Space Briefs
Kepler discovers smallest planet yet
NASA’s Kepler mission scientists have discovered
a new planetary system that is home to the smallest
planet yet found around a star similar to our sun.
The planets are located in a system called Kepler37, about 210 light-years from Earth in the constellation
Lyra. The smallest planet, Kepler-37b, is slightly larger
than our moon, measuring about one-third the size of
Earth. It is smaller than Mercury, which made its detection a challenge.
Astronomers think Kepler-37b does not have an atmosphere and cannot support life as we know it. The
tiny planet almost certainly is rocky in composition. Kepler-37c, the closer neighboring planet, is slightly smaller than Venus, while Kepler-37d, the farther planet, is
twice the size of Earth.
The first exoplanets found to orbit a normal star
were giants. As technologies have advanced, smaller
and smaller planets have been found, and Kepler has
shown that even Earth-size exoplanets are common.
“Even Kepler can only detect such a tiny world
around the brightest stars it observes,” said Jack Lissauer, a planetary scientist at NASA’s Ames Research
Center in Moffett Field, Calif. “The fact we’ve discovered tiny Kepler-37b suggests such little planets are
common, and more planetary wonders await as we
continue to gather and analyze additional data.”
Kepler-37’s host star belongs to the same class as our
Sun, although it is slightly cooler and smaller. All three
planets orbit the star at less than the distance Mercury
is to the sun, suggesting they are very hot, inhospitable worlds. Kepler-37b orbits every 13 days at less than
one-third Mercury’s distance from the sun. The estimated surface temperature of this smoldering planet, at
more than 800 degrees Fahrenheit (700 degrees Kelvin), would be hot enough to melt the zinc in a penny.
Kepler-37c and Kepler-37d, orbit every 21 days and 40
days, respectively.
The research team used data from NASA’s Kepler
space telescope, which simultaneously and continuously measures the brightness of more than 150,000
stars every 30 minutes. When a planet candidate transits, or passes, in front of the star from the spacecraft’s
vantage point, a percentage of light from the star is
blocked. This causes a dip in the brightness of the starlight that reveals the transiting planet’s size relative to
its star.
For more information about the Kepler mission, visit:
http://www.nasa.gov/kepler.
Image: NASA/Ames/JPL-Caltech
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