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Is There Another Planet?
 CNN Clip
 New Planet 2011
What are two similarities that you heard in these two
videos?
But if the goal is to find planets with
evidence of life, the ones discovered so far
are not good candidates.
Most of new discoveries are gas giants like
Jupiter or Saturn and in the wrong location.
The right location in our solar system.
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Many of the new planets get too
hot or too cold to support life.
Too hot!
Just right!
Too cold!
Most of them have highly elliptical orbits,
or are too close to their parent stars.
Requirements For Life
Needs to be…
 In a solar system with a single massive star that can
serve as stable source of energy
 A terrestrial planet (non-gaseous)
 The right distance from the sun
 If it’s too close, the water is burnt off, if it’s too far, the
water is permanently frozen
Finding another Earth won’t be easy because:
1) Earth-like planets are
small,
and
2) Planets are relatively
close in to bright stars.
The planets discovered so far are closer
in mass to Jupiter.
This is what
we’ve found
This is what we
are looking for
Jupiter’s diameter is eleven times greater than the Earth’s, and it
has over 300 times the mass.
Stars are a billion
times brighter…
…than the planet
…hidden
in the glare.
Like this firefly.
Requirements For Life
Needs to have…
 A moon of sufficient mass to stabilize the tilt of the




planet’s rotation
Plate tectonics
An oxygen-rich atmosphere
A sweeper planet to deflect space debris (comets)
Planetary neighbors that have non-eccentric orbits
And how will we know a planet supports life?
Look for evidence
of oxygen
Analyze the
reflected light from
the planet to see if
the planet has an
atmosphere
Look for liquid
water
Look for signs of
biological activity
(methane)
and rule out other explanations.
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Two Key Terms
 Habitable Zone - the zone around a star where a planet
could experience temperatures like those on Earth and
life as we know it could exist
 Goldilocks planet - is a term for a planet that falls
within a star's habitable zone, specifically used for
planets close to the size of Earth