Search for earth like planets and life
Saturday, 15 December 2007
Syed Fattahul Alim
HUMANITY is gradually reaching adulthood. The indication of this phase in human history is marked by the fact that it is now looking for its likeness elsewhere in the solar system and even beyond. What is the connection of the search for likeness with adulthood or coming of age? The hallmark of childhood is that it is fearful of strangers and is unwilling to cross the familiar setting. Adolescence is a bit more challenging and adventurous, but torn between as it were mother's call to return home before the dusk and the beckon of the mysteriously dim silhouette of the distant woods. But adulthood is the stage of life when it has already weaned from mother's apron strings and the fear of stranger has been replaced with the will to face up to the alien. Man now knows the broader meaning of life and so has launched his hunt for discovering his likes, if any, albeit in a physical shape different from him. He is no more concerned about aliens in the likeness of the Wellsian genre Martians, who are hell-bent on destroying Earth and its inhabitants. After H.G. Wells science fiction writers dreamed up a universe that was swarming with extra-terrestrial beings, most of whom are hostile to humans and, as if, straining at the leash to drink the blood of the earthlings. However, the pulp thrillers' plots were never backed by hard science and hard science on its part was always dismissive of the science fictiony narratives about life beyond earth. Interestingly though, there has been a group of scientists who kept their eavesdropping devices turned on in case any possible electromagnetic signal carrying signatures of intelligence other than human stumbled upon it) and similar other listening stations are scanning the sky round the clock to get any hint of earth-like planets where life might have flowered intelligent or not. Ian Sample narrates below how the search for new planets is faring:
Andrew Collier Cameron stretches a hand towards the charcoal skies that have gathered over the Kingdom of Fife and talks of a planet that lies far beyond the clouds. It is a planet that has never been seen, even through the most powerful space telescopes.
It revealed itself to Cameron only by casting the tiniest of shadows as it strayed in front of its parent star, 1,000 light years from his office in the physics building at St Andrew's University on the east coast of Scotland.
Though distant, the planet has given up a few of its secrets. It is a world that shows only one face to its sun: half of it basks in permanent warmth while the other lies in eternal darkness. It moves so swiftly round its star that a year there lasts only a few Earth days. It is a giant that would dwarf not just our blue-green planet but even Jupiter, the largest in the solar system, yet it is incredibly light in comparison: it has the density of willow. "It would float!" says Cameron, his fingers spread wide. "If you could only find a bath big enough!"
Here on Earth, Cameron and his team are part of a new wave of astronomers who are scouring the galaxy for glimpses of unknown worlds and, in recent years, their success has been astounding. While our own solar system lost a planet last year, thanks to the unceremonious demotion of Pluto from planet to "dwarf planet", Cameron and his peers have found more than 250 new worlds, in solar systems far, far away. With almost every week that goes by, new discoveries are made. This evening, in fact, planet hunters in America are to declare a major coup with the announcement from Nasa of a newly discovered solar system that has striking similarities to our own.
Individually, each new planet we discover adds a fragment to our understanding of the galaxy beyond our celestial backyard. But collectively, these scattered worlds point to something more profound. Scientists' ability to spot distant planets has accelerated more rapidly in the past 20 years than many dared imagine. And, for the first time, they are now talking seriously about searching for a planet that could recast the role of humanity in the universe: a second Earth.
"There's a very strong innate desire in humans to know how special our planet is," says Cameron. "There's a lot of talk about how finely tuned Earth is for life, but just how special is the Earth? How special is life? Are we alone? This is what gets people get into this."
So far, nearly all the planets discovered beyond the solar system are enormous gas giants, like our own Jupiter, only hotter and bigger. They orbit so blisteringly close to their suns that they carve out a year in a just a few Earth days, their surfaces approaching a searing 2,000C.
These huge worlds are the easiest to spot, though the vast majority are still detected indirectly, through the effects they have on their parent stars. The most successful technique to date relies on the famous Doppler effect, which affects all kinds of energy waves - from sound waves to waves of light.
When a planet swings around a star, its gravitational field has an impact on the star itself: it makes the star move in a little circle of its own. If the planet is big enough, astronomers can pick up this cosmic dance by peering at the starlight that reaches Earth tens, hundreds, even thousands of years later. If the starlight shifts to a more reddish colour, the light waves are being stretched out, so the star must be being pulled away from Earth. As the star is pulled back towards us, the light we see turns more bluish, as the waves are squashed together. By watching the shift from red to blue and back again, astronomers can deduce the mass and rough orbit of the planet doing the wrenching.
Cameron spotted his giant willow world another way. The team is part of a consortium called SuperWasp, which stands for Super Wide Angle Search for Planets, run by Don Pollacco at Queen's University in Belfast. Together, they operate two ground-based telescopes, one at the summit of La Palma, a volcanic shard of an island in the Canaries, the other on a hilltop at Sutherland in the Karoo desert, a few hours drive north east of Capetown.
Every evening, automatic covers roll back from the telescopes to reveal the stars, which are snapped every 30 seconds as they curl over the sky from sunset to sunrise. In a 10-minute period, each telescope will capture the light of 3.5m stars.
In the mornings, the previous night's images from La Palma are piped down the internet to Belfast. Those from Africa are stored on magnetic tapes and shipped back in bulk. (The internet can be less reliable there.)
At Pollacco's lab, a bank of computers then spends 12 hours a day examining every image of every star, looking for telltale dips in the brightness caused by a planet moving across the face of its sun. The most promising candidates are then beamed out to researchers such as Cameron for confirmation.
In 2005, the SuperWasp team found two huge planets this way, the willow world, in the constellation of Andromeda, and a smaller, more dense planet circling a star in the constellation of Delphinus, the dolphin. Last week, the team announced its latest discoveries - three more giant planets more than 700 light years away that pass so close to their suns that their surfaces boil.
The SuperWasp technique, known as the transit method, has its shortcomings, though. Only a tiny percentage of planets orbit their stars in the right plane to cast their shadows across the Earth, and only giant worlds that come close to their stars produce clear enough signals to reveal themselves.
But this is a fast-changing field: improvements and refinements are bringing astronomers ever closer to their ultimate goal of finding a second Earth. Earlier this year, scientists led by Stephane Udry at the European Southern Observatory in Geneva discovered a planet orbiting a faint red dwarf star in the constellation of Libra, 20 light years away. Their measurements suggest the planet, Gliese 581c, is small and rocky - only one and a half times the size of Earth. Its orbit has led some scientists to speculate that liquid water might be stable on its surface, raising the tantalising possibility that it could support life.
If life does exist on Gliese 581c, it has yet to generate enough noise to be noticed by its galactic neighbours, however. Scientists at the California-based Search for Extraterrestrial Intelligence (Seti) project have looked for radio waves emanating from the star system - the Gliese equivalents of 20-year-old TV broadcasts - and found nothing.
Just three months after Udry's announcement, a landmark discovery by Giovanna Tinetti and her team at University College London sent a further ripple of excitement through the field. They used Nasa's Spitzer Space Telescope to peer at infrared radiation coming from a star called HD 189733 that lies 63 light years from Earth. When a newly discovered planet moved close to the star, they noticed a familiar pattern in the infrared signal. The discovery, reported in the journal Nature, marked the first incontrovertible evidence of water in the atmosphere of a planet beyond our solar system.
In the canteen in the physics building at St Andrew's, a substantial pile of napkins marked with giant circles and squiggly light rays has been moved to one side and the discussion has shifted from orbital mechanics to more philosophical ground. In the coming years, expectations are running high that planet hunters will stumble across a second Earth, at least at first glance.
HUMANITY is gradually reaching adulthood. The indication of this phase in human history is marked by the fact that it is now looking for its likeness elsewhere in the solar system and even beyond. What is the connection of the search for likeness with adulthood or coming of age? The hallmark of childhood is that it is fearful of strangers and is unwilling to cross the familiar setting. Adolescence is a bit more challenging and adventurous, but torn between as it were mother's call to return home before the dusk and the beckon of the mysteriously dim silhouette of the distant woods. But adulthood is the stage of life when it has already weaned from mother's apron strings and the fear of stranger has been replaced with the will to face up to the alien. Man now knows the broader meaning of life and so has launched his hunt for discovering his likes, if any, albeit in a physical shape different from him. He is no more concerned about aliens in the likeness of the Wellsian genre Martians, who are hell-bent on destroying Earth and its inhabitants. After H.G. Wells science fiction writers dreamed up a universe that was swarming with extra-terrestrial beings, most of whom are hostile to humans and, as if, straining at the leash to drink the blood of the earthlings. However, the pulp thrillers' plots were never backed by hard science and hard science on its part was always dismissive of the science fictiony narratives about life beyond earth. Interestingly though, there has been a group of scientists who kept their eavesdropping devices turned on in case any possible electromagnetic signal carrying signatures of intelligence other than human stumbled upon it) and similar other listening stations are scanning the sky round the clock to get any hint of earth-like planets where life might have flowered intelligent or not. Ian Sample narrates below how the search for new planets is faring:
Andrew Collier Cameron stretches a hand towards the charcoal skies that have gathered over the Kingdom of Fife and talks of a planet that lies far beyond the clouds. It is a planet that has never been seen, even through the most powerful space telescopes.
It revealed itself to Cameron only by casting the tiniest of shadows as it strayed in front of its parent star, 1,000 light years from his office in the physics building at St Andrew's University on the east coast of Scotland.
Though distant, the planet has given up a few of its secrets. It is a world that shows only one face to its sun: half of it basks in permanent warmth while the other lies in eternal darkness. It moves so swiftly round its star that a year there lasts only a few Earth days. It is a giant that would dwarf not just our blue-green planet but even Jupiter, the largest in the solar system, yet it is incredibly light in comparison: it has the density of willow. "It would float!" says Cameron, his fingers spread wide. "If you could only find a bath big enough!"
Here on Earth, Cameron and his team are part of a new wave of astronomers who are scouring the galaxy for glimpses of unknown worlds and, in recent years, their success has been astounding. While our own solar system lost a planet last year, thanks to the unceremonious demotion of Pluto from planet to "dwarf planet", Cameron and his peers have found more than 250 new worlds, in solar systems far, far away. With almost every week that goes by, new discoveries are made. This evening, in fact, planet hunters in America are to declare a major coup with the announcement from Nasa of a newly discovered solar system that has striking similarities to our own.
Individually, each new planet we discover adds a fragment to our understanding of the galaxy beyond our celestial backyard. But collectively, these scattered worlds point to something more profound. Scientists' ability to spot distant planets has accelerated more rapidly in the past 20 years than many dared imagine. And, for the first time, they are now talking seriously about searching for a planet that could recast the role of humanity in the universe: a second Earth.
"There's a very strong innate desire in humans to know how special our planet is," says Cameron. "There's a lot of talk about how finely tuned Earth is for life, but just how special is the Earth? How special is life? Are we alone? This is what gets people get into this."
So far, nearly all the planets discovered beyond the solar system are enormous gas giants, like our own Jupiter, only hotter and bigger. They orbit so blisteringly close to their suns that they carve out a year in a just a few Earth days, their surfaces approaching a searing 2,000C.
These huge worlds are the easiest to spot, though the vast majority are still detected indirectly, through the effects they have on their parent stars. The most successful technique to date relies on the famous Doppler effect, which affects all kinds of energy waves - from sound waves to waves of light.
When a planet swings around a star, its gravitational field has an impact on the star itself: it makes the star move in a little circle of its own. If the planet is big enough, astronomers can pick up this cosmic dance by peering at the starlight that reaches Earth tens, hundreds, even thousands of years later. If the starlight shifts to a more reddish colour, the light waves are being stretched out, so the star must be being pulled away from Earth. As the star is pulled back towards us, the light we see turns more bluish, as the waves are squashed together. By watching the shift from red to blue and back again, astronomers can deduce the mass and rough orbit of the planet doing the wrenching.
Cameron spotted his giant willow world another way. The team is part of a consortium called SuperWasp, which stands for Super Wide Angle Search for Planets, run by Don Pollacco at Queen's University in Belfast. Together, they operate two ground-based telescopes, one at the summit of La Palma, a volcanic shard of an island in the Canaries, the other on a hilltop at Sutherland in the Karoo desert, a few hours drive north east of Capetown.
Every evening, automatic covers roll back from the telescopes to reveal the stars, which are snapped every 30 seconds as they curl over the sky from sunset to sunrise. In a 10-minute period, each telescope will capture the light of 3.5m stars.
In the mornings, the previous night's images from La Palma are piped down the internet to Belfast. Those from Africa are stored on magnetic tapes and shipped back in bulk. (The internet can be less reliable there.)
At Pollacco's lab, a bank of computers then spends 12 hours a day examining every image of every star, looking for telltale dips in the brightness caused by a planet moving across the face of its sun. The most promising candidates are then beamed out to researchers such as Cameron for confirmation.
In 2005, the SuperWasp team found two huge planets this way, the willow world, in the constellation of Andromeda, and a smaller, more dense planet circling a star in the constellation of Delphinus, the dolphin. Last week, the team announced its latest discoveries - three more giant planets more than 700 light years away that pass so close to their suns that their surfaces boil.
The SuperWasp technique, known as the transit method, has its shortcomings, though. Only a tiny percentage of planets orbit their stars in the right plane to cast their shadows across the Earth, and only giant worlds that come close to their stars produce clear enough signals to reveal themselves.
But this is a fast-changing field: improvements and refinements are bringing astronomers ever closer to their ultimate goal of finding a second Earth. Earlier this year, scientists led by Stephane Udry at the European Southern Observatory in Geneva discovered a planet orbiting a faint red dwarf star in the constellation of Libra, 20 light years away. Their measurements suggest the planet, Gliese 581c, is small and rocky - only one and a half times the size of Earth. Its orbit has led some scientists to speculate that liquid water might be stable on its surface, raising the tantalising possibility that it could support life.
If life does exist on Gliese 581c, it has yet to generate enough noise to be noticed by its galactic neighbours, however. Scientists at the California-based Search for Extraterrestrial Intelligence (Seti) project have looked for radio waves emanating from the star system - the Gliese equivalents of 20-year-old TV broadcasts - and found nothing.
Just three months after Udry's announcement, a landmark discovery by Giovanna Tinetti and her team at University College London sent a further ripple of excitement through the field. They used Nasa's Spitzer Space Telescope to peer at infrared radiation coming from a star called HD 189733 that lies 63 light years from Earth. When a newly discovered planet moved close to the star, they noticed a familiar pattern in the infrared signal. The discovery, reported in the journal Nature, marked the first incontrovertible evidence of water in the atmosphere of a planet beyond our solar system.
In the canteen in the physics building at St Andrew's, a substantial pile of napkins marked with giant circles and squiggly light rays has been moved to one side and the discussion has shifted from orbital mechanics to more philosophical ground. In the coming years, expectations are running high that planet hunters will stumble across a second Earth, at least at first glance.