Kepler space telescope detects possible earth-sized planet outside our solar system!
NASA's scientists have announced that they might have spotted a planet just about 1.5 times the diameter of Earth around a sun-like star 2000 light-years away.
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Scheduled for launch on the 5th of march 2009, the Kepler Mission will use a unique spaceborne photometer specifically designed to search for Earth-sized planets
around stars beyond our solar system. "The KeplerMission will, for the first time, enable humans to search our galaxy for Earth-size or even
smaller planets," said principal investigator William Borucki of the Planetary Systems Branch of the Space Science Division. "With this cutting-edge
capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: are there others like us in the universe?"
The Importance of Planet Detection:
The Kepler Mission is specifically designed to survey the extended solar neighborhood to detect and characterize hundreds of terrestrial and larger
planets in or near the habitable zone and provide fundamental progress and large leaps in our understanding of planetary systems. The
results will yield a broad under-standing of planetary formation, the frequency of formation, the structure of individual planetary systems and
the generic characteristics of stars with terrestrial planets.
The scientific goal of the Kepler Mission is to explore the structure and diversity of planetary systems. This is achieved by surveying a large sample
of dwarf (main-sequence) stars to:
1. Determine the frequency of terrestrial and larger
planets in or near the habitable zone of a wide
variety of spectral types of stars
2. Determine the distributions of planet sizes and
their orbital semi-major axes
3. Estimate the frequency and orbital distribution
of planets in multiple-stellar systems
4. Determine the distributions of semi-major axis,
albedo, size, mass, and density of short-period
5. Identify additional members of each photomet-rically
discovered planetary system using com-plementary
6. Determine the properties of those stars that har-bor
The Kepler Mission supports the objectives of the
Origin's theme and directly contributes to the de-sign
of the Terrestrial Planet Finder as recom-mended
in the NRC 2001 decadal survey.
Overview of the Mission:
Kepler measures repetitive stellar brightness changes on the order of 100 parts per million last-ing for 2 to 16 hours caused by transiting terrestrial
planets. The planet's orbit is calculated from the period of the transits. The size of the planet is calculated from the transit depth. The proposed
differential photometer continuously and simultaneously monitors the brightness of 100,000 dwarf stars for four years; long enough to see four transits
of a terrestrial planet in the habitable zone of a solar-like star. To obtain the required precision, the photometer must be spaceborne; this also eliminates
the day-night and seasonal cycle interruptions of ground-based observing.
Kepler Mission expects to perform a census of planets with periods from days to a few years and to detect:
Transits of terrestrial planets near 1 AU (Astronomical Unit - a distance from earth to sun)
About 50 planets if most have radii about equal to the Earth (R ~ 1.0 R ?)
About 185 planets if most have R ~ 1.3 R ?
About 640 planets if most have R ~ 2.2 R ?
Transits of thousands of terrestrial planets
If most have orbits much less than 1 AU
Modulation of the reflected light of giant inner planets
About 870 planets with periods ?1 week
Transits of giant planets
About 135 inner-orbit planets with albedos for about 100 of these giants
Densities for 35 inner-orbit planets
About 30 outer-orbit planets.
The results likely consist of a mix of all of the above. From these results, NASA can explore the structure and diversity of planetary systems. The
results are also still significant even if no planets are found, since the mission is designed to detect so many terrestrial planets.
The mission is sensitive to a large number of planets even smaller than Earth in short period orbits as a result of the larger number of observed transits.