NASA Kepler mission searches for new Earth-like exoplanets

September 18, 2009, By Thomas Antony

The Kepler space telescope was launched in March 2009, with the mission of discovering Earth-like planets orbiting starts outside the solar system ( exoplanets ) and possibly searching for signs of life on these planets.

Kepler Space Telescope. Courtesy NASA.

Kepler Space Telescope. Courtesy NASA.

The Kepler recently improved the positional data available of a Jupiter-sized exoplanet, HAT-P-7b orbiting a star in the Cygnus constellation, by observing a transit of the planet in front of its home star. HAT-P-7b planet is not a habitable one as it is located very close to its star and has daytime temperatures over 2000 degrees Celsius.  The observation of HAT-P-7b was a test which proved that the Kepler telescope is sensitive enough to detect exoplanets. Additional confirmation tests are expected to follow soon.

The main objectives of the Kepler mission are the following:

  • Determine how many Earth-sized and larger planets there are in or near the ‘habitable zone’ of a wide variety of stars. Habitable zone is that zone around a star where the conditions are just right for liquid water and Earth-like life to exist
  • Determine the range of size and shape of the orbits of these planets.
  • Estimate how many planets there are in multiple-star systems.
  • Determine the range of orbit size, brightness, size, mass and density of short-period giant planets.
  • Identify additional members of each discovered planetary system using other techniques.
  • Determine the properties of those stars that harbor planetary systems.

Kepler detects planets using the ‘transit’ method. A transit happens when a planet passes in front of its parent star causing a slight decrease in the brightness of the star. If this decrease occurs at least twice in a periodic manner, the existence of a plant is assumed.  The amount of dimming depends on the size of the star and the size of the planet. Other methods such as gravitational microlensing, and Doppler/Radial velocity methods are used to confirm the existence of the planet.  Kepler must see at least three transits to be sure the dimming was caused by a planet, and since larger planets give a signal that is easier to check, scientists expect the first reported results will be larger Jupiter sized planets in tight orbits. Smaller Earth-sized planets, and planets further from their parent star will take longer, and discovering planets comparable to Earth is expected to take three years or longer.

Kepler has a much higher probability of detecting Earth-like planets than the Hubble space telescope as it has a much wider field of view of around 100 degrees square which enables it to observe around 100,000 sun-like stars in the Cygnus region of the sky.

Scientists are expecting to find around fifty Earth-like exoplanets during the 3.5 to 6 year long mission. Kepler mission will help bring us one step closer to understanding the nature and extent of other solar systems outside of our own.

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