Planets and Flying Saucers from Outer Space

[Mike]

I recently finished reading Keyhoe's 'Flying Saucers From Outer Space,' written in 1953 and the follow up book to his 'The Flying Saucers Are Real'. The quote below caught my eye.

The possibility that the saucers came from Mars or Venus was also admitted; but it was more likely, said the Air Force, that they came from outside our solar system. In discussing nearby star systems, the Project Sign report stated:

"Outside the solar system other stars -22 in number- have satellite planets. Our sun has nine. One of these, the earth is ideal for existence of intelligent life. On two others there is a possibility of life. Therefore, astronomers believe reasonable that the thesis that there could be at least one ideally habitable planet for each of the 22 other eligible stars." [...]

What I'm wondering is where this information about the number of stars with satellite planets came from. Considering that only recently have exoplants been found to exist. The first discovered in 1992.

http://planetquest.jpl.nasa.gov/news/300Beyond.cfm

Exoplanet count tops 300 with discovery of 'super-Earths'
June 20, 2008
(PLANETQUEST) -- Just a few decades ago, scientists wondered if anyone would be able to find planets orbiting other stars - much less ones that could support life.
Now, just 13 years after the discovery of the first planet orbiting a sun-like star, scientists have found more than 300 exoplanets, from char-broiled "hot Jupiters" that orbit their stars in a matter of days, to planets closer in size and composition to our own.[...]

Maybe I'm missing something here, so thought to bring it up. FWIW Keyhoe's 2nd book on the subject of UFO gives a straightforward real time look at the UFO question and is well worth the read.