Top Ten Gamma Ray Sources from the Fermi Telescope
Written by Nancy Atkinson
This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. Credit: NASA/DOE/Fermi LAT Collaboration
The Fermi Telescope is seeing a Universe ablaze with Gamma Rays! A new map combining nearly three months of data from the Fermi Gamma-ray Space Telescope is giving astronomers an unprecedented look at the high-energy cosmos."Fermi has given us a deeper and better-resolved view of the gamma-ray sky than any previous space mission," said Peter Michelson, the lead scientist for the spacecraft's Large Area Telescope (LAT) at Stanford University, Calif. "We're watching flares from supermassive black holes in distant galaxies and seeing pulsars, high-mass binary systems, and even a globular cluster in our own." The sources of these gamma rays come from within our solar system to galaxies billions of light-years away. To show the variety of the objects the LAT is seeing, the Fermi team created a "top ten" list comprising five sources within the Milky Way and five beyond our galaxy.
The top five sources within our galaxy are:
The Sun. Now near the minimum of its activity cycle, the sun would not be a particularly notable source except for one thing: It's the only one that moves across the sky. The sun's annual motion against the background sky is a reflection of Earth's orbit around the sun.
"The gamma rays Fermi now sees from the sun actually come from high-speed particles colliding with the sun's gas and light," Thompson notes. "The sun is only a gamma-ray source when there's a solar flare." During the next few years, as solar activity increases, scientists expect the sun to produce growing numbers of high-energy flares, and no other instrument will be able to observe them in the LAT's energy range.
LSI +61 303. This is a high-mass X-ray binary located 6,500 light-years away in Cassiopeia. This unusual system contains a hot B-type star and a neutron star and produces radio outbursts that recur every 26.5 days. Astronomers cannot yet account for the energy that powers these emissions.
PSR J1836+5925. This is a pulsar — a type of spinning neutron star that emits beams of radiation — located in the constellation Draco. It's one of the new breed of pulsars discovered by Fermi that pulse only in gamma rays.
47 Tucanae. Also known as NGC 104, this is a sphere of ancient stars called a globular cluster. It lies 15,000 light-years away in the southern constellation Tucana.
The Large Area Telescope (LAT) on Fermi detects gamma-rays through matter (electrons) and antimatter (positrons) they produce after striking layers of tungsten. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab
Click here to view an animation of the LAT
Unidentified. More than 30 of the brightest gamma-ray sources Fermi sees have no obvious counterparts at other wavelengths. This one, designated 0FGL J1813.5-1248, was not seen by previous missions, and Fermi's LAT sees it as variable. The source lies near the plane of the Milky Way in the constellation Serpens Cauda. As a result, it's likely within our galaxy — but right now, astronomers don't know much more than that.
The top five sources beyond our galaxy are:
NGC 1275. Also known as Perseus A, this galaxy at the heart of the Perseus Galaxy Cluster is known for its intense radio emissions. It lies 233 million light-years away.
Hubble Space Telescope image of a blazar galaxy. Credit: NASA
3C 454.3. This is a type of active galaxy called a "blazar." Like many active galaxies, a blazar emits oppositely directed jets of particles traveling near the speed of light as matter falls into a central supermassive black hole. For blazars, the galaxy happens to be oriented so that one jet is aimed right at us. Over the time period represented in this image, 3C 454.3 was the brightest blazar in the gamma-ray sky. It flares and fades, but for Fermi it's never out of sight. The galaxy lies 7.2 billion light-years away in the constellation Pegasus.
PKS 1502+106. This blazar is located 10.1 billion light-years away in the constellation Boötes. It appeared suddenly, briefly outshone 3C 454.3, and then faded away.
PKS 0727-115. This object's location in the plane of the Milky Way would lead one to expect that it's a member of our galaxy, but it isn't. Astronomers believe this source is a type of active galaxy called a quasar. It's located 9.6 billion light-years away in the constellation Puppis.
Unidentified. This source, located in the southern constellation Columba, is designated 0FGL J0614.3-3330 and probably lies outside the Milky Way. "It was seen by the EGRET instrument on NASA's earlier Compton Gamma Ray Observatory, which operated throughout the 1990s, but the nature of this source remains a mystery," Thompson says.
The LAT scans the entire sky every three hours when operating in survey mode, which is occupying most of the telescope’s observing time during Fermi's first year of operations. These snapshots let scientists monitor rapidly changing sources.
The all-sky image released today shows us how the cosmos would look if our eyes could detect radiation 150 million times more energetic than visible light. The view merges LAT observations spanning 87 days, from August 4 to October 30, 2008.
Source: NASA
Filed under: Astronomy, Satellites
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March 11th, 2009 at 10:53 am
The picture shows activity in a narrow band as you might guess from Milky Way sources, yet the text says half the sources are outside the galaxy. Is this an artifact of how the instrument works?
March 11th, 2009 at 12:16 pm
Oh no, more proof of black holes
Let the debates begin!
March 11th, 2009 at 12:21 pm
Wow, that magical "gravity" stuff must be real. Holy crap XD
March 11th, 2009 at 12:45 pm
Echoing the first comment…I think we are seeing all those bright sources, save but for a few, in the plane of our own galaxy. As Occam's razor cuts, that means that they are not extragalactic, and the theoritical edifice of these supposedly enourmously energetic sources is about to crumble.
The only saving grace would be if the instrument is mostly aimed into the milky way galactic plane. That makes little experimental sense.
If that's not the galactic plane, theory is in even worst shape, as why would the sources distribute into a plane that spans the universe?
March 11th, 2009 at 1:16 pm
Maybe there are more known sources outside the galactic plane, but those in galactic plane appear brighter because they are much closer? Only logical thinking…
March 11th, 2009 at 1:33 pm
Next time I'll check the original article first. From the Fermi site: "To better show individual sources, the new map was processed to suppress emissions from gas in the plane of our galaxy, the Milky Way." So the preponderance of the energetic extragalactic sources really are mostly in a plane – from our viewpoint here in Sol system in the Milky Way. I would now like to know if the deleted sources from our galactic plane just happened to coincide with the plane of the extragalactic sources. Either way this is going to take some explaining. So much for isotropy.
March 11th, 2009 at 1:35 pm
Bill Davis: Im trying to figure out what youre trying to say….what Theory are you talking about? the one thats supposed to crumble, as you say… Gravity? black holes? gamma rays? Can you clarify please?
The text does *NOT* say half the sources are out of our galaxy…they gave a top ten list, 5 from within our galaxy, 5 without…nowhere does it say, or even imply, that half of the gamma ray sources seen by the Fermi Telescope are extragalactic, as you are implying.
As bobo said, it is quite logical to think that the galactic gamma ray sources are brighter, because they are *much* closer than extra-galactic gamma ray sources. Gamma rays are just a high energy, high frequency form of light….
March 11th, 2009 at 1:53 pm
Magic, reread the quote from Fermi (maybe though you missed the second post of mine). They show no galactic sources in the image. By theory I meant the notion that these sources really are extragalactic. Other theorists, who think there are problems with the redshift correlation to distance, purport that the sources appear so bright because they are much closer and have "intrinsic redshift". This has controversial support in images of high redshift objects in front of or connected to low redshift objects…search on Halton Arp. Certainly, if the purported extragalactic sources shown in the image were in the galactic plane, they are likely within the galaxy, for why else would the planes coincide? The Fermi site does not specify yea or nay.
March 11th, 2009 at 1:59 pm
Yeah your second post came as i was writing my reply. Thanks for the info, ill have a look into it.
Cheers.
March 11th, 2009 at 2:22 pm
Bill Davis:
They didn't DELETE SOURCES from within our Galaxy – they SUPPRESSED emissions from GAS – because those would fog everything.
The galactic plane shows up because that's where all sources of any kind of radiation anywhere in the sky appear to be most densely packed, as seen and resolved from Planet Earth.
March 11th, 2009 at 2:51 pm
Bill: Ive been doing some reading about Halton Arp and Intrinsic redshift, and have found that intrinsic redshift is a highly controversial hypothesis based upon non-standard cosmology, originally hypothesized by Halton Arp. The 'other theorists' you mention are very few in number, and have yet to provide enough support of their theories to overcome the currently accepted explanation for redshift of distant galaxies.
Due to this, i cannot take it too seriously, as non standard cosmology does not have the same level of evidence and rigor as currently accepted cosmological theory..otherwise that theory would then become the currently accepted theory, which has not happened ( this is how Science works )…therefore what you have been saying does not appear to be terribly conclusive.
Feenix has rightly corrected the assumptions you made about the suppression of gamma ray emissions of gas, and your second post arguments were based upon the assumption that half the gamma ray sources were extragalactic, which has been shown to be a false assumption.
March 11th, 2009 at 2:57 pm
The created a top 10 list, 5 if them in our own galaxy, 5 of them outside our galaxy, where one seem to be in the galactic plane but isn't.
Those outside our galaxy will of course be distributed all around is.
One thing I am wondering, can the combined gravity of our Milky way not have some gravity lensing effect so that distant objects seem a bit more concentrate in or around the galactic plane?
March 11th, 2009 at 3:12 pm
Olaf,
Actually gravitational lensing should have the opposite affect. That's assuming there is any appreciable gravitational lensing from the Milky Way.
en.wikipedia.org/wiki/Gravitational_lensing
Check out the Einstein cross. The lensed images of background quasar appears positioned farther away from the galaxy.
March 11th, 2009 at 3:19 pm
Wouldnt the lensing effect be too small because we are within the milky way? There would be a lensing effect for a distant observer far away from the milky way, where the milky way is close to the line of sight to the gamma ray source…the curving of light could be too small to have an appreciable effect when the observer is within the milky way?? Im not too sure…
March 11th, 2009 at 3:24 pm
Actually, here is an excerpt from the wiki article on gravitational lensing…
"Unlike an optical lens, maximum 'bending' occurs closest to, and minimum 'bending' furthest from, the center of a gravitational lens."
So you would have to be at the center point to have the maximum bending effect, and as we are 'inside' the massive body, the effect would be at its minimum for us.
March 11th, 2009 at 3:24 pm
Good grief. Do some people actually think that they know more about this stuff than the people who study it every day for years on end?
March 11th, 2009 at 3:28 pm
Exactly my point to Bill Andrew
Believe the majority of experts over the minority is usually the best way to go. Once the minority truly prove the majority wrong, the minority and majority merge to become one…..wow…so deep…
March 11th, 2009 at 3:36 pm
Andrew,
Yes. Such people do exist.
ThereIsNoSuchThingAsMagic,
The bending affect would depend on the direction you're looking out of the milky way no? If you're looking towards the bulge, you're probably looking towards the max amount of matter you'll see in other directions. I'm betting that any gravitational lensing would be around the bulge and very slight and obscured by the brightness of the bulge itself. I'm completely guessing here.
March 11th, 2009 at 3:49 pm
ND: Yeah, i think youre right about the bulge.
In the end, i dont see anything in the article gamma ray image thats controversial about anything. If there was, im pretty darned sure the scientists involved would have picked up on it. They sure as heck know more about the subject than I do
March 11th, 2009 at 3:52 pm
I agree that in skimming I misinterpreted the display: so the plane is the galactic plane with its intragalactic sources, with the extragalactic objects seen outside the plane.
Yes, controversial. Regarding Arp, there is still the matter of the matter bridge between NGC 4319 and Markarian 205, different redshifted objects; I have not seen a credible refutation (the best is a coincidental alignment, but that is used too often). Some reprints have it processed out. No law against questioning the experts. Read Jeremy Dunning-Davies regarding current practices in science.
I wonder what the source of the diffuse gamma ray "fog" is. I know the conventional answer is shocked gas. If the intensity of this intragalactic interstellar glow in the image overwhelms concentrated sources such as pulsars, one has to wonder how this tenuous gas can produce such an intensity.
March 11th, 2009 at 4:31 pm
ThereIsNoSuchThingAsMagic,
Well, scientists are human and they could miss things, but yeah I don't think there is anything here that disproves the idea that bright sources of gamma rays are from our galaxy. But I have no choice but to leave that to actual, real-life, professional astronomers to figure out. It's their job
March 11th, 2009 at 4:34 pm
Bill Davis,
Is there any evidence that the bridge actually contacts the two differently redshifted objects? What's the best evidence for this?
March 11th, 2009 at 6:28 pm
# ND Says:
March 11th, 2009 at 4:34 pm
Bill Davis,
"Is there any evidence that the bridge actually contacts the two differently redshifted objects? What's the best evidence for this?"
Not really any at all. There is simply a little bit of 'nebulosity' that appears between the two, and Arp conjectured that this was a bridge in support of his theory that redshift was not a cosmological effect. It has to be remembered that cosmology was in it's infancy back then (not that it is fully mature today!), and Arp's theory, though contentious even at the time, was not simply madness – it had to be taken at least with some amount of seriousness.
These days, much more powerful telescopes have been brought to bear on the region, and astronomers almost universally believe that the alignment is nothing more than chance. There is strong evidence to support this, such as absorption lines appearing in the Markarian object's spectrum due to the intervening material that is a part of the NGC system.
It is summed up rather concisely on the Hubble Heritage Site:
" What's the issue about the redshifts?
NGC 4319 has a redshift (the fractional amount that observed wavelengths of spectral lines in a galaxy are shifted relative to the wavelengths at rest, (lobs – l rest) / lrest ) of 0.00468, while Mrk 205 has a redshift of 0.071. If redshifts imply distance, as almost all astronomers believe, then Mrk 205 is almost 15 times farther away than NGC 4319.
Mrk 205 is projected in the sky within the spiral arms of NGC 4319. In 1971 Halton Arp, who compiled an important catalog of peculiar galaxies called the Arp Catalog, wondered if this is not just a chance superposition, but rather evidence that the quasar-like galaxy really lies within NGC 4319. He found support for this view in the filamentary structure between the two objects.
If this were so, then redshifts would not be distance indicators in all cases. Needless to say it was a radical suggestion that, if true, would have upset some of the fundamental tenets of cosmology. It stirred up a lot of controversy about the meaning of redshifts and whether they were "cosmological," that is, due to the universal expansion, in all cases. Arp found numerous other examples of quasars near galaxies, although few as dramatic as this one.
In the view of most astronomers, the juxtapositions are just due to chance. The filamentary connection became less convincing as better images became available. John Bahcall and collaborators made a noteworthy contribution when they showed that NGC 4319 absorbs some of the light from Mrk 205, just as expected if NGC 4319 is projected in front of Mrk 205 (Astrophysical Journal 1992). In time, many quasars were found to lie in galaxies with exactly the same redshift, providing powerful evidence that quasars are an event that occurs in the nucleus of galaxies.
Today the redshift controversy has almost faded from view. Only a few astronomers still think there is reasonable evidence for noncosmological redshifts; a recent summary making their case was published by Geoffrey Burbidge (Publications of the Astronomical Society of the Pacific 2001). The vast majority of astronomers think that the evidence is overwhelming that redshifts show distances to objects in the expanding universe. "
March 11th, 2009 at 9:40 pm
Astrofiend,
Thanks for the summary. When I got home I found the page you're quoting from and an image:
heritage.stsci.edu/2002/23/big.html
I can see how visually in the picture it looks like they are connected.
This page heritage.stsci.edu/2002/23/supplemental.html has links at the bottom discussing the redshift issue.
March 12th, 2009 at 7:52 am
This is not a comment on the current page, but I was wondering regarding a question on the BBC,some years ago, where the interviewer asked an astrophysicist, if the Big Bang theory is why are some red-shift stars so close to some blue-shift stars, The Astrophysicist replied that it was a moot point as to whether or not it was correct. I believe the late Sir Fred Hoyle was the inventor of the name, though he did not believe in the theory.
March 12th, 2009 at 10:53 am
Considering the exotica that "modern" astronomy insists exists, such as "dark" matter (used to explain how galaxy rotation speed doesn't pull galaxies apart), "dark" energy ( used to explain how the super large structures [superclusters] are filimentary in construction), "black holes" (used to explain the intense energy concentration and emission at the center of galaxies), "neutron" stars (used to explain intense x-ray emission objects), and "gravity waves" (never been detected), one can question the basic assumptions of "modern" astronomy.
What do all these supposed objects and phenomenon have in common. One, they have never be observed & measured, and, two, they are all abstract, theoretical constructs of the gravity "only" model required or the gravity "only" model is falsified.
"Adopt or die."
So to simply suppose that when a majority of astronomers agree to something, that means it's right is seriously misguided.
A majority of "scientists" at one time believed in the Ptolomaic crystal spheres system of planetary orbits, and what's more important, they had the mathematics to prove it.
Actually the mathematics was very accurate, that's why so many scientists in the day believed it.
We now know it was totally false.
March 12th, 2009 at 11:11 am
You know what is even more striking and astounding than my proceeding observations when you think about?
"Modern" astronomy requires that over 70% of the matter in the Universe is UNDETECTED!!! ("dark matter")
Put in those stark terms, it becomes clear, anywhere else somebody said, "yes, over 70% of what we say can't be proved, but, 'trust us'," the reaction of hard headed realists would be to burst out laughing.
And, "shamen," and, " carnival barker" would be the muttered talk of those walking away.
"Modern" astronomy needs to wake up.
March 12th, 2009 at 11:52 am
You're up to your old rhetoric again Anaconda?
I think scientists understand what the scientific method, scientific theories, evidence and science in general is all about without you lecturing.
"So to simply suppose that when a majority of astronomers agree to something, that means it's right is seriously misguided."
No, it all means that X is the concensus of the majority of scientists in that field, given the observation and evidence a, b c etc. And X can (and needs to be allowed to) change given that a, b c etc can never be a complete observation of nature.
"Actually the mathematics was very accurate,"
How accurate was the Ptolomaic crystal spheres system?
March 12th, 2009 at 12:34 pm
@ ND:
Oh, wise one…tell us about all that "discovered" dark matter you were so quick to link to previously…ha ha ha.
Rhetoric? Hardly. Notice ND doesn't dispute one observation, not one.
And you know what? I'll quit my lecturing when "modern" astronomers actually DO start basing their "theories" on observation & measurement, instead of abstract, theoretical constructs, and then invent "crutches" when they find out the patient can't walk.
Take a "neutron" star for instance, astronomers call for the density to be 100 million tons per cubit centimeter.
That's 100 million tons in the tip of my pinkie finger. That violates the laws of physics.
"Success of Ptolemaic system:
Provided accurate enough description of what could be observed with instruments of that day. Predicted future paths of planets; when discrepancies arose, flexible enough that could be tinkered with to remove problem. Explains naturally why fixed stars show no annual parallax ."
"Predicted future paths of the planets [based on calculations, mathematics]".
"[F]lexible enough that could be tnkered with to remove problem." Sound familiar?
"His [Ptolomy] Planetary Hypotheses went beyond the mathematical model of the Almagest to present a physical realization of the universe as a set of nested spheres, in which he used the epicycles of his planetary model to compute the dimensions of the universe." Per Wikipedia.
Get real, ND. You set yourself up as the gatekeeper, but gatekeepers should never link to "news" reports that claim "dark" matter was "discovered" 70 years ago.
It makes you look ignorant.
March 12th, 2009 at 1:22 pm
@ Astrofiend:
The primary reason Halton Arp's observations & measurements have been discounted by "modern' astronomy have little to do with the actual observations & measurements he has made.
Rather, if you accept his interpretation of intrinsic redshift as being due to age and not distance or speed of galactic phenomenon it wholly falsifies the "big bang".
The falsification of the "big bang" hypothesis is the 'hang up" that keeps "modern" astronomy from accepting Arp's work.
Your recitation of the case against Arp's work ignores this central motivation in the astronomical "community".
March 12th, 2009 at 7:59 pm
Anaconda: "Rhetoric? Hardly. Notice ND doesn't dispute one observation, not one."
The observations you listed have been discussed in length in various blog threads. Notice I said "You're up to your *old* rhetoric again"
"gatekeeper"?! What does that even mean? How am I a gatekeeper? If this is a Ghostbuster reference, it's not working.
Anaconda: "to "news" reports that claim "dark" matter was "discovered" 70 years ago. "
You linked to a lot of news articles yourself. What's your point? Besides I referenced other sources that talked about the history of dark matter observations. In fact I pointed out to you how DM research really didn't pick up until 30-40 years ago. And you repeated that elsewhere.
March 12th, 2009 at 9:37 pm
And as for looking ignorant, here's the top ten list from the Bad Astronomy discussions about the things you have said.
blogs.discovermagazine.com/badastronomy/2009/01/28/the-roar-of-the-centaur/#comment-153591
I still can't get over your comment:
“In my comment, I discounted the antimatter concept, no, I rejected it. The case for antimatter is theoretical.”