Seth Shostak/SETI Institute/Corbis, edit by Ian O'Neill
The Allen Telescope Array listens for ET. But the popular image of UFOs is driven by myth, not science.
Cowboys & Aliens are Coming!
July 29, 2011 --
If aliens are going out of their way to kick up dust in the Wild West, as they do in the upcoming movie "Cowboys & Aliens," they must be coming from somewhere. Life could take root on a moon or a meteorite. But to nurture the kind of life that could destroy our saloons and harass our livestock, a planet might be the most suitable. So far, Kepler, a NASA orbiting telescope that searches for planets beyond our solar system, has detected over 1,200 exoplanets. Surely there must be a few candidates among this group that could meet some of the most basic requirements to host life? Explore some far-out worlds that could support aliens, be they cattle-rustling characters or a more peaceful people.
First, let's lay out some basic criteria. Kepler hasn't identified many rocky worlds and a solid surface is essential for life to take root. Size matters: The mass of the planet helps astrophysicists infer what it's made of. Some planets are Earth-sized. Others are several times the size of our planet. And then there are gas giants, which can range from "Neptune sized" to "super-Jupiters." Orbit: To support life, a planet must be in a stable orbit around its star -- no planets with wonky orbits that will eventually dump them into their star for a fiery death. Goldilocks Zone: This is a region not too hot or too cold that gives the planet enough distance from its parent star to have liquid water, key for life. Loner Stars: Single stars make better parents. In 2010, a pair of closely orbiting binary stars was spotted surrounded by what could be the debris of former planets. Unknowns: Some factors for life can't be confirmed one way or the other from the data available about extrasolar planets. These include: water, chemical compounds such as ammonia; a nitrogen-rich atmosphere; a magnetic field to repel solar and cosmic radiation; and more. BUT, some planets do have a head-start, beginning with Gliese 581D.
Located a mere 20 light-years away, practically our backyard in cosmic terms, Gliese 581d is situated on the "outer fringes" of the Goldilocks zone, orbiting a red dwarf star. The planet may be warm enough and wet enough to support life in much the same manner as Earth. It might also contain a thick carbon atmosphere. If we ever need a new Earth and have the means to get there, Gliese 581d may be our best bet for now.
When it was first detected and reported last year in Astrophysical Journal, Gliese 581g appeared to be the perfect candidate for a true "Earth-like" planet. Located in the same star system as Gliese 581d (and detected earlier), Gliese 581g seemed to be the right size and located within a habitable zone away from its parent star. Gliese 581g was said to have three times the mass of Earth, making it possible for the planet to hold an atmosphere. However, since its discovery, follow-up studies have alleged that Gliese 581g might have been a false alarm. In other words, the planet might not exist at all.
Dubbed a "waterworld" and located a mere 42 light-years from Earth, GJ 1214b orbits near a red dwarf star about one-fifth the size of our sun. What makes this planet unique is that it appears to be primarily composed of water, although GJ 1214b is 6.5 times the mass of Earth and 2.7 times wider, which classifies it as a "super-Earth." This planet also has a steamy atmosphere composed of thick, dense clouds of hydrogen, which, although it might not the case with this planet, could incubate life.
Situated 150 light-years from Earth, HD 209458b is a planet that holds traces of water vapor in its atmosphere, and also contains basic organic compounds that, on Earth, foster the development of life. But there are two factors working against HD 209458b as a suitable habitat. The planet is very hot due to its close proximity to its parents star, and it's a gas giant, so no solid surfaces.
If Kepler-10b were located further from its parent star, it might have had a chance of hosting life. Kepler-10b was the first "iron-clad proof of a rocky planet beyond our solar system" back in 2001. It was even dubbed the "missing link" of extrasolar planetary research. When it comes to the search for life, though, Kepler 10-b is missing a lot of other ingredients -- just minor things like water or an atmosphere.
When venturing to a new star system to explore the possibility of extraterrestrial life, trying a star that has already shown itself to nurture planets -- even if they're not the kind you're looking for -- could be a promising strategy. Project Icarus, an ambitious five-year study into launching an unmanned spacecraft to an interstellar destination, has identified two stars located within 15 light-years that might fit the bill: "epsilon Eridani, a single K star 10.5 light-years away, and the red dwarf GJ 674, 14.8 light-years away." Indirect evidence has also shown that epsilon Eridani may already hold smaller worlds scientists simply haven't detected yet. Also, red dwarf star systems generally may be a safe haven for life.
Are We Alone?
Taking into account the number of exoplanets that have been detected, as well as the vastly greater number that are estimated to be out there, some astrophysicists are convinced that extraterrestrial life is inevitable. After all, the Milky Way may be loaded with as many as 50 billion alien worlds. Some even think we'll find alien life by 2020. Others, however, say it may not exist at all. Recently, astrophysicists David Spiegel of Princeton University and Edwin Turner from the University of Tokyo suggested we might be alone in the universe, based on their interpretation of the Drake equation, a formula meant to determine loosely the probability of the existence of life beyond Earth. According to their analysis, just because life on Earth took shape early, endured and prospered doesn't mean the same process would naturally and inevitably occur elsewhere in the universe. Discovering life elsewhere, however, would be the only means of settling this debate. Unless the aliens find us first, of course.
The Search for Extraterrestrial Intelligence, or SETI, may becoming more mainstream, as evidenced by this week’s House Science and Technology Committee hearing, which included testimony by two well-known SETI hunters, Seth Shostak and Dan Werthimer.
But the hearing took an odd turn when U.S. Rep. Chris Collins, a New York Republican, had the floor.
“I think I might ask the question everyone in this room wants to ask,” Collins said. “Have you watched ‘Ancient Aliens’ and what’s your comment about that series?”
The television show, broadcast on The History Channel, explores purported extraterrestrials’ visits to Earth over millions of years.
Shostak, senior scientist at the California-based SETI Institute, started off diplomatically.
“The public is fascinated with the idea that we may be being visited now, or may have been visited in the past, the so-called UFO phenomenon,” he said.
Then he got down to business:
“I personally don’t share the conviction that we are being visited. I don’t think that that would be something that all the governments of the world had managed to obfuscate — to keep secret. I don’t believe that.
“The idea that maybe we were visited during the time of the ancient Egyptians and so forth, keep in mind that in the 4.5-billion year history of the Earth, the time of the ancient Egyptians was yesterday. So again, why were they there then? What was it that brought them to Earth? I have no idea and I don’t find very good evidence,” Shostak said.
“I think the pyramids, for example, were probably built by Egyptians. I know that that’s a radical idea for some people, but they were very clever and they could certainly do that,” he added.
Werthimer, director of SETI research at the University of California Berkeley, was more blunt.
“UFOS have nothing to do with extraterrestrials,” he said.
“I think some of these sightings are real phenomena. We get a lot of calls when the space station goes over, although some people embellish and they say it has windows and things.
“Some of it is people’s imagination and we know that because it ties very closely to popular culture. When Jules Verne wrote about flying saucers, everybody started seeing flying saucers. Before that people saw angels. When people watch movies then we get a lot of reports that are tied to what’s in the movies. Some of it is actually deliberate hoaxes for people making money,” Werthimer said.
A bit later, Florida Republican Bill Posey asked about Project Blue Book, a series of studies on UFOs undertaken by the U.S. Air Force between 1952 and 1969.
“I am personally quite skeptical,” Shostak reiterated, adding that since the 1960s polls show that about one-third of Americans — and people in other countries — believe that Earth is being visited by extraterrestrials.
“I don’t think that that evidence is very good. I think that if we were being visited, it would not be controversial. It’s been 60-some years since Roswell, for example,” Shostak said, referring a purported UFO crash in New Mexico in 1947.
“If you had asked the residents of Massachusetts 60 years after Columbus, ‘Do you think you’re being visited by Spaniards?’ that would not be controversial. I think if they were really here, everyone would know that,” he said.