Weekender: Exoplanets & Waterworlds – Alien Life Now Ten Times More Likely

With ever improving technology, astronomers are now able to explore the furthest reaches of our universe, mapping the continuing expansion of dark matter and detecting light from far-flung planets beyond our solar system.

After nearly a decade of development, construction, and testing, the world’s most advanced instrument for directly imaging and analyzing planets around other stars is pointing skyward and collecting light from distant worlds. The instrument, called the Gemini Planet Imager (GPI), was designed, built, and optimized for imaging faint planets next to bright stars and probing their atmospheres, and studying dusty disks around young stars. It is the most advanced such instrument to be deployed on one of the world’s biggest telescopes – the 8-meter Gemini South telescope in Chile.

GPI is a unique tool developed to see exoplanets, which it detects using infrared (heat) radiation from young Jupiter-like planets in wide orbits around other stars; these are equivalent to the giant planets in our own Solar System not long after their formation. Every planet GPI sees can be studied in detail.

“The first GPI images are just superb! We have waited for this moment for so many years” says René Doyon of UdeM, member of the GPI science team who has been closely involved in the development of GPI. “GPI is a revolution, we have demonstrated the ability of detecting planetary systems in a record time”, said Christian Marois, an astronomer at the National Research Council of Canada- Herzberg, also member of the GPI science team and leader of the discovery of the first multiple planetary system in 2008 together with professors René Doyon and David Lafrenière from UdeM. “Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we are seeing planets that used to take us an hour to detect,” says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument.

GPI carried out its first observations last November – during an extremely trouble-free debut for an extraordinarily complex astronomical instrument the size of a small car.

“This was one of the smoothest first-light runs Gemini has ever seen” says Stephen Goodsell, who manages the project for the observatory. For GPI’s first observations, the team targeted previously known planetary systems, including the well-known Beta Pictoris system where GPI obtained the first-ever spectrum of the very young planet Beta Pictoris b.

In 2014, the GPI team will begin a large-scale survey, examining 600 young stars and any giant planets orbiting around them. GPI will also be available to the whole Gemini community for other projects, ranging from studies of planet-forming disks to outflows of dust from massive, dying stars.

“Some day, there will be an instrument that will look a lot like GPI, on a telescope in space,” Macintosh predicted. “And the images and spectra that will come out of that instrument might show a little blue dot that is another Earth.”

GPI is an international project led by the Lawrence Livermore National Laboratory (LLNL) under Gemini’s supervision, with Bruce Macintosh as Principal Investigator and LLNL engineer David Palmer as project manager.

The enhanced technology now available to scientists has vastly increased the likelihood of discovering extra-terrestrial life somewhere in the vast universe that surrounds us. Planets hosting water are theoretically capable of supporting life, but inside our own solar system, only one planet is known to possess oceans and that is our dear Earth. Beyond our universal neighborhood, however, an increasing number of "water-worlds" are being discovered.

Scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) have detected a solar system that contains not one, but two water-covered planets. The "exo-planets", as those planets outside our own system are known, orbit the star Kepler-62, a type K star which is slightly smaller and cooler than our Sun. The water-worlds, which have been christened Kepler-62e and -62f, orbit their star every 122 and 267 days, respectively, and in close enough proximity to place them in the "habitable zone. "

This means that they are in close enough proximity to Kepler-62 to guarantee the degree of light and warmth necessary to support known life forms. Kepler-62e is thought to be the warmest of the two, and models suggest that it is therefore likely to have considerable cloud cover, probably more than we see here on Earth. Kepler-62f is further away from its sun, so unless there is a source of carbon dioxide is available to create a type of "greenhouse effect," it could be a huge space snowball.

"Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly," said Harvard astronomer and co-author Dimitar Sasselov."The good news is – the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future," he added.

The so-called "habitable zone" has been called into question by researchers at Aberdeen University, however, as their latest research indicates that life could theoretically survive on planets that are up to ten times further away from their host planets than previously suggested. A paper by astronomers at the University of St Andrews, published in Planetary and Space Science, suggests that even very cold, rocky environments could support life under their surface.

"The traditional habitable zone is also known as the Goldilocks zone," explains PhD student Sean McMahon. "A planet needs to be not too close to its sun but also not too far away for liquid water to persist, rather than boiling or freezing, on the surface."But that theory fails to take into account life that can exist beneath a planet’s surface. As you get deeper below a planet’s surface, the temperature increases, and once you get down to a temperature where liquid water can exist – life can exist there too."

If life does exist on Kepler-62’s planets it would most probably be aquatic as, unlike Earth, no land masses have been detected, indicating that both planets are completely submerged under a global ocean.

"These planets are unlike anything in our solar system. They have endless oceans," said lead author of the Kepler-62 project, Lisa Kaltenegger of the Max Planck Institute for Astronomy and the CfA.
The exo-planets form part of a five-planet system and were discovered by NASA’s Kepler spacecraft, which detects and measures distant planets by monitoring their passage across their host star. Measurements indicate that the exo-planets are much larger than our own Earth: Kepler-62e is 60 percent larger than the Earth while Kepler-62f is about 40 percent larger. Despite this, they are not large enough to make it possible to measure their masses, but scientists think that they are made of rock and water, without a significant gaseous envelope.

Could these planets host advanced life-forms who have developed the necessary technology to travel in space?

Scientists believe that this is an intriguing possibility, though the type of beings that could survive in such a marine environment could be very different to ourselves.

"There may be life there, but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy. Nonetheless, these worlds will still be beautiful blue planets circling an orange star – and maybe life’s inventiveness to get to a technology stage will surprise us," mused Kaltenegger.

The research team from St. Andrews believe that there is a much greater likelihood of alien life across the universe than has been previously thought.

"Rocky planets a few times larger than the Earth could support liquid water at about 5 km below the surface even in interstellar space (i.e. very far away from a star), even if they have no atmosphere because the larger the planet, the more heat they generate internally," said McMahon.

"It has been suggested that the planet Gliese 581 d, which is 20 light years away from Earth in the constellation Libra, may be too cold for liquid water at the surface. However, our model suggests that it is very likely to be able to support liquid water less than 2 km below the surface, assuming it is Earth-like."

Another paper published by the same team which suggests there could be more life below the surface of the continents on our own Earth than there is below the seafloor.Team member Sean McMahon hopes the studies will encourage other researchers to consider how life on other planets might be detected.

"The results suggest life may occur much more commonly deep within planets and moons than on their surfaces. This means it might be worth looking for signs of life outside conventional habitable zones. I hope people will study the ways in which life below the surface might reveal itself. Because it’s not unimaginable that there might be signs at the surface that life exists deep below.

If any sophisticated life forms have evolved on Kepler-62’s planets, then Harvard’s Dimitar Sasselov believes that their relative proximity to us should provide the necessary motivation for them to develop space travel:

"Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis. I can’t think of a more powerful motivation to become a space-faring society."

Read Whitley’s Journal Doorway to Other Worlds, click here.

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