Earth-like planets and life beyond Earth
Saturday, 10 November 2007
Syed Fattahul Alim
Our darling green planet Earth has been travelling in space for billions of years alone. The silence of its loneliness, however, is broken by the humming of life. It has long been an issue of profound debate, if earth is the only planet among all such solar-like systems in the universe that is pregnant with life. Commonsense logic says that life cannot be a uniquely strange anomaly limited to the third planet in the solar family at a far corner of the universe. There must be other place where life, whatever its form, is flourishing like here. However, scientists are unanimous in their view that water is the most essential ingredient for the evolution of life. Moreover, the celestial objects that are potential candidates for hosting life must be placed at such distances where it is not too hot to evaporate all the water into space, neither should it be so far away that life's chance to sprout is denied by extreme cold. There may be other Earth-like conditions to allow life to germinate, for example, the force of gravity. Very high and very low gravity may also prove to be a barrier to the growth of life. So, stars with planetary system resembling the solar system and having planets with Earth-like conditions, and of course, containing water are the most potential candidates for sustaining life.
Have astronomers any good news for those optimists who are scanning the skies to discover solar systems with planets like Earth? Of late, with the sighting, though indirectly using a combination of techniques, around 250 planets have been discovered in different stellar systems many light years away from us. Many of those planets are in gaseous state like the Jupiter and Saturn in the solar system. But still scientists are hopeful that, after all, planets are not a rarity in the universe and some day it might also be possible to stumble upon a far away planet that sustains life that is intelligent like humans on earth.
Ian Sample writes in the Guardian about the discovery of such planets:
'The discovery of a giant alien world in a distant constellation has led astronomers to believe they have located a near twin of our own solar system in a far corner of the galaxy.
Nasa scientists confirmed the discovery tonight in what is a hugely significant step towards finding a second Earth-like planet capable of harbouring extraterrestrial life.
The new planet is the fifth to be spotted orbiting what is actually a close pair of neighbouring stars collectively known as 55 Cancri that lie in the constellation of Cancer 41 light years away.
The discovery means 55 Cancri holds the record for the number of confirmed planets orbiting in its planetary system.
Four of them are huge gas giants similar to Jupiter, while the innermost is believed to resemble Neptune.
Since Pluto's demotion last year from full planet status to a more lowly "dwarf planet", our own solar system contains eight planets. The inner four are rocky worlds while those further out are massive balls of gas.
The Nasa-funded team say the newly-discovered world is similar to Saturn and orbits inside the most distant planet already known to circle around 55 Cancri.
"It is amazing to see our ability to detect extra-solar planets growing," said Alan Stern, of Nasa's Science Mission Directorate in Washington. "We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own."
The announcement is all the more significant because the new planet is the first known one outside our solar system to spend its entire orbit within what astronomers call the "habitable zone". The zone marks a Goldilocks band of space where the heat from a star leaves a planet neither too hot nor too cold to support liquid water, which is believed to be crucial for life.
The new planet weighs about 45 times the mass of Earth and completes one orbit every 260 days. The distance from its star is approximately 72.5m miles, slightly closer than Earth to our sun, but it orbits a star that is slightly fainter.
Scientists involved in the discovery believe that if the planet has a rocky moon - as they expect - any water on its surface would flow freely, dramatically increasing the odds that it could harbour life.
"The gas-giant planets in our solar system all have large moons," said Debra Fischer, an astronomer at San Francisco State University and lead author of a paper that will appear in a future issue of the Astrophysical Journal. "If there is a moon orbiting this new, massive planet, it might have pools of liquid water on a rocky surface."
The team also believe another planet lurks between the fourth and fifth that orbit 55 Cancri, which may also lie within the habitable zone.
Working with astronomer Geoff Marcy at the University of California, Berkeley, and others, Dr Fischer discovered the planet after careful observation of 2,000 nearby stars using telescopes at the Lick Observatory on Mount Hamilton near San Jose and the huge Keck Observatory in Mauna Kea, Hawaii.
The astronomers were able to infer the position and size of the new planet by analysing shifts in starlight coming from 55 Cancri, which are caused by orbiting planets wrenching the star back and forth. More than 320 measurements were required to disentangle signals from each of the planets.
"This system has a dominant gas giant planet in an orbit similar to our Jupiter. Like the planets orbiting our sun, most of these planets reside in nearly circular orbits," said Dr Fischer.
"Discovering these five planets took us 18 years of continuous observations at Lick Observatory, starting before any extra-solar planets were known anywhere in the universe," said Professor Marcy, who contributed to the paper. "But finding five extra-solar planets orbiting a star is only one small step. Earth-like planets are the next destination."
To date, more than 260 planets have been discovered beyond our solar system.
"This work marks an exciting next step in the search for worlds like our own," said Michael Briley, an astronomer at the US National Science Foundation. "To go from the first detections of planets around sun-like stars to finding a full-fledged solar system with a planet in a habitable zone in just 12 years is an amazing accomplishment and a testament to the years of hard work put in by these investigators."
About life beyond Earth, Seth Shostak, senior astronomer at the SETI Institute in California writes:
It's been more than a century since HG Wells wrote of malevolent Martians intent on invading our planet (and, as collateral damage, obliterating the natives). Since then, our conception of Red Planet residents has been downgraded from canal-crazy bipeds to microscopic muck.
But finding Lilliputian inhabitants of Mars - or any of the other worlds of our solar system - remains the lead horse in the race to show that life is more than an affliction of Earth alone, that life is a statistic, and not a miracle.
Finding aliens from afar
. A dozen years ago, astronomers finally found proof of planets around other stars. Today, thanks to hard work and enthusiasm, we know of roughly 250 such worlds. The number increases at the rate of one new discovery every two weeks.
The majority of these planets are hulky and bulky - comparable in size (and, one presumes, in properties) to Jupiter. Such worlds are likely to be wrapped in thick, toxic atmospheres but, as the discovery techniques are refined, planets more amenable to biology occasionally turn up.
Gliese 581c made the headlines in recent months as a world only slightly larger than our own, and situated at a distance from its host star that would permit water to slosh on its surface. Recently, water vapour itself seems to have been detected in the atmosphere of the hefty planet known to its friends as HD209458b.
But how could we learn if any of these far-flung worlds really do boast life, short of sending the Starship Enterprise on a reconnaissance mission? Easy calculation shows that an orbiting, infrared telescope could dissect the light that bounces off their atmospheres, and - as the attendees at Bioastronomy 2007 were told - sensitively look for the spectral features of oxygen, methane, nitrous oxide, carbon dioxide and water. These are the telltale compounds of an atmosphere that is both habitable and inhabited.
Today, the Americans and the Europeans have such telescopes on the drawing boards, where they are decorative but useless. However, if funding materialises, we might have compelling evidence of biological activity on planets dozens of light-years distant within a decade or two.
We wouldn't know what that life looks like, or much about how it's built. But if this horse crosses the finish line, we'll at least know that our part of the Galaxy has some metabolizing neighbours.
The third horse in the biology space-race is SETI, or the Search for Extraterrestrial Intelligence. The SETI approach (as dramatised in the film Contact) is to simply eavesdrop on radio signals or laser flashes beamed into space by aliens with the interest and ability to reach out.
New instruments, such as the Allen Telescope Array now under construction in California, will greatly augment these types of experiments, and within two decades could search for signals from a million star systems. That might be sufficient to turn up a transmitter, even if intelligent life is fairly rare. Should it happen, SETI researchers have signed an informal agreement that the news will be made public immediately.
SETI differs from the first two horses in that it is pounding the track in search of a conversational partner, not just extraterrestrial pond scum.
Mind you, starting a rap session with any alien society is akin to tossing bottled messages into the surf. The nearest sentients are surely hundreds of light-years distant or more, so the discourse will be tedious. Still, it would be good to know of other beings who are able to recognise their own existence and ponder the meaning of it all.
Our darling green planet Earth has been travelling in space for billions of years alone. The silence of its loneliness, however, is broken by the humming of life. It has long been an issue of profound debate, if earth is the only planet among all such solar-like systems in the universe that is pregnant with life. Commonsense logic says that life cannot be a uniquely strange anomaly limited to the third planet in the solar family at a far corner of the universe. There must be other place where life, whatever its form, is flourishing like here. However, scientists are unanimous in their view that water is the most essential ingredient for the evolution of life. Moreover, the celestial objects that are potential candidates for hosting life must be placed at such distances where it is not too hot to evaporate all the water into space, neither should it be so far away that life's chance to sprout is denied by extreme cold. There may be other Earth-like conditions to allow life to germinate, for example, the force of gravity. Very high and very low gravity may also prove to be a barrier to the growth of life. So, stars with planetary system resembling the solar system and having planets with Earth-like conditions, and of course, containing water are the most potential candidates for sustaining life.
Have astronomers any good news for those optimists who are scanning the skies to discover solar systems with planets like Earth? Of late, with the sighting, though indirectly using a combination of techniques, around 250 planets have been discovered in different stellar systems many light years away from us. Many of those planets are in gaseous state like the Jupiter and Saturn in the solar system. But still scientists are hopeful that, after all, planets are not a rarity in the universe and some day it might also be possible to stumble upon a far away planet that sustains life that is intelligent like humans on earth.
Ian Sample writes in the Guardian about the discovery of such planets:
'The discovery of a giant alien world in a distant constellation has led astronomers to believe they have located a near twin of our own solar system in a far corner of the galaxy.
Nasa scientists confirmed the discovery tonight in what is a hugely significant step towards finding a second Earth-like planet capable of harbouring extraterrestrial life.
The new planet is the fifth to be spotted orbiting what is actually a close pair of neighbouring stars collectively known as 55 Cancri that lie in the constellation of Cancer 41 light years away.
The discovery means 55 Cancri holds the record for the number of confirmed planets orbiting in its planetary system.
Four of them are huge gas giants similar to Jupiter, while the innermost is believed to resemble Neptune.
Since Pluto's demotion last year from full planet status to a more lowly "dwarf planet", our own solar system contains eight planets. The inner four are rocky worlds while those further out are massive balls of gas.
The Nasa-funded team say the newly-discovered world is similar to Saturn and orbits inside the most distant planet already known to circle around 55 Cancri.
"It is amazing to see our ability to detect extra-solar planets growing," said Alan Stern, of Nasa's Science Mission Directorate in Washington. "We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own."
The announcement is all the more significant because the new planet is the first known one outside our solar system to spend its entire orbit within what astronomers call the "habitable zone". The zone marks a Goldilocks band of space where the heat from a star leaves a planet neither too hot nor too cold to support liquid water, which is believed to be crucial for life.
The new planet weighs about 45 times the mass of Earth and completes one orbit every 260 days. The distance from its star is approximately 72.5m miles, slightly closer than Earth to our sun, but it orbits a star that is slightly fainter.
Scientists involved in the discovery believe that if the planet has a rocky moon - as they expect - any water on its surface would flow freely, dramatically increasing the odds that it could harbour life.
"The gas-giant planets in our solar system all have large moons," said Debra Fischer, an astronomer at San Francisco State University and lead author of a paper that will appear in a future issue of the Astrophysical Journal. "If there is a moon orbiting this new, massive planet, it might have pools of liquid water on a rocky surface."
The team also believe another planet lurks between the fourth and fifth that orbit 55 Cancri, which may also lie within the habitable zone.
Working with astronomer Geoff Marcy at the University of California, Berkeley, and others, Dr Fischer discovered the planet after careful observation of 2,000 nearby stars using telescopes at the Lick Observatory on Mount Hamilton near San Jose and the huge Keck Observatory in Mauna Kea, Hawaii.
The astronomers were able to infer the position and size of the new planet by analysing shifts in starlight coming from 55 Cancri, which are caused by orbiting planets wrenching the star back and forth. More than 320 measurements were required to disentangle signals from each of the planets.
"This system has a dominant gas giant planet in an orbit similar to our Jupiter. Like the planets orbiting our sun, most of these planets reside in nearly circular orbits," said Dr Fischer.
"Discovering these five planets took us 18 years of continuous observations at Lick Observatory, starting before any extra-solar planets were known anywhere in the universe," said Professor Marcy, who contributed to the paper. "But finding five extra-solar planets orbiting a star is only one small step. Earth-like planets are the next destination."
To date, more than 260 planets have been discovered beyond our solar system.
"This work marks an exciting next step in the search for worlds like our own," said Michael Briley, an astronomer at the US National Science Foundation. "To go from the first detections of planets around sun-like stars to finding a full-fledged solar system with a planet in a habitable zone in just 12 years is an amazing accomplishment and a testament to the years of hard work put in by these investigators."
About life beyond Earth, Seth Shostak, senior astronomer at the SETI Institute in California writes:
It's been more than a century since HG Wells wrote of malevolent Martians intent on invading our planet (and, as collateral damage, obliterating the natives). Since then, our conception of Red Planet residents has been downgraded from canal-crazy bipeds to microscopic muck.
But finding Lilliputian inhabitants of Mars - or any of the other worlds of our solar system - remains the lead horse in the race to show that life is more than an affliction of Earth alone, that life is a statistic, and not a miracle.
Finding aliens from afar
. A dozen years ago, astronomers finally found proof of planets around other stars. Today, thanks to hard work and enthusiasm, we know of roughly 250 such worlds. The number increases at the rate of one new discovery every two weeks.
The majority of these planets are hulky and bulky - comparable in size (and, one presumes, in properties) to Jupiter. Such worlds are likely to be wrapped in thick, toxic atmospheres but, as the discovery techniques are refined, planets more amenable to biology occasionally turn up.
Gliese 581c made the headlines in recent months as a world only slightly larger than our own, and situated at a distance from its host star that would permit water to slosh on its surface. Recently, water vapour itself seems to have been detected in the atmosphere of the hefty planet known to its friends as HD209458b.
But how could we learn if any of these far-flung worlds really do boast life, short of sending the Starship Enterprise on a reconnaissance mission? Easy calculation shows that an orbiting, infrared telescope could dissect the light that bounces off their atmospheres, and - as the attendees at Bioastronomy 2007 were told - sensitively look for the spectral features of oxygen, methane, nitrous oxide, carbon dioxide and water. These are the telltale compounds of an atmosphere that is both habitable and inhabited.
Today, the Americans and the Europeans have such telescopes on the drawing boards, where they are decorative but useless. However, if funding materialises, we might have compelling evidence of biological activity on planets dozens of light-years distant within a decade or two.
We wouldn't know what that life looks like, or much about how it's built. But if this horse crosses the finish line, we'll at least know that our part of the Galaxy has some metabolizing neighbours.
The third horse in the biology space-race is SETI, or the Search for Extraterrestrial Intelligence. The SETI approach (as dramatised in the film Contact) is to simply eavesdrop on radio signals or laser flashes beamed into space by aliens with the interest and ability to reach out.
New instruments, such as the Allen Telescope Array now under construction in California, will greatly augment these types of experiments, and within two decades could search for signals from a million star systems. That might be sufficient to turn up a transmitter, even if intelligent life is fairly rare. Should it happen, SETI researchers have signed an informal agreement that the news will be made public immediately.
SETI differs from the first two horses in that it is pounding the track in search of a conversational partner, not just extraterrestrial pond scum.
Mind you, starting a rap session with any alien society is akin to tossing bottled messages into the surf. The nearest sentients are surely hundreds of light-years distant or more, so the discourse will be tedious. Still, it would be good to know of other beings who are able to recognise their own existence and ponder the meaning of it all.