An international team of researchers publishes in a recent article in Nature Astronomy Letters new images of the basin-free spherical shape of the asteroid Hygiea. The article publishes for the first time direct observations of Hygiea’s shape, and proposes an explanation of how such an object forms in order to reach hydrostatic equilibrium.

The article provides for the first time direct observations of the Hygiea asteroid, obtained using the SPHERE instrument on the Very Large Telescope VLT, in Chile. Researchers captured the observations at twelve different epochs between 2017 and 2018, and combined them with existing photometric images – from normal telescopes - in order to see the hidden angles of the direct observations. This is the first time that researchers observe Hygiea through adaptive optics, a technique that further defines the edges of the shapes and provides a direct measurement of the body’s diameter.

A new candidate for a dwarf planet

In order to be considered as a dwarf planet, objects must meet four main criteria: to orbit around the Sun, to share its orbital neighborhood with other objects, to not be a satellite and to be in hydrostatic equilibrium and nearly spherical shaped. All of the Main Belt asteroids, including Hygiea, meet the first three criteria. The VLT-SPHERE observations allowed the researchers to study the fourth requirement. They saw that Hygiea’s shape is nearly spherical, which led them to calculate the sphericity of the asteroid. They obtained a high value of sphericity, 0.9975, close to the maximum value of 1, meaning Hygiea’s shape is in hydrostatic equilibrium and nearly spherical.

With the latter criteria accomplished, researchers propose that Hygiea might be re-classified as a dwarf planet. Nevertheless, the official designation might take a while, as it has to be stated by the International Astronomical Union. If accepted, Hygiea would join the handful of dwarf planets in our solar system, joining Pluto and Ceres.

A basin-free shape

Hygiea is the main remnant of an impact, which separated a fraction of its parent body more than 2 billion years ago, creating an asteroid family. However, when the team evaluated the images, they could not see any sign from the impact. Although the calculations showed a large-scale topography similar to the one of Ceres, they did not reveal the impact basin. Using SPH computer simulations, they argue that a possible explanation is that the formation process was the result of reaccumulation after the original impact. Using computer simulations, the astronomers showed that a space rock of approximately 100 kilometers across impacted and fragmented Hygiea’s parent body. When most of the remnants clumped back together into the space rock now known as Hygiea, they formed the smooth, spherical body seen today.

Large campaign of exoplanet observations

The project is part of the European Southern Observatory large program of exoplanet observations. More than 20 researchers from 13 different countries form the group, which was led by Professor Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille. Our researcher in Solar System and Minor bodies Toni Santana-Ros is one of the members of the team. Santana-Ros collaborated in the observation campaign, developing the object’s photometry light curve. Those images were used to obtain the outcomes of the Hygiea 3D model.

Researchers also state than several new dwarf-planet candidates will be defined once the 3D model of observations becomes available for trans-Neptunian farther objects.

You can read the whole article via Nature Astronomy.

Advanced Virgo and the two Advanced LIGO detectors resume the taking of science data on the 1st of November, 2019, following a one-month-long stop. This event marks the restart of the third observation period, named O3, which started on the 1st of April, 2019. All three of the interferometers in the global gravitational-wave observatory paused O3 on the 1st October, 2019, in order to work on improvements to enhance the performance of the detectors.

On the Virgo side, the focus was on increasing the laser power injected into the interferometer, from 19 W to 26 W. This increase has been effective in improving the detector sensitivity at high frequencies, but has required a complete re-tuning of the interferometer.

Effort was also devoted to the study of selected noise sources. The lessons learned will be useful for the future operation of the instrument.

"The month of commissioning has been quite intense. We performed many activities, both to better understand the noise that limits the sensitivity and to handle a 30% increase in the laser input power", says Matteo Tacca, researcher at Nikhef in The Netherlands, and the Virgo Commissioning Coordinator.

"We were able to find the sources of some of the noise limiting Virgo’s sensitivity. A few of them have been removed, while others require further measurements. Also mitigation strategies are under investigation. After a lot of work fine-tuning the interferometer, we were able to recover stable operation with higher input power".

Many activities were also performed at the two LIGO detectors in the US, such as the installation of special fences at the Hanford site in order to reduce wind noise. O3 will now run with no further interruptions until the 30th of April, 2020.

For more information see ligo.org and http://www.virgo-gw.eu/

You can also read about the start of the third period of observations, the detection of neutron star mash-ups and the story of the 03 so far.

With installation near completion, DESI’s new sky-surveying instrument begins final testing. The latest milestone marks the opening of DESI’s final testing toward the formal start of observations in early 2020.

A new instrument mounted atop a telescope in Arizona has aimed its robotic array of 5,000 fiber-optic “eyes” at the night sky and captured the first images showing its unique view of galaxy light.It was the first test of the Dark Energy Spectroscopic Instrument, known as DESI, with its nearly complete complement of components. The long-awaited instrument is designed to explore the mystery ofdark energy, which makes up about 68 percent of the universe and is speeding upits expansion.

The Universe’s most detailed 3D map

DESI’s components are designed to automatically point at preselected sets of galaxies, gather their light, and then split that light into narrow bands of color to precisely map their distance from Earth and gauge how much the universe expanded as this light traveled to Earth. In ideal conditions, DESI can cycle through a new set of 5,000 galaxies every 20 minutes.

Gravity had slowed this rate of expansion in the early universe, though dark energy has since been responsible for speeding up its expansion. Like a powerful time machine, DESI will peer deeply into the universe’s infancy and early development – up to about 11 billion years ago – to create the most detailed 3-D map of the universe. By repeatedly mapping the distance to 35 million galaxies and 2.4 million quasars across one-third of the area ofthe sky over its five-year run, DESI will will provide very precise measurements of the universe’s expansion rate, and will also teach us more about dark energy. Quasars, among the brightest objects in the universe, allow DESI to look deeply into the Universe’s past.

DESI's focal area overlaps with the full moon light in the night sky. The 5.000 robotic eyes cover an area 38 times bigger than the full Moon. Each one of the robotic positioners can place an optical fiber in an object in order to trace its light (the red circle indicates the location of a single positioner). The light gathered of a tiny portion of the Triangulum Galaxy by one optical fiber is split up in a spectrum - below the image -, revealing the traces of the galaxy's components. This spectrum was gathered on October, 22nd. (C) Dustin Lang, Aaron Meisner, DESI Collaboration/Imagine Sky Viewer; NASA/JPL-Caltech/UCLA; and Legacy Surveys project.

The Institute of Cosmos Sciences participates as a research Unit, led by ICREA professor Licia Verde. The team will analyze and interpret the upcoming observations during the next 5 years. Verde, recently awarded with the Catalonian National Research Award, says, “Is a fascinating moment for Cosmology because we are hoping to unveil the nature of the Universe’s components”. `La Caixa´ fellow researcher Héctor Gil-Marín explains, “DESI is going to see the Universe like no other instrument has been able to, so the precision will be maximum. We expect that the resulting information will be as unbiased,transparent and reliable as possible,” he emphasizes.

5.000 robotic “eyes”

Installation of DESI began in February 2018 at the Nicholas U. Mayall Telescope, at Kitt Peak National Observatory near Tucson, Arizona. Over the past 18 months, a bevy of DESI components were shipped to the site from institutions around the globe and installed on the telescope. “With DESI we are combining a modern instrument with a venerable old telescope to make a state-of-the-art survey machine.” said Lori Allen, director of the Kitt Peak National Observatory at the National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory.

Among the early arrivals was an assembly of lenses packaged in a large steel barrel, together weighing in at three tons. Placed at the top of the telescope, DESI’s focal plane carries 5,000 robotic positioners that swivel in a choreographed “dance” individually focusing on galaxies. It also included a collection of spectrographs designed to split up the gathered light into three separate color bands, allowing precise distance measurements of the observed galaxies across a broad range of colors. These spectrographs measure redshift, which is a shift in the color of objects to longer, redder wavelengths due to the objects’ movement away from us. Redshiftis analogous to how the sound of a fire engine’s siren shifts to lower tones as it moves away from us.

“This is a very exciting moment,”said Nathalie Palanque-Delabrouille, a DESI spokesperson and an astrophysics researcher at France’s Atomic Energy Commission (CEA) who has participated inthe selection process to determine which galaxies and other objects DESI will observe. “This is a very significant advance compared to previous experiments. By looking at objects very far away from us, we can actually map the history of the universe and see its components by looking at very different objects from different eras" she said.

In words of Gregory Tarlé, a physics professor at the University of Michigan who led the student teams that assembled the robotic positioners for DESI and related components, “I want to find out what the nature of dark energy is,” he said. “We finally have a shot at really trying to understand the nature of this stuff that dominates the Universe.”.

DESI's full focal plane with the 5,000 robotic positioners. (C) DESI Collaboration

The DESI collaboration has participation from nearly 500 researchers at 75 institutions in 13 countries.

DESI is supported by the U.S.Department of Energy’s Office of Science; the U.S. National Science Foundation,Division of Astronomical Sciences under contract to the NSF’s National Optical-Infrared Astronomy Research

Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico; the Ministry of Science, Innovation, and Universities of Spain; and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation. View the full list of DESI collaborating institutions, and learn more about DESI here: www.desi.lbl.gov.

Founded in 1931 on the belief that the biggest scientific challenges are best addressed by teams, Lawrence Berkeley National Laboratory and its scientists have been recognized with 13 Nobel Prizes. Today, Berkeley Lab researchers develops ustainable energy and environmental solutions, create useful new materials, advance the frontiers of computing, and probe the mysteries of life, matter, and the universe. Scientists from around the world rely on the Lab’s facilities for their own discovery science. Berkeley Lab is a multiprogram national laboratory, managed by the University of California for the U.S. Department ofEnergy’s Office of Science.

DOE’s Office of Science is thesingle largest supporter of basic research in the physical sciences in theUnited States, and is working to address some of the most pressing challengesof our time. For more information, please visit science.energy.gov.

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progressof science. NSF supports basic research and people to create knowledge that transforms the future.

The Gordon and Betty Moore Foundation, established in 2000, seeks to advance environmental conservation, patient care and scientific research. The Foundation’s Science Program aims to make a significant impact on the development of provocative, transformative scientific research, and increase knowledge in emerging fields.

Established in 1958 and aiming at the forefront of astronomical science, the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) conducts cutting-edge astronomical studies, operates major national facilities and develops state-of the-art technological innovations

Cosmologist Licia Verde publishes, together with colleagues Tommaso Treu from the University of California and Adam G. Riess from the John Hopkins University a meeting report at Nature Astronomy on the Tensions between the early and late Universe.

The report discusses the state-of-the-art of the Hubble constant discrepancy. They review the new results shown at the Kavli Institute for Theoretical Physics workshop in July 2019, and propose both solutions focusing on the pre-recombination era. They also remark the necessity of coordinated efforts between the theory, interpretation, data analysis and observations communities, and list some guidelines for the best practise.

Read the whole article via Springer Nature

The authors use the Gaia Data Release 2 astrometric data down to G = 20mag to characterize the structure of the Galactic warp, including the related vertical motions, and the dependency of Galactic warp on age. The authors analyze two populations out to Galactocentric distances of 16kpc: a young bright sample of OB stars and an older red giant branch star sample. The onset radius of the Galactic warp is at 12-13kpc for the young sample and 10-11kpc for the older sample. The height of the warp is of the order of 0.2kpc for the young sample and 1.0kpc for the older sample at a Galactocentric distance of 14kpc. The older sample reveals a slightly lopsided warp with a difference of ?250pc above and below the plane. The maximum line of proper motions in latitude is systematically offset from the line of nodes that is estimated from the spatial data, which is the kinematic signature of lopsidedness. The results also show a prominent wave-like pattern of a bending mode different in both the young and older stellar samples. Both positions and kinematics also reveal substructures that are not necessarily related to the large-scale Galactic warp or to the bending mode. This analysis reveals a high degree of complexity in terms of both position and velocity, which in turn shows the need for complex kinematic models that are flexible enough to combine both wave-like patterns and an S-shaped lopsided warp.

The first direct measurement of the bar-shapedcollection of stars at the centre of our Milky Way galaxy has been made bycombining data from ESA’s Gaia mission with complementary observations from ground-and space-based telescopes.

The second release of data from ESA’s Gaiastar-mapping satellite, published in 2018, has been revolutionising many fieldsof astronomy. The unprecedented catalogue contains the brightnesses, positions,distance indicators and motions across the sky for more than one billion starsin our Milky Way galaxy, along with information about other celestial bodies.

As impressive as this dataset sounds, this is really just the beginning. Whilethe second release is based on the first 22 months of Gaia’s surveys, thesatellite has been scanning the sky for five years and has many years ahead. New data releases planned in coming years will steadilyimprove measurements as well as provide extra information that will enable usto chart our home galaxy and delve into its history like never before.

Meanwhile, a team of astronomers have combined the latest Gaia data withinfrared and optical observations performed from ground and space to provide apreview of what future releases of ESA’s stellar surveyor will reveal.

Figure 1.Friedrich Anders (UB) is the first author of the Astronomy and Astrophysics paper.

“We looked in particular at two of the stellar parameters contained in the Gaia data: the surface temperature of stars and the ‘extinction’, which is basically a measure of how much dust there is between us and the stars, obscuring their light and making it appear redder,” says Friedrich Anders from University of Barcelona, Spain, lead author of the new study.

“These two parameters are interconnected, but we can estimate them independently by adding extra information obtained by peering through the dust with infrared observations.”

The team combined the second Gaia data release with several infrared surveys using a computer code called StarHorse, developed by co-author Anna Queiroz and collaborators. The code compares the observations with stellar models to determine the surface temperature of stars, the extinction and an improved estimate of the distance to the stars.

As a result, the astronomers obtained much better determination of the distances to about 150 million stars – in some cases, the improvement is up to 20% or more. This enabled them to trace the distribution of stars across the Milky Way to much greater distances than possible with the original Gaia data alone.

CREDIT: ESA/Gaia/DPAC, A. Khalatyan (AIP) & StarHorse Team; mapa artístic de la Galaxia: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

Figure 2.This colour chart, superimposed on an artistic representation of the galaxy, shows the distribution of 150 million stars in the Milky Way probed using data from the second release of ESA’s Gaia mission in combination with infrared and optical surveys, with orange/yellow hues indicating greater density of stars. Most of these stars are red giants. While the majority of charted stars are located closer to the Sun (the larger orange/yellow blob in the lower part of the image), a large and elongated feature populated by many stars is also visible in the central region of the galaxy: this is the first geometric indication of the galactic bar.

“With the second Gaia data release, we could probe a radius around the Sun of about 6500 light years, but with our new catalogue, we can extend this ‘Gaia sphere’ by three or four times, reaching out to the centre of the Milky Way,” explains co-author Cristina Chiappini from Leibniz Institute for Astrophysics Potsdam, Germany, where the project was coordinated.

There, at the centre of our galaxy, the data clearly reveals a large, elongated feature in the three-dimensional distribution of stars: the galactic bar.

“We know the Milky Way has a bar, like other barred spiral galaxies, but so far we only had indirect indications from the motions of stars and gas, or from star counts in infrared surveys. This is the first time that we see the galactic bar in 3D space, based on geometric measurements of stellar distances,” says Friedrich.

“Ultimately, we are interested in galactic archaeology: we want to reconstruct how the Milky Way formed and evolved, and to do so we have to understand the history of each and every one of its components,” adds Cristina.

“It is still unclear how the bar – a large amount of stars and gas rotating rigidly around the centre of the galaxy – formed, but with Gaia and other upcoming surveys in the next years we are certainly on the right path to figure it out.”

The team is looking forward to the next data release from the Apache Point Observatory Galaxy Evolution Experiment (APOGEE-2), as well as upcoming facilities such as the 4-metre Multi-Object Survey Telescope (4MOST) at the European Southern Observatory in Chile and the WEAVE (WHT Enhanced Area Velocity Explorer) survey at the William Herschel Telescope (WHT) in La Palma, Canary Islands.

The third Gaia data release, currently planned for 2021, will include greatly improved distance determinations for a much larger number of stars, and is expected to enable progress in our understanding of the complex region at the centre of the Milky Way.

“With this study, we can enjoy a taster of the improvements in our knowledge of the Milky Way that can be expected from Gaia measurements in the third data release,” explains co-author Anthony Brown of Leiden University, The Netherlands, and chair of the Gaia Data Processing and Analysis Consortium Executive.

“We are revealing features in the Milky Way that we could not see otherwise: this is the power of Gaia, which is enhanced even further in combination with complementary surveys,” concludes Timo Prusti, Gaia project scientist at ESA.

Article reference:
F. Anders, A. Khalatyan, C. Chiappini, A. B. Queiroz, B. X. Santiago, C. Jordi, L. Girardi,A. G. A. Brown, G. Matijeviˇc, G. Monari, T. Cantat-Gaudin, M. Weiler, S. Khan, A. Miglio, I. Carrillo, M. Romero-Gómez, I. Minchev2, R. S. de Jong, T. Antoja, P. Ramos, M. Steinmetz, H. Enk. “Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G=18”. Astronomy & Astrophysics, July 2019.


ESA' press release link

Flyby around the StarHorse Gaia DR2 density distribution of Milky Way stars from Friedrich Anders on Vimeo.

Figure 1.Member of the ICCUB, Roger Mor.

Researchers from the ICCUB, leaded by Roger Mor, and The observatory of Besançon lead the research published in Astronomy & Astrophysics and Hihlighted in the “Nature Research Highlights” of Nature. The team simulated the star formation in the Milky Way over time, and found it was in steady decline until roughly five billion years ago, when production suddenly ramped up. The researchers estimate that half of the total mass of all stars ever created in the Milky Way thin disc was produced during this period.

Figure 2.Most probable values of the mean Star Formation Rate for the age bin obtained from theposterior PDF (black dots). The vertical error bars indicate the 0.16 and 0.84 quantiles of the posterior PDF. The horizontal error bars indicate the size of the age bin. The black dashed lines is a distribution formed by a bounded exponential plus a Gaussian, fitted to the results for our fiducial case. The red solid line is the exponential part of this exponential plus Gaussian fit. Thus, the red line should be understood as the expected exponential decay of the star formation history if nothing new occurred to the disc. Finally, the green squares is the obtained Star formation history if we would force the star formation history to be an exponential shape.

The team have used Gaia data release 2 (DR2) magnitudes, colours, and parallaxes for stars with magnitudes G smaller than 12 to explore a parameter space with 15 dimensions that simultaneously includes the stellar initial mass function (IMF) and a non-parametric star formation history (SFH) for the Galactic disc. This inference is performed by combining the Besançon Galaxy Model fast approximate simulations (BGM FASt) and an approximate Bayesian computation algorithm. They have found in Gaia DR2 data an imprint of a star formation burst 2–3 Gyr ago in the Galactic thin disc domain. Their results (see Figure 1) have shown a decreasing trend of the SFR from 9–10 Gyr to 6–7 Gyr ago. This is consistent with the cosmological star formation quenching observed at redshifts z smaller than 1.8. This decreasing trend is followed by a SFR enhancement starting at about 5 Gyr ago and continuing until about 1 Gyr ago which is detected with high statistical significance by discarding the null hypothesis of an exponential Star Formation History with a p-value = 0.002. They have estimated, from their best fit model, that half of the total mass of all stars ever created in the Milky Way thin disc was produced during this period. The large timescale of this recent Star Formation Rate enhancement event, together with the large amount of mass that we estimate to be involved in it, lead us to propose that this recent event is not intrinsic to the disc but is produced by an external perturbation. Furthermore, the slow increase of the star formation process, its duration, as well as the high absolute value of the maximum suggest that this could be produced by a recent merger with a gas-rich satellite galaxy that could have started between about 5 and 7 Gyr ago. However, an analysis of other stellar parameters (e.g. metallicities) would be needed to favour this hypothesis over other possible scenarios.

Nature Research Highlights

A&A publication

On April 25, 2019, the National ScienceFoundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) and theEuropean-based Virgo detector registered gravitational waves from what appearslikely to be a crash between two neutron stars—the dense remnants of massivestars that previously exploded. One day later, on April 26, the LIGO-Virgonetwork spotted another candidate source with a potentially interesting twist:it may in fact have resulted from the collision of a neutron star and blackhole, an event never before witnessed.

"The universe is keeping us on our toes,"says Patrick Brady, spokesperson for the LIGO Scientific Collaboration and aprofessor of physics at the University of Wisconsin-Milwaukee. "We'reespecially curious about the April 26 candidate. Unfortunately, the signal israther weak. It's like listening to somebody whisper a word in a busy café; itcan be difficult to make out the word or even to be sure that the personwhispered at all. It will take some time to reach a conclusion about thiscandidate."

"NSF's LIGO, in collaboration with Virgo,has opened up the universe to future generations of scientists," says NSFDirector France Cordova. "Once again, we have witnessed the remarkablephenomenon of a neutron star merger, followed up closely by another possiblemerger of collapsed stars. With these new discoveries, we see the LIGO-Virgocollaborations realizing their potential of regularly producing discoveriesthat were once impossible. The data from these discoveries, and others sure tofollow, will help the scientific community revolutionize our understanding ofthe invisible universe."

The discoveries come just weeks after LIGO andVirgo turned back on. The twin detectors of LIGO—one inWashington and one in Louisiana—along with Virgo, located at the EuropeanGravitational Observatory (EGO) in Italy, resumed operations April 1, after undergoinga series of upgrades to increase their sensitivities to gravitational waves—ripplesin space and time. Each detector now surveys larger volumes of the universe thanbefore, searching for extreme events such as smash-ups between black holes andneutron stars.

"Joining human forces and instruments across the LIGOand Virgo collaborations has been once again the recipe of an incomparablescientific month, and the current observing run will comprise 11 more months,"says Giovanni Prodi, the Virgo Data AnalysisCoordinator, at the University of Trento and theIstituto Nazionale di Fisica Nucleare (INFN) in Italy. "The Virgodetector works with the highest stability, covering the sky 90 percent of thetime with useful data. This is helping in pointing to the sources, both whenthe network is in full operation and at times when only one of the LIGOdetectors is operating. We have a lot of groundbreaking research work ahead."

In addition to the two new candidatesinvolving neutron stars, the LIGO-Virgo network has, in this latest run, spottedthree likely black hole mergers. In total, since making history with thefirst-ever direct detection of gravitational wavesin 2015, the network has spotted evidence for two neutron star mergers; 13black hole mergers; and one possible black hole-neutron star merger.

When two black holes collide, they warp thefabric of space and time, producing gravitational waves. When two neutron starscollide, they not only send out gravitational waves but also light. That meanstelescopes sensitive to light waves across the electromagnetic spectrum canwitness these fiery impacts together with LIGO and Virgo. One suchevent occurred in August 2017: LIGO andVirgo initially spotted a neutron star merger in gravitational waves and then,in the days and months that followed, about 70 telescopes on the ground and inspace witnessed the explosive aftermath in light waves, including everythingfrom gamma rays to optical light to radio waves.

In the case of the two recent neutron starcandidates, telescopes around the world once again raced to track the sourcesand pick up the light expected to arise from these mergers. Hundreds ofastronomers eagerly pointed telescopes at patches of sky suspected to house thesignal sources. However, at this time[MOU1] , neither of the sources has beenpinpointed.

"The search for explosive counterparts ofthe gravitational-wave signal is challenging due to the amount of sky that mustbe covered and the rapid changes in brightness that are expected," saysBrady. "The rate of neutron star merger candidates being found with LIGOand Virgo will give more opportunities to search for the explosions over thenext year."

The April 25 neutron star smash-up, dubbed S190425z,is estimated to have occurred about 500 million light-years away from Earth. Onlyone of the twin LIGO facilities picked up its signal along with Virgo (LIGOLivingston witnessed the event but LIGO Hanford was offline.) Because only twoof the three detectors registered the signal, estimates of the location in thesky from which it originated were not precise, leaving astronomers to survey nearlyone-quarter of the sky for the source.

The possible April 26 neutron star-black holecollision (referred to asS190426c) is estimated to have taken placeroughly 1.2 billion light-years away. It was seen by all three LIGO-Virgofacilities, which helped better narrow its location to regions covering about 1,100square degrees, or about 3 percent of the total sky.

"The latest LIGO-Virgo observing run isproving to be the most exciting one so far," says David H. Reitze ofCaltech, Executive Director of LIGO. "We're already seeing hints of thefirst observation of a black hole swallowing a neutron star. If it holds up,this would be a trifecta for LIGO and Virgo—in three years, we'll have observedevery type of black hole and neutron star collision. But we've learned thatclaims of detections require a tremendous amount of painstaking work—checkingand rechecking—so we'll have to see where the data takes us."

LIGOis funded by NSF and operated by Caltech and MIT, which conceived of LIGO andled the Initial and Advanced LIGO projects. Financial support for the AdvancedLIGO project was led by the NSF with Germany (Max Planck Society), the U.K.(Science and Technology Facilities Council) and Australia (Australian ResearchCouncil-OzGrav) making significant commitments and contributions to theproject. Approximately 1,300 scientists from around the world participate inthe effort through the LIGO Scientific Collaboration, which includes the GEOCollaboration. A list of additional partners is available at https://my.ligo.org/census.php.

TheVirgo Collaboration is currently composed of approximately 350 scientists,engineers, and technicians from about 70 institutes from Belgium, France,Germany, Hungary, Italy, the Netherlands, Poland, and Spain. The EuropeanGravitational Observatory (EGO) hosts the Virgo detector near Pisa in Italy,and is funded by Centre National de la Recherche Scientifique (CNRS) in France,the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, and Nikhef in theNetherlands. A list of the Virgo Collaboration members can be found at http://public.virgo-gw.eu/the-virgo-collaboration/. More information is available on the Virgo websiteat http://www.virgo-gw.eu.

MEDIA CONTACTS

Caltech
Whitney Clavin
wclavin@caltech.edu
626-390-9601

MIT
Abigail Abazorius
abbya@mit.edu
617-253-2709

Virgo
Livia Conti
livia.conti@pd.infn.it
+39 049 8068 826

National Science Foundation
Josh Chamot
jchamot@nsf.gov
703-292-4489

LIGO Scientific CollaborationSpokesperson/University of Wisconsin-Milwaukee
John Schumacher
schuma63@uwm.edu
(414) 229-6778

[MOU1]We should double check this is still true before we press send

Astronomers have discovered rapidly swinging jets coming from a black hole almost 8000 light-years from Earth.

Schematic artist’s impression of the changing jet orientation in V404 Cygni. Each segment (as separated by the clock hands) shows the jets at a different time, oriented in different directions as seen in our high angular resolution radio imaging.

Published today in the journal Nature, the research shows jets from V404 Cygni's black hole behaving in a way never seen before on such short timescales. The jets appear to be rapidly rotating with high-speed clouds of plasma—potentially just minutes apart—shooting out of the black hole in different directions. They used observations from the Very Long Baseline Array, a continent-sized radio telescope made up of 10 dishes across the United States, from the Virgin Islands in the Caribbean to Hawaii.

The lead author is the Associate Professor James Miller-Jones, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR). He considers black holes as the most extreme objects in the Universe. “This is one of the most extraordinary black hole systems I’ve ever come across,” Associate Professor Miller-Jones says, “Like many black holes, it’s feeding on a nearby star, pulling gas away from the star and forming a disk of material that encircles the black hole and spirals towards it under gravity”.

V404 Cygni was first identified as a black hole in 1989, when it released a big outburst of jets and material. “What’s different in V404 Cygni is that we think the disk of material and the black hole are misaligned, probably causing the inner part of the disk to wobble like a spinning top, and fire jets out in different directions as it changes orientation.”

Artist's impression of V404 Cygni seen close up. The binary star system consists of a normal star in orbit with a black hole. Material from the star falls towards the black hole and spirals inwards in an accretion disk, with powerful jets being launched from the inner regions close to the black hole. Credit: ICRAR

Astronomers had found previous outbursts looking at archival photographic plates from 1938 and 1956. When V404 Cygni experienced a two-week long outburst in 2015, telescopes around the world tuned in to study what was going on. The team then saw its jets behaving in a way never seen before. Where jets are usually thought to shoot straight out from the poles of black holes, these ones were shooting out in different directions at different times.

Professor Miller-Jones thought that the change in the movement of the jets was because of the accretion disk, which in V404 Cygni’s measures 10 million kilometres wide, “You can thinkof it like the wobble of a spinning top as it slows down—only in this case, the wobble is causedby Einstein’s theory of general relativity.”

Artist's impression of the inner parts of the accretion disk in V404 Cygni. The black hole rotates about a different axis to the binary orbit. As the spinning black hole drags spacetime around with it, the puffed-up inner accretion disk wobbles around like a spinning top. The jets launched from the innermost parts of the flow are redirected, either by the puffed-up inner disk or the strong winds being driven off it by the intense radiation. Credit: ICRAR

One of the co-authors of the study is Alex Tetarenko, a recent PhD graduate from the University of Alberta and currently an East Asian Observatory fellow working in Hawaii.“Typically, radio telescopes produce a single image from several hours of observation,” shesaid. “But these jets were changing so fast that in a four-hour image we just saw a blur. It was like trying to take a picture of a waterfall with a one-second shutter speed.” Instead, the researchers produced 103 individual images, each about 70 seconds long, and joined them together into a movie so they could see those changes over a very short time period.

This paper is the latest of a series of publications, resulting from a long project to study relativistic jets in binary systems of black holes and neutron stars. The astrophysicist Dr. Simone Migliari is a visiting scholar at ICCUB, and currently works as a Senior Operations Scientist at the XMM-Newton Science Operations Centre of European Space Agency. He has been collaborating with the project during several years. In this concrete publication, he participated in the theoretical discussion of the results, particularly in those concerning the relations between the radio jet and the X-ray emission from the misaligned disk.

“Because of the effects of its extreme gravity, you wouldn’t expect matter to be able to escape from the region of the disk closest to the black hole. Yet, from this very region, matter is ejected at a significant fraction of the speed of light in form of jets”, Migliari says. This study unveils more information about the closest regions to the black hole, still a matter of a study. “The misalignment between the disk of material and the black hole gives us information about the geometry and the behaviour of the matter around it”.

This finding adds knowledge to the recent discoveries of the gravitational waves and the first image of a black hole.

The project intends to develop a new hybrid detector with a very high time resolution, close to 10 ps, even for a single photon and for large detection areas. The performance of this sensor will be at least one order of magnitude better than any existing technology. It shall bring a revolution in medical imaging by enabling reconstruction-less PET based on Time-Of-Flight (TOF) measurements. Other application areas as transport, autonomous driving, cargo scanning, molecular imaging or particle physics experiments would also benefit from 10 ps TOF. The project will be carried out in close collaboration with CERN microelectronics and detector groups.

The ATTRACT Consortium launched the call last August, searching for the 170 best ideas. The received proposals have been peer-reviewed by an Independent R&D&I Committee of top experts in the field of detection and imaging technologies. The selected proposals will receive €100,000 of seed funding each to develop the concepts further during one year. At the end of that period, the funded projects will then present their results in a Final Assessment Conference in Brussels. The first meeting will take place on May 20th, at the CERN headquarters in Switzerland, where the proposals and projects will be presented.

The ATTRACT Consortium is a research initiative born in August 2018. Funded by the European Union’s Horizon 2020 and participated by several institutions, it is a pioneer initiative aimed to bring together both the European’s fundamental research and the industry.

The main goal is to enhance the growth and potential of fundamental research in the development of breakthrough detection and imaging technologies, for both scientific and commercial use. The project also wants to promote a bigger return on Europe’s scientific investment, that will benefit both the economy and society, building bridges between the research infrastructures and the private sector.