Exoplanets & Habitability
What is an exoplanet?
A planet that orbits a star outside our solar system
What shape did Kepler discover planets orbit in?
Ellipse
What force keeps planets in orbit around the Sun?
Gravity
What does eccentricity measure?
How circular or stretched an orbit is
What is a satellite?
An object that orbits another object
What do scientists look for to determine if an exoplanet could support life?
Liquid water, habitability, size, orbit
What is Kepler’s First Law?
Planets move in ellipses with the star at one focus
What two forces must be balanced to keep an object in orbit?
Momentum & Gravity
Which planet in our solar system would have the shortest period of revolution in our Solar System?
Mercury
Why do scientists care about the "habitable zone"?
Scientists want to see if there is possible life.
Why is a planet’s orbit shape important for habitability?
It affects whether the planet stays in the habitable zone
What part of the orbit tells us the average distance from the planet to the star?
Semi-major axis
Why doesn’t the Moon crash into Earth or fly away into space?
Because of the balance between gravity and its forward motion (Velocity)
Which exoplanet has the most elongated orbit? Massive Exoplanets or Smaller Exoplanets?
Massive Exoplanets
What word describes how likely a planet is to have the right conditions for life, such as liquid water and the right temperature?
Habitability
What do many small Earth-sized exoplanets have in common with our solar system’s planets?
Nearly circular orbits
What are the two foci in an orbit?
The star and the center of mass
What happens if you turn off gravity in a simulator?
The object moves in a straight line instead of orbiting
Based on the graph of distance vs. orbital period, what is the relationship?
The longer the distance the longer the orbital period.
How has our view of planetary systems changed since discovering exoplanets?
We now know most stars have planets, and orbits vary
Why is a circular orbit better for life than a highly eccentric one?
It supports a more stable climate year-round
What does a high eccentricity number mean?
The orbit is more stretched or elongated
Why do planets farther from the Sun have longer orbital periods?
Hint: Think Gravity, Think Distance
They have weaker gravity from the Sun and travel a longer distance
How do you find the distance between foci using eccentricity and the major axis?
Distance = eccentricity × major axis
Why are exoplanets hard to see directly?
They're far away, dim, and close to their bright stars