Our Changing Worlds View

2 Some planets were known to the ancients who watched them move against the night sky.

Mercury, Venus, Mars, Jupiter, and Saturn were the “ Wandering Stars ” “ Planet ” comes from the Greek word for “ wanderer. ”

“ There are infinite worlds both like and unlike this world of ours...We must believe that in all worlds there are living creatures and planets and other things we see in this world. ” Epicurus c. 300 BC But what about more distant worlds? Thousands of years ago, Greek philosophers speculated about other worlds like our own.

More recent scholars also speculated on distant worlds like ours. the year 1584 "There are countless suns and countless earths all rotating around their suns in exactly the same way as the seven planets of our system... The countless worlds in the universe are no worse and no less inhabited than our Earth ” Giordano Bruno in De L'infinito Universo E Mondi 4

With the advent of the telescope, nearby planets came into view The Moon seemed alive, perhaps with seas and canals. Wandering stars resolved as planets with features, phases, and even their own moons. Galileo’s sketches shown here.

The possibilities were limitless and our imaginations flourished.

While Hollywood worked on the public imagination, scientists started to turn science fiction into science fact.

Stars are a billion times brighter…

…than a planet …hidden in the glare

like this firefly.

In 1995, a breakthrough: the first planet around a stable star. A Swiss team discovers a planet – 51 Pegasi – 48 light years from Earth. Didier Queloz and Michel Mayor

1995

2000

2005

2010

2013

1) Wobble 2) Transit 3) Direct Observation 4) Microlensing… Planet Finding Methods

Star Wobble If an unseen planet tugs the star back and forth… …the light from the star shifts slightly to the red as the star moves away from you. …and slightly to the blue as it moves toward you. Astronomers can detect these shifts by very carefully observing the spectra (or colors) of the stars. This is called the radial velocity method.

Scientists also look for the star ’ s light to dim slightly when a planet passes in front. Launched in 2009, Kepler found planets using a specialized one-meter diameter telescope called a photometer to measure the small changes in brightness caused by these passing planets (or transits). This is called the transit method

What are we Finding?

The planets being found are nothing like what we expected 7

And there are always new surprises

Many of the new planets get too hot or too cold to support life. Too hot! Too cold!Just right! Could any of these planets harbor life? Many are too big. Most probably don’t.

While astronomers were exploring the cosmos, biologists were finding new life forms here on Earth… … broadening our definition of “habitable”

The Search is on for Water

There are uncountable planets, many Earth-sized. And some could sustain liquid water!

We shall not cease from exploration And the end of all our exploring Will be to arrive where we started And know the place for the first time. T.S. Eliot Four Quartets For more information go to And if we discover life beyond Earth, we might turn again to the poets and philosophers…

Additional Information For more information go to: planetquest.jpl.nasa.gov NASA ’ s Vision: To reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind.

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Additional slides

You can even see some of the stars that have planets in the night sky…

…if you know where to look

Kepler’s Field of View

Just how far are these new planets? from Mars… it would take ten minutes from the nearest extrasolar planet… it would take more than four years! from the Moon… it would take one second IF YOU WANTED TO RADIO HOME FOR YOUR WORDS TO REACH EARTH

These stars are too far away to visit, but not very distant on a cosmic scale. would be the size of the United States Our Milky Way Galaxy Our whole Solar System would be this big Imagine, if you shrunk our solar system with all its planets to a little larger than a quarter: The next nearest planetary system Would be the size of another quarter, just across the park