A Search for Habitable Planets Transit Tracks: Finding Extrasolar Planets a science & math activity

A Search for Habitable Planets “transit”

A Search for Habitable Planets “transit”

A Search for Habitable Planets “transit”

A Search for Habitable Planets What’s this?

A Search for Habitable Planets A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, so that Venus blocks a small spot of the Sun’s disk. Since the Sun is over 100 times larger in diameter than Venus, the spot is very small indeed.

A Search for Habitable Planets Account of Jeremiah Horrock’s observations of the transit of Venus

A Search for Habitable Planets TIME BRIGHTNESS 0 0 Imagine you have a light sensor aimed at the star. What would the transit of a book look like if you made a graph of light intensity vs time?

A Search for Habitable Planets Like this? TIME 0 0 BRIGHTNESS

A Search for Habitable Planets What would the transit of a planet look like if you made a graph of light intensity vs time? TIME 0 0 BRIGHTNESS

A Search for Habitable Planets TIME 0 0 Perhaps like this? Such graphs are called “light curves.” How would a planet’s size and orbit period affect the transit—light curve? BRIGHTNESS

A Search for Habitable Planets The light curve can lead to finding the SIZE of the planet and its DISTANCE from the star. Why would those characteristics be important?

A Search for Habitable Planets

Is there a relationship between the planet’s period (time for one orbit) and how its distance from the star?

A Search for Habitable Planets Kepler’s 3 rd Law

A Search for Habitable Planets

A 3 = p 2

A Search for Habitable Planets

Kepler 4-b

A Search for Habitable Planets

Planet’s Size: Deducing the Planet’s Radius from Transit Data A p /A s = Z Converting to a percentage 100 ( A p /A s ) = Z% 100 (π r p 2 / π r s 2 ) = Z% 100 ( r p 2 / r s 2 ) = Z% r p 2 / r s 2 = Z%/100 r p 2 = r s 2 (Z%/100) r p = r s /10 √ Z% area of a circle = π r 2 The Sun is about 100 times the radius of the Earth. r sun = 100 r earth Substituting: r p = 100 r earth /10 ( √ Z% ) r p = 10 r earth ( √ Z% )

A Search for Habitable Planets

A guy who’s thought a lot about planets ( By permission Sternwarte Kremsmünster)