SJSU in the News: Physics Professor Describes Discovery of Two Earth-Size Exoplanets

“In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University (NASA image).

NASA: Earth-size planets, Kepler-20e and Kepler-20f, discovered

Originally published by The State Column Dec. 20. 2011.

NASA’s Kepler mission trumpeted the discovery of several Earth-size planets circling a sun-like star outside our solar system Tuesday. While Kepler-20e and Kepler-20f (the newly discovered, Earth-size planets) are too close to the sun-like star to be in the “habitable zone,” where the formation of liquid water is possible on a planet’s surface, they are the smallest exoplanets (planets outside our solar system) ever validated around a sun-like star.

For NASA, the monumental discovery is the next milestone in the ongoing search for Earth-like planets. According to a NASA press release, the two Earth-like planets are believe to be rocky. Kepler-20e is a bit smaller than Venus or 0.87 times the radius of Earth. However, Kepler-2of is slightly larger than Earth or 1.03 times the radius of Earth. The Earth-size plants are part of a five-planet system named Kepler-20. Kepler-2o is roughly 1,000 light-years away from Earth in the constellation Lyra.

NASA reports that Kepler-20e circles a sun-like star every 6.1 days, while Kepler 20f orbits the same star every 19.6 days. Both of the Earth-size planets are similar to Earth in size only. The short orbits of the Earth-size planets corresponds to extremely hot and uninhabitable conditions on the planet. For example, Kepler-2of (8000 degree Fahrenheit) is similar to the planet Mercury as far as temperature is concerned. However, Kepler-2oe is even hotter (1,400 degrees Fahrenheit). Kepler-20e would melt glass.

“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, lead author of a new study published in the journal Nature, said in a NASA press release.

“This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them,” Mr. Fressin added.

The Kepler-20 system has other planets that are not Earth-like in size. Three of the other planets are bigger than Earth, but tinier than Neptune. NASA reports that Kepler-2ob, Kepler-20c and Kepler-2od, circle a sun-like star every 3.7 days, 10.9 days and 77.6 days. Additionally, all five planets in the Kepler-20 system have orbits that are similar to Mercury’s orbit. The planets of the Kepler-20 system orbit a star that is a bit smaller and cooler than the sun.

NASA also reports that the Kepler-20 system has a strange arrangement. In our solar system, rocky planets circle close to the sun, while large, gaseous planets circle farther out. However, in the Kepler-20 system, the planets are positioned in alternating size.

“The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system,” Jack Lissauer, planetary scientist and Kepler science team member at NASA’s Ames Research Center in Moffett Field, California, said in a NASA press release.

“The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy,” Mr. Lissauer added.

While scientists are not sure why the Kepler-20 system is arranged the way it is, they do not believe that the planets originated from the locations they are in now. According to NASA, scientists believe that the planets were constructed a greater distance from the sun-like star than they are now and eventually moved closer.

The Kepler space telescope looks for planets and possible planets by looking at “dips” in the brightness of more than 150,00o stars to reveal planets that are “crossing in front, or transiting, their stars.” After three transits, the Kepler science team knows that a planet has been discovered.

The Kepler science team deploys ground-based telescopes and the Spitzer Space Telescope to examine discoveries on possible planets that are located by the spacecraft. However, the star field that Kepler examines in the constellations Cygnus and Lyra can only be seen from ground-based observatories in the spring, summer and early fall. The data from the ground-based telescopes and the Spitzer Space Telescope help scientists confirm the discovery of planets.

Astronomer utilized a computer program called Blender to confirm the discovery of the Earth-size planets, Kepler-20e and Kepler-2of. Blender used simulations to determine whether other “astrophysical phenomena” were disguised as planets.

Back on December 5th, the Kepler team announced the discovery of Kepler-22b. Kepler-22b was found in the habitable zone of its parent star.

“In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University, said in a NASA press release.

“We are on the edge of our seats knowing that Kepler’s most anticipated discoveries are still to come,” Ms. Batalha said.

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