The epic achievements in planetary discovery since a Swiss and then very quickly a US team declared in 1996 discovery of worlds orbiting other stars have not all been smooth sailing. But an overall success it has been, with the roll call of confirmed alien planets at 1,737, with more than 4,200 candidates to be screened after popping up in data from the Kepler Space Telescope.
But one (actually, two, more on that below), Gliese 581g, is no longer on the archive that NASA keeps while the agency awaits further study of reason to doubt it exists.
Several news outlets have the news. The latest skeptics – this planet has been star-crossed for awhile – are a team at Penn State who published on it in Science last week. The paper title gets right to it: Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581. They say that this presumed, large, rocky companion of this red dwarf just 20 light years away appears to be a misinterpretation of the distortion of the star’s spectrum as star spots, huge storms and waves of sloshing plasma roil its outer atmosphere. The star does apparently have several planets, betrayed by the motions of the overall star as they orbit rapidly around it and nudge it here and there with their gravity. But the faint signal of planet g – one that got enormous news attention at the time – and a second as well look very doubtful, the team says. That’d be too bad for, if a real planet, it would seem to have an orbit and size suitable for liquid water and life.
So it goes in science. The team that originally declared the planet to be a planet is keeping pretty quiet, but has stuck to its guns during previous outbreaks of doubt. A round up of stories follows shortly.
It is possible that a certain specialist in stellar photospheres is chuckling a bit at the planet’s possible refutation. That would be David Gray of the University of Western Ontario. In early 1997, little more than a year into the parade of exoplanets inferred from doppler shift method for detection, he put a paper in Nature that declared several and potentially all of those known were, actually, just waves on their stars that made it look like planets were circling them. A kerfuffle followed. It died away as other specialists found even stronger reasons to think the planets to be real. Gray later agreed that the specific object of his doubts, a companion of the star 51 Pegasi and the first on the list, is indeed most likely a planet.
And a few years after that, a science writing colleague of mine at another newspaper, in San Francisco, became convinced that noted astronomers including Geoff Marcy, Paul Butler, Steven Vogt, and Debra Fischer were, with yet other colleagues, foisting bad science on the entire world when they said they were finding planets around other stars. He rattled their nerves with angry, e-mailed accusations of hyped results, threatening to expose them to the “public scrutiny you deserve”. Nothing came of that, either. But ironically several of those same scientists – irrefutable lions of the art of finding planets – were and perhaps still are champions of Gliese 581g.
The news coverage in recent days covers well the up-and-down saga of the planet’s acceptance within the academy of astronomy.
Stories:
- Washington Post – Sandhya Somashekhar: Study debunks a ‘Goldilocks’ planet thought to potentially support alien life ;
- Universe Today – Elizabeth Howell: A Brief History Of Gliese 581d and 581g, The Planets That May Not Be ;
- The Register (UK) Brid-Aine Parnell: ANGRY ALIENS hit by BEPO SPAMGASM probably don’t exist ; Humanity seemingly spared justifiable interstellar retribution ; Don’t ask me. Totally gonzo story went over my head with allusions to stuff I don’t know about. Also funny.
- Liberty Voice – Rebecca Savastio: Exoplanets Gliese 581d and 581g Proven Fake: Is the Search Futile?; You can suspect a reporter isn’t serious if the listed sources are the Register piece just above and the aggregator sources Red Orbit and Science Alert. Look at the head, “proven fake”? Not many scientists prove anything, that’s for mathematicians. They may accept conclusions or reject them, of course. It says here some commentators are now calling the exoplanet search futile, but has no example. Sigh.
- The Daily Beast – Matthew R. Francis: The Exoplanet that Wasn’t There ; Nice line – “Now the verdict is in: Gliese 581g is an ex-planet, not an exoplanet.” Francis also uses well the freedom of bloggy columnizing when he writes: Your first response may be to say, “Stupid scientists! How could they get this so wrong?!” (You aren’t a very nice person, you know.) But that’s a mistake. The story of Gliese 581g highlights how hard exoplanet hunting is, adn how science at its best is self-correcting. Bravo.
- National Geographic – Michael D. Lemonick: One of the Most earthlike Planets Ever found May Not Exist ; Fine explanation of what happened, why the results were so beguiling, and why several colleagues of the planet’s discoverers were unconvinced from the start.
- Space.com – Charles Q. Choi: Are 2 Potentially Habitable Alien Planets Just Cosmic Illusions? ; Nice job, covers the bases. But call the editor! Did Charles, who knows what he’s doing with great reliability, really write that “581d and 581g appeared to lay within their star’s habitable zone”? Hmmm. No lie, maybe they laid an egg is what transpired.
- Popular Science – Sarah Fecht: The First “Potentially Habitable” Exoplanet Was Probably Just a Sunspot. Oops.
- Boing Boing – Maggie Koerth-Baker: Once hyped planet does not exist ;
- Could go on, but it’s dinner time.
Grist for the Mill: Penn State Press Release ;
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