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Planetary Radio: Looking for Intelligence in a Flash

The All-Sky OSETI Search Gets Even Better

Posted by Mat Kaplan

05-11-2013 10:58 CST

Topics: Planetary Society Projects, Planetary Radio, explaining technology, Planetary Society People, Planetary Society, SETI, Bill Nye

There was a good story on NPR this morning about the just published work indicating that one in five stars probably has an Earth-sized planet in its habitable zone.  The Morning Edition host introduced it by saying (roughly), "...there may be billions and billions of planets like Earth!  Well, maybe not that many."  Argh!  Yes, yes!  Billions and billions!  And that's something to celebrate.  And to explore. 

This week on Planetary Radio I visit with two such explorers.  Paul Horowitz and Curtis Mead are watching the entire sky every clear night.  The Planetary Society Optical SETI telescope, or "light collector," as Paul prefers to call it, is designed to catch a burst of laser light sent our way by some galactic neighbor.  There's much more to the story of how they do this, including a truly amazing detector designed by Curtis.  Listen to the show and read Bruce Betts' blog to learn more.  You'll learn why I'm so proud that the Society is behind this project.

As always, PlanRad is a multi-course feast.  If you follow Emily Lakdawalla, you know she stayed up late last night to watch the successful launch of India's Mars Orbiter Mission.  She shares some of what she has learned on the show.  NASA Administrator Charles Bolden made a pretty bold statement before a hearing in Washington.  Bill Nye shares his thoughts about it.  Regarding What's Up, do you wonder if Bruce Betts and I are really enjoying ourselves as much as it sounds?  We are, and this week's segment is a good example.  Clear skies!

See other posts from November 2013


Or read more blog entries about: Planetary Society Projects, Planetary Radio, explaining technology, Planetary Society People, Planetary Society, SETI, Bill Nye


Enzo: 11/05/2013 04:23 CST

I find the claim that "one in five stars probably has an Earth-sized planet in its habitable zone" profoundly misleading and not backed by Kepler's data. Kepler has found many earth size planets, but not one in the habitable zone (HZ). If you look at the abstract of their paper : You will see that they include planets from 1-2x earth radius and a solar flux from 4 to 1/4 of earth's. All modern studies about the earth HZ, indicate that earth is right on the edge. This indicates a max solar flux of ~1.1x . HZ is defined as the volume of space where a planet can have stable liquid water on the surface. A solar flux of 4x is the same of 0.5 AU, just .12 AUs from Mercury. Venus is 0.7 AUs. Secondly, the Kepler mission initially set earth like planet radius to 1.3x earth radius. Now it's become 2x earth radius. This is way too optimistic because, for the few exoplanets of that size we know the density of, they are more like mini-Neptunes than earths : Even if they were rocky, at that size, they would be massive and starting to hold onto helium and hydrogen in the atmosphere. This, in turn, results in greenhouse effect that moves the habitability outwards. See here : Moving the HZ outwards is fine, except that Kepler has found little for longer periods (possibly because longer observations were needed). I could give more details, but, to make a long story short, if you plug more sensible values in the list of KOIs (Kepler Object of Interest) like 1.1 max solar flux and earth radius max 1.4x, then Kepler has found nothing. Maybe Kepler 62f. I find very disturbing that the public know thinks that "one in five G stars has an earth-like planet in the HZ". Kepler has observed 90,000 G stars for 3 years and has not found such result. That does not mean that they do not exist, just rarer.

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