Controversial Extinction Theory Is Tested : Scientists Sift Skies for the Death Star
A team of astrophysicists from Lawrence Berkeley Laboratory is trying to answer a question that many scientists believe may not be answerable for millions of years:
Does the sun have a companion star, known as the Death Star or the Nemesis, that sweeps past the solar system once every 26 million to 30 million years, causing comets and asteroids to rain down on Earth, wiping out entire species?
If the answer is yes, the star would be so far away that it would be barely visible from Earth and so seemingly insignificant that its gradual movement across the sky would have escaped detection by the thousands of telescopes that have been turned toward the heavens during nearly four centuries of telescopic research.
New Evidence
The search for the Death Star has taken on new interest because of mounting evidence that many scientists believe indicates that dinosaurs and other lesser species died millions of years ago because of a cataclysmic collision of the Earth with a foreign body, probably an asteroid or huge comet. According to the theory, the collision kicked up enough dust to plunge Earth into darkness for months or years, killing the vegetation that sustained the giant beasts that ruled Earth until their 150-million-year reign ended about 65 million years ago.
The Nemesis theory is based on the idea that if another star passed close to the sun, its gravitational field would dislodge comets and possibly asteroids from their normal positions in the solar system, and some would probably collide with Earth.
A number of scientists have tried to find the Nemesis, only to be discouraged by the prospect of an endless search of possibly millions of candidates, a search that may never lead to solid results.
“I feel completely agnostic” on the question of whether there is a Death Star, said one scientist who has pondered the question, Robert Harrington of the U.S. Naval Observatory in Washington. “In principle it’s perfectly possible for there to be such a thing, but there is no way to know if it is there. I have no reason one way or the other to believe or not believe.”
Others dismiss the idea as nonsense, contending that if the sun has a companion that comes around only once every 26 million years or so, it is a rare companion indeed. Most stars in the Milky Way galaxy are paired in binary systems, but generally they revolve around each other quickly, frequently in a matter of weeks or months. There is no known binary system with a period of millions of years.
Scientists from the Lawrence Berkeley Laboratory on the campus of the University of California, Berkeley, think there is reason to believe that there is such a star, and they have set out to find it with a 30-inch telescope usually used to train the university’s budding astronomers.
Astrophysicist Richard Muller, who is leading the effort, said the team has used previous sky surveys to narrow down the field of candidates in the area of the sky that is visible from the Northern Hemisphere.
“We have eliminated all but 3,000 stars,” Muller said, in the belief that the Nemesis would be a small, inconspicuous red star. The stars most visible from Earth are blue or white and have a much higher luminosity than the stars that appear reddish because of their cooler temperatures.
Would Be Bright
“We started with about half a million stars, and we could eliminate them in the following way,” Muller said in a telephone interview. “We know this star is very close” in order to orbit the sun, “and if it were intrinsically bright, it would be one of the brightest stars in the sky” because it is so close.
If it were that bright, it would already have attracted so much attention that astronomers would have studied it intensely and “it would have had its distance measured,” he said.
“So it must be a red star” that would have escaped serious study because it seemed so like the millions of other stars in the Milky Way galaxy that appear reddish, Muller added. He concluded that even though it would not have been studied individually, it should have been included in one of the numerous sky surveys conducted by astronomers who compile “catalogues” of stars.
“We found a catalogue of red stars, and based on the estimate of how bright it would be, we eliminated all but 3,000,” he added.
If the Nemesis is one of those 3,000 stars, its position should change slightly when viewed from Earth as the planet revolves around the sun, because it would be viewed from different positions on Earth’s orbit.
Change in Angle
Thus over several months, the angle to the star as viewed from Earth, called its parallax, should change noticeably. That would be true only for a star as close as the Death Star, because other stars are so far away that the Earth’s orbit is not large enough to affect the parallax.
As scientists photograph the 3,000 suspects repeatedly during the next few months with the computer-driven telescope, the Nemesis should stand out from the others because its parallax will have changed while the parallaxes of other stars remain the same, Muller said.
Muller is undaunted by the fact that there is no known binary system with a period of 26 million years. He said there could be many such systems, but it would be hard to detect them because the distance between the stars would be so great.
If the search is unsuccessful, it could mean that the Nemesis is only visible from the Southern Hemisphere, and the search there will be far more difficult, he added.
The southern sky has not been studied as extensively as the northern sky because most observatories are in the Northern Hemisphere, so if Muller and his team move south, they will have to begin their search from scratch.
There is no catalogue of red stars for the southern sky, he said, so the team would have to first conduct a sky survey, a time-consuming prospect that could delay the search for years.
“I hope we will never have to go down to the Southern Hemisphere,” Muller said.
Created His Own Fate
Muller’s fate is one he helped create several years ago when he was one of the first to postulate the Nemesis theory as the explanation for periodic mass extinctions on Earth.
Muller, UC Berkeley astronomer Marc Davis and Piet Hut, an astronomer with the Institute for Advanced Study at Princeton, disclosed their theory in an article in the British scientific journal Nature in 1984, when the scientific world was abuzz with stories about the work of UC Berkeley geologist Walter Alvarez.
Alvarez was collecting samples from a limestone formation near the Italian village of Gubbio in 1977 when he discovered a layer of clay containing fossilized marine creatures that dated to the time when the dinosaurs died out. He returned to Berkeley and teamed up with his father, Nobel laureate physicist Luis Alvarez of the Berkeley lab.
Subsequent analysis revealed that the clay contained rich samples of iridium, an element that is rare in the Earth’s crust. During the next years, the father-son team postulated that the iridium found in the clay came from a huge comet or asteroid that hit Earth in a collision that had an impact 6 billion times greater than the Hiroshima atomic bomb.
The collision would have sent clouds of debris, including iridium, into the upper atmosphere, obscuring the sun and plunging Earth into prolonged darkness. Over the course of months or years, the iridium would have rained down upon Earth, leaving a historical record of the cataclysm.
Found Other Evidence
Other geologists took up the banner and searched the world for similar evidence, and last year several teams reported during the San Francisco meeting of the American Geophysical Society that they had found evidence of the iridium layer in widely separated areas around the world.
Those findings added to a growing consensus among geologists that the dinosaurs were wiped out by an asteroid, although paleontologists have largely rejected that hypothesis.
Robert Bakker of the University of Colorado has argued vociferously that the dinosaurs died out over a period of several million years, not as a result of a single cataclysmic event. Muller contends that one advantage of the Nemesis theory is that it could explain a prolonged extinction because the passage of the Death Star could have caused comets to strike Earth over a long period, while a collision with an errant asteroid would have been a single event.
Other scientists, including David Raup and John Sepkoski of the University of Chicago, have argued that many species, not just the dinosaurs, died out through mass extinctions, and the record indicates that those calamities occurred at periodic intervals ranging from 26 million to 30 million years.
Highly Controversial
That hypothesis, although highly controversial among scientists from many disciplines, fits neatly with the concept of a Death Star that sweeps past the sun just in time to cause havoc every 26 million to 30 million years and then, like Halley’s comet, returns to the darkness of space and anonymity.
Muller and his team, which includes physicists Saul Perlmutter, Carl Pennypacker, Frank Crawford and Roger Williams, hope that within a year they will have the suspect cornered.
Incidentally, their calculations suggest that the star is at its farthest point from the sun, so it should not pass this way again for about 15 million years.
NEMESIS: THE ‘DEATH STAR’ Some scientists believe there may be a “death star” that swoops close to the solar system every 26 to 30 million years. If so, its gravity would pluck comets and asteroids from their normal positions and send many of them plunging to the Earth, causing climatic changes and wiping out entire species. Astrophysicists with the Lawrence Berkeley Laboratory are trying to find the star, and they think it would now be near its most distant point from the sun. That distance, as well as the star’s probable dimness, is why it has not been discovered before, they believe. Source: Lawrence Berkeley Laboratory
