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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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.

From UCSC: ” Novel search strategy advances the hunt for primordial black holes”

UC Santa Cruz

February 21, 2018
Tim Stephens
stephens@ucsc.edu

Some theories of the early universe predict density fluctuations that would have created small “primordial black holes,” some of which could be drifting through our galactic neighborhood today and might even be bright sources of gamma rays.

Researchers analyzing data from the Fermi Gamma-ray Space Telescope for evidence of nearby primordial black holes have come up empty, but their negative findings still allow them to put an upper limit on the number of these tiny black holes that might be lurking in the vicinity of Earth.

NASA/Fermi Gamma Ray Space Telescope

NASA’s Fermi Gamma-ray Space Telescope is a powerful space observatory that opens a wide window on the universe. Primordial black holes are a potential source of gamma rays, the highest-energy form of light. (Illustration credit: NASA)

“Understanding how many primordial black holes are around today can help us understand the early universe better,” said Christian Johnson, a graduate student in physics at UC Santa Cruz who developed an algorithm to search data from Fermi’s Large Area Telescope (LAT) for the signatures of primordial black holes. Johnson is a corresponding author of a paper on the findings that has been accepted for publication in The Astrophysical Journal.

Low-mass black holes are expected to emit gamma rays due to Hawking radiation, a theoretical prediction from the work of physicist Stephen Hawking and others. Hawking showed that quantum effects can give rise to particle-antiparticle pairs near the event horizon of a black hole, allowing one of the particles to fall into the black hole and the other to escape. The result is that the black hole emits radiation and loses mass.

A small black hole that isn’t absorbing enough from its environment to offset the losses from Hawking radiation will steadily lose mass and eventually evaporate entirely. The smaller it gets, the brighter it “burns,” emitting more and more Hawking radiation before exploding in a final cataclysm. Previous searches for primordial black holes using ground-based gamma-ray observatories have looked for these brief explosions, but Fermi should be able to detect the “burn phase” occurring over a period of several years.

A limitation of the Fermi search was that it could only extend a relatively short distance from Earth (a small fraction of the distance to the nearest star). The advantage of looking nearby, however, is that primordial black holes could be distinguished from other sources of gamma rays by their movement on the sky.

“It’s like looking at the sky at night and trying to decide if something is an airplane or a star,” Johnson explained. “If it’s an airplane, it will move, and if it’s a star it will stay put.”

Any primordial black holes still around today would have started out much larger and have been gradually losing mass for billions of years. To detect one with Fermi, it would have to have reached the final burn phase during the roughly four-year observation period of the study. Over a period of a few years, it would go from undetectably dim to extremely bright, and would burn brightly for several years before exploding, Johnson said.

“Even though we didn’t detect any, the non-detection sets a limit on the rate of explosions and gives us better constraints than previous research,” he said.

In addition to Johnson, the other corresponding authors of the paper include Steven Ritz, professor of physics and director of the Santa Cruz Institute of Particle Physics at UCSC; and Stefan Funk and Dmitry Malyshev at the Erlangen Centre for Astroparticle Physics in Germany. Other members of the Fermi-LAT Collaboration also contributed to this work and are coauthors of the paper.

See the full article here .

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Shane Telescope at UCO Lick Observatory, UCSC

Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

UCSC is the home base for the Lick Observatory.

Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

Search for extraterrestrial intelligence expands at Lick Observatory
New instrument scans the sky for pulses of infrared light
March 23, 2015
By Hilary Lebow

The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

“Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

“The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

“We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

“This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

“Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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UCSC is the home base for the Lick Observatory.

From Goddard: “NASA’s SuperTIGER Balloon Flies Again to Study Heavy Cosmic Particles”

NASA Goddard Space Flight Center

Dec. 6, 2017
Francis Reddy
francis.j.reddy@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

A science team in Antarctica is preparing to loft a balloon-borne instrument to collect information on cosmic rays, high-energy particles from beyond the solar system that enter Earth’s atmosphere every moment of every day. The instrument, called the Super Trans-Iron Galactic Element Recorder (SuperTIGER), is designed to study rare heavy nuclei, which hold clues about where and how cosmic rays attain speeds up to nearly the speed of light.

NASA’s Super-TIGER balloon

The launch is expected by Dec. 10, weather permitting.

Explore this infographic [on the full article] to learn more about SuperTIGER, cosmic rays and scientific ballooning.
Credits: NASA’s Goddard Space Flight Center

Download infographic as PDF

“The previous flight of SuperTIGER lasted 55 days, setting a record for the longest flight of any heavy-lift scientific balloon,” said Robert Binns, the principal investigator at Washington University in St. Louis, which leads the mission. “The time aloft translated into a long exposure, which is important because the particles we’re after make up only a tiny fraction of cosmic rays.”

The most common cosmic ray particles are protons or hydrogen nuclei, making up roughly 90 percent, followed by helium nuclei (8 percent) and electrons (1 percent). The remainder contains the nuclei of other elements, with dwindling numbers of heavy nuclei as their mass rises. With SuperTIGER, researchers are looking for the rarest of the rare — so-called ultra-heavy cosmic ray nuclei beyond iron, from cobalt to barium.

“Heavy elements, like the gold in your jewelry, are produced through special processes in stars, and SuperTIGER aims to help us understand how and where this happens,” said lead co-investigator John Mitchell at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’re all stardust, but figuring out where and how this stardust is made helps us better understand our galaxy and our place in it.”

When a cosmic ray strikes the nucleus of a molecule of atmospheric gas, both explode in a shower of subatomic shrapnel that triggers a cascade of particle collisions. Some of these secondary particles reach detectors on the ground, providing information scientists can use to infer the properties of the original cosmic ray. But they also produce an interfering background that is greatly reduced by flying instruments on scientific balloons, which reach altitudes of nearly 130,000 feet (40,000 meters) and float above 99.5 percent of the atmosphere.

The most massive stars forge elements up to iron in their cores and then explode as supernovas, dispersing the material into space. The explosions also create conditions that result in a brief, intense flood of subatomic particles called neutrons. Many of these neutrons can “stick” to iron nuclei. Some of them subsequently decay into protons, producing new elements heavier than iron.

Supernova blast waves provide the boost that turns these particles into high-energy cosmic rays.

NASA’s Fermi Proves Supernova Remnants Produce Cosmic Rays. February 14, 2013.

NASA/Fermi Telescope

NASA/Fermi LAT

As a shock wave expands into space, it entraps and accelerates particles until they reach energies so extreme they can no longer be contained.

On Dec. 1, SuperTIGER was brought onto the deck of Payload Building 2 at McMurdo Station, Antarctica, to test communications in preparation for its second flight. Mount Erebus, the southernmost active volcano on Earth, appears in the background.
Credits: NASA/Jason Link

Over the past two decades, evidence accumulated from detectors on NASA’s Advanced Composition Explorer satellite and SuperTIGER’s predecessor, the balloon-borne TIGER instrument, has allowed scientists to work out a general picture of cosmic ray sources. Roughly 20 percent of cosmic rays were thought to arise from massive stars and supernova debris, while 80 percent came from interstellar dust and gas with chemical quantities similar to what’s found in the solar system.

“Within the last few years, it has become apparent that some or all of the very neutron-rich elements heavier than iron may be produced by neutron star mergers instead of supernovas,” said co-investigator Jason Link at Goddard.

Neutron stars are the densest objects scientists can study directly, the crushed cores of massive stars that exploded as supernovas. Neutron stars orbiting each other in binary systems emit gravitational waves, which are ripples in space-time predicted by Einstein’s general theory of relativity. These waves remove orbital energy, causing the stars to draw ever closer until they eventually crash together and merge.

Theorists calculated that these events would be so thick with neutrons they could be responsible for most of the very neutron-rich cosmic rays heavier than nickel. On Aug. 17, NASA’s Fermi Gamma-ray Space Telescope and the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory detected the first light and gravitational waves from crashing neutron stars. Later observations by the Hubble and Spitzer space telescopes indicate that large amounts of heavy elements were formed in the event.

“It’s possible neutron star mergers are the dominant source of heavy, neutron-rich cosmic rays, but different theoretical models produce different quantities of elements and their isotopes,” Binns said. “The only way to choose between them is to measure what’s really out there, and that’s what we’ll be doing with SuperTIGER.”

SuperTIGER is funded by the NASA Headquarters Science Mission Directorate Astrophysics Division.

The National Science Foundation (NSF) Office of Polar Programs manages the U.S. Antarctic Program and provides logistic support for all U.S. scientific operations in Antarctica. NSF’s Antarctic support contractor supports the launch and recovery operations for NASA’s Balloon Program in Antarctica. Mission data were downloaded using NASA’s Tracking and Data Relay Satellite System.

For more information about NASA’s Balloon Program, visit:

http://www.nasa.gov/balloons

See the full article here.

Please help promote STEM in your local schools.

Stem Education Coalition

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