Flight Engineer Drew Feustel will test the automated nourishment of lettuce and mizuna greens grown in the Veggie facility. The plants will be harvested and samples sent back to Earth for analysis.

Botanical samples are just one example of the multiple types of research and cargo that is sent to Earth packed inside the SpaceX Dragon cargo craft. Radiation monitors that recorded exposure levels in the station’s crew quarters were collected by Japanese astronaut Norishige Kanai today for stowage inside Dragon. Engineers on the ground will examine the radiation data and determine the exposure risk to the crew and develop countermeasures.


Image above: Astronauts Scott Tingle (left) and Ricky Arnold wrap up spacesuit work following a successful spacewalk on March 29, 2018. The duo scrubbed cooling loops, performed the iodination of ion filters and tested the water conductivity inside a pair of U.S. spacesuits. Image Credit: NASA.

NASA astronauts Scott Tingle and Ricky Arnold disassembled an external television camera group (ETVCG) brought in from last month’s spacewalk. Tingle then replaced a failed light bulb in a light to be used on another ETVCG which will be installed on the next spacewalk scheduled for mid-May. Parts from the old ETVCG will be shipped back to Earth in Dragon for refurbishment.

Dragon is due for two more work days of packing before its return to Earth next week. Ground controllers will remotely detach Dragon from the Harmony module before releasing it from the grips of Canadarm2 into space at 10:22 a.m. EDT Wednesday, May 2. Tingle will monitor the robotics activities as NASA TV broadcasts the departure activities live starting at 10 a.m. Splashdown in the Pacific Ocean is planned for 4:02 p.m. and will not be seen on NASA TV.

Related links:

NASA TV: https://www.nasa.gov/multimedia/nasatv/index.html#public

SpaceX Dragon: https://www.nasa.gov/spacex

Expedition 55: https://www.nasa.gov/mission_pages/station/expeditions/expedition55/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Image (mentioned), Text, Credits: NASA/Mark Garcia.

Best regards, Orbiter.ch

Stellar Dust Survey Paves Way for Exoplanet Missions











NASA logo.

April 25, 2018


Image above: This artist’s illustration shows what the sky might look like from a planet in a particularly dusty solar system. Dust that orbits a star in the plane of the solar system is called zodiacal dust, and the light reflected and scattered by that dust is called zodiacal light. The Hunt for Observable Signatures of Terrestrial Systems, or HOSTS, survey was tasked with learning more about the effect of zodiacal dust on the search for new worlds, to help guide the design of future planet-hunting missions. Image Credits: NASA/JPL-Caltech.

Veils of dust wrapped around distant stars could make it difficult for scientists to find potentially habitable planets in those star systems. The Hunt for Observable Signatures of Terrestrial Systems, or HOSTS, survey was tasked with learning more about the effect of dust on the search for new worlds. The goal is to help guide the design of future planet-hunting missions. In a new paper published in the Astrophysical Journal, HOSTS scientists report on the survey’s initial findings.

Using the Large Binocular Telescope Interferometer, or LBTI, on Mount Graham in Arizona, the HOSTS survey determines the brightness of warm dust floating in the orbital planes of other stars (called exozodiacal dust). In particular, HOSTS has studied dust in nearby stars’ habitable zones, where liquid water could exist on the surface of a planet. The LBTI is five to 10 times more sensitive than the previous telescope capable of detecting exozodiacal dust, the Keck Interferometer Nuller.


Image above: The Large Binocular Telescope Interferometer, or LBTI, is a ground-based instrument connecting two 8-meter class telescopes on Mount Graham in Arizona to form the largest single-mount telescope in the world. The interferometer is designed to detect and study stars and planets outside our solar system. Image Credits: NASA/JPL-Caltech.

Among the findings detailed in the new paper, the HOSTS scientists report that a majority of Sun-like stars in their survey do not possess high levels of dust -- good news for future efforts to study potentially-habitable planets around those stars. A final report on the full HOSTS survey results is expected early next year.

More information about the new findings from HOSTS and the search for Earthlike planets beyond our solar system is available in this news release from the University of Arizona: https://uanews.arizona.edu/story/ualed-nasa-survey-seen-steppingstone-astronomy

The LBTI is funded by NASA's Exoplanet Exploration Program office and managed by the agency's Jet Propulsion Laboratory in Pasadena, California. JPL is a division of Caltech, also in Pasadena. Six JPL scientists co-authored the new research paper. The LBTI is an international collaboration among institutions in the U.S., Italy and Germany, and it is managed and headquartered at the University of Arizona in Tucson.

NASA is taking a multifaceted approach to finding and studying planets outside our solar system. On April 18, NASA launched its newest planet-hunting observatory, the Transiting Exoplanet Survey Satellite (TESS), which is expected to find thousands of new exoplanets, mostly around stars smaller than our Sun.

Large Binocular Telescope Interferometer (LBTI): https://www.jpl.nasa.gov/news/news.php?feature=4450

Exoplanets: https://www.nasa.gov/content/the-search-for-life

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Calla Cofield/University of Arizona/Doug Carroll.

Greetings, Orbiter.ch

Gaia creates richest star map of our Galaxy – and beyond












ESA - Gaia Mission patch.

25 April 2018

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.

Gaia’s sky in colour

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 observations collected by Gaia are redefining the foundations of astronomy,” says Günther Hasinger, ESA Director of Science.

“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 Galactic census takes shape

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

“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.” 

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.

Asteroid survey

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

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.

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.”

Gaia spacecraft

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. 

Hertzsprung-Russell diagram

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.”

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.


Rotation of the Large Magellanic Cloud

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.

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.

Globular cluster and dwarf galaxy orbits

“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.”

Star motions in the sky

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. http://www.esa.int/www.cosmos.esa.int/web/gaia/dr2-papers

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.

Related article:

Gaia’s billion-star map hints at treasures to come (Gaia first data release)
http://orbiterchspacenews.blogspot.ch/2016/09/gaias-billion-star-map-hints-at.html

ESA Gaia: http://www.esa.int/Our_Activities/Space_Science/Gaia

Images, Videos, Text, Credits: ESA/Markus Bauer/Timo Prusti/Fred Jansen/INAF, Astronomical Observatory of Padua/Antonella Vallenari/Leiden Observatory/Anthony Brown/ESA/Gaia/DPAC/CC BY-SA 3.0 IGO.

Best regards, Orbiter.ch

What Uranus Cloud Tops Have in Common With Rotten Eggs





GEMINI Observatory logo.

April 25, 2018


Image above: 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. Image Credits: NASA/JPL-Caltech.

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.

Gemini North telescope on Hawaii's Mauna Kea. Image Credits: CNRC-NRC

"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: https://www.gemini.edu/node/21050

Caltech in Pasadena, California, manages JPL for NASA.

Images (mentioned), Text, Credits: NASA/JoAnna Wendel/JPL/Gretchen McCartney/Gemini Observatory/Peter Michaud.

Greetings, Orbiter.ch

mardi 24 avril 2018

NASA Upgrades Space Station Emergency Communications Ground Stations










NASA - SCaN Mission logo.

April 24, 2018

Since the launch of the International Space Station’s first component in 1998, communications infrastructure has been critical to the station’s success and crew safety. NASA is currently implementing upgrades to very high frequency (VHF) communications ground stations that backup the station’s primary communications system, the Space Network, and communicate with Soyuz spacecraft when out of Russia’s range.

The International Space Station. Image Credit: NASA

NASA’s VHF ground stations provide two-way, audio-only communications and transmit over two frequencies, VHF1 and VHF2. VHF1 is used for emergency communications with the International Space Station. VHF2 communicates with Soyuz spacecraft.

Russia also operates a VHF network independently from NASA's. The combination of the two networks ensures VHF communications are available on every orbit of the space station and Soyuz.

The space station hosts two VHF1 antennas, 180 degrees apart. They flank the Zvezda Service Module, an early Russian contribution to the station that served as an early cornerstone for its habitation. Astronauts and cosmonauts can communicate with mission control from any module of the station via VHF1.


Image above: An upgraded VHF antenna capable of supporting both the VHF1 and VHF2 frequencies. Image Credit: NASA.

“Maintaining the availability of utility-like communications between the crew and the ground is paramount to enabling mission success and ensuring crew safety,” said Mark Severance, Human Spaceflight Communications and Tracking Network director. “The NASA VHF network, in combination with the VHF network operated by our Russian partners, does just that.”

Under normal circumstances, the station relies on NASA’s Space Network, a series of Tracking and Data Relay Satellites in geosynchronous orbit. The network provides near-continuous communications coverage between the station and mission control centers around the world who make sure the station’s systems function properly. The Space Network also enables the transmission of high-resolution science data, ultra-high definition video and special downlinks like student contacts with astronauts. VHF1 would only be used in the unlikely event that the space station was unable to communicate via the Space Network.

A Soyuz with VHF2 antenna toward the aft of the spacecraft. Image Credit: NASA

Russian Soyuz spacecraft sport a single VHF2 antenna towards their tail. Russia uses VHF2 as their primary system for voice communications from launch at the Baikonur Cosmodrome in Kazakhstan to docking with the space station and upon undocking and returning to Earth.

On most Soyuz missions, the spacecraft docks with the space station prior to exiting Russia’s VHF network coverage. The same is true on return to Earth. However, on Soyuz missions that require a longer, 34-orbit rendezvous, the NASA VHF network stands by to provide emergency communications while the Soyuz is outside of Russia’s range, orbiting over the continental United States. NASA’s VHF network could also provide emergency communications in the event a problem required the Soyuz to stay in orbit for an extended period of time.

NASA’s upgrades to VHF network ground antennas, currently underway, involve improvements to numerous electronic components and installation of new software for tracking the space station and Soyuz. Additionally, new antennas at the ground stations, able to operate at VHF1 and VHF2 simultaneously, will add redundancy to the network so that if one system fails, the other system will be able to take over immediately.


Image above: A VHF ground antenna at NASA’s Wallops Flight Facility in Wallops Island, Virginia. Image Credit: NASA.

“The purpose of these upgrades is to ensure the VHF ground stations remain a robust capability for backup and emergency communications,” said Severance. “The addition of redundancy, the ‘belt and suspenders’ approach, is particularly important given that these systems would only be employed due to failure of the primary space station communications system or an emergency onboard the Soyuz.”

NASA maintains VHF ground stations in two locations: Wallops Flight Facility in Wallops Island, Virginia, and NASA’s Armstrong Flight Research Center in Edwards, California. These ground stations are strategically placed to maximize contact with the station and Soyuz as they orbit above North America. The Russian VHF ground stations are located throughout Russia, providing contact as the space station and Soyuz orbit above Asia and Europe.

NASA’s VHF system is managed by NASA’s Goddard Space Flight Center’s Exploration and Space Communications projects division. NASA’s Space Communications and Navigation program office provides programmatic oversight to the network.

Related links:

NASA’s Goddard Space Flight Center: https://www.nasa.gov/goddard

Exploration and Space Communications : https://esc.gsfc.nasa.gov/

NASA’s Space Communications and Navigation: https://www.nasa.gov/directorates/heo/scan/index.html

SCaN (Space Communications and Navigation): https://www.nasa.gov/directorates/heo/scan/index.html

NASA’s Armstrong Flight Research Center: https://www.nasa.gov/centers/armstrong/home/index.html

Wallops Flight Facility: https://www.nasa.gov/centers/wallops/home

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Danny Baird.

Greetings, Orbiter.ch