Astrogator's Logs

New Words, New Worlds
Artist, Heather Oliver             

To Each Their Own Gliese 581c

It was six men of Indostan
To learning much inclined,
Who went to see the Elephant
(Though all of them were blind),
That each by observation
Might satisfy his mind.

from The Blind Men and the Elephant
by John Godfrey Saxe, based on a story from India


“Sunset from the Surface of Gliese 581c” by Karen Wehrstein

The recent indirect discovery of a planet orbiting red dwarf Gliese 581 raised strong ripples of interest and speculation. The smallest exoplanet yet discovered, it has been called earth-like based on three attributes: its calculated radius is one and a half times that of earth; its orbit appears to be inside its star’s habitable zone (by definition, the region where water can remain liquid); and its conjectured temperature falls within terrestrial norms.

The planet’s other intrinsics are quite un-earthly. Ten times closer to its dim, flare-racked primary than earth is to the sun, Gliese 581c completes an orbit in 13 days. It is five times the mass of earth, making its gravity about twice as strong. Because of its proximity to its star, it is probably tidally locked, with hurricane winds raking the twilight zone, and tides several hundred times the strength of terrestrial ones tugging its seas, if it has any. Nevertheless, the planet may also harbor a stable atmosphere — and if that is combined with the presence of water, the question of life automatically rears its head.

Most scientists were ecstatic that a small planet (probably rocky, possibly containing oceans) had finally been discovered, taking us one more step to the right across the terms of the Drake equation. Hopeful artists created wishful views of the planet. But there were some interesting negative reactions as well.

Adherents of the Singularity scenario argued that such planets are beside the point, because by the time a rocket reaches the Gliese system (just 20 light years away, yet still a journey of millennia with our present propulsion means), we will have evolved past our present “carbon-bound” configuration. Others warned of the dangers of sending out long-generation colonists without supervision, so to speak. Still others recalled the Fermi paradox, and lamented that if earth-like planets are as common as this, the deafening silence that SETI has garnered bodes ill for the frequency of advanced life or the surivival of technological civilizations in our galaxy.

The naysayers, in their sophistication, missed a crucial point. Whether Gliese 581c is so hospitable that we could live there or so hostile that we could only visit it vicariously through robotic orbiters and rovers, if it harbors life — even bacterial life, often mistakenly labeled “simple” — the impact of such a discovery will exceed that of most other discoveries combined. Unless supremely advanced Kardashev III level aliens seeded the galaxy like the Hainish in Ursula LeGuin’s Ekumen, this life will be an independent genesis, enabling biologists to define which requirements for life are universal and which are parochial.

At this point, we cannot determine if Gliese 581c has an atmosphere, let alone life signatures. If it has developed non-technological life, without a doubt it will be so different that we may not recognize it. Nor is it a given, despite our fond dreaming in science fiction, that we will be able to communicate with it if it is sentient. In practical terms, a second life sample may exist much closer to home — on Mars, Europa, Titan or Enceladus. But those who were enthusiastic about this discovery articulated something beyond its potential seismic impact on biology and culture: the desire of humanity for companions among the sea of stars, a potent myth and an equally potent engine for inner and outer exploration.

19 Responses to “To Each Their Own Gliese 581c”

  1. intrigued_scribe says:

    Wonderfully written. 🙂 Despite the assertions of naysayers, the positive aspects of discovery and exploration make themselves clear here, and this:

    “But those who were enthusiastic about this discovery articulated something beyond its potential seismic impact on biology and culture: the desire of humanity for companions among the sea of stars, a potent myth and an equally potent engine for inner and outer exploration.”

    The closing statement expresses the core sentiment perfectly.

  2. Athena says:

    Searching for companions is one way to make sense of the universe — which is breathtaking but indifferent to us. I think, too, that the human need to explore and understand is fundamental. Our spirit withers if we are tightly confined.

  3. Walden2 says:

    An amateur astronomer has seen this transiting exoworld:

    Amazing what amateurs can do now that professionals just
    a few decades ago would’ve killed for. Well, not literally.

  4. Athena says:

    Yes, the exponentially increased ability to observe exoplanets is nothing short of remarkable! And who knows how it would improve if we were to set facilities up on the dark side of the moon.

  5. Walden2 says:

    Athena! There is no permanent dark side of the Moon! :%)

  6. Athena says:

    The one away from us… where all the alien artifacts are! (*laughs*)

  7. Walden2 says:

    No, silly, they’re buried under Tycho, awaiting our discovery.

  8. Athena says:

    What?! No black monolith looming? Object, protest…

  9. rocketscientist says:

    Every time we find a new planet it’s a great leap forward in our growing understanding of the universe. It’s no wonder that some people will immediately become optimistic to the point of wild speculation, or the reverse in a desire not to get too worked up.

    Your point about the human longing for others like ourselves is well made. 🙂

  10. Athena says:

    There is more on the Gliese 581 system since the news first broke. Here is a link with an interesting update that bears on the habitability of the planets in the system:

    There is no question that each such discovery is a great leap in knowledge. Now if only we detect biomarkers on one of them!

  11. Walden2 says:

    Space artist Don Dixon has created several pieces about
    the Gliese 581 system here:

  12. Athena says:

    Truly evocative! And, of course, the choice of Dvorzak’s New World Symphony as accompaniment for that marvelous animation doesn’t surprise me…

  13. Walden2 says:

    Newfound Planet Has Earth-Like Orbit

    By Ker Than

    Staff Writer

    posted: 02 August 2007

    03:09 pm ET

    A planet outside our solar system with a year roughly equal to Earth’s has been discovered around a dying, red giant star.

    Only about 10 red giant stars are known to harbor planets; the new solar system is among the most distant of these.

    Our sun will become a red giant in a few billion years, likely vaporizing Earth.

    The finding, to be detailed in the November issue of Astrophysical Journal, was made by a team led by Penn State astronomer Alex Wolszczan, who in 1992 discovered the first planets outside our solar system around a deadly, radiation-spewing star.

    Full article here:

  14. Walden2 says:

    Considerations for the habitable zone of super-Earth planets in Gliese 581

    Authors: P. Chylek, M.R. Perez

    (Submitted on 10 Sep 2007)

    Abstract: We assess the possibility that planets Gliese 581 c and d are within the habitable zone. In analogy with our solar system, we use an empirical definition of the habitable zone. We include assumptions such as planetary climates, and atmospheric circulation on gravitationally locked synchronous rotation.

    Based on the different scenarios, we argue that both planets in Gliese 581 could develop conditions for a habitable zone. In an Earth-like environment planet d could be within a habitable zone, if an atmosphere producing greenhouse effect of 100K could have developed. If the planets are gravitationally locked-in, planet c could develop atmospheric circulation that would allow it to reach temperatures consistent with the existence of surface liquid water, which in turn could support life.

    Comments: 4 pages, 3 figures

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0709.1476v1 [astro-ph]

    Submission history

    From: Mario Perez [view email]

    [v1] Mon, 10 Sep 2007 20:11:07 GMT (278kb)

  15. Walden2 says:

    A depiction of Gliese 581c and its parent star at
    Orion’s Arm here:

  16. Walden2 says:

    Dynamical evolution of the Gliese 581 planetary system

    Authors: Herve Beust (LAOG), Xavier Bonfils (LAOG), Xavier Delfosse (LAOG, OSUG), Stephane Udry

    (Submitted on 12 Dec 2007)

    Abstract: We address the issue of the dynamical evolution of the Gliese 581 planetary system. It is crucial when considering the planets’ habitability because the secular evolution of the orbits may regulate their climate, even in the case where the system is stable. We have numerically integrated the planetary system over 10^8 yrs, starting from the present fitted solution. In all cases, the system appears dynamically stable, even in close to pole-on configurations. Only a limited range of inclinations can be excluded.

    The climate on the planets is expected to be secularly stable, thus not precluding the development of life. Gl 581 remains the best candidate for a planetary system with planets that potentially bear primitive forms of life.

    Comments: 7 pages. Astronomy & Astrophysics (2007) accepted

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0712.1907v1 [astro-ph]

    Submission history

    From: Herve Beust [view email] [via CCSD proxy]

    [v1] Wed, 12 Dec 2007 10:49:59 GMT (209kb)

  17. Walden2 says:

    An A&A press release on the above Arvix paper,
    complete with a diagram showing the various
    models for habitability zones with Gliese 581.,en/

    Apparently at least one planet should be in the
    HZ, according to these models, at least enough
    for simple life forms.

  18. […] the American Southwest cultures, who may entice us thither. I will conclude with the final words of my first article on Gliese 581: Whether Gliese 581c [g] is so hospitable that we could live there or so hostile that we could only […]

  19. Walden2 says:

    Update on potentially habitable exoplanets and the Habitable Exoplanet Catalog

    Posted on September 24, 2011 by Paul Scott Anderson

    There is a new report from the Planetary Habitability Laboratory (PHL), part of the University of Puerto Rico at Arecibo, regarding the number of currently known exoplanets which are potentially habitable. The findings are limited to confirmed exoplanets and exoplanet candidates, from the available Kepler data, which are within the habitable zone of their stars and with either a radius less than two Earth radii or a mass less than 10 Earth masses.

    As of now, the number stands at 16, two from the confirmed list of 687 and 14 from the candidates list of 1,235. That may not sound like a lot, but if, as now thought by Kepler scientists, that the number of exoplanets in our galaxy alone is in the millions if not billions, then you extrapolate from there…

    Full article here: