From National Aeronautics and Space Administration (US) Chandra X-ray Telescope (US): “MG B2016+112 “X-ray Magnifying Glass” Enhances View of Distant Black Holes”

From National Aeronautics and Space Administration (US) Chandra X-ray Telescope (US)

National Aeronautics and Space Administration(US) Chandra X-ray telescope(US)

August 31, 2021

Media contacts:
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu

Molly Porter
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
molly.a.porter@nasa.gov

Astronomers have used an “X-ray magnifying glass” to study a black hole system in the early Universe.

The amplification and magnification of light by an intervening galaxy allowed the detection of two distant X-ray-emitting objects.

The objects are either two growing supermassive black holes, or one such black hole and a jet.

This result helps us understand the growth of black holes in the early Universe and the possible existence of systems with multiple black holes.

By taking advantage of a natural lens in space, astronomers have captured an unprecedented look at X-rays from a black hole system in the early Universe.

This magnifying glass was used to sharpen X-ray images for the first time using NASA’s Chandra X-ray Observatory. It captured details about black holes that would normally be too distant to study using existing X-ray telescopes.

Astronomers applied a phenomenon known as “gravitational lensing” that occurs when the path taken by light from distant objects is bent by a large concentration of mass, such as a galaxy, that lies along the line of sight.

Gravitational Lensing National Aeronautics Space Agency (USA) and European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)

This lensing can magnify and amplify the light by large amounts and create duplicate images of the same object. The configuration of these duplicate images can be used to decipher the complexity of the object and sharpen images.

The gravitationally-lensed system in the new study is called MG B2016+112. The X-rays detected by Chandra were emitted by this system when the Universe was only 2 billion years old compared to its current age of nearly 14 billion years.

“Our efforts to see and understand such distant objects in X-rays would be doomed if we didn’t have a natural magnifying glass like this,” said Dan Schwartz of The Center for Astrophysics | Harvard & Smithsonian (CfA), who led the study.

The latest research builds on earlier work led by co-author Cristiana Spingola, currently at the Institute for Radio Astronomy of Bologna [Istituto di Radioastronomia di Bologna] (IT). Using radio observations of MG B2016+112, her team found evidence for a pair of rapidly growing supermassive black holes separated by only about 650 light years. They found that both of the black hole candidates possibly have jets.

Using a gravitational lensing model based on the radio data, Schwartz and his colleagues concluded that the three X-ray sources they detected from the MG B2016+112 system must have resulted from the lensing of two distinct objects. These two X-ray-emitting objects are likely a pair of growing supermassive black holes or a growing supermassive black hole and its jet. The estimated separation of these two objects is consistent with the radio work.

Previous Chandra measurements of pairs or trios of growing supermassive black holes have generally involved objects much closer to Earth, or with much larger separations between the objects. An X-ray jet at an even larger distance from Earth has previously been observed, with light emitted when the Universe was only 7% of its current age. However, the emission from the jet is separated from the black hole by about 160,000 light years.

The present result is important because it provides crucial information about the speed of growth of black holes in the early Universe and the detection of a possible double black hole system. The gravitational lens amplifies the light from these far-flung objects that otherwise would be too faint to detect. The detected X-ray light from one of the objects in MG B2016+112 may be up to 300 times brighter than it would have been without the lensing.

“Astronomers have discovered black holes with masses billions of times greater than that of our Sun being formed just hundreds of millions of years after the big bang, when the Universe was only a few percent of its current age,” said Spingola. “We want to solve the mystery of how these supermassive black holes gained mass so quickly.”

The boosts from gravitational lensing may enable researchers to estimate how many systems containing two supermassive black holes have separations small enough to produce gravitational waves observable in the future with space-based detectors.

“In many ways, this result is an exciting proof-of-concept of how this ‘magnifying glass’ can help us reveal physics of the distant supermassive black holes in a novel approach. Without this effect Chandra would have had to observe it a few hundred times longer and even then would not reveal the complex structures,” said co-author Anna Barnacka of the CfA and Jagiellonian University Krakow [Uniwersytet Jagielloński] Astronomical Observatory (PL), who developed the techniques for turning gravitational lenses into high-resolution telescopes to sharpen the images.

“Thanks to gravitational lensing much longer Chandra observations may be able to distinguish between the black hole pair and the black hole plus jet explanations. We also look forward to applying this technique in the future, especially as surveys by major new optical and radio facilities that will soon come on line will supply tens of thousands of targets,” concluded Schwartz.

The uncertainty in the X-ray position of one of the objects in MG B2016+112 is 130 light years in one dimension and 2,000 light years in the other, perpendicular dimension. This means that the size of the area where the source is likely located is more than 100 times smaller than the corresponding area for a typical Chandra source that is not lensed. Such precision in a position determination is unparalleled in X-ray astronomy for a source at this distance.

A paper describing these results appears in the August issue of The Astrophysical Journal.

See the full article here and here.

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

In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to National Aeronautics and Space Administration (US) by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at NASA’s Marshall Space Flight Center(US) and the Harvard Smithsonian Center for Astrophysics(US) . In the meantime, in 1978, NASA launched the first imaging X-ray telescope, Einstein (HEAO-2), into orbit. Work continued on the AXAF project throughout the 1980s and 1990s. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments. AXAF’s planned orbit was changed to an elliptical one, reaching one third of the way to the Moon’s at its farthest point. This eliminated the possibility of improvement or repair by the space shuttle but put the observatory above the Earth’s radiation belts for most of its orbit. AXAF was assembled and tested by TRW (now Northrop Grumman Aerospace Systems) in Redondo Beach, California.

AXAF was renamed Chandra as part of a contest held by NASA in 1998, which drew more than 6,000 submissions worldwide. The contest winners, Jatila van der Veen and Tyrel Johnson (then a high school teacher and high school student, respectively), suggested the name in honor of Nobel Prize–winning Indian-American astrophysicist Subrahmanyan Chandrasekhar. He is known for his work in determining the maximum mass of white dwarf stars, leading to greater understanding of high energy astronomical phenomena such as neutron stars and black holes. Fittingly, the name Chandra means “moon” in Sanskrit.

Originally scheduled to be launched in December 1998, the spacecraft was delayed several months, eventually being launched on July 23, 1999, at 04:31 UTC by Space Shuttle Columbia during STS-93. Chandra was deployed from Columbia at 11:47 UTC. The Inertial Upper Stage’s first stage motor ignited at 12:48 UTC, and after burning for 125 seconds and separating, the second stage ignited at 12:51 UTC and burned for 117 seconds. At 22,753 kilograms (50,162 lb), it was the heaviest payload ever launched by the shuttle, a consequence of the two-stage Inertial Upper Stage booster rocket system needed to transport the spacecraft to its high orbit.

Chandra has been returning data since the month after it launched. It is operated by the SAO at the Chandra X-ray Center in Cambridge, Massachusetts, with assistance from Massachusetts Institute of Technology(US) and Northrop Grumman Space Technology. The ACIS CCDs suffered particle damage during early radiation belt passages. To prevent further damage, the instrument is now removed from the telescope’s focal plane during passages.

Although Chandra was initially given an expected lifetime of 5 years, on September 4, 2001, NASA extended its lifetime to 10 years “based on the observatory’s outstanding results.” Physically Chandra could last much longer. A 2004 study performed at the Chandra X-ray Center indicated that the observatory could last at least 15 years.

In July 2008, the International X-ray Observatory, a joint project between European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), NASA and Japan Aerospace Exploration Agency (JAXA) (国立研究開発法人宇宙航空研究開発機構](JP), was proposed as the next major X-ray observatory but was later cancelled. ESA later resurrected a downsized version of the project as the Advanced Telescope for High Energy Astrophysics (ATHENA), with a proposed launch in 2028.

European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Athena spacecraft depiction

On October 10, 2018, Chandra entered safe mode operations, due to a gyroscope glitch. NASA reported that all science instruments were safe. Within days, the 3-second error in data from one gyro was understood, and plans were made to return Chandra to full service. The gyroscope that experienced the glitch was placed in reserve and is otherwise healthy.

From ALMA(CL): “EHT pinpoints dark heart of the nearest radio galaxy”

European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU)/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

From ALMA(CL)

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An international team anchored by the Event Horizon Telescope (EHT) Collaboration, which is known for capturing the first image of a black hole in the galaxy Messier 87, has now imaged the heart of the nearby radio galaxy Centaurus A in unprecedented detail. The astronomers pinpoint the location of the central supermassive black hole and reveal how a gigantic jet is being born. Most remarkably, only the outer edges of the jet seem to emit radiation, which challenges our theoretical models of jets. This work, led by Michael Janssen from the MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) in Bonn and Radboud University Nijmegen [Radboud Universiteit](NL) is published in Nature Astronomy on July 19th.

At radio wavelengths Centaurus A emerges as one of the largest and brightest objects in the night sky. After it was identified as one of the first known extragalactic radio sources in 1949, Centaurus A has been studied extensively across the entire electromagnetic spectrum by a variety of radio, infrared, optical, X-ray, and gamma-ray observatories. At the center of Centaurus A lies a black hole with the mass of 55 million suns, which is right between the mass scales of the Messier 87 black hole (six and a half billion suns) and the one in the center of our own galaxy (about four million suns).

In a new paper in Nature Astronomy, data from the 2017 EHT observations have been analyzed to image Centaurus A in unprecedented detail. “This allows us for the first time to see and study an extragalactic radio jet on scales smaller than the distance light travels in one day. We see up close and personally how a monstrously gigantic jet launched by a supermassive black hole is being born”, says astronomer Michael Janssen.

Highest resolution image of Centaurus A obtained with the Event Horizon Telescope on top of a color composite image of the entire galaxy. Credit: Radboud University; European Southern Observatory [Observatoire européen austral][Europäische Südsternwarte] (EU) (CL)/WFI; MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) A. Weiss et al./ESO/APEX/; National Aeronautics Space Agency (US)/Chandra X-ray Center (US)/ R. Kraft et al.Harvard Smithsonian Center for Astrophysics (US)/; M. Janssen et al. EHT.

National Aeronautics and Space Administration Chandra X-ray telescope(US)

Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla (CL)

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE)European Southern Observatory(EU)2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

European Southern Observatory(EU) MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

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Event Horizon Telescope Array

Arizona Radio Observatory

University of Arizona Radio Observatory(US) at NOAO Kitt Peak National Observatory(US), AZ USA, U Arizona Department of Astronomy and Steward Observatory(US) at altitude 2,096 m (6,877 ft).

ESO APEX
European Southern Observatory(EU) MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE) ESO’s Atacama Pathfinder Experiment(CL) high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

CARMA
Combined Array for Research in Millimeter-wave Astronomy (CARMA Array for Research in Millimeter-wave Astronomy(US)), in the Inyo Mountains to the east of the California Institute of Technology Owens Valley Radio Observatory(US), at a site called Cedar Flat, Altitude 1,222 m (4,009 ft), relocated to Owens Valley Radio Observatory, Altitude 1,222 m (4,009 ft).

NAOJ Atacama Submillimeter Telescope Experiment (ASTE)

NAOJ Atacama Submillimeter Telescope Experiment (ASTE) deployed to its site on Pampa La Bola, near Cerro Chajnantor and the Llano de Chajnantor, Observatory in northern Chile, Altitude 4,800 m (15,700 ft).

CfA Submillimeter Observatory

CFA Harvard Smithsonian Submillimeter Array on MaunaKea, Hawaii, USA, Altitude 4,205 m (13,796 ft).

Greenland Telescope

The Greenland Telescope is an international collaboration between: The Academia Sinica Institute of Astronomy and Astrophysics(project leaders); The Smithsonian Astrophysical Observatory of the Harvard–Smithsonian Center for Astrophysics (US) The The National Radio Astronomy Observatory(US); and The Haystack Observatory of the Massachusetts Institute of Technology(US) at an altitude of 3,210 meters (10,530 feet).

(IRAM) 30m
Institute of Radio Astronomy [Institut de Radioastronomie Millimétrique](ES) 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada, Altitude 2,850 m (9,350 ft).

IRAM NOEMA, France

IRAM-Institut de Radioastronomie Millimetrique (FR) NOEMA Interferometer in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter interferometer Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters.

James Clerk Maxwell Telescope

East Asian Observatory James Clerk Maxwell Telescope MaunaKea Hawai’i(US)altitude 4207 m (13802 ft) above sea level.

Large Millimeter Telescope Alfonso Serrano

The University of Massachusetts Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica MX Large Millimeter Telescope Alfonso Serrano, Mexico, at an altitude of 4850 meters on top of the Sierra Negra.

ESO/NRAO/NAOJ ALMA Array.
European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.[/caption]

South Pole Telescope

South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including The University of Chicago (US); The University of California Berkeley (US); Case Western Reserve University (US); Harvard/Smithsonian Astrophysical Observatory (US); The University of Colorado-Boulder (US); McGill University(CA); The University of Illinois, Urbana-Champaign (US); The University of California-Davis (US); Ludwig Maximilians Universität München(DE); DOE’s Argonne National Laboratory (US); and The National Institute for Standards and Technology (US). It is funded by the National Science Foundation(US)

Future Array/Telescopes

California Institute of Technology Owens Valley Radio Observatory(US), located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft).

Caltech Owens Valley Radio Observatory.
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Compared to all previous high-resolution observations, the jet launched in Centaurus A is imaged at a tenfold higher frequency and sixteen times sharper resolution. With the resolving power of the EHT, we can now link the vast scales of the source, which are as big as 16 times the angular diameter of the Moon on the sky, to their origin near the black hole in a region of merely the width of an apple on the Moon when projected on the sky. That is a magnification factor of one billion.

Understanding jets

Supermassive black holes residing in the center of galaxies like Centaurus A are feeding off gas and dust that is attracted by their enormous gravitational pull. This process releases massive amounts of energy and the galaxy is said to become ‘active’. Most matter lying close to the edge of the black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space: Jets – one of the most mysterious and energetic features of galaxies – are born.

Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still do not know exactly how jets are launched from its central region and how they can extend over scales that are larger than their host galaxies without dispersing out. The EHT aims to resolve this mystery.

The new image shows that the jet launched by Centaurus A is brighter at the edges compared to the center. This phenomenon is known from other jets, but has never been seen so pronouncedly before. “Now we are able to rule out theoretical jet models that are unable to reproduce this edge-brightening. It’s a striking feature that will help us better understand jets produced by black holes”, says Matthias Kadler, TANAMI leader and professor for astrophysics at the Julius Maximilian University of Würzburg [Julius-Maximilians-Universität Würzburg] (DE) in Germany.

Future observations

With the new EHT observations of the Centaurus A jet, the likely location of the black hole has been identified at the launching point of the jet. Based on this location, the researchers predict that future observations at an even shorter wavelength and higher resolution would be able to photograph the central black hole of Centaurus A. This will require the use of space-based satellite observatories.

“These data are from the same observing campaign that delivered the famous image of the black hole in M87. The new results show that the EHT provides a treasure trove of data on the rich variety of black holes and there is still more to come”, says Heino Falcke, EHT board member and professor for Astrophysics at Radboud University.

Additional Information

To observe the Centaurus A galaxy with this unprecedentedly sharp resolution at a wavelength of 1.3 mm, the EHT collaboration used Very Long Baseline Interferometry (VLBI), the same technique with which the famous image of the black hole in M87 was made.

European Very Long Baseline Interferometry Network

An alliance of eight telescopes around the world, of which ALMA is the most sensitive element, joined together to create the virtual Earth-sized Event Horizon Telescope. The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, North and South America.

The EHT consortium consists of 13 stakeholder institutes: the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona (US), the University of Chicago (US), the East Asian Observatory, Goethe University [Goethe-Universität] Frankfurt(DE), Institut de Radioastronomie Millimétrique (MPG/CNRS/IGN), Large Millimeter Telescope, MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE), MIT Haystack Observatory (US), National Astronomical Observatory of Japan [国立天文台](JP), Perimeter Institute for Theoretical Physics (CA), Radboud University Nijmegen [Radboud Universiteit](NL) and the Center for Astrophysics | Harvard Smithsonian Center for Astrophysics (US).

See the full article here .

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The Atacama Large Millimeter/submillimeter Array (ALMA) (CL) , an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO) (EU), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) (CA) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

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

ALMA is a time machine!

ALMA-In Search of our Cosmic Origins

From Netherlands Institute for Radio Astronomy (ASTRON) (NL) : “ASTRON reveals life cycle of supermassive black hole”

From Netherlands Institute for Radio Astronomy (ASTRON) (NL)

12 January 2021 [Just now in social media.]

Astronomers have used, for the first time, the combination of LOFAR [below] and WSRT-Apertif, the phased array upgrade of the Westerbork Synthesis Radio Telescope [below], to measure the life cycle of supermassive black holes emitting radio waves. This study, part of the LOFAR deep fields surveys, opens the possibility of timing this cycle for many objects in the sky and explore the impact it has on galaxy evolution.

Supermassive black holes are an important component of galaxies. When in their active phase, they eject huge amounts of energy, which eventually can expel gas and matter from galaxies and impact the entire formation of new stars.

These ejections represent only a phase in the lifecycle of a supermassive black hole. They are believed to last from tens of millions to a few hundreds of millions of years, only a short moment in the life of a galaxy. After this, the supermassive black hole enters a quiet phase. However, astronomers think that this cycle can actually repeat multiple times in which the black hole starts a new phase of ejections. But timing this cycle is hard because the timescales involved are far too long to be directly probed: other ways to easily measure them in a large number of objects are needed.

Radio wave ejections

Some of the energy – also called ‘flux’ – is ejected by the supermassive black hole in the form of radio waves. Both radio waves at low and high frequencies are emitted and can be detected by sensitive radio telescopes like LOFAR (low frequency radio waves) and WSRT-Apertif (high frequency radio waves). “High frequency radio waves quickly lose their energy – and, as consequence, their flux – while those in the lower frequency do so much more slowly,” Prof. Dr. Raffaella Morganti, first author of the paper in Astronomy and Astrophysics says.

Observing these supermassive black holes with both LOFAR and WSRT-Apertif, scientists have been able to say which supermassive black holes are, at present, ‘switched off’ and how long ago it happened. They also have identified a case where the ejection phase of the supermassive black hole has ‘recently’ restarted.

Dying supermassive black holes

In a previous study, LOFAR was used to find possible supermassive black holes in the dying or restarting phase, by taking advantage of their properties at low frequencies. In this study these same sources were surveyed also using WSRT-Apertif, and thus measuring radio waves at higher frequencies. The relative strength of the emission at these two frequencies is used to derive, to first order, how old a radio source is and whether it is already in a dying phase (see Figure 1).

Figure 1: LOFAR and WSRT-Apertif detection of supermassive black hole radio waves. The difference in flux at which LOFAR and WSRT-Apertif detect a supermassive black hole determines if it is in its ejection phase (a) or not (b). The lower the flux of b, the longer it has been since the supermassive black hole was in its ejection phase. © Studio Eigen Merk/ASTRON.

Morganti: “Because of our earlier studies using LOFAR, we knew the expected relative difference in flux between the lower and higher frequencies if the supermassive black holes are in the active, ejection phase. Comparing them with the, now available, Apertif data, we were able to tell, for each of them, whether the on-going activity was confirmed or whether the ejected phase had stopped.

“Interestingly, the relative number of radio galaxies found in the ‘out’ phase is also telling for how long a supermassive black hole has been ‘switched off’. These objects are rare, therefore large surveys are necessary to collect enough data about them so that we have a large enough data size for statistical analysis.”

Great combination

With this proof of concept study Morganti and colleagues have demonstrated that a combined survey of LOFAR and WSRT-Apertif can indeed detect the phase in which a supermassive black hole currently is. Morganti: “LOFAR is unique in sensitivity and spatial resolution at the low frequencies. And while there are other radio telescopes that can observe the higher frequencies, Apertif is now covering in-depth large areas of the northern sky, instead of focusing on a single source.” That is key, because Morganti and colleagues plan to chart all detectable supermassive black holes with radio emission, in order to learn more about the birth and life cycles of galaxies.

A next step will be to create an automated way to detect these sources over much larger areas, using the large surveys that LOFAR and Apertif are doing. This is too big a job to do manually for a small group and approaches like Radio Galaxy Zoo and machine learning will be the way forward.

Figure 2: Part of the radio sky observed by this project where many galaxies with supermassive black holes emitting radio waves can be seen. The colours give an indication of the phase in the active life of the supermassive black hole. The red colours represent emission from black holes, in the later phase, at the end of their active life. Greener colours represent black holes in their “youth”. © ASTRON.

See the full article here .

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ASTRON is the ASTRON-Netherlands Institute for Radio Astronomy [Nederlands Instituut voor Radioastronomie] (NL). Its main office is in Dwingeloo in the Dwingelderveld National Park in the province of Drenthe. ASTRON is part of Netherlands Organisation for Scientific Research (NWO).

ASTRON’s main mission is to make discoveries in radio astronomy happen, via the development of new and innovative technologies, the operation of world-class radio astronomy facilities, and the pursuit of fundamental astronomical research. Engineers and astronomers at ASTRON have an outstanding international reputation for novel technology development, and fundamental research in galactic and extra-galactic astronomy. Its main funding comes from NWO.

ASTRON’s programme has three principal elements:

The operation of front line observing facilities, including especially the Westerbork Synthesis Radio Telescope and LOFAR,
The pursuit of fundamental astronomical research using ASTRON facilities, together with a broad range of other telescopes around the world and space-borne instruments (e.g. Sptizer, HST etc.)
A strong technology development programme, encompassing both innovative instrumentation for existing telescopes and the new technologies needed for future facilities.

In addition, ASTRON is active in the international science policy arena and is one of the leaders in the international SKA project. The Square Kilometre Array will be the world’s largest and most sensitive radio telescope with a total collecting area of approximately one square kilometre. The SKA will be built in Southern Africa and in Australia. It is a global enterprise bringing together 11 countries from the 5 continents.

Radio telescopes

ASTRON operates the Westerbork Synthesis Radio Telescope (WSRT), one of the largest radio telescopes in the world. The WSRT and the International LOFAR Telescope (ILT) are dedicated to explore the universe at radio frequencies ranging from 10 MHz to 8 GHz.

Westerbork Synthesis Radio Telescope, an aperture synthesis interferometer near World War II Nazi detention and transit camp Westerbork, north of the village of Westerbork, Midden-Drenthe, in the northeastern Netherlands.

In addition to its use as a stand-alone radio telescope, the Westerbork array participates in the European Very Long Baseline Interferometry Network (EVN) of radio telescopes.

ASTRON is the host institute for the Joint Institute for VLBI in Europe (JIVE).

European Very Long Baseline Interferometry Network

Its primary task is to operate the EVN MkIV VLBI Data Processor (correlator). JIVE also provides a high-level of support to astronomers and the Telescope Network. ASTRON also hosts the NOVA Optical/ Infrared instrumentation group.

LOFAR is a radio telescope composed of an international network of antenna stations and is designed to observe the universe at frequencies between 10 and 250 MHz. Operated by ASTRON (NL), the network includes stations in the Netherlands, Germany, Sweden, the U.K., France, Poland and Ireland.

ASTRON Institute for Radio Astronomy(NL) LOFAR Radio Antenna Bank(NL)

From EarthSky: “How the world came to understand black holes” We cannot get enough of these stories.

From EarthSky

October 25, 2020
Sayali Avachat

Roger Penrose, Reinhard Genzel and Andrea Ghez. They are joint winners of 2020’s Nobel Prize in physics for their work on black holes. Credit: Nobel Media.

Earlier this month (October 6, 2020), the Nobel Prize in physics was announced for two groundbreaking discoveries in astrophysics, both centered on black holes. Half of 2020’s prize went to mathematician Roger Penrose of the University of Oxford (UK) “for the discovery that black hole formation is a robust prediction of the general theory of relativity.” The other half went jointly to Reinhard Genzel of the MPG Institut für extraterrestrische Physik(DE) in Germany and Andrea Ghez of University of California, Los Angeles, “for the discovery of a supermassive compact object at the center of our galaxy.”

It was a great moment for black hole physics as well as for the astronomy and astrophysics field in general. And it’s a wonderful time to contemplate the fascinating history of black hole science.

What are black holes?

Black holes are exotic objects in space. The classic scenario for black hole formation centers on a massive star that runs out of the internal fuel it needs to shine. The star collapses under the pull of its own self-gravity, leaving behind a high-density, compact object with an immense gravitational pull. A black hole is a place in space containing an object so dense and so compact that it forms a region around itself from which light cannot escape. The boundary of this region is known as an event horizon. Once past a black hole’s event horizon, the gravitational pull of the hole is inexorable.

If there is material in space near the black hole – and if this material draws too close – it’s pulled inside. But it doesn’t just drop all at once into the hole; instead, it forms a glowing disk surrounding the black hole called an accretion disk. Friction within the accretion disk can heat the disk to billions of degrees, causing it to emit radiation across the electromagnetic spectrum. Thus, although no light can escape a black hole, astronomers can observe black holes in space via their accretion disks.

What’s more, in the process of conservation of angular momentum, black holes can cause outbursts which come out perpendicular to the accretion disk. These outbursts are called jets by astronomers, and they can propel material out into space at relativistic speeds, that is, speeds that are a significant fraction of the speed of light (186,000 miles or 300,000 km per second). Astronomers can study black hole jets, too, to learn more about black holes.

Development of theories of black holes

All of the above was theory, developed in the 20th century. Albert Einstein’s General Theory of Relativity, published in 1916, contained the seeds of the modern concept of black holes, although the first ever mention of a similar concept is found in 1783, when an English natural philosopher by the name of John Michell theorized the existence of massive objects from which light cannot escape.

Einstein’s theory of relativity discusses the curvature of space-time as a result of gravity. This curvature causes an object to move along a curved path equivalent to a straight line in the absence of gravity. The theory allowed for the existence of matter packed in small and infinitely warped space. The theory was published as The Field Equations of Gravitation in 1915.

While serving in the German Army during World War I, astronomer and director of the Astrophysical Observatory in Potsdam Karl Schwarzschild was the first to solve Einstein’s field equations. His solution successfully described how space-time is curved, not just around a planet or a star, but also around theoretical high-density masses, such as black holes. In the space around an object that’s dense enough, and massive enough, gravity is so strong that even light – the fastest-moving stuff in the universe at 186,000 miles (300,000 km) per second – cannot escape. Thus it was Schwarzschild who first conceived of the event horizon, or boundary region around a black hole. Today, physicists speak of the Schwarzschild radius, which is (basically) the radius of a black hole’s event horizon. Schwarzschild’s solution to Einstein’s field equations also elegantly explained the concept of a singularity – the central point of a black hole – a point in space where all the laws of physics break down.

At first, this concept was considered a mathematical curiosity. Scientists, including Einstein, had no idea such objects could exist in nature.

But 50 years later, in 1965, Roger Penrose, working with the great theoretical physicist and cosmologist Stephen Hawking, showed that the black holes can indeed exist in nature and that they can form through a stable and robust process. And in fact, for some stars, black holes are the ultimate fate, an unavoidable outcome of stellar collapse.

The momentous work by Penrose and Hawking opened a new era in the study of black holes. Penrose’s work was also pivotal in showing how black holes emit energy through the Penrose process, in the form of jets and outbursts.

In the meantime, it was physicist John Wheeler who, in 1967, popularized the term black hole. Wheeler summarized Einstein’s equations as:

“Space-time tells matter how to move; matter tells space-time how to curve.”

Observations of black holes

Astronomers didn’t discover the first stellar-mass black hole – Cygnus X-1 – until after the middle of the 20th century.

Left: Image of Cygnus X-1 as observed by the Chandra X-ray observatory. Right: By now iconic artist’s concept of black hole accreting matter from its companion star. Image via (left) NASA/ CXC/ SAO; (right) NASA/ CXC/ M.Weiss.

A 1964 rocket flight revealed Cygnus X-1 as one of the strongest sources of X-rays that had yet been seen from Earth. By the 1970s, most astronomers believed Cygnus X-1 was indeed a black hole. It’s now thought to be a black hole with a mass some 14.8 times that of our sun and an event horizon with a radius of around 27 miles (44 km). That’s in contrast to our sun’s radius of about 433,000 miles (696,000 km).

Stellar-mass black holes are hard to find because of their quiescent nature. They might display short and unpredictable outbursts when some passing material strikes their accretion disks, after which they might go quiet for decades.

That is why it took the discovery of supermassive black holes at the centers of most galaxies, including our own Milky Way, to give black hole science its real boost.

Supermassive black holes

Today, astronomers believe that most galaxies harbor supermassive black holes in their centers. Supermassive black holes have masses equivalent to millions to billions of solar masses and are believed to form in the centers of galaxies around the same time as the galaxy is forming. Over 100,000 supermassive black hole candidates have been observed to date, many more than the number of known stellar-mass black holes.

Among the many observed black hole candidates, the one at the center of our own Milky Way galaxy is called Sagittarius A* (Sgr A*, pronounced Sagittarius A-star). Two independent studies carried out in the last 25 years, led by Andrea Ghez and Reinhard Genzel – joint winners of half of 2020’s Nobel prize in physics – mapped the stars orbiting an invisible object at the center of our Milky Way. Using the powerful telescopes at Keck Observatory in Hawaii and the Very Large Telescope in Chile, the teams focused on one star known as S0-2. S0-2 orbits closer to our galaxy’s central supermassive black hole than any other observed star.

Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, altitude 4,207 m (13,802 ft).

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

Knowing the orbital period of the star S0-2, its very elongated elliptical orbit and the distance of its closest approach to our galaxy’s central black hole enabled scientists to calculate the mass of Sgr A* as the equivalent of 4 million solar masses. The teams were able to observe two full orbits of the star S0-2 around the central black hole, which further bolstered their claims and also proved, through observations, what Einstein, Schwarzchild, and Penrose had predicted in theory about black holes.

SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the Milky Way.

Further validation of Einstein’s general theory of relativity came when, on April 10, 2019, the Event Horizon Telescope collaboration released the first-ever image of [the event horizon] of a black hole* in the relatively nearby (by cosmic standards) galaxy known as Messier 87, visible in the constellation Virgo.

The gargantuan black hole in Messier 87’s center, Messier 87*, weighs a whopping 6.5 billion solar masses.

Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration released on 10 April 2019.

The galaxy Messier 87 and its famous jet – an energetic outflow of high energy particles from its center – had been observed for several decades. However, this was the first ever successful attempt at direct imaging of its [event horizon]. The image shows a bright ring formed by the bending of light at the boundary of the black hole’s event horizon, caused by its extreme gravitational pull.

*One cannot speak of the image of the black hole itself, because no light emerges from the black hole. It is, after all, black. All that can be imaged is the event horizon which is the thin area which surrounds the black hole.

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From phys.org: “Black holes: devourers of stars reveal their secrets”

From phys.org

October 6, 2020

Messier 87 imaged by the Event Horizon Telescope.

EHT map.

A trio of scientists were awarded the Nobel Physics Prize on Tuesday for their research into black holes, some of the most mysterious objects in the universe that gobble stars like specks of dust.

Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the University of Oxford.
Andrea Ghez, UCLA Galactic Center Group.
Reinhard Genzel, Max Planck Institute for Extraterrestrial Physics, University of California, Berkeley.

So powerful they bend the laws of nature, not even Albert Einstein, the father of general relativity, was convinced they could exist.

Two varieties

A black hole is a celestial object that compresses a huge mass into an extremely small space. Their gravitational pull is so strong nothing can escape their maw, not even light.

This has made these exotic entities difficult to spot. But scientists now know a lot about black holes from the impact they have on their surroundings.

There are two kinds.

The first are garden-variety black holes that form when the centre of a very big star collapses in on itself, creating a supernova.

These can be up to 20 times more massive than the Sun, but are tiny in space.

Trying to see the one closest to Earth would be like looking for a human cell on the surface of the moon.

In contrast, so-called supermassive black holes—such as the one sitting at the centre of the Milky Way for which two of Tuesday’s laureates were awarded prizes—are at least a million times bigger than the Sun.

Last month, teams of scientists from the US and Europe detected for the first time a so-called “intermediate mass” black hole with 142 times the mass of the Sun. It was formed, they determined, from the merger of two smaller black holes.

Time stoppers

When he released it in November 1915, Einstein’s general theory of relativity upended all previously held concepts of space and time.

It described how everything, from the tiniest atom to the largest supernova, is held in the grip of gravity.

Since gravity is proportionate to mass, an extremely heavy entity has such a strong gravitational pull that it can bend space and slow time.

According to Einstein’s theory, an extremely heavy mass, such as a black hole, could stop time altogether.

Yet Einstein himself was not convinced that black holes existed.

It took British physicist Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the University of Oxford—honoured with the Nobel on Tuesday—to show that general relativity could result in these enormous, all-devouring objects.

Supermassive black hole

Perhaps the most famous black hole of all sits at the centre of our galaxy. At more than four million times the mass of our Sun, Sagittarius A* is a monster object responsible for the characteristic swirl of the stars in the Milky Way.

SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory.

SGR A and SGR A* from Penn State and NASA/Chandra.

But, since black holes devour light and are therefore invisible, for decades it was impossible to spot.

In the early 1990s, physicists Reinhard Genzel and Andrea Ghez each led a team of researchers using the latest technology to gaze at the heart of our galaxy.

But even with the world’s largest telescopes the teams were limited in what they could see by distortion caused by Earth’s atmosphere.

Keck Observatory, operated by Caltech and the University of California, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level.

The same effect that makes stars twinkle in the night sky was ruining the clarity of images taken of the Milky Way.

Genzel and Ghez helped develop new technology, including more sensitive digital light sensors and better smart optics, improving image resolution more than one thousandfold.

They used their new methods to track 30 of the brightest stars near the centre of the Milky Way.

One star, S2, was found to complete its orbit of the galaxy in less than 16 years. Our own Sun, by contrast, takes more than 200 million years to complete its lap.

Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the Milky Way.

The speed at which the stars were moving allowed both teams to conclude that it was a supermassive black hole driving the galactic swirl.

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From The New York Times: “At the Edge of Time, a Litter of Galactic Puppies”

From The New York Times

Oct. 1, 2020
Dennis Overbye

Eighteen quasars observed by the European Southern Observatory’s Very Large Telescope, one of several telescopes around the world that contributed to the discovery of SDSS J1030+0524 and its cluster or proto-galaxies. Credit: Borisova et al./ESO

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

Astronomers announced on Thursday that they had discovered a giant black hole surrounded by a litter of young protogalaxies that date to the early universe — the beginning of time.

The black hole, which powers a quasar known as SDSS J1030+0524, weighed in at a billion solar masses when the universe was only 900 million years old. It and its brood, the astronomers said, represented the infant core of what became a vast cluster of galaxies millions of light years across and encompassing a trillion suns worth of matter.

The discovery should help astronomers understand the origins of galactic clusters— the largest structures in the universe — and how supermassive black holes could have grown so quickly in the early universe. And it provides a rare glimpse of the cosmic web, a network of filaments spanning the cosmos that determine the large-scale distribution of matter in the universe.

“This research was mainly driven by the desire to understand some of the most challenging astronomical objects — supermassive black holes in the early universe,” said Marco Mignoli, an astronomer at the National Institute for Astrophysics in Bologna, Italy, in a statement. “These are extreme systems, and to date we have had no good explanation for their existence.”

Dr. Mignoli was the lead author of a paper published Thursday in Astronomy & Astrophysics summarizing a decade-long observation campaign that used some of the biggest and most powerful telescopes in the world, including the Hubble Space Telescope, the European Southern Observatory’s Very Large Telescope in Chile [above], the Keck II Telescope on Mauna Kea in Hawaii and the Large Binocular Telescope on Mount Graham in Arizona.

NASA/ESA Hubble Telescope.

Keck Observatory, two 10 meter telescopes operated by Caltech and the University of California, Maunakea Hawaii USA, altitude 4,207 m (13,802 ft).

U Arizona Large Binocular Telescope, Interferometer, or LBTI, is a ground-based instrument connecting two 8-meter class telescopes on Mount Graham, Arizona, USA, Altitude 3,221 m (10,568 ft.) 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 credit: NASA/JPL-Caltech.

Astronomers have long thought that black holes and massive galaxies should appear earliest and grow fastest at the dense nodes where these filaments cross, where there is abundant gas to feed them. The new results suggest this is true, said team member Colin Norman of Johns Hopkins University, in an email.

Although the idea of the cosmic web is widely accepted, Alan Dressler of the Carnegie Observatories, who was not part of this work, said in an email that the web has not been “mapped” in the usual sense of the word. “Only a few places, near galaxies (like this one, the big one with the black hole) where it is sufficiently ‘lit up,’” he said. “And even then, it took a big telescope, a remarkable instrument, and a lot of time to see this structure.”

Dr. Mignoli and an international team of astronomers have been searching for signs of over-density around very distant, very early quasars.

Astronomers measure cosmic time and distance in the expanding universe by the degree to which light from receding objects has been lengthened, or redshifted, in wavelength, by the same phenomenon that makes a retreating siren drop in pitch.

The quasar SDSS J1030+0524 clocked in with a redshift of 6.31, meaning that light waves from it — indeed, the size of the whole universe — have been stretched by a factor of 7.31 since the time of the quasar. That corresponds to when the universe was 900 million years old, according to conventional cosmological calculations. That means it took 12.9 billion years for the light from that quasar to reach Earth, making it one of the most distant quasars ever discovered.

In images from the Hubble and other telescopes, the quasar was surrounded by myriad faint objects. The astronomers proceeded to track them down and make spectroscopic measurements.

“These objects are actually star-forming galaxies,” said Roberto Gilli, another team member. The objects were selected for further study based partly on their very red colors and other spectral characteristics, he said. Six had similar redshifts — between 6.129 and 6.355 — over a volume in space of about 27 billion cubic light-years.

Within that volume, the authors determined, were about a trillion solar masses of material, about as much material as is contained in a giant cluster of galaxies today, making that region twice as dense as regular space.

“This is the first spectroscopic identification of a galaxy overdensity around a supermassive black hole in the first billion years of the universe,” the astronomers wrote in their paper. The finding, they added, lent support to the idea that the most distant and massive black holes formed and grew within massive halos of dark matter in large-scale structures, “and that the absence of earlier detections of such systems is likely due to observational limitations.”

But those limitations will last forever, Dr. Dressler noted. One of the primary goals for the next generation of “super telescopes,” like the Giant Magellan Telescope and the European Extremely Large Telescope, both now being built in Chile, and the Thirty Meter Telescope proposed for Hawaii’s Mauna Kea, is to map out this web with greater fidelity.

Giant Magellan Telescope, 21 meters, to be at the Carnegie Institution for Science’s Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high.

ESO/E-ELT, 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

TMT-Thirty Meter Telescope, proposed and now approved for Mauna Kea, Hawaii, USA4,207 m (13,802 ft) above sea level, the only giant 30 meter class telescope for the Northern hemisphere.

“The added light-gathering power of the next generation will allow us to use faint young galaxies to serve as the back lights” illuminating the faint filaments of atomic matter, Dr. Dressler said. Until now, what is known about the web has come from using quasars as back lights. But faint galaxies are 10 to 100 times more plentiful on the sky, Dr. Dressler said, “so you can start making a good ‘picture’ of the web.”

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From European Southern Observatory: “ESO telescope spots galaxies trapped in the web of a supermassive black hole”

From European Southern Observatory

1 October 2020

Marco Mignoli
INAF Bologna
Bologna, Italy
Tel: +39 051 6357 382
Email: marco.mignoli@inaf.it

Roberto Gilli
INAF Bologna
Bologna, Italy
Tel: +39 051 6357 383
Email: roberto.gilli@inaf.it

Barbara Balmaverde
INAF Torino
Pino Torinese, Italy
Email: barbara.balmaverde@inaf.it

Colin Norman
Johns Hopkins University
Baltimore, USA
Email: norman@stsci.edu

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: pio@eso.org

With the help of ESO’s Very Large Telescope (VLT) [below] , astronomers have found six galaxies lying around a supermassive black hole when the Universe was less than a billion years old. This is the first time such a close grouping has been seen so soon after the Big Bang and the finding helps us better understand how supermassive black holes, one of which exists at the centre of our Milky Way, formed and grew to their enormous sizes so quickly.

Sgr A* from ESO VLT.

SGR A and SGR A* from Penn State and NASA/Chandra.

It supports the theory that black holes can grow rapidly within large, web-like structures which contain plenty of gas to fuel them.

“This research was mainly driven by the desire to understand some of the most challenging astronomical objects — supermassive black holes in the early Universe. These are extreme systems and to date we have had no good explanation for their existence,” said Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna, Italy, and lead author of the new research published today in Astronomy & Astrophysics.

The new observations with ESO’s VLT revealed several galaxies surrounding a supermassive black hole, all lying in a cosmic “spider’s web” of gas extending to over 300 times the size of the Milky Way. “The cosmic web filaments are like spider’s web threads,” explains Mignoli. “The galaxies stand and grow where the filaments cross, and streams of gas — available to fuel both the galaxies and the central supermassive black hole — can flow along the filaments.”

The light from this large web-like structure, with its black hole of one billion solar masses, has travelled to us from a time when the Universe was only 0.9 billion years old. “Our work has placed an important piece in the largely incomplete puzzle that is the formation and growth of such extreme, yet relatively abundant, objects so quickly after the Big Bang,” says co-author Roberto Gilli, also an astronomer at INAF in Bologna, referring to supermassive black holes.

The very first black holes, thought to have formed from the collapse of the first stars, must have grown very fast to reach masses of a billion suns within the first 0.9 billion years of the Universe’s life. But astronomers have struggled to explain how sufficiently large amounts of “black hole fuel” could have been available to enable these objects to grow to such enormous sizes in such a short time. The new-found structure offers a likely explanation: the “spider’s web” and the galaxies within it contain enough gas to provide the fuel that the central black hole needs to quickly become a supermassive giant.

But how did such large web-like structures form in the first place? Astronomers think giant halos of mysterious dark matter are key. These large regions of invisible matter are thought to attract huge amounts of gas in the early Universe; together, the gas and the invisible dark matter form the web-like structures where galaxies and black holes can evolve.

“Our finding lends support to the idea that the most distant and massive black holes form and grow within massive dark matter halos in large-scale structures, and that the absence of earlier detections of such structures was likely due to observational limitations,” says Colin Norman of Johns Hopkins University in Baltimore, US, also a co-author on the study.

The galaxies now detected are some of the faintest that current telescopes can observe. This discovery required observations over several hours using the largest optical telescopes available, including ESO’s VLT. Using the MUSE and FORS2 instruments on the VLT at ESO’s Paranal Observatory in the Chilean Atacama Desert, the team confirmed the link between four of the six galaxies and the black hole.

ESO MUSE on the VLT on Yepun (UT4).

ESO FORS2 VLT mounted on Unit Telescope 1 (Antu).

“We believe we have just seen the tip of the iceberg, and that the few galaxies discovered so far around this supermassive black hole are only the brightest ones,” said co-author Barbara Balmaverde, an astronomer at INAF in Torino, Italy.

These results contribute to our understanding of how supermassive black holes and large cosmic structures formed and evolved. ESO’s Extremely Large Telescope, currently under construction in Chile, will be able to build on this research by observing many more fainter galaxies around massive black holes in the early Universe using its powerful instruments.

More information

The team is composed of M. Mignoli (INAF, Bologna, Italy), R. Gilli (INAF, Bologna, Italy), R. Decarli (INAF, Bologna, Italy), E. Vanzella (INAF, Bologna, Italy), B. Balmaverde (INAF, Pino Torinese, Italy), N. Cappelluti (Department of Physics, University of Miami, Florida, USA), L. Cassarà (INAF, Milano, Italy), A. Comastri (INAF, Bologna, Italy), F. Cusano (INAF, Bologna, Italy), K. Iwasawa (ICCUB, Universitat de Barcelona & ICREA, Barcelona, Spain), S. Marchesi (INAF, Bologna, Italy), I. Prandoni (INAF, Istituto di Radioastronomia, Bologna, Italy), C. Vignali (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy & INAF, Bologna, Italy), F. Vito (Scuola Normale Superiore, Pisa, Italy), G. Zamorani (INAF, Bologna, Italy), M. Chiaberge (Space Telescope Science Institute, Maryland, USA), C. Norman (Space Telescope Science Institute & Johns Hopkins University, Maryland, USA).

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ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre EEuropean Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

ESO/Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres.

ESO VLT at Cerro Paranal in the Atacama Desert.

ESO VLT 4 lasers on Yepun.

Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

ESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. a large project known as the Čerenkov Telescope Array, composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison, and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

From ARC Centres of Excellence for Gravitational Wave Discovery via phys.org- “Detecting colliding supermassive black holes: The search continues”

From ARC Centres of Excellence for Gravitational Wave Discovery

via

phys.org

September 10, 2020

Artist’s iconic illustration of a supermassive black hole. Credit: NASA/JPL/CALTECH.

In a new study, researchers have developed an innovative method to detect colliding supermassive black holes. The study has just been published in The Astrophysical Journal and was led by postdoctoral researcher Xingjiang Zhu from the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav) at Monash University.

At the center of every galaxy in the universe, there is a supermassive black hole millions to billions times the mass of the sun. Big galaxies are assembled from smaller galaxies merging together, so collisions of supermassive black holes are expected to be common in the cosmos. But merging supermassive black holes remain elusive: No conclusive evidence of their existence has been found so far.

One way to look for these mergers is through their emission of gravitational waves—ripples in the fabric of space and time. A distant merging pair of supermassive black holes emit gravitational waves as they spiral in around each other. Since the black holes are so large, each wave takes many years to pass by Earth. Astronomers have used a technique known as pulsar timing array to observe gravitational waves from supermassive binary black holes—so far to no avail.

In parallel, astronomers have been looking for the collision of supermassive black holes with light. A number of candidate sources have been identified by looking for regular fluctuations in the brightness of distant galaxies called quasars. Quasars are extremely bright, believed to be powered by the accumulation of gas clouds onto supermassive black holes.

If the center of a quasar contains two black holes orbiting around each other (instead of a single black hole), the orbital motion might change the gas cloud accumulation and lead to periodic variation in its brightness. Hundreds of candidates have been identified through such searches, but astronomers are yet to find the smoking-gun signal.

“If we can find a pair of merging supermassive black holes, it will not only tell us how galaxies evolved, but also reveal the expected gravitational-wave signal strength for pulsar watchers,” says Zhu.

The OzGrav study seeks to settle the debate, determining if any of the identified quasars are likely to be powered by colliding black holes. The verdict? Probably not.

“We’ve developed a new method allowing us to search for a periodic signal and measure quasar noise properties at the same time,” says Zhu. “Therefore, it should produce a reliable estimate of the detected signal’s statistical significance.”

Applying this method to one of the most prominent candidate sources, called PG1302-102, the researchers found strong evidence for periodic variability; however, they argued that the signal is likely to be more complicated than current models.

“The commonly assumed model for quasar noise is wrong,” adds Zhu. “The data reveal additional features in the random fluctuations of gas accumulation onto supermassive black holes.”

“Our results are showing that quasars are complicated,” says collaborator and OzGrav Chief Investigator Eric Thrane. “We’ll need to improve our models if we are going to use them to identify supermassive binary black holes.”

See the full article here .

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OzGrav

THE ARC CENTRE of excellence FOR GRAVITATIONAL WAVE DISCOVERY
A new window of discovery.
A new age of gravitational wave astronomy.
One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas.

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The objectives for the ARC Centres of Excellence are to to:

undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

offer Australian researchers opportunities to work on large-scale problems over long periods of time

establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

From Astronomy Magazine: “Blanet: A new class of planet that could form around black holes”

From Astronomy Magazine

August 12, 2020

Supermassive black holes are typically surrounded by vast disks of gas and dust, as seen in this artist’s concept. And now, researcher think planets might form in these wild environments. Credit: Jurik Peter/Shutterstock.

Supermassive black holes are among the most exciting and puzzling objects in the universe. These are the giant, massive bodies that sit at the heart of most, perhaps all, galaxies. Indeed, they may be the seeds from which all galaxies grow.

Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

Supermassive black holes are at least a hundred thousand times the mass of our Sun. They are often surrounded by thick clouds of gas that radiate vast amounts of energy. When this happens, they are called active galactic nuclei. Discovering the properties of these clouds, and their curious central residents, is an ongoing exercise for astrophysicists.

Now researchers have a new phenomenon to consider — the idea that planets can form in the massive clouds of dust and gas around supermassive black holes. Last year, Keichi Wada at Kagoshima University in Japan, and a couple of colleagues showed that under certain conditions planets ought to form in these clouds. These black hole planets, or blanets as the team call them, would be quite unlike any conventional planet and raise the possibility of an entirely new class of objects for astronomers to dream about.

Protoplanetary Disk

The generally agreed theory of planet formation is that it occurs in the protoplanetary disk of gas and dust around young stars. When dust particles collide, they stick together to form larger clumps that sweep up more dust as they orbit the star. Eventually, these clumps grow large enough to become planets.

Wada and Co say a similar process should occur around supermassive black holes. These are surrounded by huge clouds of dust and gas that bear some similarities to the protoplanetary disks around young stars. As the cloud orbits the black hole, dust particles should collide and stick together forming larger clumps that eventually become blanets.

The scale of this process is vast compared to conventional planet formation. Supermassive black holes are huge, at least a hundred thousand times the mass of our Sun. But ice particles can only form where it is cool enough for volatile compounds to condense.

This turns out to be around 100 trillion kilometers from the black hole itself, in an orbit that takes about a million years to complete. Birthdays on blanets would be few and far between!

Next the team considered how large these bodies might grow. An important limitation is the relative velocity of the dust particles in the cloud. Slow moving particles can collide and stick together, but fast-moving ones would constantly break apart in high-speed collisions. Wada and Co calculated that this critical velocity must be less than about 80 meters per second.

At the same time, the rate of collisions must be high enough for blanets to form during the lifetime of an active galactic nuclei, thought to be perhaps a hundred million years. That leaves just a small parameter of space in which blanets can form, unless there is another factor that promotes blanet formation.

The focus of the team’s current work is on just such a factor: the impact of radiation on the dust cloud. The radiation from an active galactic nucleus would tend to drive dust particles away from the black hole, creating a constant “wind” of fresh material for blanet formation.

Active Galactic Nucleus

That has a significant impact, say Wada and Co. Under these conditions, blanets grow faster and can reach sizes up to 3,000 times the mass of Earth (beyond which they would be massive enough to form brown dwarfs). Without this dust wind, blanets would grow to no more than six times the mass of Earth. “Our results suggest that blanets could be formed around relatively low-luminosity active galactic nuclei during their lifetime,” say Wada and co.

Just what these bodies would be like is an open question. Wada and Co say they cannot be gaseous giants like Jupiter or Neptune. “The gaseous envelope of a blanet should be negligibly small compared with the blanet mass,” they say. And neither would they be much like Earth. “Blanets are extraordinarily different from the standard Earth-type planets,” add the team.

For the moment, the work is entirely theoretical, and the prospect of observing a blanet does not seem high. The closest active galactic nucleus, Centaurus A, is 11 million light-years from Earth, well beyond the scope of current exoplanet searches, which stretch just a few thousand light years.

But if blanets do exist, the next question is whether they might support life. Exactly this question arose following the release of the movie Interstellar, which included a potentially habitable planet orbiting a black hole. The answer: probably not, although that is no reason for astronomers to stop looking. Happy blanet hunting!

See the full article here .

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Astronomy is a magazine about the science and hobby of astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

Astronomy was founded in 1973 by Stephen A. Walther, a graduate of the University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at the University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

From Science Alert: “Astronomers Detect Strange Gas Movements Near The Centre of Our Galaxy”

From Science Alert

17 FEB 2020
MICHELLE STARR

(noLimit46/iStock)

Astronomers have detected unusual movements of gas clouds near the centre of our galaxy, and they could be pointing the way to the most elusive species of black hole, according to a new study. For the longest time, we weren’t even sure if these types of black holes existed.

Researchers tracking the gasses in the middle of the Milky Way have concluded the clouds are orbiting an object 10,000 times the mass of the Sun – and yet, when they look at where that object should be, nothing is there.

The most obvious explanation is a quiescent black hole, one that isn’t actively feeding, and therefore is emitting no detectable radiation.

It is, the researchers say, the fifth such candidate in the galactic centre, mounting evidence that not only do intermediate mass black holes exist, but that they’re abundant in the heart of the Milky Way.

Intermediate mass black holes are exactly what they sound like. We know stellar mass black holes, up to 100 times the mass of the Sun, exist. The biggest black hole we’ve detected in this mass range is 62 solar masses, created by the merger of two black holes in the gravitational wave event GW150914.

We also know supermassive black holes exist, like those that power galaxies. They start at around 100,000 solar masses, but they can get almost incomprehensibly massive, by means we have yet to discover.

The class that sits in between them – between 1,000 and 100,000 solar masses – is called intermediate mass black holes. They have remained extraordinarily elusive. This raises questions such as “do they exist?” and “if they don’t exist, why?” and “if they do exist, why can’t we find them?”

Because black holes don’t emit any detectable radiation of their own, scientists have to get creative in their search. Instead of looking for the black holes, they look for the effects black holes would have on other objects in nearby space.

Astrophysicist Shunya Takekawa of the National Astronomical Observatory of Japan and colleagues have been studying the motion of the high-velocity clouds of gas in the centre of the Milky Way to help answer these questions.

Their paper has been accepted by The Astrophysical Journal.

Previously, they used the gas-tracking method to identify an intermediate mass black hole candidate clocking in at around 32,000 solar masses, which would produce an event horizon – the spherical region of space around a black hole past which light cannot escape – roughly the size of Jupiter.

Now, they’ve applied it to a high-velocity gas cloud called HCN-0.085-0.094. It mainly consists of three smaller clumps; one of those clumps seems to be swirling around – but not being accreted by – a black hole.

“One of the three clumps has a ring-like structure with a very steep velocity gradient,” the researchers wrote in their paper.

“This kinematical structure suggests an orbit around a point-like object with a mass of ∼104 solar masses. The absence of stellar counterparts indicates that the point-like object may be a quiescent black hole.”

For a handy comparison, at that mass range, the black hole’s event horizon would be a little bigger than Uranus or Neptune.

Oddly behaving clumps of gas and dust aren’t the only way to find intermediate mass black holes.

Amongst other candidate observations is a star caught moving at incredible speed from the centre of the Milky Way, on a trajectory into intergalactic space. Analysis has shown that an intermediate mass black hole is the most likely thing to have given that star the punt it needed to achieve such velocity.

There was also a tremendous flare of multi-wavelength radiation that started in 2003, and gradually died down over the course of a decade. The distribution of the photons suggested that it was an intermediate mass black hole, a few tens of thousands of solar masses.

Newly released analysis of follow-up observations supports this, making it one of the best candidates yet, but it’s 740 million light-years away. The galactic centre is a lot closer, which means if we find any intermediate mass black holes there, they may be easier to study.

That could help us figure out such questions as – how do they form? And how do supermassive black holes form? A census could help us to understand how common or rare intermediate mass black holes are, and how they are distributed across galaxies.

So far, the results of the research indicate that looking at swirling gas at the heart of the Milky Way is a reliable method to search for intermediate mass black hole candidates; but we are yet to confirm one of them for sure. Watch this space.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition