Imagine the Universe!
Imagine Home  |   Ask A High Energy Astronomer  |  
Ask a High-Energy Astronomer

The Question

(Submitted September 24, 1997)

What are the chances of life existing outside our solar system?

The Answer

This is a question that astronomers first started to quantify in the early 1960s. In 1961, a radio astronomer named Frank Drake developed an equation to stimulate discussion of the Search for Extraterrestrial Intelligence (SETI). This equation, which is now called the Drake equation, states that the number of communicating civilizations in our galaxy likely depends on a number of factors which must combine to yield a habitable planet where life has the chance develop to a certain level of technological know-how. These factors include the rate of formation of stars like the Sun, the fraction of those with planets, the fraction of Earth-like planets, the fraction of such planets where life develops, the fraction of those where the life becomes intelligent, the fraction of intelligent species who can communicate in a way we would detect, and the lifetime of the communicating civilizations. As you may imagine, there is a lot of debate about reasonable values for most of these factors. As we learn more about the likelihood of planets around other stars, we are able to better estimate one of these parameters. For the other parameters, the estimates vary widely. Frank Drake's own current estimate puts the number of communicating civilizations in the galaxy at 10,000.

You can find out more about the Drake Equation from

http://www.setileague.org/general/drake.htm

http://seds.lpl.arizona.edu/~rme/drake.html (http://seds.lpl.arizona.edu/%7Erme/drake.html)

http://www.ishipress.com/aliens.htm

Cheers,
Padi Boyd
for the Ask a High-Energy Astronomer

Questions on this topic are no longer responded to by the "Ask a High-Energy Astronomer" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html for help on other astronomy Q&A services.

Previous question
Prev
Main topic
Main
Next question
Next
Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Nicholas White (Director), within the Laboratory for High Energy Astrophysics at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Jim Lochner
All material on this site has been created and updated between 1997-2004.

CD Table of Contents