Interesting Astronomy article in AP

[jmercer]

Associated Press
Light Spotted From Beyond Solar System

A NASA telescope peering far beyond our solar system has for the first time directly measured light from two Jupiter-sized gas planets closely orbiting distant stars, adding crucial features to astronomy's portrait of faraway worlds.

Studies of the infrared light streaming from the two giant planets suggest they are made of hot, swirling gases that reach a broiling 1,340 degrees Fahrenheit or higher.

"It's an awesome experience to realize we are seeing the glow of distant worlds," said astronomer David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., whose team captured light from a planet in the constellation Lyra. "The one thing they can't hide is their heat."

Since the mid-1990s, scientists have discovered more than 130 of these so-called extrasolar planets. But the stars they orbit are so distant and shine so brightly that they tend to overwhelm the planets from view.

To find them, astronomers indirectly measure the tiny gravitational wobble that orbiting planets exert on their suns, or the brief dimming of starlight that occurs when a planet's orbit carries it in front of the star.

But hot celestial objects like these gas planets also emit infrared light. NASA's Spitzer Space Telescope has detectors to collect these infrared signals. Infrared light contains specific signatures in different wave lengths that reveal more scientific characteristics about a space object than visible light.

One planet is known as HD 209458b, nicknamed Osiris. It orbits a sun-like star 150 light-years from Earth in the constellation of Pegasus. Its infrared signature was measured by astronomers at the NASA Goddard Spaceflight Center in Greenbelt, Md. Details will appear Wednesday in the online version of the journal Nature.

The other extrasolar planet measured by the Harvard-Smithsonian team is known as TRes-1. It is located 500 light-years from Earth in the constellation Lyra. Results will be published in the June 20 issue of Astrophysical Journal.

Both planets circle their stars in less than four days at a distance of less than 4 million miles, explaining their very high temperatures.

In contrast, Earth orbits an average of 93 million miles from the sun.

© Copyright 2005 CSC Holdings, Inc.

 

[davefoc]

Yes, I found that story interesting but only mildly so. I always figured it was likely that there were planets orbiting other stars so wasn't too jazzed when they were able to prove it.

Your post did inspire me to look up the Drake equation and see if somebody had taken any of the new information about how common planets are into account when calculating an answer.

I found this site:
http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html

It suggested a value of 50% for the fraction of stars with planets.

I don't know how plausible that is but that number struck me as it might be ok and maybe consitent with the number of planets that have been found.

The number they suggested for the fraction of planets per star that could support life though struck me as way off. Based on an article in scientific american a few years ago I thought it had been pretty well established that there aren't many habitable planets in the bulk of the interior of our galaxy. I think because they lacked sufficient amounts of metallic elements for life and maybe because of too much radiation because of the closer proximity of stars. If I remember that correctly the smallest fraction (.33) they allow in their calculator sounds like it might be way too high.

Anyway I plugged my own uninformed guesses into their calculator and came up with 660 planets in our galaxy capable of communicating. Not a very large number and it would have been smaller if they had let me put in a smaller fraction for the percentage of stars with habitable planets. And I used 10,000 years for the life span of a civilization capable of communication. I suspect that's optimistic and the number is actually far smaller because I think with communication skills comes the blow yourself up skills and eventually the blow yourself up skills are used and that ends the civilization long before it makes it to the 10,000 year mark.

Anyway, with some disapointment, I suspect that the human species will never receive a communication from another sentient species and determine it as such.

 

[Dylab]

Just out of curosity what did you put down for Fi and Fl? The fraction of planets with life and the fraction of that with intelligence?

 

[davefoc]

I went with the defaults
Fl=50% of planets that can develop life do
Fi=20% of planets that have life develop intelligent life


I suspect though that Fl is 100%
I don't have any feel for Fi except that was what was there so I went with it

My numbers
N* - 100 billion (default)
fp - 50% (default)
ne - .33% (this is the one I suspect should be much lower)
fl- 50% (default)
fi - 20% (default)
fc - 20% (default, but my guess is sentient life eventually discovers radio communication so could believe number is higher unless this means capability for radio communication over vast distances (very large antennas, powerful transmitters, low noise receivers) and an inclination to deploy that stuff so I went with 20%
Fl - 10,000 years (default)

What were your values? I see that I mostly went with the defaults since I figured they knew more than me except with ne where I think they are probably way off based only on vague recollection of scientific american article.