October 20, 2012
New Planet Discoveries Reignite Search For Alien Life
April Flowers for redOrbit.com — Your Universe Online
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In the past week, two new exoplanets have been confirmed; one by the Planet Hunters citizen science project that uses NASA's Kepler mission data, and the other by a European team. The existence of PH1 and the as-yet unnamed planet in Alpha Centauri will reignite the race to find an Earth-like planet that could host extraterrestrial life.
The most powerful telescopes ever built are about to come online, adding more fuel to the discussion about where life could exist. Scientific discussion about the possibility of alien life forms is becoming more mainstream as well.
"I think scientists are very happy having a rational conversation about the likelihood of life out there," said Bob Nichol, an astronomer at Portsmouth University in Britain.
This conversation is partly driven by the planetary discoveries. Over 800 of these exoplanets have been discovered since the early 1990s.
The high number of planets makes it more likely that life will be found, according to Nichol. He cites the many formats of life that are found on Earth as indirect evidence that life is out there.
A research team from the Geneva Observatory reported that the newest planet found is too close to its own sun to support life; however, previous studies have suggested that when one planet is found orbiting a star, there are usually others in the same system.
The planet in the Alpha Centauri system is Earth-sized, but far from Earthlike. It circles its parent star, Alpha Centauri B, in just 3.2 days, making it likely that the surface is molten with temperatures in excess of 2,000 degrees Fahrenheit. Just finding a new planet so close to Earth, even one inhospitable to life, is a huge success for exoplanetology. It raises the possibility that smaller, more hospitable planets could be found in the same system.
The Alpha Centauri system is 4.3 light-years from Earth in the Centaurus constellation. There are two stars in the system; Alpha Centauri A is a yellow star, slightly larger and brighter than our Sun, and Alpha Centauri B is a red star, fainter than our Sun. The two circle around a common center of gravity, taking about 80 years to complete a circuit. There is a third star, Proxima, which is a very dim red dwarf star. Proxima is actually the closest known star to our Sun.
The new exoplanet was discovered by the High Accuracy Radial Velocity Planet Searcher (HARPS) project using Doppler techniques. Doppler, aka wobble, measures shifts in a star's spectrum, indicating how fast a star is approaching or receding from Earth. More than 150 exoplanets have been found by HARPS using this method. Confirming this new planet took nearly three years, as the gravitational pull it exerted was so small that it approached the limits of the spectrograph's sensitivity.
Alpha Centauri's proximity to Earth has made it a favorite focus for science fiction literature and movie speculation as the most logical first destination for a space probe when man is finally ready to start venturing among the stars.
The reality is, even though Alpha Centauri is the closest to Earth, the distances are still enormous. The New Horizons mission, launched in 2006, isn't scheduled to pass Pluto until 2015. At that speed, it would take 70,000 years to reach Alpha Centauri. Because our astronauts haven't left low-orbit in 40 years, and NASA is continually scaling down the size and costs of missions, this new molten planet isn't likely to spur exploration. What it will do, is push scientists to redouble their efforts to find a truly Earthlike planet.
Regardless of these limitations, some scientists are still focused on interstellar travel. The 100 Year Starship Project is a joint venture between NASA and DARPA and is funding efforts towards developing interstellar travel within the next 100 years.
The power of new telescopes is a leap forward in technology, which will broaden and deepen the search. This makes it entirely likely we will see alien life long before we can touch it, unless there is some surprising discovery made on Mars.
"I think it is realistic to expect to be able to infer within a few decades whether a planet like Earth has oxygen/ozone in its atmosphere, and if it is covered with vegetation," Martin Rees, Britain's Astronomer Royal.
The Square Kilometer Array (SKA), a huge radio telescope sited in South Africa and Australia will come online in the next decade, along with Europe's Extremely Large Telescope (E-ELT), which will be on a mountaintop in Chile's Atacama Desert. E-ELT will be the largest optical telescope ever built.
The main task of these new instruments will be to probe the origins and nature of galaxies. They will, however, also look for signs of life on planets that we currently can only see in the roughest of detail.
"I think the capabilities of new telescopes means that the detection of an ETI (extraterrestrial intelligence) is more likely in the next few decades, than it was in the last," said Mike Garrett, general director of Astron, the Netherlands Institute for Radio Astronomy.
The E-ELT will reveal planets orbiting other stars and will produce images that are 16 times sharper than those available from the Hubble Space Telescope, using a mirror that is almost 40 meters in diameter.
The new telescope will boost the search for life elsewhere, according to Isobel Hook, an Oxford University astrophysicist working on the E-ELT project.
"The ELT should also allow us to study the atmospheres of extra-solar planets and look for ℠bio-markers' such as water, carbon dioxide and oxygen molecules in their spectra," she said.
The E-ELT may be able to use spectroscopy to detect signs of vegetation on distant planets, Hooks says.
The SKA radio scope, when it is completed in 2024, will comprise 3,000 50-foot-wide dishes, along with many antennae. Together, these will be able to see 10 times farther into the Universe and detect signals that are 10 times older.
The SKA would be able to detect radiation given off by military radar from any of the nearest million or so stars.
"So," said Nichol, "if there are advanced civilizations on planets around those stars, we could see them".
Until the present time, the search for alien life has been constrained by the dogma of a "goldilocks zone" around faraway suns. A goldilocks zone is just right — neither too hot nor too cold — to allow liquid water, which is essential for life as we understand it.
The goldilocks zone theory is being challenged, vastly expanding the potential area in which life could exist. Alternative heat sources have been identified and scientists are developing radical new ideas about the myriad forms life could take after studying Earth organisms that live in some of the most inhospitable places.
Xavier Bonfils of the Institute of Planetology and Astrophysics in Grenoble estimates tens of billions of rocky planets in our galaxy alone that might have the right temperatures to support life. Other researchers are working on a computer model that suggests a sharp increase in the number of planets capable of hosting life.
Sean MacMahon argues that the heat generated from inside a planet could be enough for large reservoirs of liquid water, even if the planet is outside the "habitable zone" where scientists would expect any surface water to be frozen.
Studies of Earth life forms in places similar to the area of Mars being probed by the Curiosity rover have altered conventional wisdom about extraterrestrial life as well.
Felipe Gomez leads a team from Centro de AstrobiologÃa in Madrid, which studies organisms in the sun-baked Chott el Jerid salt pan in Tunisia, Deception Island's permafrost in the Antarctic, and Southern Spain's acidic Rio Tinto.
Another team of scientists from North Carolina State University recently published a paper concerning a single-celled organism living in a hot spring near Mount Vesuvius in Italy. The microbe is able to eat uranium and draw energy from it.
These studies and more suggest planets hostile to humans might be hospitable to these so-called extremophiles. This leads to what Duncan Forgan at the Royal Observatory in Edinburgh calls "a much more complicated and richer concept of the habitable zone."
The problem, most scientists say, is one of scale. The Universe is roughly 100,000 light years across, so even if there is life sending signals out there, astronomers say the chances of not hearing them are still rather considerable.