By Marc Kaufman
Tuesday, December 22, 2009
HAT CREEK, CALIF. -- The wide dishes, 20 feet across and raised high on their pedestals, creaked and groaned as the winds from an approaching snowstorm pushed into this highland valley. Forty-two in all, the radio telescopes laid out in view of some of California's tallest mountains look otherworldly, and now their sounds conjured up visions of deep-space denizens as well.
The instruments, the initial phase of the planned 350-dish Allen Telescope Array, are designed to systematically scan the skies for radio signals sent by advanced civilizations from distant star systems and planets. Fifty years after it began -- and 18 years since Congress voted to strip taxpayer money from the effort -- the nation's search for extraterrestrial intelligence is alive and growing.
"I think there's been a real sea change in how the public views life in the universe and the search for intelligent life," said Jill Tarter, a founder of the nonprofit SETI Institute and the person on whom Carl Sagan's book "Contact," and the movie that followed, were loosely based.
"We're finding new extra-solar planets every week," she said. "We now know microbes can live in extreme environments on Earth thought to be impossible for life not very long ago, and so many more things seem possible in terms of life beyond Earth."
The Hat Creek array, which began operation two years ago, is a joint project of the SETI Institute and the nearby radio astronomy laboratory of the University of California at Berkeley. Made possible by an almost $25 million donation from Microsoft co-founder Paul Allen, the array is unique and on the cutting edge of radio astronomy. SETI and Berkeley share both the facility, 290 miles northeast of San Francisco, and all the data it collects.
The dishes also represent a coming-of-age for SETI Institute enthusiasts and its sometimes hailed, sometimes ridiculed mission. While their effort was long associated with UFOs, over-excited researchers and little green men, it is now broadly embraced as important and rigorous science, and astronomers and astrobiologists in an increasing number of nations have become involved in parallel efforts.
"This is legitimate science, and there's a great deal of public interest in it," said Alan Stern, a former assistant administrator at NASA who, in 2007, decided that proposals for extraterrestrial search programs should not be banned from the agency, as they had been since the early 1990s. The National Science Foundation had come to a similar decision a few years before.
"It was not a big or difficult decision to change the policy," said Stern, who invited Tarter in to describe her program to NASA officials. "The technology and science had advanced, and so it made no sense to block applications."
Limited search programs for intelligent extraterrestrials in the 1970s and 1980s abruptly lost their federal funding in 1992, after NASA proposed a greater effort. Former Sen. Richard Bryan (D-Nev.) led the charge in Congress, telling the Senate at one point: "The Great Martian Chase may finally come to an end. As of today, millions have been spent and we have yet to bag a single little green fellow. Not a single Martian has said, 'Take me to your leader,' and not a single flying saucer has applied for FAA approval."
The funding was eliminated, even though SETI listens for radio signals from distant planets and has nothing to do with Mars or with a supposed search for flying saucers or other space oddities.
But when NASA informed Congress that it was going to allow SETI to once again compete for funds, there were no objections, Stern said. Rita Colwell, who was director of the National Science Foundation when it approved a small-scale SETI Institute proposal in 2004, said several prominent astronomers endorsed the group, saying that the institute had become an important player in the field of radio astronomy.
Still, search activity by the institute and others is often criticized for its lack of results. It has been 50 years since astronomer Frank Drake first used a radio antenna at the Green Bank National Radio Astronomy Observatory in West Virginia to listen for extraterrestrial signals, and so far no messages have been detected and confirmed. UCLA physicist and astronomer Ben Zuckerman often lectures on what he considers the overly optimistic predictions of search advocates, and he argues that if the Milky Way were home to technologically advanced civilizations we would know it by now. "I think very strong arguments can be brought to bear that the number of technological civilizations in the galaxy is one -- us," he said.
Although disappointing to scientists searching for intelligent life beyond Earth, the absence of contact is something they consider far from surprising. As Tarter described the effort, the number of star systems studied so far for possible communications is minuscule compared with the number of stars in the sky -- on the same scale as if a person searched for a fish in the Earth's combined oceans by drawing out a single cup of water.
"The chances of finding a fish in that one cup are obviously very small," she said. As she and others often point out, astronomers think the universe contains something on the order of 1,000,000,000,000,000,000,000,000 stars and, given the discovery so far of more than 400 extra-solar planets, it is generally assumed that billions or trillions more are orbiting in distant systems.
What's more, it remains far from certain that listening for radio signals is the right approach. Radio is a relatively primitive form of communication, and advanced civilizations could be sending signals in many different ways. Given that possibility, astronomers have begun using optical telescopes to search for nanosecond laser blips and beeps that might be coming our way.
A Harvard-Princeton University collaboration has resulted in some of the most sophisticated optical searches, and the effort now has worldwide appeal. In November, for instance, a group of 30 optical and radio observatories and amateur astronomers dedicated two nights to simultaneously viewing one particular star system in search of radio signals or laser pulses. The effort, led by Shin-ya Narusawa of the Nishi-Harima Observatory in southern Japan, targeted a system described in 1993 by Sagan and Paul Horowitz (leader of the optical search team at Harvard) as potentially habitable.
"In Japan, our telescopes are all open to the regular people, and when they come in we want to know what are their big interests in astronomy," Narusawa said during the nighttime observation. "The top two are these: Is there an end, a border, to the universe? And is there life, especially intelligent life, anywhere other than Earth?"
Narusawa said he hoped to cooperate with the SETI Institute in the future, as well as with more fledgling SETI programs in South Korea and Australia. Drake, the man who first began listening for intergalactic signals in 1960 and chairman emeritus of the SETI Institute's board, remains engaged in the search. When different channels, sensitivities and computing power are factored in, the technology now being brought to the effort is 100 trillion times more powerful than what he started with, Drake said. The explosion of radio "noise" from high-definition television, cellphones and military satellite communication makes it more difficult to identify a true signal from elsewhere, but ever more powerful computers are being used to read the data coming in.
In addition to his work in institutionalizing the search effort and broadening the SETI Institute's mission to include more traditional astronomy, Drake is known for the "Drake Equation," an effort to quantify how likely it is that intelligent life exists elsewhere in the universe.
The equation has been firmed up somewhat in recent years as a scientific consensus has grown that extra-solar planets are commonplace in other solar systems, but it remains essentially speculative since it relies on estimates of the likelihood of life's beginning and evolving on seemingly habitable planets. However, the equation could become more precise in the years ahead if NASA's Kepler mission, launched last year, finds the Earth-size planets it is designed to detect (and which many astronomers believe are prevalent in the Milky Way and other galaxies).
Based on the Drake Equation, there should be an intelligent civilization orbiting one in 10 million stars. Although that is a tiny fraction, it is nonetheless a lot of potential intelligent extraterrestrials given the vastness of the universe; the Milky Way alone is believed to have more than 100 billion stars. That fraction also explains why SETI pioneers such as Drake are not surprised that no signals have been detected so far.
"We've looked at far, far fewer than 10 million stars since 1960, and so we really can't say anything worthwhile yet about whether or not intelligent life is out there," Drake said. "Given our capabilities now, we might have something useful to say one way or another in 25 years."
That's not the kind of time scale generally used in science programs, but SETI is hardly a typical scientific effort. Drake, who is nearly 80 years old, says he doubts he will be around when a signal is detected, but he is more than pleased with what his initial two-month effort in 1960 (named Project Ozma) has spawned.
Finding private money to expand the Allen array has proven difficult, but he said SETI now has an application in with the National Science Foundation to help with the construction and operation. "At the beginning, there were maybe four or five people in the room when we'd call a meeting to discuss SETI," Drake said. "It was definitely on the fringe."
"Now SETI and the field of astrobiology are mainstream, and a meeting might bring in 1,000 people," he said. "I never, never could have imagined that when I started."
Tuesday, December 22, 2009
Wednesday, December 16, 2009
Earth-Like Planet Nearby
Scientists spot nearby 'super-Earth'
By John D. Sutter, CNN
December 16, 2009 5:12 p.m. EST
(CNN) -- Astronomers announced this week they found a water-rich and relatively nearby planet that's similar in size to Earth.
While the planet probably has too thick of an atmosphere and is too hot to support life similar to that found on Earth, the discovery is being heralded as a major breakthrough in humanity's search for life on other planets.
"The big excitement is that we have found a watery world orbiting a very nearby and very small star," said David Charbonneau, a Harvard professor of astronomy and lead author of an article on the discovery, which appeared this week in the journal Nature.
The planet, named GJ 1214b, is 2.7 times as large as Earth and orbits a star much smaller and less luminous than our sun. That's significant, Charbonneau said, because for many years, astronomers assumed that planets only would be found orbiting stars that are similar in size to the sun.
Because of that assumption, researchers didn't spend much time looking for planets circling small stars, he said. The discovery of this "watery world" helps debunk the notion that Earth-like planets could form only in conditions similar to those in our solar system.
"Nature is just far more inventive in making planets than we were imagining," he said.
In a way, the newly discovered planet was sitting right in front of astronomers' faces, just waiting for them to look. Instead of using high-powered telescopes attached to satellites, they spotted the planet using an amateur-sized, 16-inch telescope on the ground.
There were no technological reasons the discovery couldn't have happened long ago, Charbonneau said.
The planet is also rather near to our solar system -- only about 40 light-years away.
Planet GJ 1214b is classified as a "super-Earth" because it is between one and 10 times as large as Earth. Scientists have known about the existence of super-Earths for only a couple of years. Most planets discovered by astronomers have been gassy giants that are much more similar to Jupiter than to Earth.
Charbonneau said it's unlikely that any life on the newly discovered planet would be similar to life on Earth, but he didn't discount the idea entirely.
"This planet probably does have liquid water," he said.
By John D. Sutter, CNN
December 16, 2009 5:12 p.m. EST
(CNN) -- Astronomers announced this week they found a water-rich and relatively nearby planet that's similar in size to Earth.
While the planet probably has too thick of an atmosphere and is too hot to support life similar to that found on Earth, the discovery is being heralded as a major breakthrough in humanity's search for life on other planets.
"The big excitement is that we have found a watery world orbiting a very nearby and very small star," said David Charbonneau, a Harvard professor of astronomy and lead author of an article on the discovery, which appeared this week in the journal Nature.
The planet, named GJ 1214b, is 2.7 times as large as Earth and orbits a star much smaller and less luminous than our sun. That's significant, Charbonneau said, because for many years, astronomers assumed that planets only would be found orbiting stars that are similar in size to the sun.
Because of that assumption, researchers didn't spend much time looking for planets circling small stars, he said. The discovery of this "watery world" helps debunk the notion that Earth-like planets could form only in conditions similar to those in our solar system.
"Nature is just far more inventive in making planets than we were imagining," he said.
In a way, the newly discovered planet was sitting right in front of astronomers' faces, just waiting for them to look. Instead of using high-powered telescopes attached to satellites, they spotted the planet using an amateur-sized, 16-inch telescope on the ground.
There were no technological reasons the discovery couldn't have happened long ago, Charbonneau said.
The planet is also rather near to our solar system -- only about 40 light-years away.
Planet GJ 1214b is classified as a "super-Earth" because it is between one and 10 times as large as Earth. Scientists have known about the existence of super-Earths for only a couple of years. Most planets discovered by astronomers have been gassy giants that are much more similar to Jupiter than to Earth.
Charbonneau said it's unlikely that any life on the newly discovered planet would be similar to life on Earth, but he didn't discount the idea entirely.
"This planet probably does have liquid water," he said.
Tuesday, December 8, 2009
New Theory on Large Black Holes
Do Big Stars Spawn Giant Black Holes?
By Clara Moskowitz
,
Space.com
(Dec. 8, 2009) -- The biggest black holes in the universe are also the most perplexing. Scientists have long been confused about just how the earliest, most massive black holes formed, but new evidence now suggests they could have originated inside giant cocoon-like stars.
This idea is at odds with the prevailing thinking that large black holes are created by the clumping together of smaller black holes.
A University of Colorado scientists says the universe's biggest black holes may have been created by massive stars that formed soon after the Big Bang.
Not so, says University of Colorado at Boulder astrophysicist Mitchell Begelman. Rather, these behemoth black holes likely formed in the middle of even larger supermassive stars that could have held tens of millions of times the mass of our sun, according to Begelman.
"Until recently, the thinking by many has been that supermassive black holes got their start from the merging of numerous, small black holes in the universe," Begelman said. "This new model of black hole development indicates a possible alternate route to their formation."
Begelman studied how these gigantic stars could have formed, and how massive their cores might have been, to understand how they might have given rise to huge black holes. The results of his investigation will be published in an upcoming issue of the Monthly Notices of the Royal Astronomical Society in London.
The monster stars probably started forming within the first few hundred million years after the Big Bang, which is thought to have created the universe around 14 billion years ago, Begelman found. When the cores of these giant stars had burned all their hydrogen, they would have collapsed, forming dense black holes. Meanwhile the outside gas layers of the stars remained as a shroud. Eventually, though, the black holes would have swallowed all the remaining stellar matter within their reach, ballooning rapidly to staggering weights, the study suggests.
This scenario could be more likely than the clumping process as the origin of supermassive black holes, Begelman said, though it's also possible that both methods have occurred.
"The problem that most people see in the clumping mechanism is whether you get these small black holes to merge frequently enough," Begelman told SPACE.com. "I'm working on trying to compare the rates of these two processes."
Over time, the resulting black boles might have merged with other giant black holes to form even larger leviathans.
"Big black holes formed via supermassive stars could have had a huge impact on the evolution of the universe, including galaxy formation," Begelman said.
Astronomers think most galaxies, including the Milky Way in which the Earth's solar system resides, have supermassive black holes at their centers. These black holes are probably responsible for a cosmic phenomenon called quasars, which are thought to occur when mass pours onto huge black holes, and some material is flung away in bright jets of high-energy radiation that can be seen across the universe.
By Clara Moskowitz
,
Space.com
(Dec. 8, 2009) -- The biggest black holes in the universe are also the most perplexing. Scientists have long been confused about just how the earliest, most massive black holes formed, but new evidence now suggests they could have originated inside giant cocoon-like stars.
This idea is at odds with the prevailing thinking that large black holes are created by the clumping together of smaller black holes.
A University of Colorado scientists says the universe's biggest black holes may have been created by massive stars that formed soon after the Big Bang.
Not so, says University of Colorado at Boulder astrophysicist Mitchell Begelman. Rather, these behemoth black holes likely formed in the middle of even larger supermassive stars that could have held tens of millions of times the mass of our sun, according to Begelman.
"Until recently, the thinking by many has been that supermassive black holes got their start from the merging of numerous, small black holes in the universe," Begelman said. "This new model of black hole development indicates a possible alternate route to their formation."
Begelman studied how these gigantic stars could have formed, and how massive their cores might have been, to understand how they might have given rise to huge black holes. The results of his investigation will be published in an upcoming issue of the Monthly Notices of the Royal Astronomical Society in London.
The monster stars probably started forming within the first few hundred million years after the Big Bang, which is thought to have created the universe around 14 billion years ago, Begelman found. When the cores of these giant stars had burned all their hydrogen, they would have collapsed, forming dense black holes. Meanwhile the outside gas layers of the stars remained as a shroud. Eventually, though, the black holes would have swallowed all the remaining stellar matter within their reach, ballooning rapidly to staggering weights, the study suggests.
This scenario could be more likely than the clumping process as the origin of supermassive black holes, Begelman said, though it's also possible that both methods have occurred.
"The problem that most people see in the clumping mechanism is whether you get these small black holes to merge frequently enough," Begelman told SPACE.com. "I'm working on trying to compare the rates of these two processes."
Over time, the resulting black boles might have merged with other giant black holes to form even larger leviathans.
"Big black holes formed via supermassive stars could have had a huge impact on the evolution of the universe, including galaxy formation," Begelman said.
Astronomers think most galaxies, including the Milky Way in which the Earth's solar system resides, have supermassive black holes at their centers. These black holes are probably responsible for a cosmic phenomenon called quasars, which are thought to occur when mass pours onto huge black holes, and some material is flung away in bright jets of high-energy radiation that can be seen across the universe.
Sunday, December 6, 2009
Theory on the Near Extinction of Humans
(Dec. 3) -- A massive volcanic eruption that occurred in the distant past killed off much of central India's forests and may have pushed humans to the brink of extinction, according to a new study that adds evidence to a controversial topic.
The Toba eruption, which took place on the island of Sumatra in Indonesia about 73,000 years ago, released an estimated 800 cubic kilometers of ash into the atmosphere that blanketed the skies and blocked out sunlight for six years. In the aftermath, global temperatures dropped by as much as 28 degrees Fahrenheit and life on Earth plunged deeper into an ice age that lasted around 1,800 years.
In 1998, Stanley Ambrose, an anthropology professor at the University of Illinois, proposed in the Journal of Human Evolution that the effects of the Toba eruption and the Ice Age that followed could explain the apparent bottleneck in human populations that geneticists believe occurred between 50,000 and 100,000 years ago. The lack of genetic diversity among humans alive today suggests that during this time period humans came very close to becoming extinct.
Satellite images show smoldering underground fires on the island of Sumatra, Indonesia, in 1997. A new study finds that a volcanic eruption on the same island 73,000 years ago had devastating effects on Earth.
To test his theory, Ambrose and his research team analyzed pollen from a marine core in the Bay of Bengal that had a layer of ash from the Toba eruption. The researchers also compared carbon isotope ratios in fossil soil taken from directly above and below the Toba ash in three locations in central India — some 3,000 miles from the volcano — to pinpoint the type of vegetation that existed at various locations and time periods.
Heavily forested regions leave carbon isotope fingerprints that are distinct from those of grasses or grassy woodlands.
The tests revealed a distinct change in the type of vegetation in India immediately after the Toba eruption. The researchers write in the journal Palaeogeography, Palaeoclimatology, Palaeoecology that their analysis indicates a shift to a "more open vegetation cover and reduced representation of ferns," which grow in humid conditions, all of which "would suggest significantly drier conditions in this region for at least 1,000 years after the Toba eruption."
The dryness probably also indicates a drop in temperature "because when you turn down the temperature you also turn down the rainfall," Ambrose said. "This is unambiguous evidence that Toba caused deforestation in the tropics for a long time."
He also concluded that the disaster may have forced the ancestors of modern humans to adopt new cooperative strategies for survival that eventually permitted them to replace Neanderthals and other archaic human species.
Although humans survived the event, researchers have detected increasing activity underneath a caldera at Yellowstone National Park, where some suspect another supervolcanic eruption will eventually take place. Though not expected to occur anytime soon, a Yellowstone eruption could coat half the United States in a layer of ash up to 3 feet deep.
The Toba eruption, which took place on the island of Sumatra in Indonesia about 73,000 years ago, released an estimated 800 cubic kilometers of ash into the atmosphere that blanketed the skies and blocked out sunlight for six years. In the aftermath, global temperatures dropped by as much as 28 degrees Fahrenheit and life on Earth plunged deeper into an ice age that lasted around 1,800 years.
In 1998, Stanley Ambrose, an anthropology professor at the University of Illinois, proposed in the Journal of Human Evolution that the effects of the Toba eruption and the Ice Age that followed could explain the apparent bottleneck in human populations that geneticists believe occurred between 50,000 and 100,000 years ago. The lack of genetic diversity among humans alive today suggests that during this time period humans came very close to becoming extinct.
Satellite images show smoldering underground fires on the island of Sumatra, Indonesia, in 1997. A new study finds that a volcanic eruption on the same island 73,000 years ago had devastating effects on Earth.
To test his theory, Ambrose and his research team analyzed pollen from a marine core in the Bay of Bengal that had a layer of ash from the Toba eruption. The researchers also compared carbon isotope ratios in fossil soil taken from directly above and below the Toba ash in three locations in central India — some 3,000 miles from the volcano — to pinpoint the type of vegetation that existed at various locations and time periods.
Heavily forested regions leave carbon isotope fingerprints that are distinct from those of grasses or grassy woodlands.
The tests revealed a distinct change in the type of vegetation in India immediately after the Toba eruption. The researchers write in the journal Palaeogeography, Palaeoclimatology, Palaeoecology that their analysis indicates a shift to a "more open vegetation cover and reduced representation of ferns," which grow in humid conditions, all of which "would suggest significantly drier conditions in this region for at least 1,000 years after the Toba eruption."
The dryness probably also indicates a drop in temperature "because when you turn down the temperature you also turn down the rainfall," Ambrose said. "This is unambiguous evidence that Toba caused deforestation in the tropics for a long time."
He also concluded that the disaster may have forced the ancestors of modern humans to adopt new cooperative strategies for survival that eventually permitted them to replace Neanderthals and other archaic human species.
Although humans survived the event, researchers have detected increasing activity underneath a caldera at Yellowstone National Park, where some suspect another supervolcanic eruption will eventually take place. Though not expected to occur anytime soon, a Yellowstone eruption could coat half the United States in a layer of ash up to 3 feet deep.
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