The Great Neutrino Catch: A Bunch of Articles


U Wisconsin ICECUBE neutrino detector at the South Pole

IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated


From Nature Magazine Single subatomic particle illuminates mysterious origins of cosmic rays

When a subatomic particle from space streaked through Antarctica last September, astrophysicists raced to find the source.

13 July 2018
Davide Castelvecchi

A single subatomic particle detected at the South Pole last September is helping to solve a major cosmic mystery: what creates electrically charged cosmic rays, the most energetic particles in nature.

Follow-up studies by more than a dozen observatories suggest that researchers have, for the first time, identified a distant galaxy as a source of high-energy neutrinos

This discovery could, in turn, help scientists pin down the still mysterious source of protons and atomic nuclei that arrive to Earth from outer space, collectively called cosmic rays. The same mechanisms that produce cosmic rays should also make high-energy neutrinos.

Multiple teams of researchers from around the world describe the neutrino’s source in at least seven papers released on 12 July.

“Everything points to this as the ultra-bright, energetic source — a gorgeous source,” says Elisa Resconi, an astroparticle physicist at the Technical University of Munich in Germany.

Astrophysicists have proposed a number of scenarios for astrophysical phenomena that could produce both high-energy neutrinos and their electrically charged counterparts: protons and atomic nuclei collectively called cosmic rays. But until now, they had not managed to unambiguously trace any of these particles back to their source. This is especially difficult with cosmic rays, whose electric charges make their paths curve on their way to Earth, whereas neutrinos travel in straight lines.

The finding also underscores the promise of ‘multi-messenger’ astronomy, a nascent field that combines signals from different types of observatory to pin down details of celestial events.

Muon alert

The story began on 22 September 2017, when an electrically charged particle called a muon streaked through the Antarctic ice cap at close to the speed of light. IceCube — an array of more than 5,000 sensors buried in a cubic kilometre’s worth of ice — detected flashes of light that the muon produced in its wake. The particle appeared to emerge from below the detector — an orientation that indicated that it was the decay product of a neutrino that had come from below the horizon. Muons can only travel so far inside matter, whereas neutrinos often pass through the entire planet unimpeded; most of the ones that IceCube detects have crashed with a particle inside Earth to produce a muon (see ‘Neutrino observatory’).

Within seconds, a computer cluster at the US National Science Foundation’s Amundsen–Scott South Pole Station, which sits atop Earth’s southernmost point, had reconstructed the precise path of the particle and recognized that the muon had come from a highly energetic neutrino; 43 seconds after the event, the station sent an automated alert to a network of astronomers via a satellite link. It tagged the neutrino as IceCube-170922A.

After receiving the alert, Derek Fox, an astrophysicist at Pennsylvania State University in University Park, quickly secured observing time on the X-ray observatory Swift, which orbits Earth.

NASA Neil Gehrels Swift Observatory

Fox had created the automated alert system two years before, precisely in the hope that researchers could follow up on events such as this one.

He and his team found nine sources of high-energy X-rays close to where the neutrino had come from. Among them was an object called TXS 0506+056. This was a blazar, a galaxy with a supermassive black hole at the centre and a known source of γ-rays. In a blazar, the black hole stirs gas up to temperatures of millions of degrees and shoots it out of its poles in two highly collimated jets, one of which points in the direction of the Solar System. Fox’s team announced its findings to the astronomical community the next day after.


Flare up

In the following days, another team inspected data from the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope.


NASA/Fermi Gamma Ray Space Telescope

LAT constantly sweeps the sky, and among other things monitors about 2,000 blazars. These objects go through periods of increased activity that can last weeks or months, during which they become unusually bright. “When we looked at the region that IceCube said the neutrino came from, we noticed that this blazar had been flaring more than ever before,” says Regina Caputo, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is Fermi-LAT’s analysis coordinator.

On 28 September, the Fermi-LAT team sent out an alert to reveal this finding. It was at that point that other astronomers got very excited. IceCube has detected about a dozen such high-energy neutrinos each year since it started operating in 2010, but none had been associated with a particular source in the sky. “That’s what made the hair stand at the back of the neck,” Fox says.

Still, the association between the neutrino and the TXS blazar flare could have been a coincidence. To make the case stronger, researchers from both IceCube and Fermi-LAT calculated the odds that the flare and the neutrino were related, rather than coming from the same direction in the sky by chance.

“We had to calculate the chance that random neutrinos in the sky come from one of the known gamma-ray sources, and the likelihood that it was flaring at that time,” says Anna Franckowiak, an astroparticle physicist at the German Electron Synchrotron (DESY) in Zeuthen who is a member of both IceCube and Fermi-LAT. She and her collaborators found that likelihood to be good, though not at the level of statistical significance required for claiming a discovery in physics.

Evidence hunt

Finding more neutrinos and gamma rays detected during a previous flare from the same blazar would boost the evidence for TXS 0506+056 being the source. In November, IceCube researchers found that the observatory had recorded an excess of neutrinos coming from the same direction in the sky between late 2014 and 2015.

Resconi, who is a senior member of IceCube, got so excited by the discovery that she got lost while driving to a Nick Cave concert after work. “I ended up in the open countryside. My colleagues now tease me that next time we see a neutrino source, who knows where I will end up.”

Soon though, the researchers realized that this apparent flare did not seem to show up in Fermi-LAT data. “That news came as a wet blanket,” Resconi says. But in a separate study, she and her collaborators found hints of a TXS flare during that period, but with gamma rays of energies that were mostly too high for Fermi-LAT to detect.

A major missing piece of information was the blazar’s distance from Earth, says Simona Paiano of the Astronomical Observatory of Padua in Italy. To measure it, she and her team booked 15 hours of observing time on the world’s largest optical telescope, the 10.4-metre Gran Telescopio Canarias on La Palma, one of Spain’s Canary Islands.

Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

They found it to be around 1.15 billion parsecs (3.78 billion light years) away.

Together, the data pinpoint the likely source, says Kyle Cranmer, a particle physics and data-analysis expert at New York University, but “the observation isn’t unambiguous”, he says. “More follow-up is needed to conclusively establish blazars as a source of high-energy neutrinos.

Researchers hope that this is only the first of many multi-messenger events of this kind.They are especially looking forward to detecting neutrinos together with gravitational waves. The celebrated collision of two neutron stars that was discovered using gravitational waves in August 2017 should have produced neutrinos as well, but IceCube did not detect any. But if the TXS blazar flares up again, it might be possible to detect more high-energy neutrinos and other kinds of radiation coming from it.

From Astronomy Magazine

July 12, 2018
Michelle Hampson

The rare detection of a high-energy neutrino hints at how these strange particles are created.

Four billion years ago, an immense galaxy with a black hole at its heart spewed forth a jet of particles at nearly the speed of light. One of those particles, a neutrino that is just a fraction of the size of a regular atom, traversed across the universe on a collision course for Earth, finally striking the ice sheet of Antarctica last September. Coincidentally, a neutrino detector planted by scientists within the ice recorded the neutrino’s charged interaction with the ice, which resulted in a blue flash of light lasting just a moment. The results are published today in the journal Science.

This detection marks the second time in history that scientists have pinpointed the origins of a neutrino from outside of our solar system. And it’s the first time they’ve confirmed that neutrinos are created in the supermassive black holes at the centers of galaxies — a somewhat unexpected source.

Neutrinos are highly energetic particles that rarely ever interact with matter, passing through it as though it weren’t even there. Determining the type of cosmological events that create these particles is critical for understanding the nature of the universe. But the only confirmed source of neutrinos, other than our Sun, is a supernova that was recorded in 1987.

Physicists have a number of theories about what sort of astronomical events may create neutrinos, with some suggesting that blazars could be a source. Blazars are massive galaxies with black holes at their center, trying to suck in too much matter at once, causing jets of particles to be ejected outward at incredible speeds. Acting like the giant counterparts to terrestrial particle accelerators, blazar jets are believed to produce cosmic rays that can in turn create neutrinos.

“This [detection] in particular is a chance of nature,” says Darren Grant, a lead scientist of the team that first discovered the high-energy neutrino, as part of the neutrino detection project IceCube. “There’s a blazar there that just happened to turn on at the right time and we happened to capture it. It’s one of those eureka moments. You hope to experience those a few times in your career and this was one of them, where everything aligned.”

Blazars are active supermassive black holes sucking in immense amounts of material, which form swirling accretion disks and generate high-powered particle jets that churn out particles that astronomers have believed eventually result in neutrinos. DESY, Science Communication Lab

A cosmic messenger

On September 22, 2017, the neutrino reached the Antarctica ice sheet, passing by an ice crystal at just the right angle to cause a subatomic particle (called a muon) to be created from the interaction. The resulting blue flash was recorded by one of IceCube’s 5,160 detectors, embedded within the ice. Grant was in the office when the detection occurred. This neutrino was about 300 million times more energetic than those that are emitted by the Sun.

Grant and his colleague briefly admired the excellent image depicting the trajectory of the muon, which provides basic information necessary to begin tracing back the neutrino’s origin. However, they weren’t overly excited quite yet. His team observes about 10 to 20 high-energy neutrinos each year, but the right combination of events — in space, time and energy, for example — is required to precisely pinpoint the source of the neutrino. Such an alignment had eluded scientists so far. As Grant’s team began their analysis, though, they began to narrow in on a region: an exceptionally bright blazar called TXS 0506+056.

Upon the detection, an automatic alert was sent to other astronomy teams around the world, which monitor various incoming cosmic signals, such as radio and gamma rays. A few days later a team of scientists using the MAGIC telescope in the Canary Islands responded with some exciting news: the arrival of the neutrino had coincided with a burst of gamma rays – which are extremely energetic photons – also coming from the direction of TXS 0506+056.

MAGIC Cherenkov telescope array at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

Other teams analyzing the region following the initial detection observed changes in X-ray emissions and radio signals too. Collectively, the data is a huge step forward for physicists in understanding blazars, and high-energy cosmological events in general.

John Learned of University of Hawaii, Manoa, who was not involved in the study, says that the data linking the blazar as the source is “overwhelmingly convincing” and he emphasizes the importance of this finding. “This is the realization of many long-standing scientific dreams. Neutrinos at high energies can tell us about the guts of these extremely luminous objects … The implications of the finding are that we are now finally … [able] to see inside the most dense and luminous objects, and to further our grasp of the ‘deus ex machina’ which drives them and powers these awesome phenomena.”

For example, this detection also provides the first evidence that a blazar can produce the high-energy protons needed to generate neutrinos such as the one IceCube saw. Sources of high-energy protons also remain largely a mystery, so the identification of one such source is another big step forward for astronomers. “It’s really quite convincing that we’ve unlocked one piece of that puzzle,” says Grant.

Gems from the past

And it gets even better. “We looked back at [archival] data [that had been collected since 2010], in the direction of this particular blazar source, and what we discovered was really quite remarkable,” Grant says. A barrage of high-energy neutrinos and gamma rays from TXS 0506+056 reached Earth in late 2014 and early 2015. At the time, IceCube’s real-time alert system was not fully functioning, so other scientific teams were not aware of the detection. But now these previous neutrinos are on scientists’ radar, providing a more long-term glimpse into the life of a blazar.

“That was really icing on the cake, because what [the archived data indicated] was that the source had been active in neutrinos in the past, and then again, with this very high-energy neutrino in September — those are the pieces that really start to come together, to make a picture of what’s happening there,” explains Grant.

The alert IceCube sent once the neutrino’s interaction with the ice was detected resulted in follow-up observations from about 20 Earth- and space-based observatories. This immense effort resulted in the clear identification of a distant blazar as the source of the neutrino — as well as gamma rays, X-rays, radio emission, and optical light.
Nicolle R. Fuller/NSF/IceCube

Previous coverage

The data also reveal that radio emissions from TXS 0506+056 gradually increased in the 18 months leading up to the September neutrino detection. Greg Sivakoff, an associate professor at the University of Alberta who helped analyze the data, says one possibility is that the black hole began to consume surrounding matter much faster during this time, causing the jet of particles being emitted to speed up. He says, “If the jet gets too fast too quickly, it might run into some of its own material, creating what astronomers call a shock. Shocks have long been used in astronomy to explain how particles are accelerated to high energies. We are not sure that this is the answer yet, but this may be part of the story.”

Scientists are continuing to monitor TXS 0506+056, hoping to learn more about this colossal event. One team conducted a detailed analysis to determine how far away the blazar is from us, astounded to discover that it is a whopping four billion light years away. While TXS 0506+056 was always considered a bright object in the sky, this luminosity at such a distance makes it one of the brightest objects in the universe. No doubt future studies of this powerful blazar will yield valuable insights into the most energetic events to occur in our universe.

Learned says, “We are just opening a new door and I would love to be able to say what we shall find beyond. But I guarantee that initiating this new means of observing the universe will bring surprises and new insights. In an extreme analogy it is like asking Galileo what his new astronomical telescope will reveal.”

From UCSC: VERITAS supplies critical piece to neutrino discovery puzzle

July 12, 2018
Megan Watzke, CfA

Potential connection between blazar and neutrino detection by IceCube observatory marks a new advance in multi-messenger astrophysics

CfA/VERITAS, a major ground-based gamma-ray observatory with an array of four 12m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA, Altitude 2,606 m (8,550 ft)

One of the telescopes in the Very Energetic Radiation Imaging Telescope Array System (VERITAS), Located at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona, US in AZ, USA. VERITAS is operated and managed by the Smithsonian Astrophysical Observatory. (Photo by Wystan Benbow)

The VERITAS array has confirmed the detection of gamma rays from the vicinity of a supermassive black hole. While these detections are relatively common for VERITAS, this black hole is potentially the first known astrophysical source of high-energy cosmic neutrinos, a type of ghostly subatomic particle.

On September 22, 2017, the IceCube Neutrino Observatory, a cubic-kilometer neutrino telescope located at the South Pole, detected a high-energy neutrino of potential astrophysical origin. However, the observation of a single neutrino by itself is not enough for IceCube to claim the detection of a source. For that, scientists needed more information.

Very quickly after the detection by IceCube was announced, telescopes around the world including VERITAS (which stands for the “Very Energetic Radiation Imaging Telescope Array System”) swung into action to identify the source. The VERITAS, MAGIC [above], and H.E.S.S. gamma-ray observatories all looked at the neutrino position.

HESS Cherenkov Telescope Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg searches for cosmic rays, altitude, 1,800 m (5,900 ft)

In addition, two gamma-ray observatories that monitor much of the sky at lower and higher energies also provided coverage.

These follow-up observations of the rough IceCube neutrino position suggest that the source of the neutrino is a blazar, which is a supermassive black hole with powerful outflowing jets that can change dramatically in brightness over time. This blazar, known as TXS 0506+056, is located at the center of a galaxy about 4 billion light years from Earth.

“We know that the blazar jet is accelerating particles to very high energies, but it is difficult to tell from gamma rays alone if it is accelerating just electrons or also protons and heavier nuclei,” said David Williams, adjunct professor of physics at UC Santa Cruz and the Santa Cruz Institute for Particle Physics (SCIPP) and a member of the VERITAS collaboration. “If the blazar is a neutrino source, that’s a smoking gun for protons, because high-energy protons colliding with gas produce pions, which decay into neutrinos,” he said.

Initially, NASA’s Fermi Gamma-ray Space Telescope [above] observed that TXS 0506+056 was several times brighter than usually seen in its all-sky monitoring. Eventually, the MAGIC observatory made a detection of much higher-energy gamma rays within two weeks of the neutrino detection, while VERITAS, H.E.S.S., and HAWC did not see the blazar in any of their observations during the two weeks following the alert.

Given the importance of higher-energy gamma-ray detections in identifying the possible source of the neutrino, VERITAS continued to observe TXS 0506+056 over the following months, through February 2018, and revealed the source but at a dimmer state than what was detected by MAGIC.

“The VERITAS detection shows us that the gamma-ray brightness of the source changes, which is a signature of a blazar,” said Wystan Benbow of the Smithsonian Astrophysical Observatory (SAO), which operates and manages VERITAS. “Finding a link between an astrophysical source and a neutrino event could open yet another window of exploration to the extreme universe.”

Cosmic rays

The detection of gamma rays coincident with neutrinos is tantalizing, since both particles must be produced in the generation of cosmic rays. Since they were first detected over 100 years ago, cosmic rays—highly energetic particles that continuously rain down on Earth from space—have posed an enduring mystery. What creates and launches these particles across such vast distances? Where do they come from?

“The potential connection between the neutrino event and TXS 0506+056 would shed new light on the acceleration mechanisms that take place at the core of these galaxies and provide clues on the century-old question of the origin of cosmic rays,” said coauthor and VERITAS spokesperson Reshmi Mukherjee of Barnard College, Columbia University in New York.

“Astrophysics is entering an exciting new era of multi-messenger observations, in which celestial sources are being studied through the detection of the electromagnetic radiation they emit across the spectrum, from radio waves to high-energy gamma rays, in combination with non-electromagnetic means, such as gravitational waves and high-energy neutrinos,” said coauthor Marcos Santander of the University of Alabama in Tuscaloosa, who led the study.

A paper describing the deep VERITAS observations of TXS 0506+056 (“VERITAS Observations of the BL Lac Object TXS 0506+056”) has been accepted for publication in The Astrophysical Journal Letters and appears online on July 12, 2018. A paper on the IceCube and initial gamma-ray observations, including VERITAS’s, appears in the latest issue of the journal Science.

“This is a terrific step forward in multi-messenger astrophysics,” said Williams, who worked on the analysis of the VERITAS data and coordinated the VERITAS contributions to the Science paper.

VERITAS is a ground-based facility located at the SAO’s Fred Lawrence Whipple Observatory in southern Arizona. It consists of an array of four 12-meter optical telescopes that can detect gamma rays via the extremely brief flashes of blue “Cherenkov” light created when gamma rays are absorbed in the Earth’s atmosphere. The VERITAS Collaboration consists of about 80 scientists from 20 institutions in the United States, Canada, Germany and Ireland.

The Fermi-LAT Collaboration [above], which also played an important role in this research, includes researchers at the Santa Cruz Institute for Particle Physics at UC Santa Cruz.

From ESA INTEGRAL joins multi-messenger campaign to study high-energy neutrino source

12 July 2018
Erik Kuulkers
ESA INTEGRAL Project Scientist
European Space Agency
Tel: +31 6 30249526

Carlo Ferrigno
INTEGRAL Science Data Centre
University of Geneva, Switzerland

Volodymyr Savchenko
INTEGRAL Science Data Centre
University of Geneva, Switzerland

Francis Halzen
IceCube Principal Investigator
University of Wisconsin–Madison, USA

Sílvia Bravo Gallart
IceCube Press Office
University of Wisconsin–Madison, USA

Markus Bauer
ESA Science Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954

An international team of scientists has found first evidence of a source of high-energy neutrinos: a flaring active galaxy, or blazar, 4 billion light years from Earth. Following a detection by the IceCube Neutrino Observatory on 22 September 2017, ESA’s INTEGRAL satellite joined a collaboration of observatories in space and on the ground that kept an eye on the neutrino source, heralding the thrilling future of multi-messenger astronomy.


Neutrinos are nearly massless, ‘ghostly’ particles that travel essentially unhindered through space at close to the speed of light [1]. Despite being some of the most abundant particles in the Universe – 100 000 billion pass through our bodies every second – these electrically neutral, subatomic particles are notoriously difficult to detect because they interact with matter incredibly rarely.

While primordial neutrinos were created during the Big Bang, more of these elusive particles are routinely produced in nuclear reactions across the cosmos. The majority of neutrinos arriving at Earth derive from the Sun, but those that reach us with the highest energies are thought to stem from the same sources as cosmic rays – highly energetic particles originating from exotic sources outside the Solar System.

Unlike neutrinos, cosmic rays are charged particles and so their path is bent by magnetic fields, even weak ones. The neutral charge of neutrinos instead means they are unaffected by magnetic fields, and because they pass almost entirely through matter they can be used to trace a straight path all the way back to their source.

Acting as ‘messengers’, neutrinos directly carry astronomical information from the far reaches of the Universe. Over the past decades, several instruments have been built on Earth and in space to decode their messages, though detecting these particles is no easy feat. In particular, the source of high-energy neutrinos has, until now, remained unproven.

On 22 September 2017, one of these high-energy neutrinos arrived at the IceCube Neutrino Observatory at the South Pole [2]. The event was named IceCube-170922A.

The IceCube observatory, which encompasses a cubic kilometre of deep, pristine ice, detects neutrinos through their secondary particles, muons. These muons are produced on the rare occasion that a neutrino interacts with matter in the vicinity of the detector, and they create tracks, kilometres in length, as they pass through layers of Antarctic ice. Their long paths mean their position can be well defined, and the source of the parent neutrino can be pinned down in the sky.

During the 22 September event, a traversing muon deposited 22 TeV of energy in the IceCube detector. From this, scientists estimated the energy of the parent neutrino to be around 290 TeV, indicating a 50 percent chance that it had an astrophysical origin beyond the Solar System.

When the origin of a neutrino cannot be robustly identified by IceCube, like in this case, multi-wavelength observations are required to investigate its source. So, following the detection, IceCube scientists circulated the coordinates in the sky of the neutrino’s origin, inferred from their observations, to a worldwide network of ground and space-based observatories working across the full electromagnetic spectrum.

These included NASA’s Fermi gamma-ray space telescope [above] and the Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) [above] on La Palma, in the Canary Islands, which looked to this portion of the sky and found the known blazar, TXS 0506+056, in a ‘flaring’ state – a period of intense high-energy emission – at the same time the neutrino was detected at the South Pole.

Blazars are the central cores of giant galaxies that host an actively accreting supermassive black-hole at their heart, where matter spiralling in forms a hot, rotating disc that generates enormous amounts of energy, along with a pair of relativistic jets.

These jets are colossal columns that funnel radiation, photons and particles – including neutrinos and cosmic rays – tens of light years away from the central black hole at speeds very close to the speed of light. A specific feature of blazars is that one of these jets happens to point towards Earth, making its emission appear exceptionally bright.

Scientists around the world began observing this blazar – the likely source of the neutrino detected by IceCube – in a variety of wavelengths, from radio waves to high-energy gamma rays. ESA’s INTEGRAL gamma-ray observatory was part of this international collaboration [3].

“This is a very important milestone to understanding how high-energy neutrinos are produced,” says Carlo Ferrigno from the INTEGRAL Science Data Centre at the University of Geneva, Switzerland.

“There have been previous claims that blazar flares were associated with the production of neutrinos, but this, the first confirmation, is absolutely fundamental. This is an exciting period for astrophysics,” he adds.

INTEGRAL, which surveys the sky in hard X-rays and soft gamma rays, is also sensitive to transient high-energy sources across the whole sky. At the time the neutrino was detected, it did not record any burst of gamma rays from the location of the blazar, so scientists were able to rule out prompt emissions from certain sources, such as a gamma-ray burst.

After the neutrino alert from IceCube, INTEGRAL pointed to this area of the sky on various occasions between 30 September and 24 October 2017 with its wide-field instruments, and it did not observe the blazar to be in a flaring state in the hard X-ray or soft gamma-ray range.

The fact that INTEGRAL could not detect the source in the follow-up observations provided significant information about this blazar, allowing scientists to place a useful upper limit on its energy output during this period.

“INTEGRAL was important in constraining the properties of this blazar, but also in allowing scientists to exclude other neutrino sources such as gamma-ray bursts,” explains Volodymyr Savchenko from the INTEGRAL Science Data Centre, who led the analysis of the INTEGRAL data.

With facilities spread across the globe and in space, scientists now have the capability to detect a plethora of ‘cosmic messengers’ travelling vast distances at extremely high speeds, in the form of light, neutrinos, cosmic rays, and even gravitational waves.

“The ability to globally marshal telescopes to make a discovery using a variety of wavelengths in cooperation with a neutrino detector like IceCube marks a milestone in what scientists call multi-messenger astronomy,” says Francis Halzen from the University of Wisconsin–Madison, USA, lead scientist for the IceCube Neutrino Observatory.

By combining the information gathered by each of these sophisticated instruments to investigate a wide range of cosmic processes, the era of multi-messenger astronomy has truly entered the phase of scientific exploitation.

ESA’s high-energy space telescopes are fully integrated into this network of large multi-messenger collaborations, as demonstrated during the recent detection of gravitational waves with a corresponding gamma-ray burst – the latter detected by INTEGRAL – released by the collision of two neutron stars, and in the subsequent follow-up campaign, with contributions by INTEGRAL as well as the XMM-Newton X-ray observatory.

ESA/XMM Newton

Pooling resources from these and other observatories is key for the future of astrophysics, fostering our ability to decode the messages that reach us from across the Universe.

“INTEGRAL is the only observatory available in the hard X-ray and soft gamma-ray domain that has the ability to perform dedicated imaging and spectroscopy, as well as having an instantaneous all-sky view at any time,” notes Erik Kuulkers, INTEGRAL project scientist at ESA.

“After more than 15 years of operations, INTEGRAL is still at the forefront of high-energy astrophysics.”

[1] Described by Frederick Reines, one of the scientists who made the first neutrino detection, as “… the most tiny quantity of reality ever imagined by a human being,” one neutrino is estimated to contain one millionth of the mass of an electron.

[2] The IceCube Collaboration is funded primarily by the National Science Foundation and is operated by a team headquartered at the University of Wisconsin–Madison, USA. The research efforts, including critical contributions to the detector operation, are supported by funding agencies in Australia, Belgium, Canada, Denmark, Germany, Japan, New Zealand, Republic of Korea, Sweden, Switzerland, the United Kingdom, and the USA.

[3] These results are detailed in the paper Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A by The IceCube, Fermi-LAT, MAGIC, AGILE, ASAS-SN, HAWC, H.E.S.S, INTEGRAL, Kanata, Kiso, Kapteyn, Liverpool telescope, Subaru, Swift/NuSTAR, VERITAS, and VLA/17B-403 teams, published in Science. DOI:10.1126/science.aat1378