Anybody out there?

Print edition : April 19, 2013

Figure 1a: The percentages indicate the increase in the numbers of respective size category planet candidates since the last Kepler catalogue was released, in February 2012. To identify the potential planet candidates, more than 13,000 transit-like signals, called 'threshold crossing events', were analysed to eliminate known spacecraft instrumentation and astrophysical false positives, phenomena that masquerade as planetary candidates.

Figure 1b: A graph/scatter plot of radius vs period for Kepler planet candidates. This plot excludes single-transit events and includes only events with two or more transits.

Figure 2: Kepler's field of view superimposed on the night sky.

Figure 3: New candidates (yellow) in the just-right habitable zone (green bar).

Figure 4: Doppler shift in a star's spectrum: redshift (wavelength increase) of the spectral line as the star moves away; and blue shift (wavelength decrease) of the spectral line as the star approaches. The Doppler shift is converted to variations in the radial velocity of the star.

Figure 5: The drop in brightness of a star when a planet passes in front of it.

Since the mid-20th century scientists have been searching for potentially habitable extrasolar planets, or exoplanets. With the introduction of space-based observation platforms such as NASA’s Kepler Mission, the number of exoplanets that have been found is growing.

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