Posts Tagged ‘extraterrestrial life’
In astronomer and writer Chris Impey‘s 2010 Talking About Life, an anthology of his interviews with leading experts in astronomy and related fields about extraterrestrial life, there was a passage in his interview with Debra Fischer that caught my attention for its alternate history potential. Solar systems, including our own, are apparently as densely packed with planets as possible.
DF: The amazing thing I learned when we discovered the Upsilon Andromedae system is that our Solar System s actually dynamically full of planets. When people who model the Solar System try to drop in an extra planet, the whole system goes into chaos–some planets are lost, some fall into the star, some are ejected, and then everything finally settles down. Each planet has its own gravitational domain and those domains are pushed up next to each other. Our Solar System resides on the verge of instability it’s stable, but only just.
CI: Is this related to the numerical coincidence of their nearly geometric spacing?
DF: Bode’s law? Yes. They clear out disks; many lines of evidence suggest that core accretion is the correct model. Then they begin to migrate in until they come into a zone; again, if they get any closer. they’re ejected. When I noted this back in 2000, Hal Levinson raised his hand and said, “No, no, that’s not true–there a place between Mars and Jupiter where a Venus-sized planet will survive.” And I think, “How many simulations did you have to run to find that tiny little window? That doesn’t count!” [Laughs](269-270).
The WI question is obvious. What if there was a planet the mass of Venus orbiting in our solar system between Mars and Jupiter?
This planet–call it *Ceres, after the largest dwarf planet orbiting between Mars and Jupiter–would be a big one. Venus is more than 80% as massive as the Earth. Such a massive planet would be able to hold onto its volatiles–its atmosphere, its water–in a way that a nearer Mars could not. This planet might even be massive enough to be geologically active. *Ceres might provide a relatively hospitable environment, more hospitable than Venus or even Mars.
It’s important to not overstate this potential habitability. Whatever the precise nature of its orbit, *Ceres would also be very cold, orbiting outside of the orbit of Mars and likely even an elastic definition of our sun’s circumstellar habitable zone. A sufficiently dense heat-retaining atmosphere might change things, but would it warm *Ceres enough?
Given *Ceres’ location near the frost line of the solar system, and its high gravity, it’s likely to have attracted and kept quite a lot of ice. Perhaps it will be an ocean world; perhaps it will be a world with a frozen surface on top of a planet-wide ocean, a super-Europa even. As seen in the night sky from Earth, its atmosphere and icy surface may make it very bright indeed.
Space artist David A. Hardy shared the above 1972 painting, of a rocky world with pools of liquid on its surface in close orbit of Proxima Centauri, soon after the news broke of the possible discovery of a broadly Earth-like planet in orbit of the star nearest to our solar system. Matt Williams’ Universe Today article “Earth-like Planet Around Proxima Centauri Discovered” has been frequently cited.
[T]he German weekly Der Spiegel announced recently that astronomers have discovered an Earth-like planet orbiting Proxima Centauri, just 4.25 light-years away. Yes, in what is an apparent trifecta, this newly-discovered exoplanet is Earth-like, orbits within it’s sun’s habitable zone, and is within our reach. But is this too good to be true? [. . . ] Citing anonymous sources, the magazine stated:
“The still nameless planet is believed to be Earth-like and orbits at a distance to Proxima Centauri that could allow it to have liquid water on its surface — an important requirement for the emergence of life. Never before have scientists discovered a second Earth that is so close by.”
In addition, they claim that the discovery was made by the European Southern Observatory (ESO) using the La Silla Observatory‘s reflecting telescope. Coincidentally, it was this same observatory that announced the discovery of Alpha Centauri Bb back in 2012, which was also declared to be “the closest exoplanet to Earth”. Unfortunately, subsequent analysis cast doubt on its existence, claiming it was a spurious artifact of the data analysis.
However, according to Der Spiegel’s unnamed source – whom they claim was involved with the La Silla team that made the find – this latest discovery is the real deal, and was the result of intensive work. “Finding small celestial bodies is a lot of hard work,” the source was quoted as saying. “We were moving at the technically feasible limit of measurement.”
The article goes on to state that the European Southern Observatory (ESO) will be announcing the finding at the end of August. But according to numerous sources, in response to a request for comment by AFP, ESO spokesman Richard Hook refused to confirm or deny the discovery of an exoplanet around Proxima Centauri. “We are not making any comment,” he is reported as saying.
A 2013 study did suggest a 10-20 day cycle of some sort. Such, the project acknowledges, may not be spoor of a planet at all but rather a function of the star or even the instruments used. Any planet more massive than one or two Earths would already have been detected, based on previous surveys.
If everything is as reported–if!–then there could well be a planet of mass comparable to that of the Earth orbiting the nearest star to our solar system within said star’s circumstellar habitable zone. That by itself would not ensure that such a planet would be like Earth, as serious constraints to the habitability of exoplanets in red dwarf systems exist. In particular, Proxima Centauri’s nature as a violent flare star means that even if a hypothetical planet did start off with the resources needed to support life, successive flares may have eroded the planet’s surface into lifeless rock.
Even so, it goes without saying that the discovery of such a world would be epoch-making. Besides the potential of this world as itself, it signals remarkable things about the wider universe. If such an uncomprisingly dim and violent star as Proxima Centauri can support even a very broadly Earth-like planet, surely planets like ours must be quite common? How likely would it be that we are not alone?