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 |  National Geographic - 5 hours ago November 2, 2009???Star explosions can act like ultra-powerful particle colliders in space, creating what are known as cosmic rays, new research shows. Science Daily (press release) - University of Delaware - Discover Magazine -
Nov-03-2009GALAXY PICTURE: Cosmic Ray Mystery Solved?(topic overview)
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M82 is a bright galaxy located approximately 12 million light years from Earth, in the direction of the Ursa Major constellation. In the active starburst region at its center, stars are being formed at a rate approximately ten times more rapidly than in entire 'normal' galaxies like our own Milky Way. The cosmic rays produced in the formation, life and death of the massive stars in this region eventually produce diffuse gamma-ray emission via their interactions with interstellar gas and radiation. Due to its unusually high cosmic-ray and gas densities and its relative proximity, M82 is expected to be the brightest starburst galaxy in VHE gamma rays. VHE gamma rays, those with energies ranging from 100 GeV (one-hundred billion electron Volts) to 50 TeV (50 trillion electron Volts), are observed with ground-based Cherenkov telescopes. These gamma rays are absorbed in the Earth's atmosphere, where they create a short-lived shower of particles. The Cherenkov telescopes detect the faint, extremely short flashes of blue light, which these particles emit (named Cherenkov light) using extremely sensitive cameras. [1] "The core of M82 forms stars at a rate ten times greater than the entire Milky Way galaxy," said Niklas Karlsson, a postdoctoral fellow at Adler Planetarium in Chicago. He is also a member of the science team for VERITAS, an array of gamma-ray telescopes in Arizona that detected M82, which lies 12 million light-years away in the constellation Ursa Major. "These very-high-energy gamma rays probe physical processes in other galaxies that will help us understand how and where cosmic rays become accelerated," Karlsson explained. "Our sensitivity to gamma-rays -- both in space and on the ground -- has increased enormously thanks to Fermi and observatories like VERITAS," Digel said. "This is opening up the detailed study of high-energy processes in galaxies very close to home."[2] In the Nature journal study results presented Monday at the at the Fermi Science Symposium in Washington D.C., the Very Energetic Radiation Imaging Telescope Array System (VERITAS) Collaboration team shows that the M82 galaxy, which births stars at a rate 50 times higher than our own Milky Way galaxy, produces intense high-powered gamma radiation, a long-sought signature of cosmic rays.[3]
Now new results from the VERITAS gamma-ray telescope array have added fuel to that fire. VERITAS stands for Very Energetic Radiation Imaging Telescope Array System, and it's located atop a mountain in Arizona. When energetic gamma rays (a form of light) hit the Earth's air, they create a shower of subatomic particle that rains down and can be detected by the telescopes. If cosmic rays come from supernovae and massive stars, then we should see more of them coming from galaxies that have a lot of stars being born. That's because massive stars don't live long.[4] The Fermi team looked at a nearby satellite galaxy, the Large Magellanic Cloud, and found gamma-rays -- the most energetic part of the electromagnetic spectrum -- emanating from a known starburst region. This suggests that the life-and-death fury in these regions -- strong winds from massive, short-lived and hot stars, and shock waves from supernovae explosions -- is responsible for accelerating cosmic rays, which in turn create a gamma-ray signal. Cosmic rays are protons or other ionized particles, and they create light in the form of similarly high-energy gamma rays when they collide with other material. Team member J''rgen Kn''dlseder, of the Center for the Study of Space Radiation in Toulouse, France, said he was surprised to see how well confined the gamma-rays were to the starburst region.[5] The Fermi Gamma-ray Space Telescope, which records lower-energy gamma rays than does VERITAS, also found gammas from M82 and from another starburst galaxy, NGC 253, reported Keith Bechtolof the SLAC National Accelerator Laboratory in Menlo Park, Calif. In addition, Fermi recorded a diffuse gamma-ray glow from a region of intense star formation in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way, said J''rgen Kn''dlseder of the Center for the Study of Space Radiation in Toulouse, France.[6] M82 is classified as a starburst galaxy because within a small, central region it makes stars at a rate 10 times higher than that of the entire Milky Way. Although M82 is one of the closest starburst galaxies, '''it took us two years of all-out observations of M82 to acquire all the necessary data,''' said VERITAS researcher Wystan Benbowof the Smithsonian Astrophysical Observatory in Cambridge, Mass. Starburst galaxies produce a diffuse gamma-ray glow that is about one-millionth the brightness of galaxies that have active, supermassive black holes at their centers ''' the only type of galaxy from which gamma-ray telescopes had previously recorded emissions. Finding gamma rays in a starburst galaxy '''had been long predicted, but nobody had ever done it before this year,''' noted Benbow, whose team also reported the discovery online November 1 in Nature.[6]
So-called starburst galaxies should have more cosmic rays than "normal" galaxies like our Milky Way, according to the theory. That's because such galaxies have regions of rapid star formation, which give rise to more of the supermassive stars that end their lives in supernova explosions. For their study, the team searched for gamma rays, the most energetic form of light. Unlike cosmic rays, light isn't affected by magnetic fields, so we can see it from Earth and accurately trace its source.[7] In the active starburst region at the Cigar Galaxy's center, stars are being formed at a rate approximately ten times more rapidly than in "normal" galaxies like our Milky Way, Holder says. The cosmic rays produced in the formation, life, and death of the massive stars in this region eventually produce diffuse gamma-ray emission via their interactions with interstellar gas and radiation.[8] The VERITAS discovery indicates that the cosmic-ray density in M82 is approximately 500 times the average density in our Galaxy, the Milky Way, thus providing key evidence to unlocking the mystery of the origin of cosmic rays. Wystan Benbow, an astrophysicist at the Smithsonian Astrophysical Observatory (SAO), working with the VERITAS, coordinated this project for the VERITAS collaboration. The results of this study, titled "A Connection Between Star Formation Activity and Cosmic Rays in the Starburst Galaxy M82" appeared on Nov. 1, 2009, in the advance online publication of the journal Nature.[1] The VERITAS discovery confirms that expectation, indicating that the cosmic-ray density in M82 is approximately 500 times the average density in our Galaxy, the Milky Way. "This discovery provides fundamental insight into the origin of cosmic rays," said Rene Ong, a professor of physics at the University of California, Los Angeles, and the spokesperson for the VERITAS collaboration. VERITAS could not detect M82's cosmic rays directly because they are trapped within the Cigar Galaxy.[9]
Produced in violent processes in our own galaxy and beyond, cosmic rays are actually energetic particles that continually bombard Earth's atmosphere. They are important, Holder says, because they make up a large fraction of the energy budget of our galaxy, The Milky Way. The amount of energy in cosmic rays is comparable to the energy contained in both starlight, and in Galactic magnetic fields, Holder notes. "Although cosmic rays were first detected 100 years ago, their origins have been a mystery," says Holder. "One idea has been that they are produced by supernova explosions, but there was never any direct proof until now. This gamma ray measurement by VERITAS looks at a galaxy different from our own where there are 30 times as many supernovae. The fact that we see gamma rays indicates that there are many more cosmic rays being produced by these supernovae."[8] "The connection makes sense." "The tangled magnetic fields near 30 Doradus probably confine the cosmic rays to their acceleration sites," Knödlseder said. Fermi's LAT sees diffuse emission from the starburst galaxies M82 and NGC 253, both of which were also seen this year by ground-based observatories sensitive to gamma rays hundreds of times more energetic than the LAT can detect. They do this by imaging faint flashes in the upper atmosphere caused by the absorption of gamma rays carrying trillions of times the energy of visible light.[2] After hearing the news, '''I didn'''t fall out of my chair but I got a big smile on my face,''' says theorist Brian Fields of the University of Illinois at Urbana-Champaign, who is not a member of either discovery team. Although the discoveries '''bolster our confidence that cosmic rays are accelerated by supernova remnants,''' they do not clinch the case, said gamma-ray theorist Charles Dermer of the Naval Research Laboratory in Washington, D.C., a member of the Fermi collaboration. The clincher may come, he says, if an ongoing analysis of Fermi data finds that gamma-ray emissions from starburst galaxies peak at an energy of 70 million eV. That corresponds to the energy generated when a subatomic particle called a neutral pion decays into two gamma rays. Because galactic pions can only be generated by cosmic-ray collisions, finding this peak would provide compelling proof for the theory, Dermer said.[6] Astrophysicists have discovered that star-forming regions in nearby galaxies shine brightly with gamma-rays -- yet more evidence that supernovae are a driving engine behind cosmic rays, the particles that continuously bombard the Earth. The results were announced today by the Fermi gamma ray space telescope team, which is holding a symposium this week in Washington DC to celebrate its one-year results.[5]
ScienceDaily (Nov. 2, 2009) - Nearby galaxies undergoing a furious pace of star formation also emit lots of gamma rays, say astronomers using NASA's Fermi Gamma-ray Space Telescope. Two so-called "starburst" galaxies, plus a satellite of our own Milky Way galaxy, represent a new category of gamma-ray-emitting objects detected both by Fermi and ground-based observatories.[2] A new generation of gamma-ray telescopes, including the Fermi Gamma-ray Space Telescope launched in 2008, and VERITAS, an array of four 12-meter telescopes atop Mount Hopkins in Arizona, has now succeeded in detecting gamma rays from three galaxies undergoing intense waves of starbirth.[6]
The VERITAS (Very Energetic Radiation Imaging Telescope Array System) collaboration, an international team of astronomers from the United States, Canada, United Kingdom and Ireland, has discovered very high energy (VHE) gamma rays emitted by the starburst galaxy M82 (the Cigar Galaxy).[1] VERITAS has found new evidence for cosmic rays in the "Cigar Galaxy," also known as Messier 82 (M82), which is located 12 million light-years from Earth in the direction of the constellation Ursa Major. "This discovery has been predicted for almost 20 years, but until now no instrument was sensitive enough to see it," said Wystan Benbow, an astrophysicist at the Smithsonian Astrophysical Observatory. Benbow coordinated this project for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) collaboration.[9]
About 12 million light-years away, M82, the "Cigar Galaxy", likely has a density of cosmic rays 500 times higher than the Milky Way (one light-year is about 5.9 trillion miles. ) Because M82's cosmic rays are trapped within the galaxy, the VERITAS team needed to look for the gamma radiation, created when cosmic rays slam into gas interstellar clouds.[3]
As expected, the VERITAS team found higher amounts of gamma rays coming from the starburst galaxy M82 (pictured), about 12 million light-years from Earth.[7] VERITAS observed gamma rays ranging from 700 billion eV to several trillion eV from the galaxy M82, which is some 12 million light-years from Earth.[6]
I want to add something that makes me smile. The cosmic rays (which, remember, are subatomic particles) from M82 were detected because while still inside that galaxy they make gamma rays, a form of light, which then travel straight to Earth. Once those gamma rays hit our air they create subatomic particles once again, which are what VERITAS detects. There are several steps to this process, with cosmic and gamma rays going back and forth until we actually detect their effect. It goes to show that sometimes the key to our understanding the Universe can involve subtle processes piled one atop the other, and it's up to us to carefully peel back those layers to get to the underlying processes underneath.[4] Gamma rays are the most energetic form of light, far more powerful than ultraviolet light or even X-rays. When cosmic rays interact with interstellar gas and radiation within M82, they produce gamma rays, which can then escape their home galaxy and reach Earthbound detectors. It took two years of dedicated data collection to tease out the faint signal coming from M82.[9] I swear I remember many years ago seeing a chart of the electromagnetic spectrum, with long wave radio at one end, visible light in the middle, and "cosmic rays" at the other end, as if they were a form of em radiation at a higher energy than gamma rays. It's only in the last few years that I've realized that cosmic rays are not em radiation at all.[4]
The amount detected is consistent with cosmic rays being generated in the violent environment of the galaxy which then slam into the gas surrounding the stars, generating gamma rays. Another process, called inverse Compton scattering, is probably behind this as well: when a low energy particle of light called a photon hits a cosmic ray, its energy is pumped waaaay up, and it becomes a gamma ray.[4]
Krennrich said there's more work to be done to definitively trace gamma rays to cosmic rays in starburst galaxies. Researchers believe more knowledge of gamma rays could help them explore distant regions of space, help them look for evidence of dark matter, determine how much electromagnetic radiation the universe has produced and answer questions about the formation of stars and galaxies.[10] Bechtol noted that the two starburst galaxies, M82 and NGC 253, have a higher rate of supernova production and emit more gamma rays than the Large Magellanic Cloud, another clue that supernovas and cosmic rays are intrinsically linked.[6]
The VERITAS observations strongly support the long-held theory that supernovae and massive star winds are the dominant accelerators of cosmic-ray particles. Galaxies with high levels of star formation such as M82 have high numbers of supernovae and massive stars. These "starburst" galaxies would then be expected to have a higher number of cosmic rays per unit volume.[1] When a massive star explodes, the theory goes, the expanding shock wave pulls along charged particles. These particles bounce around inside the supernova remnant's magnetic field until they reach near-light speed and escape into the galaxy as cosmic rays. Until now this idea has been hard to test, since we can't trace the Milky Way's cosmic rays and we can't see the cosmic rays trapped inside other galaxies.[7] Cosmic rays are particles striking the Earth's atmosphere and are produced in violent processes in our own Milky Way galaxy and beyond. Although the Earth is constantly bombarded by cosmic rays, their origin remains a mystery nearly 100 years after their discovery.[1]
The finding, which has revealed a new class of galactic gamma-ray sources, is not unexpected. It provides new hints about the origin of many cosmic rays, the high-speed protons and other charged particles of extraordinarily high energies that bombard Earth. Kinks in a galaxy'''s magnetic field keep the particles, mainly protons and other charged particles, bouncing back and forth like ping-pong balls between the advancing shock wave and the region just in front of it, revving up the particles to these high energies, the model suggests.[6] Astronomers know that cosmic rays come from far away in the galaxy. The magnetic fields of larger objects such as planets and stars bend the particles' flight paths, making it hard to trace their exact sources. The magnetic field of the galaxy itself traps cosmic rays inside, sending them darting about like flies in a sealed mason jar.[7]
Cosmic rays are hyperfast electrons, positrons, and atomic nuclei moving at nearly the speed of light. Although Earth is constantly bombarded by these particles, their origin remains a mystery nearly a century after their discovery. Astronomers suspect that the rapidly expanding shells of exploded stars somehow accelerate cosmic ray particles to their fantastic energy.[2] These findings were published in the Nov. 1 online issue of the journal Nature, and are being featured today in a press conference at the Fermi Science Symposium in Washington, DC. The rarest cosmic rays carry over 100 billion times as much energy as generated by any particle accelerator on Earth. ("Cosmic ray" is a historical misnomer, since they are individual particles, not a ray or beam.)[9]
Fermi has detected more than a thousand point sources and hundreds of gamma-ray bursts, but the satellite also detects a broad glow that roughly follows the plane of our galaxy. This diffuse gamma-ray emission results when fast-moving particles called cosmic rays strike galactic gas or even starlight.[2] Fermi shows that the LMC's brightest diffuse emission remains close to 30 Doradus and doesn't extend across the galaxy. This implies that the stellar factory itself is the source of the cosmic rays producing the glow. "Star-forming regions produce lots of massive, short-lived stars, which explode when they die," Digel said.[2]
A nearby galaxy vigorously cranking out baby stars will therefore have lots of massive stars making cosmic rays. As a happy by-product, those same massive stars are the ones that blow up as supernovae, giving us a two-fer as far as cosmic ray production goes. Such a galaxy exists: M82, a weird-looking one located a mere 12 million light years away (it's close enough to see in binoculars, in fact).[4] M 82 is a galaxy in the direction of the Ursa Major constellation that's 12 million light years from Earth. It is classified as a starburst galaxy. Such galaxies are colliding with other galaxies, causing shockwaves that compress gases and create stars at very high rates. "What this shows is that there is a strong connection between a galaxy with high star formation, high gas density and the production of cosmic rays," Krennrich said.[10] The Cigar Galaxy (M82) is located 12 million light years from Earth, in the direction of the Ursa Major constellation. It has an active starburst region in its center.[8]
The Fermi probe also saw gamma rays coming from M82 and from the starburst galaxy NGC 253. [7] "Starburst galaxies have not been accessible in gamma rays before," said Fermi team member Seth Digel, a physicist at SLAC National Accelerator Laboratory in Menlo Park, Calif. "Most of the galaxies Fermi sees are exotic and distant blazars, which produce jets powered by matter falling into enormous black holes. These new galaxies are much closer to us and much more like our own."[2] "Galaxies with more supernovae should be more gamma ray bright, and that's what we're finding," said team member Charles Dermer, of the U.S. Naval Research Laboratory in Washington, D.C. This process creates cosmic rays only up to a certain energy level.[7] Galaxies that produce lots of newborn stars therefore have lots of dying stars that explode as supernovas and ought to have an abundance of cosmic rays. When cosmic rays collide with other atomic nuclei in surrounding gas or dust, they produce gamma rays, the most energetic form of light.[6] WASHINGTON, D.C. ''' Astronomers have for the first time traced gamma rays, the most energetic form of light, to galaxies undergoing a frenzy of star birth.[6]
The gamma rays observed by the team have energies more than a trillion times higher than the energy of visible light and are the highest-energy photons ever detected from a galaxy undergoing large amounts of star formation.[8] AMES, Iowa - Iowa State University astrophysicists contributed to the recent discovery that a galaxy quickly creating new stars is also a source of high energy gamma rays.[10]
NASA's Fermi Gamma Ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.[2] Fermi's Large Area Telescope (LAT) shows that an intense star-forming region in the Large Magellanic Cloud named 30 Doradus is also a source of diffuse gamma rays.[2] Fermi saw gamma rays coming from a star-forming region in the Large Magellanic Cloud, a small satellite of the Milky Way.[7] The Large Magellanic Cloud is close enough to the Milky Way that Kn''dlseder and his colleagues could tell that the gamma rays emanated from a region that has highly ionized gas. Such sites are places where massive stars, which produce ionizing radiation, are expected to be common.[6]
The region lights up in gamma rays for the same reason the Milky Way does -- because cosmic rays strike gas clouds and starlight.[2]
In the Milky Way, cosmic rays have been whipped into a diffuse halo by galactic magnetic fields.[5]
"Our program has been supporting studies of VHE gamma-rays and cosmic rays in separate and very different experiments for over a decade," said Jim Whitmore, program director for particle and nuclear astrophysics in NSF's Division of Physics. "This significant VERITAS discovery provides an immediate connection between the sources of these two types of very energetic particles and enhances our understanding of the early universe." [1] The discovery was made from data taken over a two-year long observing campaign. This is the first example of a very-high-energy gamma-ray source associated with a starburst galaxy, and its discovery provides fundamental insight into the origin of cosmic rays," said Rene Ong, a professor of physics at the University of California, Los Angeles, and the spokesperson for the VERITAS collaboration.[1]
The finding provides "strong evidence" that exploding stars are the origin of cosmic rays, according to Jamie Holder, assistant professor of physics and astronomy at the University of Delaware and deputy spokesperson for the VERITAS collaboration.[8] The corresponding author of the article is Wystan Benbow of the Harvard-Smithsonian Center for Astrophysics and the Whipple Observatory. Researchers discovered cosmic rays (mostly hydrogen nuclei) from space nearly a century ago and have developed theories about their origins in supernova remnants and star-forming galaxies, but hadn't found evidence to support those theories. "This is a step toward solving a 100-year-old puzzle in cosmic ray physics," said Frank Krennrich, an Iowa State professor of physics and astronomy and a collaborator on the VERITAS project.[10]
New evidence from the VERITAS telescope array shows that cosmic rays likely are powered by exploding stars and stellar "winds."[9] Krennrich said one key to current gamma ray research is the VERITAS telescope system (that's the Very Energetic Radiation Imaging Telescope Array System).[10] The Very Energetic Radiation Imaging Telescope System (VERITAS) is a collection of four 12-meter Cherenkov telescopes used to detect astrophysical sources of very-high-energy gamma rays. It is located at the Fred Lawrence Whipple Observatory just south of Tucson, Arizona.[8]
The Whipple 10-m telescope was used to detect the first Galactic and extragalactic sources of VHE gamma rays. VERITAS continues the tradition of the 10-m telescope and is also located at FLWO. It is comprised of an array of four 12-meter (39 feet) diameter Cherenkov telescopes.[1] The study reports that researchers using the VERITAS array of four telescopes at the Fred Lawrence Whipple Observatory in Arizona have detected gamma rays of a trillion electron volts coming from the M 82 galaxy.[10]
The telescopes are used to study the remnants of exploded stars, distant galaxies, powerful gamma ray bursts, and to search for evidence of mysterious dark matter particles.[1]
"We believe gamma rays are coming from cosmic rays interacting with the interstellar medium," team member Keith Bechtol, of the Kavli Institute for Particle Astrophysics and Cosmology in Stanford, California, said today during a press briefing.[7] The new instrument, Krennrich said, might finally produce the data that establishes the origins of gamma rays and cosmic rays.[10]
November 2, 2009 Star explosions can act like ultra-powerful particle colliders in space, creating what are known as cosmic rays, new research shows.[7] ScienceDaily (Nov. 3, 2009) - Nearly 100 years ago, scientists detected the first signs of cosmic rays -- subatomic particles (mostly protons) that zip through space at nearly the speed of light. The most energetic cosmic rays hit with the punch of a 98-mph fastball, even though they are smaller than an atom. Astronomers questioned what natural force could accelerate particles to such a speed.[9] Cosmic rays are little subatomic particles zipping across the Universe. We've known about them for decades, and just about any astronomer who has used a space telescope knows and loathes them; cosmic rays zap our detectors, leaving bright streaks in the images which need to be tediously cleaned out before we can do any real science.[4]
Cosmic rays, which are actually high-energy subatomic particles, are constantly bombarding Earth.[7]
Think of it like gently throwing a rubber ball in front of a speeding truck on the highway; the ball suddenly and violently finds itself with a lot more energy. This all may not seem like a big deal, but it is. For one thing, there are a lot of cosmic rays flitting about out there, so knowing what they are and how they formed is clearly a big piece of understanding the high-energy Universe. These cosmic rays may have an effect here on Earth. Scientists have been studying how they may interact with the Earth and while the effect, if any, is incredibly small (people still argue over whether there is anything to this at all, like cloud formation and such) it's worth investigating.[4] Cosmic rays, mostly protons, smack into Earth's atmosphere from our own galaxy with the force of a 98-mile-per-hour fastball.[3] Two so-called "starburst" galaxies, plus a. They show that cosmic rays from our galaxy are very efficiently accelerated in the remnants of exploded.[9] If the theory holds, then starburst galaxies should contain more cosmic rays than normal galaxies.[9]
The finding '''implies that massive star-forming regions are the main source of cosmic rays in the Large Magellanic Cloud,''' Kn''dlseder said.[6] Kn''dlseder says that perhaps the chaotic region creates an intense and tangled magnetic field that keeps the cosmic rays in place.[5]
The VERITAS result provides critical evidence to help scientists understand the origin of cosmic rays by clearly linking the processes related to the life-cycle of stars with the acceleration of cosmic rays.[1] Said team member Jrgen Kndlseder of the Centre dEtude Spatiale des Rayonnements in France, the new discovery is "one more piece of the big puzzle in understanding where cosmic rays come from."[7] The most energetic cosmic rays likely come from jets of particles being belched out by supermassive black holes, although that theory has yet to be tested.[7] Yes we have studied CR for decades and they are still fascinating. Many of the first generation of space scientists such as Jim Van Allen and Harry Elliot (Harry died this year and will be commemorated with a symposium at Imperial College, London next week) started off in space to look at cosmic rays above the atmosphere, i.e. to see the primary. It also turns out that the inner Van Allen belt is caused by the albedo of cosmic rays, (CRAND=cosmic ray albedo neutron decay).[4] Astronomers have devised ingenious methods for detecting cosmic rays that hit Earth's atmosphere.[9] Some astronomers have suggested that cosmic rays might come from supernova remnants.[7]
Carey your mind is not paying tricks on you I too remember seeing EM Spectrum charts that had cosmic rays listed on them. Robert Millikan, who I believe coined the term "Cosmic Rays", incorrectly though of them as high energy photons.[4] I think it was from my 10th grade (1986-1987) chemistry textbook. That damn electro-magnetic spectrum chart which depicted cosmic rays as if they were the highest energy part of the EM spectrum really got around.[4]
Scientists from the Veritas observatory -- a ground-based gamma-ray observatory -- chipped in with results from a two year survey. These showed that gamma-rays of even higher energy than those detected by Fermi are streaming in from two nearby galaxies with known star-forming regions. This suggests that not only are star-forming regions responsible for generating the gamma-rays (via cosmic rays), but that the regions can make very high energy particles indeed. [5] "For the first time, we're seeing diffuse emission from star-forming regions in galaxies other than our own," noted Jürgen Knödlseder, a Fermi collaborator at the Center for the Study of Space Radiation in Toulouse, France. He spoke to reporters today at the 2009 Fermi Symposium, a Washington gathering of hundreds of astrophysicists involved in the Fermi mission and related studies.[2] Now, for the first time, an international team using the Very Energetic Radiation Imaging Telescope Array System (VERITAS) and the Fermi Gamma-ray Space Telescope has found strong support for the supernova theory.[7] Holder and former postdoctoral researcher Ester Aliu and doctoral student Dana Boltuch were involved in the study from UD. Holder scheduled all of the observations as chair of the team's observing time allocation committee, and he and Aliu ran the array of telescopes based in southern Arizona to collect a significant portion of the 137 hours of data collected for the study.[8]
The rays discovered by the VERITAS researchers have a trillion times the energy of visible light.[10] "The region is an intense source of gamma rays, and the diffuse emission we see with Fermi follows the glowing gas we see in visible light," Knödlseder explained.[2] Astronomers trained VERITAS on M82 and took a very, very long exposure. What they found is that is is a weak source of gamma rays, but definitely above the background level.[4]
The $20 million instrument started operating in 2007 and is the world's most sensitive instrument for detecting gamma rays. It's not easy to detect those rays. Even with their high energies, gamma rays can't penetrate the earth's atmosphere. When they hit the atmosphere, they create showers of electrons and positrons that create a blue light known as Cerenkov radiation. Those showers move very fast. They're not very bright.[10] The images can be used to infer the arrival direction and initial energy of the primary gamma rays. This technique is used by VHE observatories throughout the world, and was pioneered under the direction of SAO's Trevor Weekes, using the 10-meter Cherenkov telescope at the Fred Lawrence Whipple Observatory (FLWO), just south of Tucson, Arizona.[1] Krennrich said Iowa State researchers are working on image-recognizing technology for the AGIS system that would help researchers by automatically separating gamma ray events from background events.[10] Now Krennrich says researchers are contemplating the next generation of gamma ray detection systems.[10]
"So there are several steps to this process, with cosmic and gamma rays going back and forth until we actually detect their effect. It goes to show that sometimes the key to our understanding the Universe can involve subtle processes piled one atop the other, and it'''s up to us to carefully peel back those layers to get to the underlying processes underneath."[4]
My high school chemistry professor had an EM spectrum poster on his wall that had cosmic rays. It was also in several of my textbooks, and in another poster at a science camp I went to when I was 7 or 8.[4] I recall seeing cosmic rays listed on an electromagnetic spectrum chart as well.[4] The finding helps to confirm the connection between supernovas and cosmic rays.[6]
Galaxies with high levels of star formation like M82, also known as "starburst" galaxies, have large numbers of supernovae and massive stars. [9] I spent a large fraction of my time with Hubble doing just that. What's generating them? They seem to come from all directions in the sky, making it difficult to pin down their source. They're moving at fantastic speeds, so they must have a huge energy source behind them. For years, astronomers have suspected that they are accelerated to high velocities in supernovae explosions as well as in the fierce solar winds from massive stars.[4] The finding shows, "an enhancement in the cosmic-ray acceleration that matches the enhancement in energy input by massive stars and supernovae," says the study. "This correlation strongly supports the long-held theory that these objects have a dominant role in cosmic-ray production."[3]
The VERITAS observations strongly support the long-held theory that supernovae and stellar winds from massive stars are the dominant accelerators of cosmic-ray particles.[9]
Massive stars live for only a few million years before exploding ''' an eyeblink in astronomical terms.[6]
The very high energy gamma-ray emission observed by VERITAS. The Black star is the active starburst. [1] This representative-color figure shows the very-high-energy gamma-ray emission observed by VERITAS coming from the Cigar Galaxy, also known as Messier 82.[9]
VERITAS looks for the rays with four reflector disks 12 meters across that look like satellite dishes. [10] Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer. He has written two books, dozens of magazine articles, and 12 bazillion blog articles. He is a skeptic, and fights misuses of science as well as praising the wonder of real science.[4] Knödlseder revealed an image captured by Fermi's Large Area Telescope (LAT) of a star-forming region known as 30 Doradus within the Large Magellanic Cloud (LMC).[2]
SOURCES
1. nsf.gov - National Science Foundation (NSF) News - VERITAS Discovers Very High Energy Gamma Rays from the Starburst Galaxy M82 - US National Science Foundation (NSF)
2. NASA's Fermi Telescope Detects Gamma Rays From 'Star Factories' In Other Galaxies
3. Exploding stars shoot out cosmic rays - Science Fair - USATODAY.com
4. Attack of the galactic subatomic particles | Bad Astronomy | Discover Magazine
5. The Great Beyond: Starburst fury leads to gamma-ray glow
6. Gamma-Ray Mystery Traced to Star-Birth Frenzy | Wired Science | Wired.com
7. GALAXY PICTURE: Cosmic Ray Mystery Solved?
8. Starburst galaxy sheds light on longstanding cosmic mystery
9. Origin Of Cosmic Rays: VERITAS Telescopes Help Solve 100-year-old Mystery
10. Iowa State researchers contribute to discovery of gamma rays from starburst galaxy
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