Other life? (Introduction)

by David Turell , Monday, June 22, 2020, 16:04 (1613 days ago)

A new estimate for the Milky Way:

https://mail.yahoo.com/d/folders/1/messages/AL_Bt1lbszqfXvC61wL10J-jvOE?.intl=us&.p...

"Maybe you think one Earth is enough. But what if there were billions? Researchers make a new estimate that the number of Earth-like planets in our Milky Way galaxy can reach us high as 6 billion. Astronomers at the University of British Columbia (UBC) analyzed data from NASA's Kepler mission to reach the stunning conclusion. The information on 200,000 stars was gathered by the Kepler planet-hunting spacecraft from 2009 to 2018. The criteria used by the scientists for selecting such a planet maintained it had to be rocky, about the same size as Earth, and orbiting a star like our Sun. This planet also had to be in the habitable zone of its star, where the conditions would be just right to potentially allow for water and life.

"UBC researcher Michelle Kunimoto says that the calculations "place an upper limit of 0.18 Earth-like planets per G-type star." In other words, that's about 5 planets per Sun. Astronomer Jaymie Matthews put this from another perspective, explaining that "Our Milky Way has as many as 400 billion stars, with seven per cent of them being G-type. That means less than six billion stars may have Earth-like planets in our Galaxy." While the scientists came up with an impressive number of possible Earths, this likely doesn't mean that's how many such planets there are and if they would have life like ours. But this new estimate definitely expands the possibility that similar planets are out there.

"Taking into account what we do know, and mixing in some assumptions about life on Earth, a team of scientists have predicted that there are 36 Communicating Extra-Terrestrial Intelligent (CETI: pronounced "chetee") civilizations in our galaxy. The scientists' calculations are a response to the Drake equation. In 1961 astronomer Frank Drake proposed that having knowledge of seven factors would allow scientists to reasonably estimate the number of intelligent alien civilizations out there. They operated on the assumption that a planet's life would have to take form between 4.5 billion and 5.5 billion years after the creation of its system's star, as it did here.

"We've only been producing radio waves to send out there for 100 years, so that's assumed to be about the minimum time a civilization would have to be in existence and broadcasting for us to detect them. More realistically, the authors expect that a CETI population would have to exist for an average of 3,060 years to be detectable, which means that if life formed in both places at the same time, we'd both need to be in existence for 6,120 years to make contact. (my bold)

"'I think it is extremely important and exciting because for the first time we really have an estimate for this number of active intelligent, communicating civilizations that we potentially could contact and find out there is other life in the universe — something that has been a question for thousands of years and is still not answered," said co-author and astrophysicist Christopher Conselice of University of Nottingham."

Comment: Alpha centuri, the closest star is 4.3 light years away. Contact must be by radio waves at the speed of light. Very few stars are close enough, unless they produced radio waves thousands of years ago as discussed..