Remember the jungle moon of Endor, the home of the Wookie cousins, the Ewoks, in the "Star Wars" saga in "Return of the Jedi?" Well, that moon may not be the fanciful, fictional proposition it has appeared to be all these years. According to a report in Phys.org (Jan. 10), a couple of researchers not only believe that there could be numerous habitable moons orbiting extrasolar planets around faraway stars, they have also calculated a moon habitability edge, a "Goldilocks Zone" border in space for moons, where these satellites might be more likely to be able to support life.
René Heller of Germany's Leibniz Institute for Astrophysics Potsdam, Rory Barnes of the University of Washington and the NASA Astrobiology Institute contributed to the research which sought to simply answer the question of whether or not exomoons (moons orbiting extrasolar worlds) could be found on planets like those already discovered (some 850 confirmed extrasolar planets exist to date). Most of the planets that have been detected thus far are gas giants circling close to their parent stars.
There have been no exomoons discovered as yet, but the researchers did not let that deter them from attempting to ascertain if the existence of such smaller worlds might at least be theoretically possible.
The team found that climatic conditions were expected to be different on extrasolar planetary moons because of tidal locking (where one side of satellite permanently faces its parent planet). That being the case, occasions of eclipse could alter living conditions on such worlds considerably.
They also found that exomoons would be affected by tidal heating, the relative effect of the smaller planetary body being close to its parent. Too close and the tidal heating would produce a massive greenhouse effect that would simply boil away any surface water, making the moon an uninhabitable satellite.
In addition to their findings, the team devised a theoretical model of at least one parameter for a habitable zone for the exomoons. This parameter was dubbed the "habitable edge," the minimum distance from a parent planet to allow habitability.
Barnes explained: "There is a habitable zone for exomoons, it's just a little different than the habitable zone for exoplanets."
The research will be published in January's edition of Astrobiology magazine.
The team's work comes as news that Planethunters.org, a part of the Oxford University-led Zooniverse project, announced that 15 new extrasolar planet candidates had been discovered in the habitable zones of their parent stars. In fact, according to Phys.org, one of the candidates had been confirmed as a planet and given a designation, PH2 b, to honor the volunteers that aided in its discovery.
So many extrasolar planets in the habitable zones of stars point at the possibility of a myriad of strange potentialities, a "traffic jam" of worlds. These worlds, of course, would not only be the planets with potential of harboring liquid water but the moons around those planets as well.
The paper outlining the research was submitted to the Astrophysical Journal.
Lead author of the paper, Dr Ji Wang of Yale University, said: "We can speculate that PH2 b might have a rocky moon that would be suitable for life. I can't wait for the day when astronomers report detecting signs of life on other worlds instead of just locating potentially habitable environments. That could happen any day now."
And so the search for other habitable, even Earth-like, planets continues, not to mention the search for moons that might be able to support life. But what was once only considered in the annals of science fiction -- like the "Star Wars" moon of Endor that circled the gas giant Yavin -- is now a theoretical reality and a much sought-after potentiality.