Space Alert: Kepler Mission Discovers 1st Rocky Exo Planet

Planet_Landscape_by_CommanderEVE NASA's Kepler mission confirmed the discovery of its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system. The discovery of this planet, called an exoplanet, is based on more than eight months of data collected by the spacecraft from May 2009 to early January 2010.

"All of Kepler's best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun," said Natalie Batalha, Kepler's deputy science team lead at NASA's Ames Research Center in Moffett Field, Calif. "The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it's beginning to pay off."

Kepler's ultra-precise photometer measures the tiny decrease in a star's brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.

Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet's surface. However, since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our sun and not in the habitable zone.

Kepler-10 was the first star identified that could potentially harbor a small transiting planet, placing it at the top of the list for ground-based observations with the W.M. Keck Observatory 10-meter telescope in Hawaii. Scientists waiting for a signal to confirm Kepler-10b as a planet were not disappointed. Keck was able to measure tiny changes in the star's spectrum, called Doppler shifts, caused by the telltale tug exerted by the orbiting planet on the star.

"The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. "Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come."

Knowledge of the planet is only as good as the knowledge of the star it orbits. Because Kepler-10 is one of the brighter stars being targeted by Kepler, scientists were able to detect high-frequency variations in the star's brightness generated by stellar oscillations, or starquakes. This analysis allowed scientists to pin down Kepler-10b's properties.

There is a clear signal in the data arising from light waves that travel within the interior of the star. Kepler Asteroseismic Science Consortium scientists use the information to better understand the star, just as earthquakes are used to learn about Earth's interior structure. As a result of this analysis, Kepler-10 is one of the most well-characterized planet-hosting stars in the universe.

Using NASA's Spitzer Space Telescope, a team of scientists found in 2008 that at least 20 percent, and possibly the majority (as many as 60 percent) of stars similar to the sun are candidates for forming rocky planets. The Legacy Science Program set out to determine whether planetary systems like ours are common or rare in the Milky Way. What they found is that many, perhaps even most, of the sun-like stars in our galaxy could well harbor Earth-like planets.

The Spitzer team found that at least 1 in 5 neighboring solar-mass stars have the right conditions to have formed terrestrial worlds. This new research indicates that worlds with potential for life may be relatively common.

The astronomers began the study by surveying groups of stars with masses comparable to our sun. The stars were then grouped by age, ranging from three-to-10 million years up to one-to-three billion years old. The Sun is about 4.6 billion years old.

With the Spitzer telescope, the team detected dust at a range of infrared wavelengths. The hottest dust is found at temperatures more than 2,000 degrees Fahrenheit and is detected at the shortest wavelengths, between 3.6 microns and 8 microns. Cool dust at 380 degrees Fahrenheit, and is detected at the longest wavelengths, between 70 microns and 160 microns. Warm dust, between minus 280 and 80 degrees Fahrenheit is traced at 24-micron wavelengths.

Since dust closest to a star is hotter than dust farther from the star, the warm dust likely traces material orbiting the star at distances comparable to the distances found between Earth and Jupiter and the Sun.

"We found that about 10 to 20 percent of the stars in each of the four youngest age groups shows 24 micron emission due to dust," team-leader Meyer said. "But we don't often see warm-dust around stars older than 300 million years. The frequency just drops off. That's comparable to the time scales thought to span the formation and dynamical evolution of our own solar system.”

Other recent studies have collaborated these findings that Earth-like planets could be quite common, hence extraterrestrial life could be relatively common as well.

Scientists are hoping that the next generation of powerful telescopes such as the Giant Magellan Telescope, known as the GMT, which is slated for completion in 2016 in northern Chile, will further shed light on the question.

UA astronomer Phil Hinz points out that "Imaging and spectroscopically characterizing an Earth-like planet is an incredibly difficult task. But if Earth-like planets really are this common, we might just be able to take the first picture of another Earth with the GMT. It's an exciting prospect!"

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