"Dawn of a New Solar System"
by Patricia King and Thomas Hayden, with Jerry Adler
NEWSWEEK April 26, 1999
Geoffrey Marcy spotted it first, late one evening in early March, and he dashed off an e-mail to a colleague in Australia before heading home. The next morning, Debra Fischer , Marcy's post-doc researcher at San Francisco State University, sat staring at an array of dots on her computer screen. The dots, data gathered over 11 years at the University of California's Lick Observatory, represented tiny shifts in the motion of Upsilon Andromedae, a roughly Sun-sized star in the constellation Andromeda. Some of those dots fell into a regular pattern that represented the gravitational tug of a large, close-in planet orbiting the star evry 4.6 days. Overlaid was a second pattern of motion, which Marcy and Fischer believed was evidence of a second planet orbiting the same star. BUt there were sti;ll some movements unaccounted for. "Something was not quite right about this star," Fischer says, and as she adjusted her mathematical models to remove the effectds of the two hypothesized planets, suddenly the left-over data arranged itself into regular undulations. A chill went up her spine, followed by a burst of pleasure at the "gorgeous" data scrolling across her screen. There weren't two planets orbiting Upsilon Andromedae after all, she realized. There were three.
If Fischer was elated, though, Marcy was "frightened"; the discovery of a new solar system with multiple planets, like our own, was so unexpected that he worried people "might think we're lunatics." Only after 10 days of exhaustively rechecking his calculations did Marcy call his collaborator Robert Noyes of Harvard, who was observing the same star at the Whipple Observatory in Arizona. His first words were: "Bob, I hope you're sitting down" and only after Noyes confirmed the pattern with his own data did the two teams anounce their findings last week. It was, after all, only four years ago that the only planets known to orbit a normal star were the nine in Earth's solar system. (A planetary system surrounding a neutron star-which emits X-rays rather than visible light-was found in 1992.) Since 1995 about 20 extrasolar planets have been discovered. But all have been solitary, raising the question of whether our nine-planet system is somehow unique. The discovery of Upsilon Andromedae's three planets, says Fischer, "implies that our Milky Way is teeming with planetary systems."
Of course, the search for other planets is also, in part, a search for extraterrestrial life. Unfortunately, none of the three planets of Upsilon Andromedae, nor any of the others discovered so far, is a likely prospect. One, designated "B," orbits only at a distance of about 5 million miles from its star (about one-twentieth the distance of the Earth from the Sun), suggesting surface temperatures far above the boiling point of water. The two others, "C" and "D" (there is no "A"), are in more temperate, highly elliptical orbits that would fit between Venus (67 million miles from the Sun) and Jupiter (484 million miles). But all of Upsilon's planets are also huge. Their exact mass can't be calculated, but even the smallest is at least 225 times Earth's mass, while the largest is four or more times as big as Jupiter. Noyes believes that planets of this size are unlikely to be solid, because-based on our solar system-there aren't sufficient quantities of heavy elements available to make them. Instead, he suspects that like Jupiter, they will be composed mostly of gas or frozen vapor, unlikely places for life to develop.
But there's no reason to assume that terrestrial planets in Earth-like orbits don't exist; big ones that orbit close to their stars are, obviously, the easiest to find. And even those require exquisitely sensitive instruments and calculations. PLanets outside the solar system cannot actually be viewed from Earth. The light they reflect from their stars is many millions of times less bright than the starlight reaching us directly. Instead, their orbits and mass are deduced from their gravitational effects on the stars themselves. Upsilon Andromedae, 44 light years (259 trillion miles) distant, is moving away from the EArth at an average speed of around 1.8 kilometers a second (about 4,000 miles per hour). As the planets circle it, their gravitational fields tug on the star and either slow it down (when they're between it and the Earth) or speed it up (when they're on the far side). But the changes are tiny, on the order of a few tens of meters a second-not much faster than a man can run. After taking into account the Earth's own rotation, turbulence in the atmosphere and other sources of possible error, researchers are now approaching the theoretical limits of detection with the equipment they now have. "If we were on an extrasolar planet observing our own soalr system," says Noyes' colleague Timothy W. Brown, "we wouldn't even find Jupiter, much less the Earth, by our method, because Jupiter is so far from the Sun."
But better instruments are on the way. NASA's Space Interferometry Mission, scheduled to be launched in 2005, will deploy much more sensitive motion detectors than Earthbound telescopes, able to detect a star's side-to-side motion as well as changes in speed ralative to Earth. Six years later, NASA hopes to launch the Terrestrial Planet Finder, which will have instruments, still being developed, that can electronically "nullify" the light coming from a star, making it possible for the first time to direcly view the reflected light of an orbiting planet. Such a device could detect Earth-sized planets in temperate orbits, and even record their surface temperatures and the composition of their atmospheres-strong indications of habitability, if not life itself.
And the existence of other multiplanet solar systems increases the likelihood of finding life-in particular, life that has been around long enough to evolve some complexity. As Marcy's colleague R. Paul Butler points out, our very own existence owes a lot to other planets in our solar system, especially Jupiter. A single Earth-sized planet would be a sitting duck for meteors, comets, and other space junk that can wipe out whole ecosystems in a flash-as the dinosaurs discovered 70 million years ago. But the immense gravity of Jupiter (and to a lesser extent the other giant outer planets) sweeps the neighboring skies almost clear of dangerous debris, like a celestial vacuum cleaner, so that "we hardly ever get pelted by anything large anymore." Rsdio astronomer Alex Wolsczan, who discovered the first neutron star solar sytem in 1992, calls the Upsilon findings "historic," a confirmation that the variety of planetary systems is more impressive than anyone could have imagined. "Sooner or later," he adds, "we'll start to find other systems like our own. There's no logical reason why we should be unique."
Whenever NEWSWEEK reports on a scientific matter, the reader must proceed with caution, due to the nature of the magazine. While NEWSWEEK is strong when it comes to reporting political happenings, it has a tendency, like most publications geared toward the general public, to present only the most exciting aspect of a scientific story, without discussing all possible implications. This certainly seems to be the case with the above article; it seems to be factually correct (although the event that led to dinosaur extinction is dated to 65 million years ago, not 70), but it also does not seem to be a balanced account.
There are certainly fascinating implications with regard to the discovery of Upsilon Andromedae's planetary system. The scientist who pointed out the limitations of Earthbound planet searching is correct: using the limited technology that we currently have, most of our own solar system would be obscured if we tried to view it from an extra-solar planet. This suggests that if we can see any surrounding Upsilon Andromedae, then there are likely other planets orbiting the star. And regardless of whether Upsilon Andromedae had more than three, it certainly appears as if our solar system is not a completely unique formation. However, I feel that the article favors the scientists who believe that the universe is "teeming" with planetary systems far too much. The discovery of Upsilon Andromedae's system is certainly exciting, but one find should not be considered enough evidence to "prove{" that there are many planetary systems surrounding normal stars like our Sun. There is no question that furtehr investigations must be conducted in order to say anything definitive about Upsilon Andromedae's system, and about the existence of other planetary systems in general.
One of the reasons that NEWSWEEK chose to run this story is undoubtedly the possible implications that it suggests with regard to extraterrestrial life, which is certainly a hot topic for both the general public and the scientific world. The article certainly does not confirm the existence of extraterrestrial life, which is a positive aspect, but it presents a narrow view of the potential for life, which many scientists perpetuate through one key assumption: that other life forms are likely to occur only in an Earth-like situation. The experiment which attempted to demonstrate the plausibility of creating organic matter through the combination of the base elements thought to have been dominant at the time of the Earth's creation demonstrates that it is probably not difficult to generate organisms, but that it is likely far more difficult to generate complex, intelligent organisms. However, we can only make an assessment of what is complex and what is intelligent based on our definitions of those states. It seems entirely possible that there are extant forms of life that cannot be described by our definitions, and as a result we could be discounting planets, like the article appears to discount the Upsilon Andromedae planets, when they could play host to organisms we have never before encountered.
I believe that one of the most important lessons from any science course, and especially from an astronomy course, is to not judge too quickly, and to continue to challenge that which is "known." The theories we have today do not prove anything; they simply support the hypotheses that we have generated. A discovery could be made tomorrow that could force us to completely re-evaluate everything we think we know about our solar system, or about the universe, and we would have to throw out all of our current notions. While this is unlikely, the possibility of it happening serves as a caveat to those reading and writing articles like the above one in NEWSWEEK: one should not take what he or she reads at face value, and should always ask him or herself whether the entire story has been presented. INthe NEWSWEEK article, it is clear that the entire story has not been presented, because no astronomer is cited who disagrees with the implicationsof the Upsilon Andromedae system. I feel that the article is an interesting one, and provides the reader with the key elements of the discovery, but that it fails to address all of the implications of the discovery, namely that planetary systems still may not be proliferate in the universe and that our definition of life is a very narrow one, so we should not jump to conclusions about which planets can sustain life and which cannot.
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