 |
|
Astronomers find first habitable Earth-like planet
April 25, 2007Astronomers have discovered the most Earth-like planet outside our Solar System to date, an exoplanet with a radius only 50% larger than the Earth and capable of having liquid water. Using the ESO 3.6-m telescope, a team of Swiss, French and Portuguese scientists discovered a super-Earth about 5 times the mass of the Earth that orbits a red dwarf, already known to harbour a Neptune-mass planet. The astronomers have also strong evidence for the presence of a third planet with a mass about 8 Earth masses.
This exoplanet - as astronomers call planets around a star other than the Sun - is the smallest ever found up to now [1] and it completes a full orbit in 13 days. It is 14 times closer to its star than the Earth is from the Sun. However, given that its host star, the red dwarf Gliese 581 [2], is smaller and colder than the Sun - and thus less luminous - the planet nevertheless lies in the habitable zone, the region around a star where water could be liquid!
"We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius, and water would thus be liquid," explains Stéphane Udry, from the Geneva Observatory (Switzerland) and lead-author of the paper reporting the result. "Moreover, its radius should be only 1.5 times the Earth's radius, and models predict that the planet should be either rocky - like our Earth - or covered with oceans," he adds.
"Liquid water is critical to life as we know it," avows Xavier Delfosse, a member of the team from Grenoble University (France). "Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X."
The host star, Gliese 581, is among the 100 closest stars to us, located only 20.5 light-years away in the constellation Libra ("the Scales"). It has a mass of only one third the mass of the Sun. Such red dwarfs are intrinsically at least 50 times fainter than the Sun and are the most common stars in our Galaxy: among the 100 closest stars to the Sun, 80 belong to this class.
"Red dwarfs are ideal targets for the search for low-mass planets where water could be liquid. Because such dwarfs emit less light, the habitable zone is much closer to them than it is around the Sun," emphasizes Xavier Bonfils, a co-worker from Lisbon University. Planets lying in this zone are then more easily detected with the radial-velocity method [3], the most successful in detecting exoplanets.
Two years ago, the same team of astronomers already found a planet around Gliese 581 (see ESO 30/05). With a mass of 15 Earth-masses, i.e. similar to that of Neptune, it orbits its host star in 5.4 days. At the time, the astronomers had already seen hints of another planet. They therefore obtained a new set of measurements and found the new super-Earth, but also clear indications for another one, an 8 Earth-mass planet completing an orbit in 84 days. The planetary system surrounding Gliese 581 contains thus no fewer than 3 planets of 15 Earth masses or less, and as such is a quite remarkable system.
The discovery was made thanks to HARPS (High Accuracy Radial Velocity for Planetary Searcher), perhaps the most precise spectrograph in the world. Located on the ESO 3.6-m telescope at La Silla, Chile, HARPS is able to measure velocities with a precision better than one metre per second (or 3.6 km/h)! HARPS is one of the most successful instruments for detecting exoplanets and holds already several recent records, including the discovery of another 'Trio of Neptunes' (ESO 18/06, see also ESO 22/04).
The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That's the speed of a person walking briskly. Such tiny signals could not have been distinguished from 'simple noise' by most of today's available spectrographs.
"HARPS is a unique planet hunting machine," says Michel Mayor, from Geneva Observatory, and HARPS Principal Investigator. "Given the incredible precision of HARPS, we have focused our effort on low-mass planets. And we can say without doubt that HARPS has been very successful: out of the 13 known planets with a mass below 20 Earth masses, 11 were discovered with HARPS!"
HARPS is also very efficient in finding planetary systems, where tiny signals have to be uncovered. The two systems known to have three low mass planets - HD 69830 and Gl 581 - were discovered by HARPS.
"And we are confident that, given the results obtained so far, finding a planet with the mass of the Earth around a red dwarf is within reach," affirms Mayor.
European Southern Observatory (ESO)
"Liquid water is critical to life as we know it," avows Xavier Delfosse, a member of the team from Grenoble University (France). "Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X."
The host star, Gliese 581, is among the 100 closest stars to us, located only 20.5 light-years away in the constellation Libra ("the Scales"). It has a mass of only one third the mass of the Sun. Such red dwarfs are intrinsically at least 50 times fainter than the Sun and are the most common stars in our Galaxy: among the 100 closest stars to the Sun, 80 belong to this class.
"Red dwarfs are ideal targets for the search for low-mass planets where water could be liquid. Because such dwarfs emit less light, the habitable zone is much closer to them than it is around the Sun," emphasizes Xavier Bonfils, a co-worker from Lisbon University. Planets lying in this zone are then more easily detected with the radial-velocity method [3], the most successful in detecting exoplanets.
Two years ago, the same team of astronomers already found a planet around Gliese 581 (see ESO 30/05). With a mass of 15 Earth-masses, i.e. similar to that of Neptune, it orbits its host star in 5.4 days. At the time, the astronomers had already seen hints of another planet. They therefore obtained a new set of measurements and found the new super-Earth, but also clear indications for another one, an 8 Earth-mass planet completing an orbit in 84 days. The planetary system surrounding Gliese 581 contains thus no fewer than 3 planets of 15 Earth masses or less, and as such is a quite remarkable system.
The discovery was made thanks to HARPS (High Accuracy Radial Velocity for Planetary Searcher), perhaps the most precise spectrograph in the world. Located on the ESO 3.6-m telescope at La Silla, Chile, HARPS is able to measure velocities with a precision better than one metre per second (or 3.6 km/h)! HARPS is one of the most successful instruments for detecting exoplanets and holds already several recent records, including the discovery of another 'Trio of Neptunes' (ESO 18/06, see also ESO 22/04).
The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That's the speed of a person walking briskly. Such tiny signals could not have been distinguished from 'simple noise' by most of today's available spectrographs.
"HARPS is a unique planet hunting machine," says Michel Mayor, from Geneva Observatory, and HARPS Principal Investigator. "Given the incredible precision of HARPS, we have focused our effort on low-mass planets. And we can say without doubt that HARPS has been very successful: out of the 13 known planets with a mass below 20 Earth masses, 11 were discovered with HARPS!"
HARPS is also very efficient in finding planetary systems, where tiny signals have to be uncovered. The two systems known to have three low mass planets - HD 69830 and Gl 581 - were discovered by HARPS.
"And we are confident that, given the results obtained so far, finding a planet with the mass of the Earth around a red dwarf is within reach," affirms Mayor.
European Southern Observatory (ESO)
Planet News and Current Planet Events RSSNew research challenges long-held assumptions of flightless bird evolution
Large flightless birds of the southern continents - African ostriches, Australian emus and cassowaries, South American rheas and the New Zealand kiwi - do not share a common flightless ancestor as once believed.
Antarctic research helps shed light on climate change on Mars
Researchers examining images of gullies on the flanks of craters on Mars say they formed as recently as a few hundred thousand years ago and in sites once occupied by glaciers. The features are eerily reminiscent of gullies formed in Antarctica's mars-like McMurdo Dry Valleys.
Study of islands reveals surprising extinction results
It's no secret that humans are having a huge impact on the life cycles of plants and animals. UC Santa Barbara's Steven D. Gaines and fellow researcher Dov Sax decided to test that theory by studying the world's far-flung islands.
GOCE Earth Explorer satellite to look at the Earth's surface and core
The European Space Agency is about to launch the most sophisticated mission ever to investigate the Earth's gravitational field and to map the reference shape of our planet - the geoid - with unprecedented resolution and accuracy.
Future for clean energy lies in 'big bang' of evolution
Amid mounting agreement that future clean, "carbon-neutral", energy will rely on efficient conversion of the sun's light energy into fuels and electric power, attention is focusing on one of the most ancient groups of organism, the cyanobacteria.
New clues to air circulation in the atmosphere
Air circulates above the Earth in four distinct cells, with two either side of the equator, says new research out today (21 August) in Science.
Psychologists show new ways to deal with health challenges in space
As NASA prepares to send humans back to the moon and then on to Mars, psychologists are exploring the challenges astronauts will face on missions that will be much longer and more demanding than previous space flights.
Dying frogs sign of a biodiversity crisis
Devastating declines of amphibian species around the world are a sign of a biodiversity disaster larger than just frogs, salamanders and their ilk, according to researchers from the University of California, Berkeley.
Strange molecule in the sky cleans acid rain, scientists discover
Researchers have discovered an unusual molecule that is essential to the atmosphere's ability to break down pollutants, especially the compounds that cause acid rain.
Microbes, by latitudes and altitudes, shed new light on life's diversity
Microbial biologists, including the University of Oregon's Jessica L. Green, may not have Jimmy Buffett's music from 1977 in mind, but they are changing attitudes about evolutionary diversity on Earth, from oceanic latitudes to mountainous altitudes.
More Planet News Articles
 | Anathem by Neal Stephenson Anathem, the latest invention by the New York Times bestselling author of Cryptonomicon and The Baroque Cycle, is a magnificent creation: a work of great scope, intelligence, and imagination that ushers readers into a recognizable—yet strangely inverted—world. Fraa Erasmas is a young avout living in the Concent of Saunt Edhar, a sanctuary for mathematicians, scientists, and... |
 | Zoe's Tale by John Scalzi How do you tell your part in the biggest tale in history?I ask because it's what I have to do. I'm Zoe Boutin Perry: A colonist stranded on a deadly pioneer world. Holy icon to a race of aliens. A player (and a pawn) in a interstellar chess match to save humanity, or to see it fall. Witness to history. Friend. Daughter. Human. Seventeen years old.Everyone on Earth knows the tale I am part of. But... |
 | Old Man's War by John Scalzi John Perry did two things on his 75th birthday. First he visited his wife’s grave. Then he joined the army. The good news is that humanity finally made it into interstellar space. The bad news is that planets fit to live on are scarce—and alien races willing to fight us for them are common. So: we fight. To defend Earth, and to stake our own claim to planetary real estate. Far from... |
 | Lost on Planet China: The Strange and True Story of One Man's Attempt to Understand the World's Most Mystifying Nation, or How He Became Comfortable Eating Live Squid by J. Maarten Troost Amazon Best of the Month, July 2008: Maarten Troost is a laowai (foreigner) in the Middle Kingdom, ill-equipped with a sliver of Mandarin, questing to discover the "essential Chineseness" of an ancient and often mystifying land. What he finds is a country with its feet suctioned in the clay of traditional culture and a head straining into the polluted stratosphere of unencumbered capitalism,... |
 | Common Wealth: Economics for a Crowded Planet by Jeffrey D. Sachs From one of the world's greatest economic minds, author of The New York Times bestseller The End of Poverty, a clear and vivid map of the road to sustainable and equitable global prosperity and an augury of the global economic collapse that lies ahead if we don't follow it The global economic system now faces a sustainability crisis, Jeffrey Sachs argues, that will overturn many of our basic... |
 | Environmental Science: Earth as a Living Planet by Daniel B. Botkin, Edward A. Keller For more than two decades, Botkin has been active in the application of ecological science to environmental management. Updated and revised to include the latest research in the field, the new Sixth Edition of Environmental Science continues to present a balanced analytical and interdisciplinary approach to the field. This approach equips readers with a solid scientific background in... |
 | Our Dumb World: The Onion's Atlas of the Planet Earth, 73rd Edition by The Onion Our Dumb World: The Onion's Atlas of The Planet Earth, 73rd Edition features incorrect statistics on all of the Earth's 168, 182, or 196 independent nations. It also features maps, including a fold-out world map at actual size. Readers will learn about every country from Afghanistan, "Allah's Cat Box," to the Ukraine, "The Bridebasket of Europe."Today's news-parody consumer cannot possibly... |
| Earth: Portrait of a Planet, Third Edition by Stephen Marshak Earth: Portrait of a Planet revolutionized the study of geology by integrating traditional geological concepts with the most recent theoretical advances in geology, including theories of plate tectonics and earth systems science. Adopted at over 300 schools worldwide, this innovative text has quickly become the best-selling introductory text in the field.Retaining the core strengths of the First... | |
 | Rising Powers, Shrinking Planet: The New Geopolitics of Energy by Michael T. Klare From the author of the now-classic Resource Wars, an indispensable account of how the world’s diminishing sources of energy are radically changing the international balance of power Recently, an unprecedented Chinese attempt to acquire the major American energy firm Unocal was blocked by Congress amidst hysterical warnings of a Communist threat. But the political grandstanding missed a... |
 | Planet of Slums by Mike Davis Celebrated urban historian's bestselling account of the global explosion of slums, with a major new introduction.According to the United Nations, more than one billion people now live in the slums of the cities of the South. In this brilliant and influential book, Mike Davis explores the future of a radically unequal and explosively unstable urban world. From the sprawling barricadas of Lima to... |
| © 2008 BrightSurf.com |