Carl Sagan on the Discovery of Exoplanets and the Significance of Earth
Wednesday, July 29, 2015 at 01:00PM In 1980, Carl Sagan, then forty-four years old, told a group of Brooklyn middle school students the following (click this link to see him say this at the 52 min. point of Cosmos, Episode Seven, The Backbone of Night):
By the time that you people are as old as I am we should know, for all the nearest stars, whether they have planets going around them. We might know dozens or even hundreds of other planetary systems and see if they're like our own or very different, or no other planets going around other stars at all. That will happen in your lifetime, and it will be the first time in the world's history that anybody found out really if there are planets around the other stars.
Image from: http://phl.upr.edu/projects/habitable-exoplanets-catalog/results
Thirty-four years later, Earth-based telescopes and NASA’s Kepler space telescope, which was launched in 2009 and ceased its planet-hunting operations due to technical difficulties in 2013, have identified 1030 Earth-sized exoplanets (planets that orbit within a “habitable-zone” around a sun-like star) and 4,696 “candidate planets” in other star systems within the Milky Way galaxy.
Image from: https://en.wikipedia.org/wiki/Kepler_%28spacecraft%29
Last week, NASA announced the discovery of Kepler-452b; located 1,4000 light-years away in the constellation Cygnus, the planet is being referred to as Earth 2.0 due to the number of similarities it shares with Earth. Jon Jenkins, data analysis for NASA's Ames Research Center said, “We can think of Kepler-452b as an older, bigger cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment. It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”
In Cosmos, Sagan goes to speak out the position of our sun in relation to the Milky Way Galaxy, as well as the position of the Milky Way in universe:
Now, the nearby stars, the ones you can see with the naked eye, those are all in the solar neighborhood. That's what astronomers call it: the neighborhood. But it's a very tiny place in the Milky Way galaxy. The Milky Way is that band of light that you see across the sky on a clear night (I can't tell if there are any more clear nights in Brooklyn), but you must've seen the Milky Way, right? A faint band of light at night. Well, that's just a hundred billion stars all seen together edge on, as in this picture. If you could get out of the Milky Way galaxy and look down on it, it would look like that picture. And if we did look down on the Milky Way where would the sun and nearby stars be? Would it be in the center where things look important or at least well-lit? No. We would be way out here in the suburbs, in the countryside of the galaxy. We're not in any important place. All the stars you could see would be in a little, little place like that. And the Milky Way would be this band of light a hundred billion stars all together. The fact that we live in the outskirts of the galaxy was discovered a long time ago, towards the end of the First World War by a man named Harlow Shapley who was mapping the position of these clusters of stars. See, every one of these is a bunch of maybe ten-thousand stars all together – it’s called a globular cluster. And you can see that they’re centered around the middle, the center of the galaxy. People used to think that the sun was at the center of the galaxy – something important about our position – it turns out to be wrong. We live in the outskirts; the globular clusters are centered around the marvelous middle of the Milky Way galaxy. And then it turned out that this isn't the only galaxy. We live in this one, but there are many others. And as this picture reminds us, there are many different kinds of galaxies of which ours might be just this one. There are, in fact, a hundred billion other galaxies, each of which contains something like a hundred billion stars. Think of how many stars and planets and kinds of life there may be in this vast and awesome universe. 
Hubble Ultra Deep Field 2014. Image from: http://hubblesite.org/gallery/album/entire/pr2014027a/
As long as there have been humans we have searched for our place in the cosmos. Where are we? Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people. We make our world significant by the courage of our questions and by the depth of our answers. We embarked on our journey to the stars .with a question first framed in the childhood of our species and in each generation asked anew with undiminished wonder: "What are the stars?" Exploration is in our nature. We began as wanderers and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.
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