Johannes Kepler was a German astronomer who made three major discoveries about planetary motion during the Scientific Revolution: (1) planets orbit the sun in ellipses, (2) the time it takes planets to traverse an arc of their orbit is proportional to the area of the sector between the planet and arc, and (3) there is an exact relationship between the squares of planetary orbital periods and the cubes of their orbital radii. Kepler disproved Nicolaus Copernicus's theory that planets orbit in perfect circles. The NASA Kepler Mission, launched in 2009, searches for Earth-sized planets using the transit method and has discovered over 1,000 exoplanets so far.

1. Bell Ringer 2/19/2016
1. How did Johannes Kepler contribute to the
Scientific Revolution?
2. Who’s theory did Kepler disprove?

2. Kepler’s Discovery
German astronomer who discovered three major laws
of planetary motion:
(1) the planets move in elliptical orbits with the Sun at one
focus;
(2) the time necessary to traverse any arc of a planetary orbit is
proportional to the area of the sector between the central body and
that arc (the “area law”); and
(3) there is an exact relationship between the squares of the
planets’ periodic times and the cubes of the radii of their orbits (the
“harmonic law”).
• He regarded them as celestial harmonies that reflected God’s
design for the universe.
• Kepler’s discoveries turned Nicolaus Copernicus’s Sun-centered
system into a dynamic universe, with the Sun actively pushing
the planets around in noncircular orbits.

3. Kepler Inspires Today!
• In 2001 NASA created a mission that honors
astronomer Johannes Kepler!
• The Kepler Mission is a NASA Discovery Program
for detecting potentially life-supporting planets
around other stars. All of the extrasolar planets
detected so far by other projects are giant
planets, mostly the size of Jupiter and bigger.
Kepler is poised to find planets 30 to 600 times
less massive than Jupiter.

4. How the Kepler Mission Works…
• By a method known as the transit method of planet
finding. When we see a planet pass in front of its
parent star it blocks a small fraction of the light from
that star. When that happens, we say that the planet
is transiting the star.
• If we see repeated transits at regular times, we have
discovered a planet! From the brightness change we
can tell the planet size. From the time between
transits, we can tell the size of the planet's orbit and
estimate the planet's temperature. These qualities
determine possibilities for life on the planet.

5. What is Kepler??
• The Kepler satellite has a 0.95-meter diameter
telescope that is a photometer having a field of view a
bit over 10 degrees square (and area of sky the size of
about two open hands). It is designed to continuously
and simultaneously monitors brightnesses of 100,000
stars brighter than 14th magnitude in the
constellations Cygnus & Lyrae.
• To detect an Earth-size planet, the photometer must
be able to sense a drop in brightness of only 1/100 of
a percent. This is akin to sensing the drop in
brightness of a car's headlight when a fruitfly moves
in front of it! The photometer must be spacebased to
obtain this precision.

6. Kepler was launched in
March 2009
• The overall size is about
2.7 meters (nine feet) in
diameter and 4.7 meters
(15.3 feet) high.
• The total mass at launch
was 2,320.1 pounds
• The Kepler Mission life
cycle cost is approximately
$600 million. This includes
the design, construction,
launch and operation of
the spacecraft as well as
the scientific analysis of
the data.

7. Kepler-425b
• In a press conference (2015 July 23), NASA's
Kepler team announced discovery of planet
Kepler-452b which has the closest match of
planet characteristics to Earth: 60% larger
than Earth, orbiting a Sun-like star in a 385 day
orbit period, that puts it in the star's habitable
zone. [Kepler confirmed planet count is now
1030.]

10. Comparing Informational Texts
• Read the 2 passages on the handout.
• Using the reading, answer the multiple choice
questions
• After answering the questions, complete the
essay. Pay close attention to what the prompt
is asking and be sure to respond
appropriately!