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MAIN ARTICLE:Of Aliens, exoplanets and the Drake Equation.

Taking a look at the Milky Way Galaxy and how to calculate the number of possible civilizations. A new paper tries to narrow down the numbers.

Poll Results: The poll yesterday had a dismal turnout, it must have been the Monday polling blues, but it was clear answer. Scroll down for the latest in space polling, click subscribe for to stay informed.

Star Trek: In the News. "Star Trek-style device may check patients' genetic suitability to different medicines"

'damnit Jim, I'm a doctor not a internet specialist'

Yesterday's Comments: "It never hurts to brown nose with 400 million at stake." - Subo03

Today's Poll: How many intelligent civilizations do you think exist in the Milky Way Galaxy.

While digging through various space blogs and websites I came across an interesting article about off world life. First, so we are all on the same page, some definitions. (all links open in a new window)



"Extraterrestrial life is life originating outside of the Earth. It is the subject of astrobiology and its existence remains hypothetical, because there is no credible evidence of extraterrestrial life which has been generally accepted by the mainstream scientific community. Hypotheses regarding the origin(s) of extraterrestrial life, if it indeed exists, are as follows: one proposes that it may have emerged, independently, from different places in the universe. An alternative hypothesis is panspermia, which holds that life emerges from one location, then spreads between habitable planets. These two hypotheses are not mutually exclusive. The study and theorization of extraterrestrial life is known as astrobiology, exobiology or xenobiology. Speculated forms of extraterrestrial life range from sapient or sentient beings, to life at the scale of bacteria."
--end quote--


"An extrasolar planet, or exoplanet, is a planet beyond the Solar System, orbiting a star other than the Sun. As of February 2009, 340 exoplanets are listed in the Extrasolar Planets Encyclopaedia.[1] The vast majority have been detected through radial velocity observations and other indirect methods rather than actual imaging.[1] Most announced exoplanets are massive gas giant planets thought to resemble Jupiter, but this is a selection effect due to limitations in detection technology. Projections based on recent detections of much smaller worlds suggest that lightweight, rocky planets will eventually be found to outnumber extrasolar gas giants."
--end quote--


Drake Equation:

"The Drake equation (also sometimes called the "Green Bank equation", the "Green Bank Formula," or often erroneously labeled the "Sagan equation") is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence (SETI).

This equation was devised by Dr. Frank Drake (now Professor Emeritus of Astronomy and Astrophysics at the University of California, Santa Cruz) in 1960, in an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. The main purpose of the equation is to allow scientists to quantify the uncertainty of the factors which determine the number of such extraterrestrial civilizations"
--end quote--


Sounds great, so what does it look like?


I guess that is meaningless without some variable definitions:

"N is the number of civilizations in our galaxy with which communication might be possible;

R* is the average rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fℓ is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space." - wiki
--end quote--

So what has happened since 1960 when Dr. Drake first proposed this equation? The discovery of the first exoplanet in 1990 and in particular the first confirmed radial velocity detection made in 1995. This was a gas giant planet in a four-day orbit around the very close '51 Pegasi' a G-type star. You can learn more about the Stellar classification of stars here. A G-type star is yellow just like our sun.

Prior to this all the variables were undefined and there wasn't any definative numbers you could plug in to the equation. Knowing the number of planets orbiting other stars in the galaxy goes a long way in building a better model. With the advances being made in planet hunting technics and new telescopes the speed of discovery is increasing.

On March 5th next month, the Drake Equation is going to get another bump as the new Kepler Telescope (see "Alien Earth hunting telescope unveiled.", 'Americans in Space', Feb 02, 2009) is launched.

Oh the article that started all this...

How many intelligent civilisations are in our galaxy?

"Now, Duncan Forgan of the University of Edinburgh in Scotland has attempted to constrain the numbers a bit better. In a paper (pdf) published in the International Journal of Astrobiology, he says estimates using the Drake equation are limited in accuracy because they rely on average values for parameters such as the lifetime of a civilisation capable of communicating with Earth.

To estimate a distribution of values instead, he created a computer model of the Milky Way's stars, generated planets around them, and assigned life to some planets in the habitable zones of their stars. Then he used equations that take into account the random nature of evolution to determine if that life went on to develop intelligence. By running the model again and again, he came up with a range of values, and put errors on the various estimates.

He looked at three different scenarios for how life could develop, and here's what he found (from a university press release):

The first scenario assumes that it is difficult for life to be formed but easy for it to evolve, and suggests there are 361 intelligent civilisations in the galaxy.
A second scenario assumes that life is easily formed, but it struggles to develop intelligence, and suggests that as many as 31,513 other forms of life are estimated to exist.

Finally, he examined the possibility that microbial life could be passed from one planet to another during asteroid collisions, which gave a result of 37,964 intelligent civilisations in existence.

So, it would seem that even in his worst-case scenario, we are not alone. (Which raises the question first voiced by Enrico Fermi - where is everybody?)"


This is a great Interactive Drake Equation calculator, just plug your numbers in and it will crank out how many civilizations you think there are in the galaxy.


Yesterday's poll: "Why is SpaceX thanking members of Congress?" was about the recent thank you on the SpaceX website. Although the turnout was low it was pretty clear what DKOS members who took part in the poll thought it mean't. 73% said it was a sign that the Obama Administration was going to fund COTS-D while 20% thought it was just hype. Six percent showed no opinion in this poll.

STAR TREK: In the News.

Star Trek-style device may check patients' genetic suitability to different medicines

"London, February 17 : A Star Trek-style, BlackBerry-sized device is being tested by scientist at Imperial College London, and its spin-out company DNA Electronics, for its effectiveness in checking patients' genetic suitability to different medicines.

The doctors say that the device, named the SNP (pronounced snip) Doctor, is th ekidn of gadget that might have been used by Dr Leonard McCoy in the original Star Trek TV series.

They say that it can analyse DNA from a drop of saliva or cheek swab to tell whether a patient has the right genetic fit for a particular drug.

They reckon that the device may be available in the market between two and five.

The Snip Doctor looks for known single nucleotide polymorphisms (SNPs), single letter changes in the genetic code, which can affect an individual's response to medical treatment."
--end quote--


"Google? An uber-progressive corporation?  
Or merely intent on world domination?" - Bill White

"I have a rotary dial stick phone for when the lights go out... all the other phones don't work but the old antique gets the dial tone each time.

lol... gotta love technology" - Statusquomustgo

"Thank you, Ferris I always feel like an interloper in these diaries because I am completely ignorant re: all things NASA, rockets, etc. -- although I have a dear friend who is trying to educate me.

Several years ago we watched a marvelous program on a group of "rocket" devotees who had a kind of jamboree.  We were astonished at the different kinds of rocket propelled thingies -- including an outhouse.  One of the great privileges of this site is that very smart people keep educating me in areas which are way over my head." - gchaucer2


Read other NASA and space diaries on DKOS.

Originally posted to Vladislaw on Tue Feb 17, 2009 at 02:55 PM PST.


How many intelligent civilizations do you think exist in the Milky Way Galaxy.

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