Posted on 01/10/2005 1:30:09 PM PST by PatrickHenry
An international team of astronomers has discovered within the heart of a nearby spiral galaxy a quasar whose light spectrum indicates that it is billions of light years away. The finding poses a cosmic puzzle: How could a galaxy 300 million light years away contain a stellar object several billion light years away?
The team’s findings, which were presented today in San Diego at the January meeting of the American Astronomical Society and which will appear in the February 10 issue of the Astrophysical Journal, raise a fundamental problem for astronomers who had long assumed that the “high redshifts” in the light spectra of quasars meant these objects were among the fastest receding objects in the universe and, therefore, billions of light years away.
“Most people have wanted to argue that quasars are right at the edge of the universe,” said Geoffrey Burbidge, a professor of physics and astronomer at the University of California at San Diego’s Center for Astrophysics and Space Sciences and a member of the team. “But too many of them are being found closely associated with nearby, active galaxies for this to be accidental. If this quasar is physically associated with this galaxy, it must be close by.”
Astronomers generally estimate the distances to stellar objects by the speed with which they are receding from the earth. That recession velocity is calculated by measuring the amount the star’s light spectra is shifted to the lower frequency, or red end, of the light spectrum. This physical phenomenon, known as the Doppler Effect, can be experienced by someone standing near train tracks when the whistle or engine sounds from a moving train becomes lower in pitch, or sound frequency, as the train travels past.
Astronomers have used redshifts and the known brightness of stars as fundamental yardsticks to measure the distances to stars and galaxies. However, Burbidge said they have been unable to account for the growing number of quasi-stellar objects, or quasars—intense concentrations of energy believed to be produced by the swirling gas and dust surrounding massive black holes—with high redshifts that have been closely associated with nearby galaxies.
“If it weren’t for this redshift dilemma, astronomers would have thought quasars originated from these galaxies or were fired out from them like bullets or cannon balls,” he added.
The discovery reported by the team of astronomers, which includes his spouse, E. Margaret Burbidge, another noted astronomer and professor of physics at UCSD, is especially significant because it is the most extreme example of a quasar with a very large redshift in a nearby galaxy.
“No one has found a quasar with such a high redshift, with a redshift of 2.11, so close to the center of an active galaxy,” said Geoffrey Burbidge.
Margaret Burbidge, who reported the team’s finding at the meeting, said the quasar was first detected by the ROSAT X-ray satellite operated by the Max-Planck Institute for Astrophysics in Garching, Germany and found to be closely associated with the nucleus of the spiral galaxy NGC 7319. That galaxy is unusual because it lies in a group of interacting galaxies called Stephan’s Quintet.
Using a three-meter telescope operated by the University of California at Lick Observatory in the mountains above San Jose and the university’s 10-meter Keck I telescope on Mauna Kea in Hawaii, she and her team measured the redshifts of the spiral galaxy and quasar and found that the quasar appears to be interacting with the interstellar gas within the galaxy.
Because quasars and black holes are generally found within the most energetic parts of galaxies, their centers, the astronomers are further persuaded that this particular quasar resides within this spiral galaxy. Geoffrey Burbidge added that the fact that the quasar is so close to the center of this galaxy, only 8 arc seconds from the nucleus, and does not appear to be shrouded in any way by interstellar gas make it highly unlikely that the quasar lies far behind the galaxy, its light shining through the galaxy near its center by “an accident of projection.”
“If this quasar is close by, its redshift cannot be due to the expansion of the universe,” he adds. “If this is the case, this discovery casts doubt on the whole idea that quasars are very far away and can be used to do cosmology.”
Other members of the team, besides Geoffrey and Margaret Burbidge, included Vesa Junkkarinen, a research physicist at UCSD; Pasquale Galianni of the University of Lecce in Italy; and Halton Arp and Stefano Zibetti of the Max-Planck Institute for Astrophysics in Garching, Germany.
IIRC, the Burbidges were among his collaborators in the past.
"DARK MATTER ANNIHILATION AT THE GALACTIC CENTER. How does the presumed massive black hole at the center of our galaxy shape the distribution of the presumed halo of dark matter in its vicinity? Paolo Gondolo of the Max Planck Institute of Physics (Munich, Germany) and Joseph Silk of Oxford (UK; also UC Berkeley) suggest the black hole sculpts the dark matter into a dense spike where particle annihilation (or, more to the point, self- annihilation, since one of the leading hypothetical dark-matter particles is the "neutralino," which is its own antiparticle) would be enhanced. Of all the annihilation products (e.g., electrons, positrons, protons, etc.) issuing from the galactic center (a region half a light year wide) neutrinos would be the most serviceable since they can travel to Earth undeflected by magnetic fields. Gondolo and Silk have calculated how present and future neutrino telescopes can probe the density of inner halo dark matter. (Physical Review Letters, 30 August [1999]; gondolo@mppmu.mpg.de, 011-49-893-235-4427.)"
One of us has it backwards. The way I see it, because time is moving very slowly for the observer on the ship (we agree on this), and distances are less too (in the direction of the ship's motion) he won't see the laser beam do very much at all.
Good link. Thanks.
Indeed, but the changes should generate novel predictions that withstand attempts at falsification. I don't really see how this is the case with 'dark matter' and 'dark energy' and all the rest of it.
Yep. Thomas Kuhn got it right. Of course, this isn't all bad - it protects against cranks and provides collective focus to the enterprise. But the price of quashing dissent is that is that it slows the rate of discovery.
The article mentions that they deduced that the quasar was associated with the host galaxy by its interactions with gasses in that galaxy. Do you have any idea what those interactions might be? Is it a re-absorption phenomenon or induced emissions in the galactic gas from the quasar? Could the quasar be so close to the galactic center that its orbital velocity could be contributing to the observed red shift. But then again, there should also be an assoicated blue shift. Or could it be an infall of matter that is creating the red shift, yet the quasar is moving at the same rate as the ost galaxy? Since the article mentions there is more than one example of this phenomenon, it doesn't sound like a coincidence or a mesurement error.
My gut reaction when I first saw that speculation was that the ASP detector (designed to detect e+e- --> invisible particles) would have seen that process right away. So I mentioned it to Prof. Robert Hollebeek, who was the spokesman of the ASP collaboration, and who is incidentally my boss. I didn't even finish my question before he said NO WAY IN HELL was such a process possible. Ruled out definitively up to the kinematic and statistical reach of ASP, and theoretically useless beyond. If such a process takes place at all, it doesn't couple to electrons and positrons, and that rules out essentially every coupling to ordinary matter.
Could the quasar be so close to the galactic center that its orbital velocity could be contributing to the observed red shift.
No, I don't think that's possible. It would have to be orbiting at relativistic velocities, so the orbital period would be extremely short (hours or minutes).
Or could it be an infall of matter that is creating the red shift, yet the quasar is moving at the same rate as the ost galaxy?
First of all, this object is much brighter than a star, so we're talking about a heck of a lot of matter.
Second, it wouldn't all be falling from the same direction; we'd see the blueshifted matter falling in from the other side, and the unshifted matter falling in from every other direction.
Third, infalling matter doesn't just, well, fall in. Almost every falling piece of matter has some non-zero angular momentum with respect to the gravitating object, which means it will try to go into orbit about the object. Now, objects are falling every which-way, and all of that stuff--mostly gas and dust--is going to crash into the other stuff that is in intersecting orbits, and almost all of that angular momentum is going to cancel.
Not all of it, however. After all the cancellations, all of the matter remaining in orbit has an angular momentum that points in the same direction--the net angular momentum of the infalling cloud. This means it flattens out into a disk, known as an accretion disk. That stays in orbit. If there's enough of it, it will form planets (as in the case of our solar system). If there's much more of it, it might even form stars (as in the case of our galaxy). But there's really no easy way to prevent such a disk from forming, and when it forms, it will be highly visible, and it won't be redshifted.
Since the article mentions there is more than one example of this phenomenon, it doesn't sound like a coincidence or a mesurement error.
That has also been said about ESP.
Is the light not moving at c with respect to him?
(Hint: when you are goooooiiiinnng sssslllloooowwwlllyyy, everything else looks much faster than it otherwise might.)
Thanks for the reply. I'm still interested in how, spectroscopically I presume, interactions between the quasar and galaxy are determined that would lead to the suggestion that the quasar and the galaxy are together. Any thoughts?
As far as I know, the main evidence that the quasar is part of the galaxy is that they are at the same place on the celestial sphere. Statistically, more quasars are visible through nearby galaxies than would be expected with a random distribution.
That's a good question. One would hope that the association isn't "a long way behind but in the line of sight."
I said:
The way I see it, because time is moving very slowly for the observer on the ship (we agree on this), and distances are less too (in the direction of the ship's motion) he won't see the laser beam do very much at all.
Phys said:
Is the light not moving at c with respect to him? (Hint: when you are goooooiiiinnng sssslllloooowwwlllyyy, everything else looks much faster than it otherwise might.)
I donno ... You're probably right, as in all such matters, but it seems to me that the observer is virtually moving as fast as a photon himself, and I just don't think photons, were they equipped with flashlights, could get much use out of them.
According to whom? In his own reference frame, he's standing still, holding a flashlight. How fast should the light come out?
You're right. Given the characteristics of the particular quasars they're talking about, they should be able to look at others to find "the same thing," whatever that might be.
I suppose you could get huge red-shifts by observing the "back end" of something collapsing into a black hole, with the BH being on the other side of the signature.
Here, I will stubbornly (for a while at least) dig in my heals. If he points his flashlight toward the front end of the ship, and he's already traveling at virtually lightspeed ... well, if he sees a "normal" beam of light, it will take him years (from a "stationary" observer's viewpoint), maybe millions of years, to achieve that perception. But you're right, I suppose that's what he will see. He won't see a luminous blob slowly emerge from the flashlight, because he and the blob are both operating in the same time. But if you and I were "stationary" and watching him fly by, we wouldn't think he was getting much pizzazz out of his flashlight.
On the other hand, if he points the flashlight toward the rear of his ship, once again he'll see just what you say -- the beam will travel at the speed of light. But (am I right in this?) a stationary observer should see that too.
it is unlikely since astronomers have not seen any sideways. it would be very unlikely that there is only *one* and we "just happen" to be looking at it edge wise... more likely they would be randomly oriented all over the universe so we would see at least some that are not 'edge on'...
Great question! Now: How do the observers each know where the leading end of the light beam is, at any given time?
(Hint: "at any given time" is a bear trap of a phrase.)
Let us assume that the ship and its flashlight are traveling through a convenient dust cloud. We, the stationary observers (you know what I mean) can watch the spreading illumination. So can the rapidly-traveling observer. However ...
In the direction of the ship's motion, from its passenger's point of view, lengths are contracted, so a little bit of progress from his beam covers what to us (stationary) seems a whole lot of territory. In other words, we all see the leading edge of the beam in the same place in the same time (so to speak).
For the backwards pointing beam, it's not the same, is it? The traveler and we, the stationary observers, will still agree about the edge of the beam, but we don't need the length contractions to accomplish it.
What would happen if the traveler had a double sided flashlight, and he could simultaneously send out a beam forward and back?
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