NASA has announced a major step in its goal of discovering planets beyond our own solar system that may support life.
Its Kepler mission, launched in 2009, has discovered that three of seven "super-Earth-sized" planets orbiting the stars Kepler-62 and Kepler-69 are in a zone that could allow liquid water, essential for developing life.
The five-planet Kepler-62 system is 1,200 light-years from Earth. One of its potentially habitable planets is 60 percent larger than Earth, another 40 percent larger; planets as large as three times the size of Earth are considered to be terrestrial or rocky, as Earth is. Larger planets typically comprise gases or a mixture of gases and rock, and aren't conducive to life.
The two-planet Kepler-69 star system is 2,700 light-years away. One of the planets exists in the inner ring of a habitable zone. But it's unclear whether the temperatures are too hot, like Venus, or more like Earth -- far enough from its host star to have liquid water and an atmosphere with cloud cover.
Justin R. Crepp, a Beaver Falls native and 2003 graduate of Penn State Erie, The Behrend College, has been involved in the NASA project.
"When [the planets] are in the habitable zone, they are the right temperature to have water, which is the Goldilocks region -- not too hot and not too cold," said Mr. Crepp, now an assistant professor of physics at the University of Notre Dame.
During a teleconference Thursday from NASA's Ames Research Center in Silicon Valley, astrophysicists celebrated the historic discoveries, with Ames Center director Peter Warden opening his comments by saying, "This is really cool." Other astrophysicists described the Kepler mission as an overwhelming success, with 122 confirmed planet discoveries to date, and 2,740 candidates that require further analysis.
New space telescopes are necessary to focus on closer star systems to calculate planets' masses, determine whether they have atmospheres and measure their spectra, or bands of light, from which the composition of the planets can be gleaned. Those in habitable zones that have oxygen, carbon dioxide and methane would be prime candidates to support life.
Some of the newly discovered planets also could be "water worlds" completely covered with water, which could support oceanic life and birds.
"Our objective is to explore the [Milky Way] galaxy looking for life, and Kepler is our first step," said Thomas Barclay, a Kepler scientist at the Bay Area Environmental Research Institute in Sonoma, Calif. "The next big thing will be a terrestrial-planet finder, where we can look for atmospheres to determine whether there is carbon dioxide and water, which is what is needed for life. If there is oxygen, it could have bigger animals."
With such discoveries, the Kepler spacecraft has emerged as "a rock star of science," said John Grunsfeld, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington, D.C., in a Kepler mission news release.
"It is only a matter of time before we know if the galaxy is home to a multitude of planets like Earth, or if we are a rarity."
The Kepler mission remains focused on 150,000 stars in the Milky Way galaxy, in the region of the Cygnus and Lyra constellations. It aims to identify planets by continuously measuring star brightness, which dims ever so slightly whenever a planet crosses the face of the star, much like a fly crossing the surface of a ceiling light.
The dimming of starlight at predictable intervals can indicate a planetary orbit. Mr. Crepp analyzes candidate planets to determine whether other cosmological factors, such as a binary star, could explain the dimming of starlight.
Kepler is revolutionizing the field of planetary discovery, he said. "This is the most exciting thing going on. The holy grail is the spectrum of Earth-sized planets in the habitable zone. Kepler tells us that the galaxy is teeming with planets. Numbers of planets exist that have conditions preferable for life."
Last week, NASA approved the Transiting Exoplanet Survey Satellite, or TESS, which will focus on the entire sky rather than one small patch, as Kepler does. TESS along with Doppler equipment Mr. Crepp is developing will work to measure the mass of planets in star systems within 10 light-years of Earth to determine whether they, like Earth, are terrestrial and might support life.
In another important advance, the James Webb Telescope, which NASA is expected to launch in 2017, will analyze planets' spectra, which serve as fingerprints of what elements exist on that planet.
"The spectrum of a planet is where we're all headed as a community, and we need to hit all the steps along the way to reach our goal," Mr. Crepp said. "We are figuring it out slowly but surely."
David Templeton: email@example.com or 412-263-1578.