`Greatest mass in the universe' may not be so great after all
`Monster mass' reports premature. When is a discovery not a discovery?
It's when news media hype the ``greatest'' or ``most spectacular'' thing of its type ever found, but a closer look shows that the report is based on uncertainties.
That's what has happened to the ``greatest mass in the universe,'' whose ``discovery'' evoked news media superlatives a few weeks ago.
The advent of this previously undetected monster mass -- equivalent to the substance of a million, billion suns -- now turns out to have been premature. To quote the British journal Nature, in a field where accurate identification of the relevant cosmic objects ``is never easy . . . it is too soon for certainty.''
To be fair to the media, we only reported what was clearly stated in announcements from the US National Science Foundation and Princeton University, and in a scientific paper published May 8 by Nature itself. We should have been more wary.
This monstrous mass defied explanation in conventional astronomical terms. Yet it fitted in neatly with current speculations of cosmic theorists. That's reason enough to be on guard against scientists' wishful thinking. Two papers in Nature's May 22 issue show how easily these speculations are invoked.
One argues that the monster mass might be an enormous black hole. When an object concentrates its mass to the point where not even light can escape its gravitational pull, it's called a black hole. Einstein's general theory of relativity predicts that such holes should form in the cosmos. There is some indirect evidence that they do exist. But none have been identified unambiguously. The so-called `cosmic string' theory.
The other paper suggests the monster mass might be part of one of the most exotic objects yet imagined -- a so-called ``cosmic string'' left over from the birth of the universe. A string would be infinitesimally thin, yet weigh in at something like 20 million, billion tons per inch of its length. It would be so taut it would snap to a point and vanish if it had any ends at all. So it would either have to close on itself in a loop or run infinitely through the cosmos.
This kind of ``gee whiz'' speculation spiced the original monster mass stories. However, as Nature observes in a companion editorial, these two papers, ``interesting in their own right, are at once tentative and suffused with a sense of what good luck it must be that observations should have led so simply to such striking inferences.'' Nature adds, ``Now, unfortunately, it appears that these endeavors have been misplaced.''
The observations in question concern an effect called ``gravitational lensing,'' which Einstein predicted 50 years ago. A massive object bends the paths of light beams passing close to it in a way that's reminiscent of an ordinary glass lens. This can split the image an astronomer sees of an object behind the lensing mass.
Astronomers have found eight such lenses. They split the images of highly compact, energetic, starlike objects called quasars (quasi-stellar radio sources). Generally, the two parts of the image are separated by only a few seconds of arc.
A research team headed by Edwin L. Turner of Princeton University, however, took a new look at two well-known quasars in the constellation Leo. As reported in a talk at the National Science Foundation and in the May 8 Nature paper, the team concluded that the two quasars are really just the split image of one object. But in this case, the split is 157 arc seconds wide -- the width of an American dime seen at a distance of 75 feet. It would take a gravitational lens 400 times more massive than any known before to split the image that much. Thus was born the monster mass. `Split image' is likely two quasars
Meanwhile, John P. Huchra, working at the Smithsonian Astrophysical Observatory near Tucson, Ariz., has also restudied these quasars. He says they probably are not a split image, but two distinct objects. They appear to be at slightly different distances from Earth, whereas two components of one image would have identical distances. P. A. Shaver and S. Christani of the European Southern Observatory in Chile have reached the same conclusion. They find too many differences between the spectra of the radiation from the two objects to believe they are the split image of a single quasar. It is this European work that has made Nature's editors cautious.
No split image, no monster mass. This does not mean that the scientific work at issue was done in vain. Astronomers now have a useful research task before them to look more critically at the tantalizing quasars. And speculations about cosmic strings may yet lead to new insights into the nature of the universe.
Meanwhile, beware of discoveries hailed as the ``biggest,'' the ``greatest,'' or the ``strangest'' things yet found in the sky. Wishful scientists may be stringing you along.
A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.