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Fermi’s Whole-Sky Portrait

I like the logo for the Fermi Gamma-Ray Space Telescope, shown at the right. It’s appropriately stylish and, with that ‘beamed’ F emerging out of a galactic core, reminds us that the instrument will be opening a data window on the supermassive black holes found in such places. Fermi was until yesterday known as GLAST (Gamma-Ray Large Area Space Telescope), so the change of name moves us out of acronym territory and personalizes the instrument in favor of one of the true pioneers of high-energy physics, as well as the author of the ever intriguing Fermi paradox.

We’ve talked about the latter in the context of the search for extraterrestrial life, wondering how Fermi’s famous ‘where are they?’ question might be answered. But the Fermi telescope, in space for just two and a half months, is giving signs of being quite a newsmaker itself, if perhaps less controversial. The image below presents a map put together from 95 hours of observation, an all-sky view showing the glow of gas and dust at gamma ray wavelengths, the result of collisions with cosmic rays. We can also see both the Crab Nebula and Vela pulsars, as well as a galaxy in Pegasus that is now undergoing a flaring episode.

Image: This all-sky view from GLAST reveals bright emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes. Credit: NASA/DOE/International LAT Team.

‘First light’ from Fermi, in other words, has been remarkably productive, especially when you factor in the years it took the earlier Compton Gamma-Ray Observatory to produce a similar image. Indeed, the Large Area Telescope (LAT) aboard the spacecraft is itself thirty times more sensitive than any previous satellite detector and will be able to survey the entire sky several times each day. What’s going to be especially useful here is the fact that Fermi’s main instruments, the LAT and the GLAST Burst Monitor (GBM), will be able to detect gamma rays in a fabulously wide range of energies spanning a factor of ten million, according to the Fermi site. Between the two instruments, we’ll see more broadly than ever before in the gamma ray spectrum.

A sign of what’s to come is the fact that the GBM found 31 gamma-ray bursts in its first month of operation. Longer lasting gamma-ray bursts (GRBs) are now thought to herald the explosive demise of massive stars, while GRBs less than two seconds in duration may be the result of the merger of two neutron stars, or the merger of a black hole and a neutron star. Fermi should be able to tell us more about the stars that produce GRBs, how gamma rays occur in the initial burst, and how jets can channel material out of a dying star. Because a single GRB can give off the same amount of energy that our Sun will radiate in its ten billion year lifetime, we have much to learn in that area alone, not to mention what Fermi will teach us about the processes at work in galactic cores.

Comments on this entry are closed.

  • James M. Essig August 27, 2008, 14:42

    Hi Folks;

    The Fermi Gamma Ray Space Telescope in indeed a remarkable instrument.

    The study of gamma ray emitting events that can produce the same amount of energy that our Sun will radiate in its ten billion year lifetime, is not only beneficial in terms of understanding, at the very least, new applied theoretical physics, but may end up saving future humanity and any other similarly developed ETI civilizations we might meet.

    If such a gamma ray burst where to occur at 1 A.U. from Earth, we would receive more than (3 x 10 EXP 7)(10 EXP 10) times the radiant flux density that we receive from the Sun. That is 3 x 10 EXP 17 time the solar flux density for 1 second. At 100,000 AU or 1.5 LY, the flux density would be 30 million times greater than that of the Sun or the equivalent gamma ray energy exposure equal to one year of solar output at 1 AU. At 1,000 light-years, the gamma ray energy flux for one second would yield 45,000 Joules per square meter and some of this radiation would be converted into highly penetrating particles such as muons within the upper atmosphere which might penetrate the ground by several dozen meters. Such a radiation does could be fatal to all humans or to any ETI persons of the side of the planet that was irradiated.

    However, that being said, my hope is that we might discover some energetic event so powerful that the relativistic mass energy equivalence relation could not explain the energy output thus perhaps leading to new physics and perhaps even the discovery of some form of mass with latent energy E > M(C EXP 2). Depending on how much greater E is compared to M(C EXP 2), the possibility of a manned intergalactic rocket might exist, with a result being that interstellar travel and perhaps even intergalactic travel would become at least in part, good old-fashioned rocket science.



  • ljk October 17, 2008, 13:48


    October 17, 2008

    Fermi Telescope Makes First Big Discovery: Gamma Ray Pulsar

    Written by Nancy Atkinson

    The pulsar lies in the CTA 1 supernova remnant in Cepheus. Credit: NASA/S. Pineault, DRAO

    NASA’s Fermi Gamma-ray Space Telescope discovered the first pulsar that beams only in gamma rays. A pulsar is a rapidly spinning neutron star, the crushed core left behind when a massive sun explodes.

    Astronomers have cataloged nearly 1,800 pulsars. Although most were found through their pulses at radio wavelengths, some of these objects also beam energy in other forms, including visible light and X-rays. However, this new object only pulses at gamma-ray energies. “This is the first example of a new class of pulsars that will give us fundamental insights into how these collapsed stars work,” said Stanford University’s Peter Michelson, principal investigator for Fermi’s Large Area Telescope.

    The gamma-ray-only pulsar lies within a supernova remnant known as CTA 1, which is located about 4,600 light-years away in the constellation Cepheus. Its lighthouse-like beam sweeps Earth’s way every 316.86 milliseconds. The pulsar, which formed about 10,000 years ago, emits 1,000 times the energy of our sun.

    “We think the region that emits the pulsed gamma rays is broader than that responsible for pulses of lower-energy radiation,” explained team member Alice Harding at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The radio beam probably never swings toward Earth, so we never see it. But the wider gamma-ray beam does sweep our way.”

    Scientists think CTA 1 is only the first of a large population of similar objects.

    “The Large Area Telescope provides us with a unique probe of the galaxy’s pulsar population, revealing objects we would not otherwise even know exist,” says Fermi project scientist Steve Ritz, also at Goddard.

    Watch an animation of pulsar.

    Fermi’s Large Area Telescope scans the entire sky every three hours and detects photons with energies ranging from 20 million to more than 300 billion times the energy of visible light. The instrument sees about one gamma ray every minute from CTA 1, enough for scientists to piece together the neutron star’s pulsing behavior, its rotation period, and the rate at which it is slowing down.

    The pulsar in CTA 1 is not located at the center of the remnant’s expanding gaseous shell. Supernova explosions can be asymmetrical, often imparting a “kick” that sends the neutron star careening through space. Based on the remnant’s age and the pulsar’s distance from its center, astronomers believe the neutron star is moving at about a million miles per hour — a typical speed

  • ljk November 7, 2008, 0:08

    Gamma Ray Astronomy and the Origin of Galactic Cosmic Rays

    Authors: Stefano Gabici (DIAS)

    (Submitted on 5 Nov 2008)

    Abstract: Diffusive shock acceleration operating at expanding supernova remnant shells is by far the most popular model for the origin of galactic cosmic rays. Despite the general consensus received by this model, an unambiguous and conclusive proof of the supernova remnant hypothesis is still missing.

    In this context, the recent developments in gamma ray astronomy provide us with precious insights into the problem of the origin of galactic cosmic rays, since production of gamma rays is expected both during the acceleration of cosmic rays at supernova remnant shocks and during their subsequent propagation in the interstellar medium. In particular, the recent detection of a number of supernova remnants at TeV energies nicely fits with the model, but it still does not constitute a conclusive proof of it, mainly due to the difficulty of disentangling the hadronic and leptonic contributions to the observed gamma ray emission.

    In this paper, the most relevant cosmic-ray-related results of gamma ray astronomy are briefly summarized, and the foreseeable contribution of future gamma ray observations to the final solution of the problem of cosmic ray origin is discussed.

    Comments: Invited review talk, to appear in the Proceedings of the XXI European Cosmic Ray Symposium

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0811.0836v1 [astro-ph]

    Submission history

    From: Stefano Gabici [view email]

    [v1] Wed, 5 Nov 2008 22:21:34 GMT (219kb)


  • ljk June 15, 2009, 12:04

    Happy birthday, Fermi Gamma-ray Space Telescope

    June 11, 2009 | 12:56 pm

    The Fermi Gamma-ray Space Telescope launched one year ago. (Photo: NASA)

    Today marks one year since the Fermi Gamma-ray Space Telescope was launched into orbit. Since then, the telescope has discovered a whole new set of pulsars, gained a new view of cosmic jets, seen the most extreme gamma-ray blasts ever, created new sky maps in gamma-rays, shown that blazars are more complex than previously thought, observed a mysterious excess of high-energy electrons from space that could be from pulsars or possibly a sign of dark matter, and spotted gamma-ray bursts that lasted for half an hour rather than the expected few minutes.

    Happy birthday, Fermi Gamma-ray Space Telescope!


  • ljk July 6, 2009, 2:38

    July 2, 2009

    By Gamma-Rays Alone: Fermi Raises the Curtain on 16 New Pulsars

    Written by Anne Minard

    For the first time, NASA’s Fermi Gamma-ray Space Telescope has spotted a new group of pulsars using only their gamma-ray emissions, in the absence of radio signals beamed to Earth. The 16 new objects are reported in this week’s edition of Science Express, in a study based out of the University of California in Santa Cruz.

    A pulsar is a rapidly spinning neutron star, the dense core left behind after a supernova explosion. Most of the 1,800 known pulsars were found through their periodic radio emissions.

    “These are the first pulsars ever detected by gamma rays alone, and already we’ve found 16,” said co-author Robert Johnson, a UC Santa Cruz physicist. “The existence of a large population of radio-quiet pulsars was suspected prior to this, but until Fermi was launched, only one radio-quiet pulsar was known, and it was first detected in x-rays.”

    Of the 16 gamma-ray pulsars, 13 are associated with unidentified gamma-ray sources detected previously by the EGRET instrument on the Compton Gamma-ray Observatory. EGRET detected nearly 300 gamma-ray point sources, but was unable to detect pulsations from those sources, most of which have remained unidentified, said Pablo Saz Parkinson, also a SCIPP postdoctoral researcher and corresponding author of the paper

    Full article here:


  • ljk July 7, 2009, 13:39

    A search for counterparts of gamma-ray pulsars detected by the FERMI Large Area Telescope

    Authors: L. Trepl, C. Y. Hui

    (Submitted on 4 Jul 2009)

    Abstract: Aims: A group of new gamma-ray pulsars has recently been detected by FERMI Large Area Telescope (LAT) in a blind search. In this paper, we report the results from searching for the multi-wavelength counterparts of these pulsars.

    Methods: To search for their counterparts, we have cross-correlated the FERMI LAT Bright gamma-ray Source List with the XMM-Newton serendipitous source catalogue (SSC), data archives of Chandra and NRAO/VLA Sky Survey as well as USNO-B1.0 optical source catalogue.

    Results: We report the identification of an X-ray source in the XMM-Newton SSC, 2XMMJ202131.0+402645, located within the 95% confidence circle of 0FGLJ2021.5+4026. With an independent archival chandra observation, we do not find any variability of this X-ray source. Together with the non-detection of any associated optical counterpart and its X-ray hardness, we suggest 2XMMJ202131.0+402645 to be the only possible X-ray counterpart located in the error circle of 0FGLJ2021.5+4026. This identification provides an X-ray position with arc-second accuracy, RA (J2000) $=20^{h}21^{m}30\fs553$, Dec (J2000) $=+40^{\circ}26’46\farcs89$ (with uncertainties $\delta$RA=1.18″ and $\delta$Dec=0.84″), which is helpful in facilitating further investigations. In the radio sky survey data, an elliptical excess as well as an orthogonal jet-like structure have been identified in the error circle of 0FGLJ2021.5+4026, which have morphologies similar to that of known pulsar wind nebulae.

    Comments: 7 pages, 6 figures, submitted to A&A main journal on 26 May 2009

    Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

    Cite as: arXiv:0907.0791v1 [astro-ph.HE]

    Submission history

    From: Chung Yue Hui David [view email]

    [v1] Sat, 4 Jul 2009 20:02:58 GMT (326kb)


  • ljk July 7, 2009, 13:44

    Post-launch performance of the Fermi Large Area Telescope

    Authors: R. Rando, for the Fermi LAT Collaboration

    (Submitted on 3 Jul 2009)

    Abstract: The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope started nominal operations on August 13, 2008, after about 60 days of instrument checkout and commissioning and is currently performing an all-sky gamma-ray survey from 30 MeV to above 300 GeV with unprecedented sensitivity and angular resolution.

    The LAT pre-launch response was tuned using Monte Carlo simulations and test beam data from a campaign necessarily limited in scope. This suggested a conservative approach in dealing with systematics that affect the reconstruction analysis of the first months of data taking.

    The first major update of the instrument performance based on flight data is now being completed. Not only are the LAT calibrations now based on flight data, but also the ground event reconstruction has been updated to accommodate on-orbit calibrations, and response was carefully verified using real data from celestial sources.

    In this contribution we describe the current best knowledge of the instrument, and our plans towards releasing public response functions to support data release in year 2.

    Comments: Contribution to the 31st ICRC, Lodz, Poland, July 2009; 4 pages, 7 figures. Minor corrections

    Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

    Cite as: arXiv:0907.0626v1 [astro-ph.IM]

    Submission history

    From: Riccardo Rando [view email]

    [v1] Fri, 3 Jul 2009 13:23:05 GMT (74kb)


  • ljk October 12, 2009, 1:30

    The First Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

    Authors: A.A. Abdo, for the Fermi LAT collaboration

    (Submitted on 8 Oct 2009)

    Abstract: The dramatic increase in the number of known gamma-ray pulsars since the launch of the Fermi Gamma-ray Space Telescope (formerly GLAST) offers the first opportunity to study a population of these high-energy objects.

    This catalog summarizes 46 high-confidence pulsed detections using the first six months of data taken by the Large Area Telescope (LAT), Fermi’s main instrument.

    Sixteen previously unknown pulsars were discovered by searching for pulsed signals at the positions of bright gamma-ray sources seen with the LAT, or at the positions of objects suspected to be neutron stars based on observations at other wavelengths. Pulsed gamma-ray emission was discovered from twenty-four known pulsars by using ephemerides (timing solutions) derived from monitoring radio pulsars. Eight of these new gamma-ray pulsars are millisecond pulsars.

    The pulsed energy spectra can be described by a power law with an exponential cutoff, with cutoff energies in the range 1 to 5 GeV. The rotational energy loss rate (\dot{E}) of these neutron stars spans 5 decades, from ~3×10^{33} erg/s to 5×10^{38} erg/s, and the apparent efficiencies for conversion to gamma-ray emission range from ~0.1% to unity, although distance uncertainties complicate efficiency estimates. The pulse shapes show substantial diversity, but roughly 75% of the gamma-ray pulse profiles have two peaks, separated by >0.2 of rotational phase.

    For most of the pulsars, gamma-ray emission appears to come mainly from the outer magnetosphere, while polar-cap emission remains plausible for a remaining few.

    Finally, these discoveries suggest that gamma-ray-selected young pulsars are born at a rate comparable to that of their radio-selected cousins and that the birthrate of all young gamma-ray-detected pulsars is a substantial fraction of the expected Galactic supernova rate.

    Comments: Submitted to the Astrophysical Journal

    Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

    Cite as: arXiv:0910.1608v1 [astro-ph.HE]

    Submission history

    From: David A. Smith [view email]

    [v1] Thu, 8 Oct 2009 20:25:07 GMT (927kb)