Kepler's Birthday

Johannes Kepler (December 27, 1571 – November 15, 1630) is not a name that most people recognize, but if you are aware of the recent discoveries of new planets, will recognize that many new planets bear his name.  Perhaps the best birthday gift we can give to this scientist is Kepler 22b, the first planet discovered in the habitable zone of a star, an earth possible planet like ours.

Kepler is best known for revealing the secrets of planetary motions. His three laws of planetary motion still apply today, and enabled Newton to give us the law of universal gravitation.
In 1596, Kepler published Mysterium Cosmographicum, where he set out arguments for the heliocentric hypothesis.
In 1609 published Astronomia Nova ... From Motibus Stellae Martis, where he presented his three laws of planetary motion that now bear his name:

• The planets describe elliptical orbits with the sun at one focus.
• The radius vector connecting the planet to the sun describes equal areas in equal times. (law of areas)
• The squares of the periods of revolution (T) are proportional to the cubes of mean distances (a) from the Sun to the planets. T² = k a³, where k is a proportionality constant.

Probably most of us will never use this information in our life, but it does well to remember that those was important intellectual achievements of Western civilization. We could even think to remember Kepler itself and its laws would be enough, but Kepler had more projects, for example, projects of the first glasses for myopia and hyperopia.

NASA Discovers First Earth-size Planets Beyond Our Solar System

This artist's conception illustrates Kepler-20e.
Image credit: NASA/Ames/JPL-Caltech

The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra.

This artist's conception illustrates Kepler-20f.
Image credit: NASA/Ames/JPL-Caltech

Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass.

from NASA