HEAPOW: A Deeper Universe (2011 Sep 12)

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HEAPOW: A Deeper Universe (2011 Sep 12)

Post by bystander » Mon Sep 12, 2011 11:44 pm

Image HEAPOW: A Deeper Universe (2011 Sep 12)
The Fermi Gamma-Ray Space Telescope has been scanning the entire Universe every 3 hours ever since launch. The gamma-ray map that Fermi accumulates grows more and more sensitive with time as more and more gamma-ray photons are added to it. Each year, the Fermi team (and other scientists) take a detailed look at this map to see what's changed, what new sources have been detected, and which strong sources have changed over this time interval. Earlier this year, the Fermi team's detailed analysis of 2 years of gamma-ray data obtained with Fermi's Large Area Telescope was published as the Fermi 2-year source catalog. The 2-year all-sky map is shown above, along with an inset showing the distribution of the types of sources seen by Fermi so far. Most of the sources seen by Fermi are blazars, types of active galaxies which are oriented in space so that the jet emanating from their central, supermassive black hole is pointing directly at us. Other identified sources include pulsars and supernova remnants, and things like globular clusters, high mass X-ray binary stars, normal galaxies and other (non-blazar) active galaxies, and a star or two. Interestingly, many of the sources detected by Fermi are as yet unidentified; what can they be?
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Re: HEAPOW: A Deeper Universe (2011 Sep 12)

Post by neufer » Tue Sep 13, 2011 12:51 am

http://abcstarstuff.tumblr.com/post/10121804601 wrote:
FERMI’S LATEST GAMMA-RAY
CENSUS HIGHLIGHTS COSMIC MYSTERIES

<<Astronomers delight in the possibility of finding new types of gamma-ray-emitting objects within the “unassociated sources” that constitute roughly a third of the FERMI GAMMA-RAY catalog. But Fermi’s LAT is revealing gamma-rays from an increasing — and sometimes, surprising — variety of astronomical objects. To highlight the range of LAT discoveries, the Fermi team created the following “top ten” list of five sources within the Milky Way and five beyond our galaxy.
----------------------------------------------------------------------------------------
The top five sources within our galaxy are:
...................................................................................
The Crab Nebula. The famous Crab Nebula, located in the constellation Taurus, is the wreckage of an exploded star whose light reached Earth in 1054. Located 6,500 light-years away, the Crab is one of the most studied objects in the sky. At the heart of an expanding gas cloud lies what’s left of the original star’s core, a superdense neutron star (also called a pulsar) that spins 30 times a second. Until recently, all of the Crab’s high-energy emissions were thought to be the result of physical processes near the pulsar that tapped into this rapid spin.

For decades, most astronomers regarded the Crab Nebula as the steadiest beacon at X-ray energies. But data from several orbiting instruments — including Fermi’s Gamma-ray Burst Monitor — now show unexpected variations. Astronomers have shown that since 2008, the nebula has faded by 7 percent at high energies, a reduction likely tied to the environment around its central neutron star.

Since 2007, Fermi and the Italian Space Agency’s AGILE satellite have detected several short-lived gamma-ray flares at energies hundreds of times higher than the nebula’s observed X-ray variations. In April, the satellites detected two of the most powerful yet recorded.

To account for these “superflares,” scientists say that electrons near the pulsar must be accelerated to energies a thousand trillion (1015) times greater than that of visible light — and far beyond what can be achieved by the Large Hadron Collider near Geneva, Switzerland, now the most powerful particle accelerator on Earth.
...................................................................................
W44. Another interesting supernova remnant detected by Fermi’s LAT is W44. Thought to be about 20,000 years old — middle-age for a supernova remnant — W44 is located about 9,800 light-years away in the constellation Aquila. The LAT not only detects this remnant, it actually reveals GeV gamma rays coming from places where the remnant’s expanding shock wave is known to be interacting with cold, dense gas clouds.

Such observations are important in solving a long-standing problem in astrophysics: the origin of cosmic rays. Cosmic rays are particles — mainly protons — that move through space at nearly the speed of light. Magnetic fields deflect the particles as they race across the galaxy, and this scrambles their paths and masks their origins. Scientists can’t say for sure where the highest-energy cosmic rays come from, but they regard supernova remnants as a best bet.

In 1949, the Fermi telescope’s namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of gas clouds. In the decades that followed, astronomers showed that the magnetic fields in the expanding shock wave of a supernova remnant is just about the best location for this process to work.

So far, LAT observations of W44 and several other remnants strongly suggest that the gamma-ray emission arises from accelerated protons as they collide with gas atoms.
...................................................................................
V407 Cygni. V407 Cygni is a so-called symbiotic binary system, one that contains a compact white dwarf and a red giant star that has swollen to about 500 times the size of the Sun. Lying about 9,000 light-years away in the constellation Cygnus, the system occasionally flares up when gas from the red giant accumulates on the dwarf’s surface and eventually explodes. The event is sometimes called a nova.

When the system’s most recent eruption occurred in March 2010, Fermi’s LAT defied expectations and detected the nova as a brilliant source. Scientists simply didn’t expect that this type of outburst had the power to produce high-energy gamma rays.
...................................................................................
Pulsar PSR J0101-6422. Pulsars — rapidly rotating neutron stars — constitute about six percent of the new catalog. In some cases the LAT can detect gamma-ray pulses directly, but in many cases pulses were first found at radio wavelengths based on suspicions that a faint LAT source might be a pulsar. PSR J0101-6422 is located in the southern constellation of Tucana, its quirky name reflecting its position in the sky.

“This pulsar turns out to be a great example of the cooperation between the Fermi team and radio astronomers — scientists working in widely separated parts of the electromagnetic spectrum,” said David Thompson at NASA’s Goddard Space Flight Center in Greenbelt, Md., who co-led the catalog team.

The Fermi team originally took notice of the object as a fairly bright but unidentified gamma-ray source in an earlier LAT catalog. Because the distribution of gamma-ray energies in the source resembled what is normally seen in pulsars, radio astronomers in Australia took a look at it using their Parkes radio telescope.

Pulsars are neutron stars, compact objects packing more mass than the Sun’s into a sphere roughly the size of Washington, D.C. Lighthouse-like beams of radiation powered by the pulsar’s rapid rotation and strong magnetic field sweep across the sky with every spin, and astronomers can detect these beams if they happen to sweep toward Earth.

The Parkes study found radio signals from a pulsar rotating at nearly 400 times a second — comparable to the spin of a kitchen blender — at the same position as the unknown Fermi source. With this information, the LAT team was able to discover that PSR J0101-6422 also blinks in gamma rays at the same incredible rate.
...................................................................................
2FGL J0359.5+5410. Fermi scientists don’t know what to make of this source, located in the constellation Camelopardalis. It resides near the populous midplane of our galaxy, which increases the chance that it’s actually an object in the Milky Way. While its gamma-ray spectrum resembles that of a pulsar, pulsations have not been detected and it
isn’t associated with a known object at other wavelengths.
----------------------------------------------------------------------------------------
The top five sources beyond our galaxy are:
...................................................................................
Centaurus A. The giant elliptical galaxy NGC 5128 is located 12 million light-years away in the southern constellation Centaurus. One of the closest active galaxies, it hosts the bright radio source designated Cen A. Much of the radio emission arises from million-light-year-wide lobes of gas hurled out by the supermassive black hole at the galaxy’s center.

Fermi’s LAT detects high-energy gamma rays from an extended region around the galaxy that corresponds to the radio-emitting lobes. The radio emission comes from fast-moving particles. When a lower-energy photon collides with one of these particles, the photon receives a kick that boosts its energy into the gamma-ray regime. It’s a process that sounds more like billiards than astrophysics, but Fermi’s LAT shows that it’s happening in Cen A.
...................................................................................
The Andromeda Galaxy (M31). At a distance of 2.5 million light-years, the Andromeda Galaxy is the nearest spiral galaxy, one of similar size and structure as our own Milky Way. Easily visible to the naked eye in a dark sky, it’s also a favorite target of sky gazers.

The LAT team expected to detect M31 because it’s so similar to our own galaxy, where a bright band of diffuse emission creates the most prominent feature in the gamma-ray sky. These gamma rays are mostly produced when high-energy cosmic rays smash into the gas between the stars.

“It took two years of LAT observations to detect M31,” said Jürgen Knödlseder at the Research Institute for Astrophysics and Planetology in Toulouse, France. Currently a visiting scientist at the SLAC National Accelerator Laboratory, he worked on the M31 study. “We concluded that the Andromeda Galaxy has fewer cosmic rays than our own Milky Way, probably because M31 forms stars — including those that die as supernovae, which help produce cosmic rays — more slowly than our galaxy.”
...................................................................................
The Cigar Galaxy (M82). What works for the Andromeda Galaxy works even better for M82, a so-called starburst galaxy that is also a favorite of amateur astronomers. M82 is located 12 million light-years away in the constellation Ursa Major.

M82’s central region forms young stars at a rate some 10 times higher than the Milky Way does, activity that also guarantees a high rate of supernovae as the most short-lived stars come to explosive ends. Eventually, M82’s superpowered star formation will subside as the gas needed to make new stars is consumed, but that may be tens of millions of years in the future. For now, it’s a bright source of gamma rays for Fermi.
...................................................................................
Blazar PKS 0537-286. At the core of an active galaxy is a massive black hole that drives jets of particles moving near the speed of light. Astronomers call the galaxy a blazar when one of these jets is pointed our way — the best view for seeing dramatic flares as conditions change within the jet.

PKS 0537-286 is a variable blazar in the constellation Leo and the second most distant LAT object. Astronomers have determined that the galaxy lies at a redshift of 3.1, more than 11.7 billion light-years away. (Expressed more precisely, the blazar’s gamma-ray photons have been traveling for at least 11.7 billion years before being detected by Fermi’s LAT).

The blazar is the farthest active galaxy in the Fermi catalog to show variability. Astronomers are witnessing changes in the jet powered by this galaxy’s supermassive black hole that occurred when the universe was just 2 billion years old, or 15 percent of its current age.
...................................................................................
2FGL J1305.0+1152. The last item is another mystery object, one located in the constellation Virgo and high above our galaxy’s midplane. It remains faint even after two years of LAT observations.

One clue to classifying these objects lies in their gamma-ray spectrum — that is, the relative number of gamma rays seen at different energies. At some energy, the spectra of many objects display what astronomers call a “spectral break,” that is, a greater-than-expected drop-off in the number of gamma rays seen at increasing energies.

If this were a pulsar, it would show a fast cutoff at higher energies. Many blazars exhibit much more gradual cutoffs. But 2FGL J1305.0+1152 shows no evidence of a spectral break at all, leaving its nature — for the time being, anyway — a true mystery.>>
Art Neuendorffer

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Re: HEAPOW: A Deeper Universe (2011 Sep 12)

Post by bystander » Tue Sep 13, 2011 1:15 am

Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries
NASA GSFC Fermi | 2011 Sep 09
Every three hours, NASA's Fermi Gamma-ray Space Telescope scans the entire sky and deepens its portrait of the high-energy universe. Every year, the satellite's scientists reanalyze all of the data it has collected, exploiting updated analysis methods to tease out new sources. These relatively steady sources are in addition to the numerous transient events Fermi detects, such as gamma-ray bursts in the distant universe and flares from the sun.

Earlier this year, the Fermi team released its second catalog of sources detected by the satellite's Large Area Telescope (LAT), producing an inventory of 1,873 objects shining with the highest-energy form of light. "More than half of these sources are active galaxies, whose massive black holes are responsible for the gamma-ray emissions that the LAT detects," said Gino Tosti, an astrophysicist at the University of Perugia in Italy and currently a visiting scientist at SLAC National Accelerator Laboratory in Menlo Park, Calif.

One of the scientists who led the new compilation, Tosti today presented a paper on the catalog at a meeting of the American Astronomical Society's High Energy Astrophysics Division in Newport, R.I. "What is perhaps the most intriguing aspect of our new catalog is the large number of sources not associated with objects detected at any other wavelength," he noted.

Indeed, if the Fermi catalog were a recipe, the two major ingredients would be active galaxies and pure mystery. To them, add in a pinch of pulsars, a dollop of supernova remnants, and a dash of other celestial objects, such as globular star clusters and galaxies like our own Milky Way.

Astronomers delight in the possibility of finding new types of gamma-ray-emitting objects within the "unassociated sources" that constitute roughly a third of the catalog. But Fermi's LAT is revealing gamma-rays from an increasing -- and sometimes, surprising -- variety of astronomical objects. To highlight the range of LAT discoveries, the Fermi team created the following "top ten" list of five sources within the Milky Way and five beyond our galaxy.

The top five sources within our galaxy are:
  • The Crab Nebula. The famous Crab Nebula, located in the constellation Taurus, is the wreckage of an exploded star whose light reached Earth in 1054. Located 6,500 light-years away, the Crab is one of the most studied objects in the sky. At the heart of an expanding gas cloud lies what's left of the original star's core, a superdense neutron star (also called a pulsar) that spins 30 times a second. Until recently, all of the Crab's high-energy emissions were thought to be the result of physical processes near the pulsar that tapped into this rapid spin.

    For decades, most astronomers regarded the Crab Nebula as the steadiest beacon at X-ray energies. But data from several orbiting instruments -- including Fermi's Gamma-ray Burst Monitor -- now show unexpected variations. Astronomers have shown that since 2008, the nebula has faded by 7 percent at high energies, a reduction likely tied to the environment around its central neutron star.

    Since 2007, Fermi and the Italian Space Agency's AGILE satellite have detected several short-lived gamma-ray flares at energies hundreds of times higher than the nebula's observed X-ray variations. In April, the satellites detected two of the most powerful yet recorded.

    To account for these "superflares," scientists say that electrons near the pulsar must be accelerated to energies a thousand trillion (1015) times greater than that of visible light -- and far beyond what can be achieved by the Large Hadron Collider near Geneva, Switzerland, now the most powerful particle accelerator on Earth.
  • W44. Another interesting supernova remnant detected by Fermi's LAT is W44. Thought to be about 20,000 years old -- middle-age for a supernova remnant -- W44 is located about 9,800 light-years away in the constellation Aquila. The LAT not only detects this remnant, it actually reveals GeV gamma rays coming from places where the remnant's expanding shock wave is known to be interacting with cold, dense gas clouds.

    Such observations are important in solving a long-standing problem in astrophysics: the origin of cosmic rays. Cosmic rays are particles -- mainly protons -- that move through space at nearly the speed of light. Magnetic fields deflect the particles as they race across the galaxy, and this scrambles their paths and masks their origins. Scientists can't say for sure where the highest-energy cosmic rays come from, but they regard supernova remnants as a best bet.

    In 1949, the Fermi telescope's namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of gas clouds. In the decades that followed, astronomers showed that the magnetic fields in the expanding shock wave of a supernova remnant is just about the best location for this process to work.

    So far, LAT observations of W44 and several other remnants strongly suggest that the gamma-ray emission arises from accelerated protons as they collide with gas atoms.
  • V407 Cygni. V407 Cygni is a so-called symbiotic binary system, one that contains a compact white dwarf and a red giant star that has swollen to about 500 times the size of the sun. Lying about 9,000 light-years away in the constellation Cygnus, the system occasionally flares up when gas from the red giant accumulates on the dwarf's surface and eventually explodes. The event is sometimes called a nova (after a Latin term meaning "new star").

    When the system's most recent eruption occurred in March 2010, Fermi's LAT defied expectations and detected the nova as a brilliant source. Scientists simply didn't expect that this type of outburst had the power to produce high-energy gamma rays.
  • Pulsar PSR J0101-6422. Pulsars -- rapidly rotating neutron stars -- constitute about six percent of the new catalog. In some cases the LAT can detect gamma-ray pulses directly, but in many cases pulses were first found at radio wavelengths based on suspicions that a faint LAT source might be a pulsar. PSR J0101-6422 is located in the southern constellation of Tucana, its quirky name reflecting its position in the sky.

    "This pulsar turns out to be a great example of the cooperation between the Fermi team and radio astronomers -- scientists working in widely separated parts of the electromagnetic spectrum," said David Thompson at NASA's Goddard Space Flight Center in Greenbelt, Md., who co-led the catalog team.

    The Fermi team originally took notice of the object as a fairly bright but unidentified gamma-ray source in an earlier LAT catalog. Because the distribution of gamma-ray energies in the source resembled what is normally seen in pulsars, radio astronomers in Australia took a look at it using their Parkes radio telescope.

    Pulsars are neutron stars, compact objects packing more mass than the sun's into a sphere roughly the size of Washington, D.C. Lighthouse-like beams of radiation powered by the pulsar's rapid rotation and strong magnetic field sweep across the sky with every spin, and astronomers can detect these beams if they happen to sweep toward Earth.

    The Parkes study found radio signals from a pulsar rotating at nearly 400 times a second -- comparable to the spin of a kitchen blender -- at the same position as the unknown Fermi source. With this information, the LAT team was able to discover that PSR J0101-6422 also blinks in gamma rays at the same incredible rate.
  • 2FGL J0359.5+5410. Fermi scientists don't know what to make of this source, located in the constellation Camelopardalis. It resides near the populous midplane of our galaxy, which increases the chance that it's actually an object in the Milky Way. While its gamma-ray spectrum resembles that of a pulsar, pulsations have not been detected and it isn't associated with a known object at other wavelengths.
The top five sources beyond our galaxy are:
  • Centaurus A. The giant elliptical galaxy NGC 5128 is located 12 million light-years away in the southern constellation Centaurus. One of the closest active galaxies, it hosts the bright radio source designated Cen A. Much of the radio emission arises from million-light-year-wide lobes of gas hurled out by the supermassive black hole at the galaxy's center.

    Fermi's LAT detects high-energy gamma rays from an extended region around the galaxy that corresponds to the radio-emitting lobes. The radio emission comes from fast-moving particles. When a lower-energy photon collides with one of these particles, the photon receives a kick that boosts its energy into the gamma-ray regime. It's a process that sounds more like billiards than astrophysics, but Fermi's LAT shows that it's happening in Cen A.
  • The Andromeda Galaxy (M31). At a distance of 2.5 million light-years, the Andromeda Galaxy is the nearest spiral galaxy, one of similar size and structure as our own Milky Way. Easily visible to the naked eye in a dark sky, it's also a favorite target of sky gazers.

    The LAT team expected to detect M31 because it's so similar to our own galaxy, where a bright band of diffuse emission creates the most prominent feature in the gamma-ray sky. These gamma rays are mostly produced when high-energy cosmic rays smash into the gas between the stars.

    "It took two years of LAT observations to detect M31," said Jürgen Knödlseder at the Research Institute for Astrophysics and Planetology in Toulouse, France. Currently a visiting scientist at the SLAC National Accelerator Laboratory, he worked on the M31 study. "We concluded that the Andromeda Galaxy has fewer cosmic rays than our own Milky Way, probably because M31 forms stars -- including those that die as supernovae, which help produce cosmic rays -- more slowly than our galaxy."
  • The Cigar Galaxy (M82). What works for the Andromeda Galaxy works even better for M82, a so-called starburst galaxy that is also a favorite of amateur astronomers. M82 is located 12 million light-years away in the constellation Ursa Major.

    M82's central region forms young stars at a rate some 10 times higher than the Milky Way does, activity that also guarantees a high rate of supernovae as the most short-lived stars come to explosive ends. Eventually, M82's superpowered star formation will subside as the gas needed to make new stars is consumed, but that may be tens of millions of years in the future. For now, it's a bright source of gamma rays for Fermi.
  • Blazar PKS 0537-286. At the core of an active galaxy is a massive black hole that drives jets of particles moving near the speed of light. Astronomers call the galaxy a blazar when one of these jets is pointed our way -- the best view for seeing dramatic flares as conditions change within the jet.

    PKS 0537-286 is a variable blazar in the constellation Leo and the second most distant LAT object. Astronomers have determined that the galaxy lies at a redshift of 3.1, more than 11.7 billion light-years away. (Expressed more precisely, the blazar's gamma-ray photons have been traveling for at least 11.7 billion years before being detected by Fermi's LAT).

    The blazar is the farthest active galaxy in the Fermi catalog to show variability. Astronomers are witnessing changes in the jet powered by this galaxy's supermassive black hole that occurred when the universe was just 2 billion years old, or 15 percent of its current age.
  • 2FGL J1305.0+1152. The last item is another mystery object, one located in the constellation Virgo and high above our galaxy's midplane. It remains faint even after two years of LAT observations.

    One clue to classifying these objects lies in their gamma-ray spectrum -- that is, the relative number of gamma rays seen at different energies. At some energy, the spectra of many objects display what astronomers call a "spectral break," that is, a greater-than-expected drop-off in the number of gamma rays seen at increasing energies.

    If this were a pulsar, it would show a fast cutoff at higher energies. Many blazars exhibit much more gradual cutoffs. But 2FGL J1305.0+1152 shows no evidence of a spectral break at all, leaving its nature -- for the time being, anyway -- a true mystery.

Fermi Gamma Ray Observatory Harvests Cosmic Mysteries
Universe Today | Tammy Plotner | 2011 Sept 12
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: HEAPOW: A Deeper Universe (2011 Sep 12)

Post by bystander » Tue Oct 18, 2011 6:42 pm

600 Mysteries in the Night Sky
NASA Science News | Dauna Coulter | 2011 Oct 18
Click to play embedded YouTube video.

NASA's Fermi team recently released the second catalog of gamma-ray sources detected by their satellite's Large Area Telescope (LAT). Of the 1873 sources found, nearly 600 are complete mysteries. No one knows what they are.

"Fermi sees gamma rays coming from directions in the sky where there are no obvious objects likely to produce gamma rays," says David Thompson, Fermi Deputy Project Scientist from Goddard Space Flight Center.

Gamma rays are by their very nature heralds of great energy and violence. They are a super-energetic form of light produced by sources such as black holes and massive exploding stars. Gamma-rays are so energetic that ordinary lenses and mirrors do not work. As a result, gamma-ray telescopes can't always get a sharp enough focus to determine exactly where the sources are.

For two thirds of the new catalog's sources the Fermi scientists can, with at least reasonable certainty, locate a known gamma ray-producing object*, such as a pulsar or blazar, in the vicinity the gamma-rays are coming from. But the remaining third – the "mystery sources" -- have the researchers stumped, at least for now. And they are the most tantalizing.

"Some of the mystery sources could be clouds of dark matter – something that's never been seen before," speculates Thompson.

About 85% of the gravitational mass of the universe is dark matter. The stuff we see makes up the rest. Dark matter is something that pulls on things with the force of its gravity but can't be detected in any other way. It doesn't shine – doesn't emit or scatter light – hence the adjective "dark."

Astronomers cannot detect dark matter directly using optical or radio telescopes. But dark matter just might shine in gamma rays.

"We've been using Fermi to search for dark matter for a long time," says the principal investigator for the Large Area Telescope, Peter Michelson of Stanford University.

Some researchers believe that when two dark matter antiparticles bump into each other, they will annihilate, producing gamma rays. Concentrated clouds of dark matter could form a gamma ray source at specific wavelengths detectable by Fermi.

"If we see a bump in the gamma-ray spectrum -- a narrow spectral line at high energies corresponding to the energy of the annihilating particles – we could be the first to 'apprehend' dark matter,” says Michelson.

The team plans to continue observing the mystery sources. Fermi scans the entire sky ever three hours, and this ongoing sequence of observations "piles up" gamma rays for the researchers to analyze. So far, too few gamma rays have been collected from the mystery sources to form definite conclusions.

Another, less-dark possibility for some of the mystery sources is colliding galaxy clusters. According to Michelson and Thompson, clashes of such magnitude would generate super large scale shock waves that would accelerate particles. Others of the sources, they say, might be some brand new phenomenon, perhaps something involving galactic black holes.

When all is said and done, many of the mystery sources could prove to be familiar. "[They] will probably turn out to be members of known source classes – things we know but haven't recognized yet, like undiscovered pulsars, binary systems, and supernova remnants," says Michelson.

"Of course we're hoping for something really exotic like dark matter, but we have to look first at all the other options," says Thompson. "Fermi is an ongoing mission. We'll continue to search for answers to these puzzles and perhaps turn up even more surprises."

Will notorious dark matter finally be nabbed? Stay tuned!
Know the quiet place within your heart and touch the rainbow of possibility; be
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Re: HEAPOW: A Deeper Universe (2011 Sep 12)

Post by neufer » Fri Apr 13, 2012 2:45 pm

http://www.universetoday.com/94552/the-heavens-are-ablaze-with-blazars/#more-94552 wrote: The Heavens are Ablaze With Blazars
by Nancy Atkinson, Universe Today: April 12, 2012

From a JPL press release: <<Astronomers are actively hunting a class of supermassive black holes throughout the universe called blazars thanks to data collected by NASA’s Wide-field Infrared Survey Explorer (WISE). The mission has revealed more than 200 blazars and has the potential to find thousands more.

Blazars are among the most energetic objects in the universe. They consist of supermassive black holes actively “feeding,” or pulling matter onto them, at the cores of giant galaxies. As the matter is dragged toward the supermassive hole, some of the energy is released in the form of jets traveling at nearly the speed of light. Blazars are unique because their jets are pointed directly at us.

“Blazars are extremely rare because it’s not too often that a supermassive black hole’s jet happens to point towards Earth,” said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto, Calif., and principal investigator of the research, published in a series of papers in the Astrophysical Journal. “We came up with a crazy idea to use WISE’s infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped.”

The findings ultimately will help researchers understand the extreme physics behind super-fast jets and the evolution of supermassive black holes in the early universe.

WISE surveyed the entire celestial sky in infrared light in 2010, creating a catalog of hundreds of millions of objects of all types. Its first batch of data was released to the larger astronomy community in April 2011 and the full-sky data were released last month.

Massaro and his team used the first batch of data, covering more than one-half the sky, to test their idea that WISE could identify blazars. Astronomers often use infrared data to look for the weak heat signatures of cooler objects. Blazars are not cool; they are scorching hot and glow with the highest-energy type of light, called gamma rays. However, they also give off a specific infrared signature when particles in their jets are accelerated to almost the speed of light.

One of the reasons the team wants to find new blazars is to help identify mysterious spots in the sky sizzling with high-energy gamma rays, many of which are suspected to be blazars. NASA’s Fermi mission has identified hundreds of these spots, but other telescopes are needed to narrow in on the source of the gamma rays.

Sifting through the early WISE catalog, the astronomers looked for the infrared signatures of blazars at the locations of more than 300 gamma-ray sources that remain mysterious. The researchers were able to show that a little more than half of the sources are most likely blazars. “This is a significant step toward unveiling the mystery of the many bright gamma-ray sources that are still of unknown origin,” said Raffaele D’Abrusco, a co-author of the papers from Harvard Smithsonian Center for Astrophysics in Cambridge, Mass. “WISE’s infrared vision is actually helping us understand what’s happening in the gamma-ray sky.”

The team also used WISE images to identify more than 50 additional blazar candidates and observed more than 1,000 previously discovered blazars. According to Massaro, the new technique, when applied directly to WISE’s full-sky catalog, has the potential to uncover thousands more. “We had no idea when we were building WISE that it would turn out to yield a blazar gold mine,” said Peter Eisenhardt, WISE project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who is not associated with the new studies. “That’s the beauty of an all-sky survey. You can explore the nature of just about any phenomenon in the universe.”>>
Blazars: Some Broad Emission Lines redshifted to the infrared:
http://en.wikipedia.org/wiki/Active_galactic_nucleus wrote:

Code: Select all

_____  Differences between active galaxy types and normal galaxies.

_________ 	Active	Emission Lines _______   Excess of     Strong  _________    Radio
 Galaxy Type  Nuclei   Narrow  Broad   X-rays   UV  Far-IR    Radio  Jets Variable  loud

Normal 	      no 	weak 	 none 	weak 	none  none 	none   none 	 no 	 no
Starburst       no 	yes 	   no 	 some 	no 	 yes    some 	no 	  no 	 no
Seyfert I      yes 	yes 	  yes 	 some 	some   yes 	few 	 no 	 yes 	 no
Seyfert II     yes 	yes 	   no 	 some 	some   yes 	few 	yes 	 yes 	 no
Quasar 	     yes 	yes 	  yes 	 some 	yes 	yes 	some   some 	yes 	10%
Blazar 	     yes 	no 	  some 	  yes 	yes 	 no 	yes 	yes 	 yes 	yes
BL Lac 	     yes 	no   none/faint   yes 	yes 	 no 	yes 	yes 	 yes 	yes
OVV   	      yes 	no   > BL Lac 	 yes 	yes 	 no 	yes 	yes 	 yes 	yes
Radio galaxy   yes 	some 	some 	 some 	some   yes 	yes 	yes 	 yes 	yes
Art Neuendorffer

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WISE Mission Sees Skies Ablaze With Blazars

Post by bystander » Sat Apr 14, 2012 7:01 pm

neufer wrote:
The Heavens are Ablaze With Blazars
by Nancy Atkinson, Universe Today: April 12, 2012
NASA's WISE Mission Sees Skies Ablaze With Blazars
NASA JPL-Caltech | WISE | 2012 Apr 12
[img3="This artist's concept shows a "feeding," or active, supermassive black hole with a jet streaming outward at nearly the speed of light. Such active black holes are often found at the hearts of elliptical galaxies. Not all black holes have jets, but when they do, the jets can be pointed in any direction. If a jet happens to shine at Earth, the object is called a blazar. (Credit: NASA/JPL-Caltech)"]http://www.nasa.gov/images/content/6384 ... 46-710.jpg[/img3]
Astronomers are actively hunting a class of supermassive black holes throughout the universe called blazars thanks to data collected by NASA's Wide-field Infrared Survey Explorer (WISE). The mission has revealed more than 200 blazars and has the potential to find thousands more.

Blazars are among the most energetic objects in the universe. They consist of supermassive black holes actively "feeding," or pulling matter onto them, at the cores of giant galaxies. As the matter is dragged toward the supermassive hole, some of the energy is released in the form of jets traveling at nearly the speed of light. Blazars are unique because their jets are pointed directly at us.

"Blazars are extremely rare because it's not too often that a supermassive black hole's jet happens to point towards Earth," said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto, Calif., and principal investigator of the research, published in a series of papers in the Astrophysical Journal. "We came up with a crazy idea to use WISE's infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped."

The findings ultimately will help researchers understand the extreme physics behind super-fast jets and the evolution of supermassive black holes in the early universe.

WISE surveyed the entire celestial sky in infrared light in 2010, creating a catalog of hundreds of millions of objects of all types. Its first batch of data was released to the larger astronomy community in April 2011 and the full-sky data were released last month.

Massaro and his team used the first batch of data, covering more than one-half the sky, to test their idea that WISE could identify blazars. Astronomers often use infrared data to look for the weak heat signatures of cooler objects. Blazars are not cool; they are scorching hot and glow with the highest-energy type of light, called gamma rays. However, they also give off a specific infrared signature when particles in their jets are accelerated to almost the speed of light.

One of the reasons the team wants to find new blazars is to help identify mysterious spots in the sky sizzling with high-energy gamma rays, many of which are suspected to be blazars. NASA's Fermi mission has identified hundreds of these spots, but other telescopes are needed to narrow in on the source of the gamma rays.

Sifting through the early WISE catalog, the astronomers looked for the infrared signatures of blazars at the locations of more than 300 gamma-ray sources that remain mysterious. The researchers were able to show that a little more than half of the sources are most likely blazars.

"This is a significant step toward unveiling the mystery of the many bright gamma-ray sources that are still of unknown origin," said Raffaele D'Abrusco, a co-author of the papers from Harvard Smithsonian Center for Astrophysics in Cambridge, Mass. "WISE's infrared vision is actually helping us understand what's happening in the gamma-ray sky."

The team also used WISE images to identify more than 50 additional blazar candidates and observed more than 1,000 previously discovered blazars. According to Massaro, the new technique, when applied directly to WISE's full-sky catalog, has the potential to uncover thousands more.

"We had no idea when we were building WISE that it would turn out to yield a blazar gold mine," said Peter Eisenhardt, WISE project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who is not associated with the new studies. "That's the beauty of an all-sky survey. You can explore the nature of just about any phenomenon in the universe."
Identification of the Infrared Non-thermal Emission in Blazars - F. Massaro et al Infrared Colors of the Gamma-Ray Detected Blazars - R. D'Abrusco et al The WISE gamma-ray strip parametrization: the nature of the gamma-ray Active Galactic Nuclei of Uncertain type - F. Massaro et al
WISE Embarks on 'Crazy' Blazar Hunt
Discovery News | Ian O'Neill | 2012 Apr 12

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