1000 Planets

"In 1961, University of California, Santa Cruz astronomer and astrophysicist Dr. Frank formulated the Drake equation. This controversial equation multiplies estimates together with the following conditions:

• Level of star formation that matches.
  
• The fraction of these stars surrounded by planets.
  
• Total world similar to Earth per-system planets.
  
• The fraction of planets where intelligent life evolved.
  
• The fraction of communicative planets possible.
  
• Age of the possible communicative civilizations.

The Drake equation is used to estimate that there are approximately 10,000 planets in the Milky Way galaxy containing intelligent life with the potential to communicate with Earth. Based on observations from the Hubble Space Telescope, there are at least 125 billion galaxies in the universe. It is estimated that at least ten percent of all stars have planetary systems similar to the sun, for example, there are 6.25 × 10^18 stars with orbiting planets in the universe. Even if we assume that only one out of a billion of these stars have planets supporting life, there will be some 6.25 × 10^9 (billion) life-supporting planetary systems in the universe." — Potential and Shortcomings for Life In the Universe, VIRGOEZ23 blog It appears that, according to astrophysicist Drake, only 6.25 billion planetary systems in our universe contain life. Given that 10% of them may be at our level of civilization, that gives us 625 million possible humanoid lifeforms, assuming that carbon-based life is the ideal. Closer to home, there are 10,000 planets with the potential for life. If ten percent of those planets have civilizations at our current level or greater, then we have one thousand potential candidates to home in on using our radio-telescopes and observatories in orbit around our Earth. Thus, it makes sense to concentrate our radio-telescopes on potential extraterrestrial life within 50 light-years of earth. My reasoning for that close a distance to Earth is that intelligent life will be able to return a message within each generation's lifetimes. Hopefully their message is as simple as the ones that NASA has sent out since the Voyager spacecraft was launched in the 1970s, as well as radio-telescope messages from the SETI project, which has gone into hiatus due to funding issues. See reference below for possible habitable planets.

---

Reference:
Potential and Shortcomings for Life In the Universe (translated from Bahasa Melayu and Indonesian):
http://translate.googleusercontent.com/translate_c?depth=1&hl=en&rurl=translate.google.com&sl=ms&tl=en&u=http://virgoez23.blogspot.ca/2013/04/potensi-dan-kelemahan-kehidupan-di-luar-planet-bumi.html&usg=ALkJrhi8sXsZe9Z0OqMRVKlM7eI3LjEONw

You might wish to change the translating language to Indonesian, as the blog's owner switches between Bahasa Melayu to Indonesian. As well, the translation is a best guess, and would need a native English speaker who understands the rules and syntax of their mother tongue.

List of habitable planets: http://en.wikipedia.org/wiki/HabCat

Caltech Scientist finds planet orbitting 3 suns

In the northern constellation Cygnus (The Swan) a planet the size of Jupiter orbits around three stars 149 light-years (1200 trillion kilometres) from Earth.

From the Caltech news release comes a challenge to the theories about planetary formations in complex solar systems.

Maciej Konacki reported this discovery in the May 2005 issue of Nature.

"If the parent star is orbited by a close stellar companion, then its gravitational pull can significantly truncate a protoplanetary disk around the main star. In the case of HD 188753, the two stellar companions would truncate the disk around the main star to a radius of only 1.3 astronomical units, leaving no space for a planet to form." - http://pr.caltech.edu/media/Press_Releases/PR12716.html

In the case of this triple star system, a red giant and an orange star orbit around a yellow star, according to SpaceFlight News http://www.spaceflightnews.com/forum/lofiversion/index.php/t1161.html.

"The new planet belongs to a common class of extrasolar planets called "hot Jupiters," which are gas giants that zip closely around their parent stars. In this case, the planet whips every 3.3 days around a star that is circled every 25.7 years by a pirouetting pair of stars locked in a 156-day orbit." - NASA Jet Propulsion Laboratory website http://planetquest.jpl.nasa.gov/


Regarding star system HD 188753, perhaps only large planetary masses can survive the combined tidal and solar forces of three stars in close orbit around each other.

My guess is that the planet, which is slightly larger than Jupiter, was too small to become a star.

Thus, in the formation of star systems, the larger masses become stars.

Any masses smaller than a certain size become planets. Judging from this example, the size limit may be slightly more than the size of Jupiter.



The size (diameter, surface area, volume and mass) of Jupiter is as follows:


Diameter: 10⁸ × 1.43 m
Surface area: 10¹⁷ × 0.641 m²
Volume: 10²⁵ × 1.52 m³
Density: 10³ × 1.3 kg/m³ (1.3 g/cm³)
Mass: 10²⁷ × 1.9 kg
Note: 10E8 = 100,000,000
cm = centimetre
m = metres
kg = kilograms
http://www.vendian.org/envelope/dir1/earth_jupiter_sun.html