From NASA Fermi Via The NASA Goddard Space Flight Center: “NASA’s Fermi Detects First Gamma-Ray Eclipses From ‘Spider’ Star Systems”

National Aeronautics and Space Administration(US) Fermi Gamma-Ray Large Area Telescope.

From NASA Fermi

Via

The NASA Goddard Space Flight Center

1.26.23
By Jeanette Kazmierczak
jeanette.a.kazmierczak@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Media Contact:
Claire Andreoli
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

NASA’s Fermi Gamma-ray Space Telescope orbits Earth in this illustration. Credit:Chris Smith (Universities Space Research Association)/ NASA’s Goddard Space Flight Center.

Scientists have discovered the first gamma-ray eclipses from a special type of binary star system using data from NASA’s Fermi Gamma-ray Space Telescope. These so-called spider systems each contain a pulsar – the superdense, rapidly rotating remains of a star that exploded in a supernova – that slowly erodes its companion.

Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at Mullard Radio Astronomy Observatory, University of Cambridge (UK), taken for the Daily Herald newspaper in 1968. Denied the Nobel.

An international team of scientists scoured over a decade of Fermi observations to find seven spiders that undergo these eclipses, which occur when the low-mass companion star passes in front of the pulsar from our point of view. The data allowed them to calculate how the systems tilt relative to our line of sight and other information.

“One of the most important goals for studying spiders is to try to measure the masses of the pulsars,” said Colin Clark, an astrophysicist at the MPG Institute for Gravitational Physics (DE) who led the work. “Pulsars are basically balls of the densest matter we can measure. The maximum mass they can reach constrains the physics within these extreme environments, which can’t be replicated on Earth.”

A paper about the study was published Jan. 26 in Nature Astronomy [below].

An orbiting star begins to eclipse its partner, a rapidly rotating, superdense stellar remnant called a pulsar, in this illustration. The pulsar emits multiwavelength beams of light that rotate in and out of view and produces outflows that heat the star’s facing side, blowing away material and eroding its partner. Credits: Aurore Simonnet/Sonoma State University/NASA.

Spider systems develop because one star in a binary evolves more swiftly than its partner. When the more massive star goes supernova, it leaves behind a pulsar. This stellar remnant emits beams of multiwavelength light, including gamma rays, that sweep in and out of our view, creating pulses so regular they rival the precision of atomic clocks.

Early on a spider pulsar “feeds” off its companion by siphoning away a stream of gas. As the system evolves, the feeding stops as the pulsar begins to spin more rapidly, generating particle outflows and radiation that superheat the companion’s facing side and erode it.

Scientists divide spider systems into two types named after spider species whose females sometimes eat their smaller mates. Black widows contain companions with less than 5% of the Sun’s mass. Redback systems host bigger companions, both in size and mass, weighing between 10% and 50% of the Sun.

“Before Fermi, we only knew of a handful of pulsars that emitted gamma rays,” said Elizabeth Hays, the Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “After over a decade of observations, the mission has identified over 300 and collected a long, nearly uninterrupted dataset that allows the community to do trailblazing science.”

Researchers can calculate the masses of spider systems by measuring their orbital motions. Visible light observations can measure how quickly the companion is traveling, while radio measurements reveal the pulsar’s speed. However, these rely on motion towards and away from us. For a nearly face-on system, such changes are slight and potentially confusing. The same signals also could be produced by a smaller, slower-orbiting system that’s seen from the side. Knowing the system’s tilt relative to our line of sight is vital for measuring mass.

The tilt’s angle is normally measured using visible light, but these measurements come with some potential complications. As the companion orbits the pulsar, its superheated side comes in and out of view, creating a fluctuation in visible light that depends on the tilt. However, astronomers are still learning about the superheating process, and models with different heating patterns sometimes predict different pulsar masses.

Gamma rays, however, are only generated by the pulsar and have so much energy that they travel in a straight line, unaffected by debris, unless blocked by the companion. If gamma rays disappear from the data set of a spider system, scientists can infer that the companion eclipsed the pulsar. From there, they can calculate the system’s tilt into our sight line, the stars’ velocities, and the pulsar’s mass.

PSR B1957+20, or B1957 for short, was the first-known black widow, discovered in 1988. Earlier models for this system, built from visible light observations, determined that it was tipped about 65 degrees into our line of sight and the pulsar’s mass was 2.4 times the Sun’s. That would make B1957 the heaviest-known pulsar, straddling the theoretical mass limit between pulsar and black hole.

By looking at the Fermi data, Clark and his team found 15 missing gamma-ray photons. The timing of the gamma-ray pulses from these objects is so dependable that 15 missing photons over a decade is significant enough that the team could determine the system is eclipsing. They then calculated that the binary is inclined 84 degrees and the pulsar weighs only 1.8 times as much as the Sun.

“There’s a quest to find massive pulsars, and these spider systems are thought to be one of the best ways to find them,” said Matthew Kerr, a co-author on the new paper and research physicist at the U.S. Naval Research Laboratory in Washington. “They’ve undergone a very extreme process of mass transfer from the companion star to the pulsar. Once we really get these models fine-tuned, we’ll know for sure whether these spider systems are more massive than the rest of the pulsar population.”

Nature Astronomy
See the science paper for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

The Fermi Gamma-ray Space Telescope , formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [NASA/ESA Hubble, NASA Chandra, NASA Spitzer, and associated programs.] NASA shares data with various national and international organizations such as from [JAXA]Greenhouse Gases Observing Satellite.

From The NASA Goddard Space Flight Center: “NASA Missions Probe Game-Changing Cosmic Explosion”

From The NASA Goddard Space Flight Center

12.7.22
By Jeanette Kazmierczak
jeanette.a.kazmierczak@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md

Media Contact:
Claire Andreoli
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md

Gamma-ray burst 211211A, the location of which is circled in red, erupted on the outskirts of a spiral galaxy around 1 billion light-years away in the constellation Boötes. The NASA/ESA Hubble Space Telescope captured the image with its Wide Field Camera 3 and Advanced Camera for Surveys. Credit: NASA, ESA, Rastinejad et al. (2022), and Gladys Kober (Catholic Univ. of America)

The National Aeronautics and Space Agency European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU) Hubble Space Telescope Instrumentation annotated.

National Aeronautics Space Agency/European Space Agency [La Agencia Espacial Europea][Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU) Hubble Wide Field Camera 3.

National Aeronautics Space Agency/European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganization](EU) Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope.

On Dec. 11, 2021, NASA’s Neil Gehrels Swift Observatory and Fermi Gamma-ray Space Telescope detected a blast of high-energy light from the outskirts of a galaxy around 1 billion light-years away. The event has rattled scientists’ understanding of gamma-ray bursts (GRBs), the most powerful events in the universe.

National Aeronautics and Space Administration Neil Gehrels Swift X-ray, and UV/Visible light Observatory.

National Aeronautics and Space Administration Fermi Gamma-Ray Large Area Telescope.

National Aeronautics and Space Administration Fermi Gamma Ray Space Telescope.

For the last few decades, astronomers have generally divided GRBs into two categories. Long bursts emit gamma rays for two seconds or more and originate from the formation of dense objects like black holes in the centers of massive collapsing stars. Short bursts emit gamma rays for less than two seconds and are caused by mergers of dense objects like neutron stars. Scientists sometimes observe short bursts with a following flare of visible and infrared light called a kilonova.

“This burst, named GRB 211211A, was paradigm-shifting as it is the first long-duration gamma-ray burst traced to a neutron star merger origin,” said Jillian Rastinejad, a graduate student at Northwestern University in Evanston, Illinois, who led one team that studied the burst.

Merging neutron stars. Image Credit: Mark Garlick, University of Warwick (UK).

“The high-energy burst lasted about a minute, and our follow-up observations led to the identification of a kilonova. This discovery has deep implications for how the universe’s heavy elements came to be.”

NASA’s Fermi, Swift Capture Revolutionary Gamma-Ray Burst.
Watch to learn how an event called GRB 211211A rocked scientists’s understanding of gamma-ray bursts – the most powerful explosions in the cosmos. Credit: NASA’s Goddard Space Flight Center.

A classic short gamma-ray burst begins with two orbiting neutron stars, the crushed remnants of massive stars that exploded as supernovae. As the stars circle ever closer, they strip neutron-rich material from each other. They also generate gravitational waves, or ripples in space-time – although none were detected from this event.

Gravitational waves. Credit: W.Benger-Zib. MPG Institute for Gravitational Physics (DE)

Eventually the neutron stars collide and merge, creating a cloud of hot debris emitting light across multiple wavelengths. Scientists hypothesize that jets of high-speed particles, launched by the merger, produce the initial gamma-ray flare before they collide with the wreckage. Heat generated by the radioactive decay of elements in the neutron-rich debris likely creates the kilonova’s visible and infrared light. This decay results in the production of heavy elements like gold and platinum.

Scientists may have detected violent collision between neutron star and a black hole, “All the Gold in the Universe” from The University of California-Santa Cruz 2017.

“Many years ago, Neil Gehrels, an astrophysicist and Swift’s namesake, suggested that neutron star mergers could produce some long bursts,” said Eleonora Troja, an astrophysicist at the University of Rome who led another team that studied the burst. “The kilonova we observed is the proof that connects mergers to these long-duration events, forcing us to rethink how black holes are formed.”

Fermi and Swift detected the burst simultaneously, and Swift was able to rapidly identify its location in the constellation Boötes, enabling other facilities to quickly respond with follow-up observations. Their observations have provided the earliest look yet at the first stages of a kilonova.

Many research groups have delved into the observations collected by Swift, Fermi, the Hubble Space Telescope, and others.

Some have suggested the burst’s oddities could be explained by the merger of a neutron star with another massive object, like a black hole. The event was also relatively nearby, by gamma-ray burst standards, which may have allowed telescopes to catch the kilonova’s fainter light. Perhaps some distant long bursts could also produce kilonovae, but we haven’t been able to see them.

Two neutron stars begin to merge in this illustration, blasting a jet of high-speed particles and producing a cloud of debris. Scientists think these kinds of events are factories for a significant portion of the universe’s heavy elements, including gold. Credits: A. Simonnet (Sonoma State Univ.) and NASA’s Goddard Space Flight Center.

The light following the burst, called the afterglow emission, also exhibited unusual features. Fermi detected high-energy gamma rays starting 1.5 hours post-burst and lasting more than 2 hours. These gamma rays reached energies of up to 1 billion electron volts. (Visible light’s energy measures between about 2 and 3 electron volts, for comparison.)

“This is the first time we’ve seen such an excess of high-energy gamma rays in the afterglow of a merger event. Normally that emission decreases over time,” said Alessio Mei, a doctoral candidate at the Gran Sasso Science Institute in L’Aquila, Italy, who led a group that studied the data. “It’s possible these high-energy gamma rays come from collisions between visible light from the kilonova and electrons in particle jets. The jets could be weakening ones from the original explosion or new ones powered by the resulting black hole or magnetar.”

Scientists think neutron star mergers are a major source of the universe’s heavy elements. They based their estimates on the rate of short bursts thought to occur across the cosmos. Now they’ll need to factor long bursts into their calculations as well.

A team led by Benjamin Gompertz, an astrophysicist at the University of Birmingham in the United Kingdom, looked at the entire high-energy light curve, or the evolution of the event’s brightness over time. The scientists noted features that might provide a key for identifying similar incidents – long bursts from mergers – in the future, even ones that are dimmer or more distant. The more astronomers can find, the more they can refine their understanding of this new class of phenomena.

On Dec. 7, 2022, papers led by Rastinejad, Troja, and Mei were published in the scientific journal Nature [below], and a paper led by Gompertz was published in Nature Astronomy [below].

“This result underscores the importance of our missions working together and with others to provide multiwavelength follow up of these kinds of phenomenon,” said Regina Caputo, Swift project scientist, at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Similar coordinated efforts have hinted that some supernovae might produce short bursts, but this event is the final nail in the coffin for the simple dichotomy we’ve used for years. You never know when you might find something surprising.”

NASA’s Goddard Space Flight Center manages the Swift and Fermi missions.

Swift is a collaboration with The Pennsylvania State University, the DOE’s Los Alamos National Laboratory in New Mexico, and Northrop Grumman Space Systems in Dulles, Virginia, with important contributions from partners in the United Kingdom and Italy.

Fermi is a collaboration with the U.S. Department of Energy, with important contributions from partners in France, Germany, Italy, Japan, Sweden, and the United States.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). Goddard manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

Science papers:
Nature
https://www.nature.com/articles/s41586-022-05390-w
Nature
https://www.nature.com/articles/s41586-022-05327-3
Nature
https://www.nature.com/articles/s41586-022-05404-7
Nature Astronomy
https://www.nature.com/articles/s41550-022-01819-4

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

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Please help promote STEM in your local schools.

Stem Education Coalition

NASA/Goddard Campus

NASA’s Goddard Space Flight Center, Greenbelt, MD is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

GSFC also operates two spaceflight tracking and data acquisition networks (the NASA Deep Space Network and the Near Earth Network); develops and maintains advanced space and Earth science data information systems, and develops satellite systems for the National Oceanic and Atmospheric Administration.

GSFC manages operations for many NASA and international missions including the NASA/ESA Hubble Space Telescope; the Explorers Program; the Discovery Program; the Earth Observing System; INTEGRAL; MAVEN; OSIRIS-REx; the Solar and Heliospheric Observatory ; the Solar Dynamics Observatory; Tracking and Data Relay Satellite System ; Fermi; and Swift. Past missions managed by GSFC include the Rossi X-ray Timing Explorer (RXTE), Compton Gamma Ray Observatory, SMM, COBE, IUE, and ROSAT. Typically, unmanned Earth observation missions and observatories in Earth orbit are managed by GSFC, while unmanned planetary missions are managed by the Jet Propulsion Laboratory (JPL) in Pasadena, California.

Goddard is one of four centers built by NASA since its founding on July 29, 1958. It is NASA’s first, and oldest, space center. Its original charter was to perform five major functions on behalf of NASA: technology development and fabrication; planning; scientific research; technical operations; and project management. The center is organized into several directorates, each charged with one of these key functions.

Until May 1, 1959, NASA’s presence in Greenbelt, MD was known as the Beltsville Space Center. It was then renamed the Goddard Space Flight Center (GSFC), after Robert H. Goddard. Its first 157 employees transferred from the United States Navy’s Project Vanguard missile program, but continued their work at the Naval Research Laboratory in Washington, D.C., while the center was under construction.

Goddard Space Flight Center contributed to Project Mercury, America’s first manned space flight program. The Center assumed a lead role for the project in its early days and managed the first 250 employees involved in the effort, who were stationed at Langley Research Center in Hampton, Virginia. However, the size and scope of Project Mercury soon prompted NASA to build a new Manned Spacecraft Center, now the Johnson Space Center, in Houston, Texas. Project Mercury’s personnel and activities were transferred there in 1961.

The Goddard network tracked many early manned and unmanned spacecraft.

Goddard Space Flight Center remained involved in the manned space flight program, providing computer support and radar tracking of flights through a worldwide network of ground stations called the Spacecraft Tracking and Data Acquisition Network (STDN). However, the Center focused primarily on designing unmanned satellites and spacecraft for scientific research missions. Goddard pioneered several fields of spacecraft development, including modular spacecraft design, which reduced costs and made it possible to repair satellites in orbit. Goddard’s Solar Max satellite, launched in 1980, was repaired by astronauts on the Space Shuttle Challenger in 1984. The Hubble Space Telescope, launched in 1990, remains in service and continues to grow in capability thanks to its modular design and multiple servicing missions by the Space Shuttle.

Today, the center remains involved in each of NASA’s key programs. Goddard has developed more instruments for planetary exploration than any other organization, among them scientific instruments sent to every planet in the Solar System. The center’s contribution to the Earth Science Enterprise includes several spacecraft in the Earth Observing System fleet as well as EOSDIS, a science data collection, processing, and distribution system. For the manned space flight program, Goddard develops tools for use by astronauts during extra-vehicular activity, and operates the Lunar Reconnaissance Orbiter, a spacecraft designed to study the Moon in preparation for future manned exploration.

The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs.] NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

From NASA Fermi : “NASA’s Fermi Confirms Star Wreck as Source of Extreme Cosmic Particles”

National Aeronautics and Space Administration(US) Fermi Gamma-Ray Large Area Telescope.

From NASA Fermi

8.10.22
Francis Reddy
francis.j.reddy@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Media Contact:
Claire Andreoli
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md
(301) 286-1940

Astronomers have long sought the launch sites for some of the highest-energy protons in our galaxy. Now a study using 12 years of data from NASA’s Fermi Gamma-ray Space Telescope [above] confirms that one supernova remnant is just such a place.

Found: A PeVatron.
Explore how astronomers located a supernova remnant that fires up protons to energies 10 times greater than the most powerful particle accelerator on Earth. Credits: NASA’s Goddard Space Flight Center.

Fermi has shown that the shock waves of exploded stars boost particles to speeds comparable to that of light. Called cosmic rays, these particles mostly take the form of protons, but can include atomic nuclei and electrons. Because they all carry an electric charge, their paths become scrambled as they whisk through our galaxy’s magnetic field. Since we can no longer tell which direction they originated from, this masks their birthplace. But when these particles collide with interstellar gas near the supernova remnant, they produce a tell-tale glow in gamma rays – the highest-energy light there is.

“Theorists think the highest-energy cosmic ray protons in the Milky Way reach a million billion electron volts, or PeV energies,” said Ke Fang, an assistant professor of physics at the University of Wisconsin, Madison. “The precise nature of their sources, which we call PeVatrons, has been difficult to pin down.”

Trapped by chaotic magnetic fields, the particles repeatedly cross the supernova’s shock wave, gaining speed and energy with each passage. Eventually, the remnant can no longer hold them, and they zip off into interstellar space.

Boosted to some 10 times the energy mustered by the world’s most powerful particle accelerator, the Large Hadron Collider, PeV protons are on the cusp of escaping our galaxy altogether.

Astronomers have identified a few suspected PeVatrons, including one at the center of our galaxy. Naturally, supernova remnants top the list of candidates. Yet out of about 300 known remnants, only a few have been found to emit gamma rays with sufficiently high energies.

One particular star wreck has commanded a lot of attention from gamma-ray astronomers. Called G106.3+2.7, it’s a comet-shaped cloud located about 2,600 light-years away in the constellation Cepheus. A bright pulsar caps the northern end of the supernova remnant, and astronomers think both objects formed in the same explosion.

Fermi’s Large Area Telescope [above], its primary instrument, detected billion-electron-volt (GeV) gamma rays from within the remnant’s extended tail. (For comparison, visible light’s energy measures between about 2 and 3 electron volts.) The Very Energetic Radiation Imaging Telescope Array System (VERITAS) at the Fred Lawrence Whipple Observatory in southern Arizona recorded even higher-energy gamma rays from the same region.

The University of Arizona Veritas – Four Čerenkov telescopes – A novel gamma ray telescope under construction at The Fred Lawrence Whipple Observatory Smithsonian Astrophysical Observatory-Center for Astrophysics , Mount Hopkins, Arizona, altitude 2,606 m 8,550 ft.

And both the High-Altitude Water Čerenkov Gamma-Ray Observatory in Mexico and the Tibet AS-Gamma Experiment in China have detected photons with energies of 100 trillion electron volts (TeV) from the area probed by Fermi and VERITAS.

HAWC High Altitude Čerenkov Experiment, a US Mexico Europe collaboration located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters (13500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays.

Tibet AS-Gamma Experiment

Revealing a peculiar supernova remnant G106.3+2.7 as a petaelectronvolt proton accelerator with X-ray observations.
Credit: ScienceDirect.

“This object has been a source of considerable interest for a while now, but to crown it as a PeVatron, we have to prove it’s accelerating protons,” explained co-author Henrike Fleischhack at the Catholic University of America in Washington and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The catch is that electrons accelerated to a few hundred TeV can produce the same emission. Now, with the help of 12 years of Fermi data, we think we’ve made the case that G106.3+2.7 is indeed a PeVatron.”

A paper detailing the findings, led by Fang, was published Aug. 10 in the journal Physical Review Letters [below].

The pulsar, J2229+6114, emits its own gamma rays in a lighthouse-like beacon as it spins, and this glow dominates the region to energies of a few GeV. Most of this emission occurs in the first half of the pulsar’s rotation. The team effectively turned off the pulsar by analyzing only gamma rays arriving from the latter part of the cycle. Below 10 GeV, there is no significant emission from the remnant’s tail.

Above this energy, the pulsar’s interference is negligible and the additional source becomes readily apparent. The team’s detailed analysis overwhelmingly favors PeV protons as the particles driving this gamma-ray emission.

“So far, G106.3+2.7 is unique, but it may turn out to be the brightest member of a new population of supernova remnants that emit gamma rays reaching TeV energies,” Fang notes. “More of them may be revealed through future observations by Fermi and very-high-energy gamma-ray observatories.”

NASA explores cosmic mysteries – and this particular puzzle took more than a decade of cutting-edge observations to solve.

Science paper:
Physical Review Letters

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Fermi Gamma-ray Space Telescope, formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [NASA/ESA Hubble, NASA Chandra, NASA Spitzer, and associated programs.] NASA shares data with various national and international organizations such as from [JAXA]Greenhouse Gases Observing Satellite.

From NASA Fermi : “NASA’s Fermi Hunts for Gravitational Waves From Monster Black Holes”

National Aeronautics and Space Administration(US) Fermi Gamma-Ray Large Area Telescope.

From NASA Fermi

Apr 7, 2022

By Jeanette Kazmierczak
jeanette.a.kazmierczak@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md

Media Contact:
Claire Andreoli
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md

Black holes distort a starry background, capture light, and produce black hole silhouettes in this simulation. Each has a mass about 500,0000 times the Sun’s and a distinctive feature called a photon ring outlining the black hole. Credit: NASA’s Goddard Space Flight Center; background, The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Gaia/ESA DPAC Consortium – Gaia – Cosmos [Data Processing and Analysis Consortium] (EU).

European Space Agency [La Agencia Espacial Europea][Agence spatiale européenne][Europäische Weltraumorganisation](EU) GAIA satellite.

Our universe is a chaotic sea of ripples in space-time called gravitational waves. Astronomers think waves from orbiting pairs of supermassive black holes in distant galaxies are light-years long and have been trying to observe them for decades, and now they’re one step closer thanks to NASA’s Fermi Gamma-ray Space Telescope [below].

Fermi detects gamma rays, the highest-energy form of light. An international team of scientists examined over a decade of Fermi data collected from pulsars, rapidly rotating cores of stars that exploded as supernovae.

Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at Mullard Radio Astronomy Observatory, University of Cambridge(UK), taken for the Daily Herald newspaper in 1968. Denied the Nobel.

They looked for slight variations in the arrival time of gamma rays from these pulsars, changes which could have been caused by the light passing through gravitational waves on the way to Earth. But they didn’t find any.

While no waves were detected, the analysis shows that, with more observations, these waves may be within Fermi’s reach.

“We kind of surprised ourselves when we discovered Fermi could help us hunt for long gravitational waves,” said Matthew Kerr, a research physicist at the U.S. Naval Research Laboratory in Washington. “It’s new to the fray – radio studies have been doing similar searches for years. But Fermi and gamma rays have some special characteristics that together make them a very powerful tool in this investigation.”

The results of the study, co-led by Kerr and Aditya Parthasarathy, a researcher at The MPG Institute for Radio Astronomy [MPG Institut für Radioastronomie](DE), were published online by the journal Science on April 7, 2022.

The length of a gravitational wave, or ripple in space-time, depends on its source, as shown in this infographic. Scientists need different kinds of detectors to study as much of the spectrum as possible. Credits: NASA’s Goddard Space Flight Center Conceptual Image Lab.

When massive objects accelerate, they produce gravitational waves traveling at light speed. The ground-based Laser Interferometer Gravitational Wave Observatory – which first detected gravitational waves in 2015 – can sense ripples tens to hundreds of miles long from crest to crest, which roll past Earth in just fractions of a second. The upcoming space-based Laser Interferometer Space Antenna will pick up waves millions to billions of miles long.

Gravity is talking. Lisa will listen. Dialogos of Eide.

The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU)National Aeronautics and Space Administration eLISA space based, the future of gravitational wave research., due to launch in 2037.

_____________________________________________________________________________________
LIGO–VIRGO–KAGRA

Caltech /MIT Advanced aLigo.

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA.

Caltech/MIT Advanced aLigo Hanford, WA, USA installation.

VIRGO Gravitational Wave interferometer, near Pisa, Italy.

KAGRA Large-scale Cryogenic Gravitational Wave Telescope Project (JP).
_____________________________________________________________________________________

LIGO Virgo Kagra Masses in the Stellar Graveyard. Credit: Frank Elavsky and Aaron Geller at Northwestern University.

Kerr and his team are searching for waves that are light-years, or trillions of miles, long and take years to pass Earth. These long ripples are part of the gravitational wave background, a random sea of waves generated in part by pairs of supermassive black holes ­in the centers of merged galaxies across the universe.

To find them, scientists need galaxy-sized detectors called pulsar timing arrays. These arrays use specific sets of millisecond pulsars, which rotate as fast as blender blades. Millisecond pulsars sweep beams of radiation, from radio to gamma rays, past our line of sight, appearing to pulse with incredible regularity – like cosmic clocks.

As long gravitational waves pass between one of these pulsars and Earth, they delay or advance the light arrival time by billionths of a second. By looking for a specific pattern of pulse variations among pulsars of an array, scientists expect they can reveal gravitational waves rolling past them.

Radio astronomers have been using pulsar timing arrays for decades, and their observations are the most sensitive to these gravitational waves. But interstellar effects complicate the analysis of radio data. Space is speckled with stray electrons. Across light-years, their effects combine to bend the trajectory of radio waves. This alters the arrival times of pulses at different frequencies. Gamma rays don’t suffer from these complications, providing both a complementary probe and an independent confirmation of the radio results.

“The Fermi results are already 30% as good as the radio pulsar timing arrays when it comes to potentially detecting the gravitational wave background,” Parthasarathy said. “With another five years of pulsar data collection and analysis, it’ll be equally capable with the added bonus of not having to worry about all those stray electrons.”

Within the next decade, both radio and gamma-ray astronomers expect to reach sensitivities that will allow them to pick up gravitational waves from orbiting pairs of monster black holes.

“Fermi’s unprecedented ability to precisely time the arrival of gamma rays and its wide field of view make this measurement possible,” said Judith Racusin, Fermi deputy project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Since it launched, the mission has consistently surprised us with new information about the gamma-ray sky. We’re all looking forward to the next amazing discovery.”

The Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by Goddard. Fermi was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the United States.

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Fermi Gamma-ray Space Telescope, formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [NASA/ESA Hubble, NASA Chandra, NASA Spitzer, and associated programs.] NASA shares data with various national and international organizations such as from [JAXA]Greenhouse Gases Observing Satellite.

From NASA Fermi: “NASA Missions Unmask Magnetar Eruptions in Nearby Galaxies”

NASA/Fermi LAT.

From NASA Fermi

Jan. 13, 2021

Francis Reddy
francis.j.reddy@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Media contact:
Claire Andreoli
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

On April 15, 2020, a brief burst of high-energy light swept through the solar system, triggering instruments on several NASA and European spacecraft. Now, multiple international science teams conclude that the blast came from a supermagnetized stellar remnant known as a magnetar located in a neighboring galaxy.

This finding confirms long-held suspicions that some gamma-ray bursts (GRBs) – cosmic eruptions detected in the sky almost daily – are in fact powerful flares from magnetars relatively close to home.

NASA Missions Unveil Magnetar Eruptions in Nearby Galaxies
A pulse of X-rays and gamma rays lasting just 140 milliseconds swept across the solar system on April 15, 2020. The event was a giant flare from a magnetar, a type of city-sized stellar remnant that boasts the strongest magnetic fields known. Watch to learn more. Credit: NASA’s Goddard Space Flight Center.

“This has always been regarded as a possibility, and several GRBs observed since 2005 have provided tantalizing evidence,” said Kevin Hurley, a Senior Space Fellow with the Space Sciences Laboratory at the University of California, Berkeley, who joined several scientists to discuss the burst at the virtual 237th meeting of the American Astronomical Society. “The April 15 event is a game changer because we found that the burst almost certainly lies within the disk of the nearby galaxy NGC 253.”

Papers analyzing different aspects of the event and its implications were published on Jan. 13 in the journals Nature and Nature Astronomy.

GRBs, the most powerful explosions in the cosmos, can be detected across billions of light-years. Those lasting less than about two seconds, called short GRBs, occur when a pair of orbiting neutron stars – both the crushed remnants of exploded stars – spiral into each other and merge. Astronomers confirmed this scenario for at least some short GRBs in 2017, when a burst followed the arrival of gravitational waves – ripples in space-time – produced when neutron stars merged 130 million light-years away.

Magnetars are neutron stars with the strongest-known magnetic fields, with up to a thousand times the intensity of typical neutron stars and up to 10 trillion times the strength of a refrigerator magnet. Modest disturbances to the magnetic field can cause magnetars to erupt with sporadic X-ray bursts for weeks or longer.

Rarely, magnetars produce enormous eruptions called giant flares that produce gamma rays, the highest-energy form of light.

Most of the 29 magnetars now cataloged in our Milky Way galaxy exhibit occasional X-ray activity, but only two have produced giant flares. The most recent event, detected on Dec. 27, 2004, produced measurable changes in Earth’s upper atmosphere despite erupting from a magnetar located about 28,000 light-years away.

Shortly before 4:42 a.m. EDT on April 15, 2020, a brief, powerful burst of X-rays and gamma rays swept past Mars, triggering the Russian High Energy Neutron Detector aboard NASA’s Mars Odyssey spacecraft, which has been orbiting the Red Planet since 2001.

NASA/Mars Odyssey Spacecraft

About 6.6 minutes later, the burst triggered the Russian Konus instrument aboard NASA’s Wind satellite, which orbits a point between Earth and the Sun located about 930,000 miles (1.5 million kilometers) away.

NASA Wind Spacecraft

After another 4.5 seconds, the radiation passed Earth, triggering instruments on NASA’s Fermi Gamma-ray Space Telescope [above], as well as on the European Space Agency’s INTEGRAL satellite and Atmosphere-Space Interactions Monitor (ASIM) aboard the International Space Station.

ESA/Integral.

ESA ASIM

The eruption occurred beyond the field of view of the Burst Alert Telescope (BAT) on NASA’s Neil Gehrels Swift Observatory, so its onboard computer did not alert astronomers on the ground.

NASA Neil Gehrels Swift Observatory.

However, thanks to a new capability called the Gamma-ray Urgent Archiver for Novel Opportunities (GUANO), the Swift team can beam back BAT data when other satellites trigger on a burst. Analysis of this data provided additional insight into the event.

The pulse of radiation lasted just 140 milliseconds – as fast as the blink of an eye or a finger snap.

The giant flare, cataloged as GRB 200415A, reached detectors on different NASA spacecraft at different times. Each instrument pair established its possible location in different swaths of the sky, but the bands intersect in the central part of the bright spiral galaxy NGC 253. This is the most precise position yet established for a magnetar located well beyond our galaxy.
Credits: NASA’s Goddard Space Flight Center and Adam Block/Mount Lemmon SkyCenter/University of Arizona.

The Fermi, Swift, Wind, Mars Odyssey and INTEGRAL missions all participate in a GRB-locating system called the InterPlanetary Network (IPN). Now funded by the Fermi project, the IPN has operated since the late 1970s using different spacecraft located throughout the solar system. Because the signal reached each detector at different times, any pair of them can help narrow down a burst’s location in the sky. The greater the distances between spacecraft, the better the technique’s precision.

The IPN placed the April 15 burst, called GRB 200415A, squarely in the central region of NGC 253, a bright spiral galaxy located about 11.4 million light-years away in the constellation Sculptor. This is the most precise sky position yet determined for a magnetar located beyond the Large Magellanic Cloud, a satellite of our galaxy and host to a giant flare in 1979, the first ever detected.

Giant flares from magnetars in the Milky Way and its satellites evolve in a distinct way, with a rapid rise to peak brightness followed by a more gradual tail of fluctuating emission. These variations result from the magnetar’s rotation, which repeatedly brings the flare location in and out of view from Earth, much like a lighthouse.

Observing this fluctuating tail is conclusive evidence of a giant flare. Seen from millions of light-years away, though, this emission is too dim to detect with today’s instruments. Because these signatures are missing, giant flares in our galactic neighborhood may be masquerading as much more distant and powerful merger-type GRBs.

A detailed analysis of data from Fermi’s Gamma-ray Burst Monitor (GBM) and Swift’s BAT provides strong evidence that the April 15 event was unlike any burst associated with mergers, noted Oliver Roberts, an associate scientist at Universities Space Research Association’s Science and Technology Institute in Huntsville, Alabama, who led the study.

In particular, this was the first giant flare known to occur since Fermi’s 2008 launch, and the GBM’s ability to resolve changes at microsecond timescales proved critical. The observations reveal multiple pulses, with the first one appearing in just 77 microseconds – about 13 times the speed of a camera flash and nearly 100 times faster than the rise of the fastest GRBs produced by mergers. The GBM also detected rapid variations in energy over the course of the flare that have never been observed before.

“Giant flares within our galaxy are so brilliant that they overwhelm our instruments, leaving them to hang onto their secrets,” Roberts said. “For the first time, GRB 200415A and distant flares like it allow our instruments to capture every feature and explore these powerful eruptions in unparalleled depth.”

Giant flares are poorly understood, but astronomers think they result from a sudden rearrangement of the magnetic field. One possibility is that the field high above the surface of the magnetar may become too twisted, suddenly releasing energy as it settles into a more stable configuration. Alternatively, a mechanical failure of the magnetar’s crust – a starquake – may trigger the sudden reconfiguration.

Roberts and his colleagues say the data show some evidence of seismic vibrations during the eruption. The highest-energy X-rays recorded by Fermi’s GBM reached 3 million electron volts (MeV), or about a million times the energy of blue light, itself a record for giant flares. The researchers say this emission arose from a cloud of ejected electrons and positrons moving at about 99% the speed of light. The short duration of the emission and its changing brightness and energy reflect the magnetar’s rotation, ramping up and down like the headlights of a car making a turn. Roberts describes it as starting off as an opaque blob – he pictures it as resembling a photon torpedo from the “Star Trek” franchise – that expands and diffuses as it travels.

The torpedo also factors into one of the event’s biggest surprises. Fermi’s main instrument, the Large Area Telescope (LAT), also detected three gamma rays, with energies of 480 MeV, 1.3 billion electron volts (GeV), and 1.7 GeV – the highest-energy light ever detected from a magnetar giant flare. What’s surprising is that all of these gamma rays appeared long after the flare had diminished in other instruments.

Nicola Omodei, a senior research scientist at Stanford University in California, led the LAT team investigating these gamma rays, which arrived between 19 seconds and 4.7 minutes after the main event. The scientists conclude that this signal most likely comes from the magnetar flare. “For the LAT to detect a random short GRB in the same region of the sky and at nearly the same time as the flare, we would have to wait, on average, at least 6 million years,” he explained.

Magnetar Giant Flare Produces Gamma Rays
Astronomers explain the observations of GRB 200415A with the sequence of events illustrated here. A sudden reconfiguration of the magnetar’s magnetic field produced a quick, powerful pulse of X-rays and gamma rays. The event also ejected a blob of matter, which followed the pulse traveling at about 99% the speed of light. After a few days, they both reached the boundary, called a bow shock, where a steady outflow from the magnetar causes a pile-up of interstellar gas. Light from the flare passed through, followed many seconds later by the ejected cloud. The fast-moving matter interacted with gas at the bow shock, creating shock waves that accelerated particles and produced high-energy gamma rays. This accounts for the delay in the arrival of the most energetic gamma rays detected by NASA’s Fermi spacecraft. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR).

A magnetar produces a steady outflow of fast-moving particles. As it moves through space, this outflow plows into, slows, and diverts interstellar gas. The gas piles up, becomes heated and compressed, and forms a type of shock wave called a bow shock.

In the model proposed by the LAT team, the flare’s initial pulse of gamma rays travels outward at the speed of light, followed by the cloud of ejected matter, which is moving nearly as fast. After several days, they both reach the bow shock. The gamma rays pass through. Seconds later, the cloud of particles – now expanded into a vast, thin shell – collides with accumulated gas at the bow shock. This interaction creates shock waves that accelerate particles, producing the highest-energy gamma rays after the main burst.

The April 15 flare proves that these events constitute their own class of GRBs. Eric Burns, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge, led a study investigating additional suspects using data from numerous missions. The findings will appear in The Astrophysical Journal Letters. Bursts near the galaxy M81 in 2005 and the Andromeda galaxy (M31) in 2007 had already been suggested to be giant flares, and the team additionally identified a flare in M83, also seen in 2007 but newly reported. Add to these the giant flare from 1979 and those observed in our Milky Way in 1998 and 2004.

“It’s a small sample, but we now have a better idea of their true energies, and how far we can detect them,” Burns said. “A few percent of short GRBs may really be magnetar giant flares. In fact, they may be the most common high-energy outbursts we’ve detected so far beyond our galaxy – about five times more frequent than supernovae.”

See the full article here .

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

The Fermi Gamma-ray Space Telescope, formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

From Ethan Siegel: “Antimatter Mystery Likely Due To Pulsars, Not Dark Matter”

From Ethan Siegel
Jan 2

NASA’s Fermi Satellite has constructed the highest resolution, high-energy map of the Universe ever created. Without space-based observatories such as this one, we could never learn all that we have about the Universe, nor could we even accurately measure the gamma-ray sky. (NASA/DOE/FERMI LAT COLLABORATION)

NASA/Fermi LAT

NASA/Fermi Gamma Ray Space Telescope

For years, astronomers have been puzzled by an excess of antimatter particles. Unfortunately, dark matter is probably not the solution.

When you look out at the Universe, what you see is only a tiny portion of what’s actually out there. If you examine the Universe solely with what’s perceptible to your eyes, you’ll miss out on a whole slew of information that exists in wavelengths of light that are invisible to us. From the highest-energy gamma rays to the lowest-energy radio waves, the electromagnetic spectrum is enormous, with visible light representing just a tiny sliver of what’s out there.

However, there’s an entirely different method to measure the Universe: to collect actual particles and antiparticles, a science known as cosmic ray astronomy. For more than a decade, astronomers have seen a signal of cosmic ray positrons — the antimatter counterpart of the electron — that they’ve struggled to explain. Could it be humanity’s best clue towards solving the dark matter mystery? A new study says no, it’s probably just pulsars. [Physical Review D]

Women in STEM – Dame Susan Jocelyn Bell Burnell

Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

Dame Susan Jocelyn Bell Burnell 2009

Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

Here’s why.

Cosmic rays produced by high-energy astrophysics sources can reach any object in the Solar System, and appear to permeate our local region of space omnidirectionally. When they collide with Earth, they strike atoms in the atmosphere, creating particle and radiation showers at the surface, while direct detectors in space, above the atmosphere, can measure the original particles directly. (ASPERA COLLABORATION / ASTROPARTICLE ERANET)

There are a great many things in the Universe that are known to create positrons, the antimatter counterpart of electrons. Whenever you have a high-enough energy collision between two particles, there’s a certain amount of energy that will be available with the potential to create new particle-antiparticle pairs. If that available energy is greater than the equivalent mass of the new particle(s) you want to create, as defined by Einstein’s E = mc2, there’s a finite probability of generating those new particles.

There are all sorts of high-energy processes that can lead to this type of energy becoming available, including particles accelerated by black holes, high-energy protons colliding with the galactic disk, or particles accelerated in the vicinity of neutron stars. Based on the known physics and astrophysics of the Universe, we know that a certain amount of positrons must be generated irrespective of any new physics.

Two bubbles of high-energy signatures are evidence that electron/positron annihilation is occurring, likely powered by processes at the galactic center. Here on Earth, more positrons than can be explained by conventional physics are seen via direct cosmic ray experiments, putting forth the exciting possibility that dark matter might be the cause of both that excess and the galactic center gamma rays. (NASA’S GODDARD SPACE FLIGHT CENTER)

However, we also expect that there is some new physics out there, because of the overwhelming astrophysical evidence for dark matter. While the true nature of dark matter will remain a mystery until the particle (or at least one of the particles) responsible for it is detected directly, many dark matter scenarios exist where not only is dark matter its own antiparticle, but that dark matter annihilations will also produce electron-positron pairs.

Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

Fritz Zwicky from http:// palomarskies.blogspot.com

Coma cluster via NASA/ESA Hubble

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

LSST telescope, The Vera Rubin Survey Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

Dark Matter Research

Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

[caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

Dark Matter Particle Explorer China

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

LBNL LZ Dark Matter project at SURF, Lead, SD, USA

Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

Whenever you have multiple possible physical explanations for what could cause an observable phenomenon, the key to telling which one matches reality is to tease out differences between the explanations. In particular, positrons due to dark matter should experience a cutoff at specific energies (corresponding to the mass of the dark matter particles), while positrons generated by conventional astrophysics should fall off more gradually.

NASA/AMS02 device on the ISS

In 2011, the Alpha Magnetic Spectrometer experiment (AMS-02) was launched with the goal of further investigating this mystery. After arriving at the International Space Station aboard the final mission of the Space Shuttle Endeavor, it was quickly set up and began sending data back to Earth within 3 days. During its operational phase, it collected and measured more than ten billion cosmic ray particles per year.

What’s remarkable about AMS-02 is that it didn’t just measure cosmic ray particles, but was able to sort them both by type and by energy, providing us with an unprecedented set of data to evaluate whether the positrons appeared to be due to dark matter or not. At low energies, the data matched the predictions of cosmic rays colliding with the interstellar medium, but at higher energies, something else was clearly at play.

If the AMS-02 experiment had not experienced any failures or required any repairs, it would have collected sufficient data to distinguish between pulsars (blue) or annihilating dark matter (red) as the source of the excess positrons. Either way, collisions of cosmic rays with the interstellar medium can only explain the low-energy signature, with another explanation required for the high-energy signatures. (AMS COLLABORATION)

However, that’s not a slam dunk for dark matter by any means. At higher energies, it’s also possible that pulsars, which accelerate matter particles to incredible energies through a combination of their gravitational and electromagnetic forces, could produce a peaked excess of positrons at high energies.

Although AMS-02 sees evidence (at 4-sigma, or 99.99% confidence) that there’s a peak and then a falloff in the observed energies of positrons, its sensitivity and event rate peters out at exactly the types of energies that would enable us to differentiate between a positron signal arising from pulsars versus one arising from annihilating dark matter. With spacewalks currently ongoing to attempt to repair AMS-02 and bring it back online to continue its observations, it may eventually collect enough data to discern, on its own, whether pulsars or dark matter provide the best fit to the data.

The Vela pulsar, like all pulsars, is an example of a neutron star corpse. The gas and matter surrounding it is quite common, and is capable of providing fuel for the pulsing behavior of these neutron stars. Matter-antimatter pairs, as well as high-energy particles, are produced in copious amounts by neutron stars, offering up the possibility that they, and not dark matter, are responsible for the excess signals observed by AMS-02. (NASA/CXC/PSU/G.PAVLOV ET AL.)

However, there’s more than one way to tell these two scenarios apart, as positrons produced by pulsars should also generate an additional signal that falls well outside the measurements that AMS-02 or any cosmic ray experiment could detect: gamma rays.

If pulsars truly generate the positrons that could be responsible for the signal that cosmic ray experiments are seeing, then a significant fraction of those positrons will have the misfortune of colliding with electrons in the interstellar medium long before they arrive at our cosmic ray detectors. When positrons collide with electrons, they annihilate, with each reaction producing two gamma rays with a very specific energy signature: 511 keV of energy, the rest-energy equivalent of an electron’s (or positron’s) mass, also obtained from Einstein’s E = mc2.

The production of matter/antimatter pairs (left) from pure energy is a completely reversible reaction (right), with matter/antimatter annihilating back to pure energy. When a photon is created and then destroyed, it experiences those events simultaneously, while being incapable of experiencing anything else at all. If you operate in the center-of-momentum (or center-of-mass) rest frame, particle/antiparticle pairs (including two photons) will zip off at 180 degree angles to one another, with energies equal to the rest-mass equivalent of each of the particles, as defined by Einstein’s E = mc². (DMITRI POGOSYAN / UNIVERSITY OF ALBERTA)

However, pulsars should theoretically be able to accelerate these electrons and positrons up to extraordinarily high energies: energies that even the world’s most powerful terrestrial particle accelerator, the Large Hadron Collider, struggles to reach. When photons — even normal-energy starlight — interact with these ultra-relativistic (near light-speed) particles, they can get boosted to extraordinary energies through a process known as inverse Compton scattering.

Based on physical parameters like the properties of the pulsar, the matter in the pulsar’s vicinity, the electrons and positrons generated, and the amount of starlight present nearby, a specific energy spectrum will be created for the photons generated from this process. Sum them all up for all of the nearby, relevant pulsars, and your gamma ray signature might indicate that pulsars, and not dark matter, cause this positron excess.

Particles traveling near light speed can interact with starlight and boost it to gamma-ray energies. This animation shows the process, known as inverse Compton scattering. When light ranging from microwave to ultraviolet wavelengths collides with a fast-moving particle, the interaction boosts it to gamma rays, the most energetic form of light. (NASA / GSFC)

About 800 light-years away, incredibly close by astronomical standards, one of the brightest gamma-ray pulsars in the entire sky can be found: Geminga. It was only discovered in 1972, and had its nature revealed in 1991, when the ROSAT mission measured evidence for a neutron star spinning at a rate of 4.2 revolutions-per-second.

Geminga. Patrizia Caraveo (INAF/IASF), Milan

ROSAT X-ray satellite built by DLR , with instruments built by West Germany, the United Kingdom and the United States

Fast-forward to the present day, where NASA’s Fermi Large Area Telescope — with enormously improved spatial and energy resolution — is now the world’s most sophisticated gamma ray observatory. By subtracting out the gamma ray signal arising from cosmic rays colliding with interstellar gas clouds, the remnant signal from starlight interacting with accelerated electrons and positrons could be revealed.

When a team of researchers led by Mattia di Mauro analyzed the Fermi data [Physical Review D], what they saw was spectacular: an energy-dependent signal that, at its largest, spanned some 20 degrees in the sky at the exact energies that AMS-02 was most sensitive to.

This model of Geminga’s gamma-ray halo shows how the emission changes at different energies, a result of two effects. The first is the pulsar’s rapid motion through space over the decade Fermi’s Large Area Telescope has observed it. Second, lower-energy particles travel much farther from the pulsar before they interact with starlight and boost it to gamma-ray energies. This is why the gamma-ray emission covers a larger area at lower energies. (NASA’S GODDARD SPACE FLIGHT CENTER/M. DI MAURO)

Explaining this glow, which decreases in size as Fermi looks at progressively higher energies, fit the models perfectly by leveraging a combination of inverse Compton scattering with the pulsar’s motion through interstellar space. According to Fiorenza Donato, coauthor on the recent Fermi study that measured gamma rays from Geminga Physical Review D [above],
Lower-energy particles travel much farther from the pulsar before they run into starlight, transfer part of their energy to it, and boost the light to gamma rays. This is why the gamma-ray emission covers a larger area at lower energies. Also, Geminga’s halo is elongated partly because of the pulsar’s motion through space.

The measurement of the gamma rays from Geminga alone suggests that this one pulsar could be responsible for as much as 20% of the high-energy positrons seen by the AMS-02 experiment.

This animation shows a region of the sky centered on the pulsar Geminga. The first image shows the total number of gamma rays detected by Fermi’s Large Area Telescope at energies from 8 to 1,000 billion electron volts (GeV) — billions of times the energy of visible light — over the past decade. By removing all bright sources, astronomers discovered the pulsar’s faint, extended gamma-ray halo, concluding that this one pulsar could be responsible for up to 20% of the positrons detected by the AMS-02 experiment. (NASA/DOE/FERMI LAT COLLABORATION)

Whenever there’s an unexplained phenomenon that we’ve measured or observed, it presents a tantalizing possibility to scientists: that perhaps there’s something new at play beyond what’s presently known. We know there are mysteries about our Universe that require new physics at some level — mysteries like dark matter, dark energy, or the cosmic matter-antimatter asymmetry — whose ultimate solution has yet to be discovered.

However, we cannot claim evidence for a new discovery until everything that represents what’s already known is quantified and accounted for. By factoring in the effect of pulsars, the positron excess observed by the Alpha Magnetic Spectrometer collaboration may turn out to be explicable entirely by conventional high-energy astrophysics, with no need for dark matter. Right now, it appears that pulsars may be responsible for 100% of the observed excess, requiring scientists to go back to the drawing board for a direct signal that reveals our Universe’s elusive dark matter.

See the full article here .

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“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

From Discover Magazine: “Using Gamma Rays, Scientists Map Out 21 New Constellations”

From Discover Magazine

October 19, 2018
Chelsea Gohd

The Godzilla constellation in the gamma-ray sky — a new set of constellations based off of gamma-ray emissions observed with NASA’s Fermi Gamma-ray Space Telescope. (Credit: NASA)

NASA/Fermi LAT

NASA/Fermi Gamma Ray Space Telescope

Gamma-Ray Sky

For countless years, humans have gazed up at the sky and made sense of the stars by finding shapes in them — constellations of heroes, animals, and well-worn tales. Now, to celebrate the 10th mission year of NASA’s Fermi Gamma-ray Space Telescope, scientists have used the telescope to develop a new set of constellations that correspond with gamma-ray emissions [Future post].

Gamma rays are the most powerful in the electromagnetic spectrum, and they’re typically only produced by very powerful objects. Supermassive black holes at the center of galaxies emit gamma rays, and gamma rays can also spring from explosive gamma-ray bursts, pulsars, the debris of supernova explosions, and more. The Fermi telescope has spent the last decade scanning the sky to compile list of gamma ray sources in the observable universe. That’s given them an array of points, similar to the stars we see shining in the visible spectrum.

In what is known as the “gamma-ray sky,” scientists have devised constellations inspired by many of the same things that inspired the starlight constellations our ancestors gazed at.

The “original” constellations primarily fall into three categories: myths and legends, meaningful topics and common creatures and items, NASA Goddard’s Elizabeth Ferrara, who led the constellation project, explained in a teleconference. The Fermi constellations from the gamma-ray sky are also derived from three categories: modern legends, team partners, and Fermi science. To make sure they didn’t look too much like stars, the team behind these constellations used artificial color to distinguish them.

Familiar Shapes

There are 21 Fermi constellations, including the Hulk (created from a gamma-ray mishap), Godzilla, the Starship Enterprise from “Star Trek: The Next Generation”, the TARDIS from “Doctor Who”, gamma-ray bursts, dark lightning, spider pulsars. Important landmarks from partner nations show up as well: Mt. Fuji for Japan, the Colosseum to represent Italy and more. The constellations even include a Saturn V rocket to represent Huntsville, Alabama where the gamma-ray burst monitor team is centered.

(Credit: NASA)
The Godzilla constellation in the gamma-ray sky — a new set of constellations based off of gamma-ray emissions observed with NASA’s Fermi Gamma-ray Space Telescope. (Credit: NASA)
Gamma-Ray Sky

For countless years, humans have gazed up at the sky and made sense of the stars by finding shapes in them — constellations of heroes, animals, and well-worn tales. Now, to celebrate the 10th mission year of NASA’s Fermi Gamma-ray Space Telescope, scientists have used the telescope to develop a new set of constellations that correspond with gamma-ray emissions.

Gamma rays are the most powerful in the electromagnetic spectrum, and they’re typically only produced by very powerful objects. Supermassive black holes at the center of galaxies emit gamma rays, and gamma rays can also spring from explosive gamma-ray bursts, pulsars, the debris of supernova explosions, and more. The Fermi telescope has spent the last decade scanning the sky to compile list of gamma ray sources in the observable universe. That’s given them an array of points, similar to the stars we see shining in the visible spectrum.

In what is known as the “gamma-ray sky,” scientists have devised constellations inspired by many of the same things that inspired the starlight constellations our ancestors gazed at.

The “original” constellations primarily fall into three categories: myths and legends, meaningful topics and common creatures and items, NASA Goddard’s Elizabeth Ferrara, who led the constellation project, explained in a teleconference. The Fermi constellations from the gamma-ray sky are also derived from three categories: modern legends, team partners, and Fermi science. To make sure they didn’t look too much like stars, the team behind these constellations used artificial color to distinguish them.

Familiar Shapes

There are 21 Fermi constellations, including the Hulk (created from a gamma-ray mishap), Godzilla, the Starship Enterprise from “Star Trek: The Next Generation”, the TARDIS from “Doctor Who”, gamma-ray bursts, dark lightning, spider pulsars. Important landmarks from partner nations show up as well: Mt. Fuji for Japan, the Colosseum to represent Italy and more. The constellations even include a Saturn V rocket to represent Huntsville, Alabama where the gamma-ray burst monitor team is centered.

“The hope, of course, is to make the gamma-ray sky more acceptable,” Ferrara said. “By creating constellations that tie into themes that people already know and think about, we hope to bring gamma-ray science into their thoughts.”

Ferrara and Daniel Kocevski, from NASA’s Marshall Space Flight Center, have developed an interactive webpage so that the public can easily engage with these constellations. The interactive site uses a map of the gamma-ray sky from Fermi and artwork from Aurore Simonnet, an illustrator at Sonoma State University in Rohnert Park, California.

Users on the site can explore the gamma-ray sky themselves and learn about the name, artwork, and details behind each constellation.

See the full article here .

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From NASA Fermi: “NASA’s Fermi Traces Source of Cosmic Neutrino to Monster Black Hole”

From NASA Fermi

July 12, 2018

Felicia Chou
Headquarters, Washington
202-358-0257
felicia.chou@nasa.gov

Dewayne Washington
Goddard Space Flight Center, Greenbelt, Md.
301-286-0040
dewayne.a.washington@nasa.gov

For the first time ever, scientists using NASA’s Fermi Gamma-ray Space Telescope have found the source of a high-energy neutrino from outside our galaxy. This neutrino traveled 3.7 billion years at almost the speed of light before being detected on Earth. This is farther than any other neutrino whose origin scientists can identify.

High-energy neutrinos are hard-to-catch particles that scientists think are created by the most powerful events in the cosmos, such as galaxy mergers and material falling onto supermassive black holes. They travel at speeds just shy of the speed of light and rarely interact with other matter, allowing them to travel unimpeded across distances of billions of light-years.

The neutrino was discovered by an international team of scientists using the National Science Foundation’s IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station.

U Wisconsin ICECUBE neutrino detector at the South Pole

Lunar Icecube

IceCube DeepCore annotated

IceCube PINGU annotated

DM-Ice II at IceCube annotated

Fermi found the source of the neutrino by tracing its path back to a blast of gamma-ray light from a distant supermassive black hole in the constellation Orion.

“Again, Fermi has helped make another giant leap in a growing field we call multimessenger astronomy,” said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington. “Neutrinos and gravitational waves deliver new kinds of information about the most extreme environments in the universe. But to best understand what they’re telling us, we need to connect them to the ‘messenger’ astronomers know best—light.”

Scientists study neutrinos, as well as cosmic rays and gamma rays, to understand what is going on in turbulent cosmic environments such as supernovas, black holes and stars. Neutrinos show the complex processes that occur inside the environment, and cosmic rays show the force and speed of violent activity. But, scientists rely on gamma rays, the most energetic form of light, to brightly flag what cosmic source is producing these neutrinos and cosmic rays.

“The most extreme cosmic explosions produce gravitational waves, and the most extreme cosmic accelerators produce high-energy neutrinos and cosmic rays,” says Regina Caputo of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the analysis coordinator for the Fermi Large Area Telescope Collaboration. “Through Fermi, gamma rays are providing a bridge to each of these new cosmic signals.”

The discovery is the subject of two papers published Thursday in the journal Science.

The source identification paper also includes important follow-up observations by the Major Atmospheric Gamma Imaging Cherenkov Telescopes and additional data from NASA’s Neil Gehrels Swift Observatory and many other facilities.

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)

NASA Neil Gehrels Swift Observatory

On Sept. 22, 2017, scientists using IceCube detected signs of a neutrino striking the Antarctic ice with energy of about 300 trillion electron volts—more than 45 times the energy achievable in the most powerful particle accelerator on Earth. This high energy strongly suggested that the neutrino had to be from beyond our solar system. Backtracking the path through IceCube indicated where in the sky the neutrino came from, and automated alerts notified astronomers around the globe to search this region for flares or outbursts that could be associated with the event.

Data from Fermi’s Large Area Telescope revealed enhanced gamma-ray emission from a well-known active galaxy at the time the neutrino arrived. This is a type of active galaxy called a blazar, with a supermassive black hole with millions to billions of times the Sun’s mass that blasts jets of particles outward in opposite directions at nearly the speed of light. Blazars are especially bright and active because one of these jets happens to point almost directly toward Earth.

Fermi scientist Yasuyuki Tanaka at Hiroshima University in Japan was the first to associate the neutrino event with the blazar designated TXS 0506+056 (TXS 0506 for short).

“Fermi’s LAT monitors the entire sky in gamma rays and keeps tabs on the activity of some 2,000 blazars, yet TXS 0506 really stood out,” said Sara Buson, a NASA Postdoctoral Fellow at Goddard who performed the data analysis with Anna Franckowiak, a scientist at the Deutsches Elektronen-Synchrotron research center in Zeuthen, Germany. “This blazar is located near the center of the sky position determined by IceCube and, at the time of the neutrino detection, was the most active Fermi had seen it in a decade.”

For more about NASA’s Fermi mission, visit:

https://www.nasa.gov/fermi

See the full article here .

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The Fermi Gamma-ray Space Telescope , formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

From NASA Goddard and NASA/Fermi via phys.org: “Multiple gamma-ray emission regions detected in the blazar 3C 279”

From NASA Goddard Space Flight Center

NASA Fermi

phys.org

May 23, 2018
Tomasz Nowakowski

An example composite image of 3C 279 convolved with a beam size of 0.1 mas (circle in the bottom left corner). The contours represent the total intensity while the color scale is for polarized intensity image of 3C 279. The line segments (length of the segments is proportional to fractional polarization) marks the EVPA direction. Credit: Rani et al., 2018.

Using very long baseline interferometry (VLBI), astronomers have investigated the magnetic field topology of the blazar 3C 279, uncovering the presence of multiple gamma-ray emission regions in this source. The discovery was presented May 11 in a paper published in The Astrophysical Journal.

Blazars, classified as members of a larger group of active galaxies that host active galactic nuclei (AGN), are the most numerous extragalactic gamma-ray sources. Their characteristic features are relativistic jets pointed almost exactly toward the Earth. In general, blazars are perceived by astronomers as high-energy engines serving as natural laboratories to study particle acceleration, relativistic plasma processes, magnetic field dynamics and black hole physics.

NASA’s Fermi Gamma-ray Space Telescope is an essential instrument for blazar studies. The spacecraft is equipped with in the Large Area Telescope (LAT), which allows it to detect photons with energy from about 20 million to about 300 billion electronvolts. So far, Fermi has discovered more than 1,600 blazars.

NASA/Fermi LAT

A team of astronomers led by Bindu Rani of NASA’s Goddard Space Flight Center has analyzed the data provided by LAT and by the U.S.-based Very Long Baseline Array (VLBA) to investigate the blazar 3C 279.

NRAO VLBA

The studied object, located in the constellation Virgo. It is one of the brightest and most variable sources in the gamma-ray sky monitored by Fermi. The data allowed Rani’s team to uncover more insight into the nature of gamma-ray emission from this blazar.

“Using high-frequency radio interferometry (VLBI) polarization imaging, we could probe the magnetic field topology of the compact high-energy emission regions in blazars. A case study for the blazar 3C 279 reveals the presence of multiple gamma-ray emission regions,” the researchers wrote in the paper.

Six gamma-ray flares were observed in 3C 279 between November 2013 and August 2014. The researchers also investigated the morphological changes in the blazar’s jet.

The team found that ejection of a new component (designated NC2) during the first three gamma-ray flares suggests the VLBI core as the possible site of the high-energy emission. Furthermore, a delay between the last three flares and the ejection of a new component (NC3) indicates that high-energy emission in this case is located upstream of the 43 GHz core (closer to the blazar’s black hole).

The astronomers concluded that their results are indicative of multiple sites of high-energy dissipation in 3C 279. Moreover, according to the authors of the paper, their study proves that VLBI is the most promising technique to probe the high-energy dissipation regions. However, they added that still more observations are needed to fully understand these features and mechanisms behind them.

“The Fermi mission will continue observing the GeV sky at least for next couple of years. The TeV missions are on their way to probe the most energetic part of the electromagnetic spectrum. High-energy polarization observations (AMEGO, IXPE, etc.) will be of extreme importance in understanding the high-energy dissipation mechanisms,” the researchers concluded.

See the full article here.

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Stem Education Coalition

The Fermi Gamma-ray Space Telescope , formerly referred to as the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden.

NASA’s Goddard Space Flight Center is home to the nation’s largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Named for American rocketry pioneer Dr. Robert H. Goddard, the center was established in 1959 as NASA’s first space flight complex. Goddard and its several facilities are critical in carrying out NASA’s missions of space exploration and scientific discovery.

NASA/Goddard Campus

From ANU: “Mysterious signal comes from very old stars at centre of our galaxy”

Australian National University

March 12, 2018
No writer credit found.

FOR INTERVIEW:
Dr Roland Crocker
Research School of Astronomy and Astrophysics
ANU College of Science
P: +61 2 6125 0253
M: +61 438 499 129
E: Roland.Crocker@anu.edu.au

Will Wright
ANU Media Team
+61 2 6125 7979,
+61 478 337 740
media@anu.edu.au

No image caption or credit.

A team of astronomers involving The Australian National University (ANU) has discovered that a mysterious gamma-ray signal from the centre of the Milky Way comes from 10 billion-year-old stars, rather than dark matter as previously thought.

The Fermi view of the gamma-ray sky. (NASA/DOE/Fermi LAT Collaboration)

NASA/Fermi LAT

NASA/Fermi Gamma Ray Space Telescope

Co-researcher Dr Roland Crocker from ANU said the team had a working hypothesis that the signal was being emitted from thousands of rapidly spinning neutron stars called millisecond pulsars.

“At the distance to the centre of our galaxy, the emission from many thousands of these whirling dense stars could be blending together to imitate the smoothly distributed signal we expect from dark matter,” said Dr Crocker from the ANU Research School of Astronomy and Astrophysics.

“Millisecond pulsars close to the Earth are known to be gamma-ray emitters.”

Dr Crocker said the findings ruled out a provocative theory that dark matter, which is not well understood by scientists, was the origin of the gamma-ray signal.

There is broad scientific consensus that dark matter – matter that scientists cannot see – is widely present in the Universe and helps explain how galaxies hold together rather than fly apart as they spin.

“It is thought that dark matter is composed of Weakly Interacting Massive Particles, which would be expected to gather in the centre of our galaxy,” Dr Crocker said.

“The theory is that, very occasionally, these particles crash into each other and radiate light a billion times more energetic than visible light.”

The Fermi Gamma-Ray Space Telescope, which has been in a low Earth orbit since 2008, has given scientists their clearest ever view of the gamma-ray sky in this energy range.

“While the centre of our galaxy may be rich in dark matter, it is also populated by ancient stars that make up a structure called the Galactic bulge,” Dr Crocker said.

He said the signal detected by Fermi closely traces the distribution of stars in the Galactic bulge.

“Ongoing observational and theoretical work is underway to verify or refute the hypothesis that the gamma-ray signal comes from millisecond pulsars,” Dr Crocker said.

ANU and research institutions in the United States, New Zealand and Germany conducted the study, which was led by Virginia Tech in the US.

The study is published in Nature Astronomy.

See the full article here .

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ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.