Most Habitable Exoplanets Found By NASA’s Kepler Aren’t So, Hints Gaia

Yes, before science becomes straightforward, it’s made of crooked timber: something we held as sure, and a great discovery of the last few years, is often revealed, on second examination, as in need of serious tweaking: the initial breakthrough survives, but transmogrified. As an interlude between aspects of the civilization bandwagon, with more lofty essays, let’s look at the future… space. Yes, the future is space: it is to us what the savannah, was to the genus Homo. The savanna, in combination with necessity, will, and the Élan vital of colonization, evolved us. The same Élan vital spurs space colonization. Élan vital, popularized by Nobel laureate philosopher Henri Bergson,was central to Lucretius-Epicurus philosophy of 23 centuries ago (philosophy which Christianism eradicated by burning its books, and killing its practitioners and defenders).  

It’s pretty clear that humanity, barring a deplorable accident, will be able to spawn across the galaxy: there are plenty of habitable planets out there, and, thanks to NASA, Elon Musk and his ilk, cheap access to space will come very soon.

However, the complementary technology we need for mass space colonization, compact controlled thermonuclear technology, has not yet arrived… Indeed, “habitable planet” doesn’t mean life appeared there, let alone advanced life, or civilization. So planets will be found, ripe for colonization, yet life-less. Colonizing Europa, for example, is feasible: there is plenty of water. Yet it will necessitate to harness fusion power (except if battery tech leaps ahead, and photovoltaics could be used after all…).

Nearly 4,000 exoplanets have been found by 2018.

Artist’s illustration of how rocky, potentially habitable worlds elsewhere in our galaxy might appear (from data found so far). Data gathered by telescopes in space and on the ground suggest that small, rocky planets are common (some system as Trappist, have many, close together… although not as close as here, ha ha ha.)
Credit: R. Hurt (SSC-Caltech)/NASA/JPL-Caltech

Supposedly, NASA’s prolific Kepler space telescope has discovered about 30 roughly Earth-size exoplanets in their host stars’ “habitable zone” — the range of orbital distances at which liquid water can likely exist on a world’s surface.

One doesn’t want planets to be too large: they would crush life as we know it, and retain light gases, making them “mini-Neptunes”.

However observations by the European Space Agency’s (ESA) Gaia spacecraft suggest that the actual number of habitable planets among them is probably only between two and 12, NASA officials said today. Ooops.

Before the scoffing starts, let me observe that this means, mostly, that the habitable zones have to be computed again: so planets in systems viewed as inhabitable, maybe, actually habitable, after all. And vice versa. So may be only a couple of habitable Kepler planets are habitable, but others may be.

Gaia launched in December of 2013 to create an ultraprecise 3D map of our giant galaxy, the Milky Way. So far, this map includes position information for about 1.7 billion stars and distance data for about 1.3 billion stars.

Gaia’s observations suggest that some of the Kepler host stars are brighter and bigger than previously believed. Planets orbiting such stars are therefore likely larger and hotter than previously thought. questions complete

A larger, brighter star releases more light, hence more heat. The “larger” correlation is a consequence of that. Kepler uses the “transit method.”

Kepler records the brightness dips caused when a planet crosses its parent star’s face from the Kepler telescope’s perspective. Estimates of such planets’ sizes are derived from the percentage of the stellar disk they block during these “transits.” So, if the stars’ diameter is revised upward, because it’s brighter, so is the size of the planet.

Astronomers, astrobiologists and planetary scientists still have a lot to learn about exoplanet habitability. So philosophers can strike: I pointed out that life may be common in the galaxy, but not so advanced life.

I pointed out too that the Earth nuclear reactor enables plate tectonic, and that the latter, hence the former, may be necessary for life. So may have to consider a radioactive belt, not just a water belt…

And in more details:

“We’re still trying to figure out how big a planet can be and still be rocky,” declared Jessie Dotson, astrophysicist at NASA’s Ames Research Center in Silicon Valley. Dotson is the project scientist for Kepler’s current, extended mission, known as K2. That will depend in part upon the nature of the planet’s rock, especially its density.

As I have pointed out, The concept of the habitable zone can’t be based solely on water and orbital size relative to the star’s output. That would ignore important planetary characteristics, such as mass, which influences a world’s ability to hold onto an atmosphere, and which sort of atmosphere it holds. Then, there’s atmospheric composition, which greatly affects a planet’s temperature, and depends upon the planet’s gravity.

Life may not require liquid water on the surface. A number of frozen-over moons outside our own solar system’s habitable zone, such as Jupiter’s Europa and Saturn’s Enceladus, have giant buried oceans that may be capable of having evolved life as we know it: at first sight, they seem to have had warm, liquid water, for even longer than Earth. Indeed their heat is gravitationally generated, from massaging the moon with the giant planet’s gravity.

(An old consideration has also been life as we don’t know it, which would depend on something other than water as a solvent; however, the combination water-carbon seems impossible to beat in the wealth of possibilities…)

The $600 million Kepler mission launched in March 2009, following a successful pioneering French satellite, named after another astronomer, Corot. The first confirmed exoplanet was discovered at the French Observatoire de Haute Provence.  As of 1 October 2018, there are 3,851 confirmed exoplanets in 2,871 stellar systems, with 636 systems having more than one planet.

Further philosophy out of all this?

Of course!

Next: the related, and philosophically as deep as it gets Big Silence From Necessary Malevolence?

Patrice Ayme



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6 Responses to “Most Habitable Exoplanets Found By NASA’s Kepler Aren’t So, Hints Gaia”

  1. Gloucon X Says:

    “Colonizing Europa, for example, is feasible: there is plenty of water. Yet it will necessitate to harness fusion power…”

    We can’t ignore the physiology that evolution on THIS planet gave to us. It can make living on a planet too different from our own in vital ways very infeasible. Europa’s gravity is only 15% of Earth’s. That would produce a devastating deterioration of the human bone structure.


    • Patrice Ayme Says:

      Correct. And it has turned out to be a very practical problem, see ISS… There may be ways around it, though, like short stays in a high gravity space station in Europa, or Jupiter orbit. We just don’t know. We are going to know soon, though, as deep space colonization is on the way (metal is being forged, carbon glued together…)


      • Gloucon X Says:

        Europa is a six year trip at today’s rocket speeds, so they would definitely need a ship that can spin up some gravity. Nasa should be all about building an orbiting station that can produce an artificial gravity and station people there for several years raising families and living on their own food supply to see if true permanent independent colonization is possible. They will have to show that healthy births and raising a child can be done. Problem is the Biosphere experiments showed that even here on Earth they failed to establish a self-sustaining habitat.


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