GHOSTLY PLANET GOES BOO

Enthusiastic astronomers claimed the discovery of an exoplanet in the habitable zone of a nearby star, declaring: “…the chances of life on this planet are 100%.”

Two weeks later, other astronomers, through more careful analysis, showed this and other promising planets are just ghostly apparitions.

Gliese 581 is a mundane red dwarf star, remarkable only for being home to the most non-existent “habitable” planets.

About 20 light-years away (120 trillion miles), and less than a third of our Sun’s size and mass, Gliese radiates only 1/80th as much energy as our Sun. Most of its light is infrared, invisible to human eyes. It also radiates body-piercing x-rays.

Gliese 581b was the first planet discovered orbiting this star. (The naming convention is: suffix “a” denotes the star; its planets are named “b”, “c”, “d”,… in the order of discovery.) Gliese 581b is the size of Uranus in our Solar System, but is so close to its star that its year lasts only 5 Earth-days, making it an ghoulish inferno.

Then came “c”, the first Gliese planet that was declared “habitable.” Gliese 581c is at least 5.5 times Earth’s mass, and orbits its star in 13 Earth-days. Astronomers initially said its surface temperature was balmy 20ºC (68ºF). Later analysis using planet climate models raised that estimate to 500ºC (932ºF), hot enough to boil anyone’s cauldron.

Next came “d”, said to orbit in 83 days, which was later revised to 67 days. The closer orbit gave “d” 30% of the light energy that Earth receives (by comparison, life-less Mars gets 40% of Earth’s light intensity). Some claimed “d” could be habitable if it had a dense atmosphere. Recent analysis concluded that planet “d” does not exist !

Gliese 581e is a real planet, with twice Earth’s mass and an orbital period of 3 days. It is ten times closer to its star than Mercury is to our Sun. Everyone agrees that “e” is hellish.

The last zombies to emerge from the darkness were “f” and “g”, with “f” being too cold for life, but “g” being right in the middle of the habitable zone, the region where water is liquid.

Stephen Vogt of University of California at Santa Cruz is the lead author of the paper in the Astrophysical Journal that announced the discoveries of “f” and “g”, based on 11 years of observations using the mammoth 10-meter Keck telescope. In a TV interview, Vogt proclaimed a “100%” probability of life on Gliese 581g, and his paper says: “…our Milky Way could be teaming with potentially habitable planets.” Indeed, Vogt estimated 1 in 5 stars have a habitable planet.

Based on his findings, Vogt proposed a $100 million research program for his field. When a science paper makes a pitch for money, one wonders if it’s trick-or-treat time.

Vogt claims the probability of his analysis being wrong — the probability of false-positive detections  — is only: 1 in 400,000 for Gliese 581d; 1 in 100,000 for Gliese 581f; and 1 in 370,000 for the “100%-er” Gliese 581g.

The truth is, it’s very likely that none of these claimed exoplanets actually exist.  Subsequent analysis, published in Science Magazine, shows that Gliese 581 is a dynamic star. That variability, coupled with its rotation, led to the erroneous “discovery” of three exoplanets that actually don’t exist. This study shows that Gliese 581 truly has just three planets, not six.

NASA / JPL / Caltech maintain the world’s official list of confirmed exoplanets. They have removed Gliese 581’s ghost planets, retaining only b, c, and e.  Meanwhile, Vogt is sticking to his claims; he’s a true believer.

Scientific discovery is a rocky road best traversed with great persistence and healthy skepticism. It is easy to be blinded by exuberance, self-confidence, and practical career pressures. Some will find what they desperately seek, even if it isn’t there. Public media and some journals eagerly publish spectacular claims, even without compelling evidence.

Fortunately, in the dogfight for funding, tenure, and prestige, scientists are policed by other scientists eager to prove their “colleagues” wrong.

   Earth and Artist’s Concept of the Non-Existent

   Exoplanet with “100% Chance of Life”

Have a Happy & Safe Halloween!

Best Regards,
Robert

October 30, 2014

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