The technology of planet hunting
Kepler is the first NASA mission capable of finding Earth-sized planets around other stars.
Keplerv Telescope
Kepler, named after the noted German astronomer Johannes Kepler who invented the Keplerian Telescope, is the first NASA mission capable of finding Earth-sized planets around other stars. Launched in 2009, its main goal is to generate a base estimate, or census, of the number of such planets orbiting within habitable zones, where conditions are right for liquid water to exist.
The instrument package doesn’t orbit the Earth in a satellite: It’s housed within a spacecraft 9 feet in diameter and 15.3 feet in height, that orbits the sun, trailing our home planet.
Kepler uses a very wide field telescope and a photometer — an instrument for measuring the intensity of light — to measure brightness variations in more than 156,000 stars simultaneously. It takes these readings every 30 minutes because transits can require from an hour to half a day, depending on the planet’s orbit and the type of star involved.
The Cygnus-Lyra neighbourhood (constellations in the Milky Way) was chosen as the study area because it is well-populated with stars and lies high enough above the Earth’s orbital plane that the sun, Earth and moon won’t get in the way of Kepler’s observations. The stars are between 600 and 3,000 light-years away. Kepler finds planets via the photometric or transit method, which entails detection of the small drop-off in a star’s brightness occurring when an orbiting planet passes between the star and the viewer. Once the data analysis identifies a dimming event, scientists look for further dips of the same magnitude, duration and period to confirm the planet’s existence.
This is no easy task: An Earth-sized planet crossing in front of a sun-sized star dims its light by a mere 0.01 percent. Scientists at NASA like to say that detecting such a tiny dip is like “spotting a flea crawling across a headlight from several miles away”. Bigger planets, like those of the size of Jupiter, cast a bigger shadow. Nevertheless, viewed from outside our solar system, Jupiter’s transit only reduces our sun’s brightness by 1 to 2 percent. So far the Kepler telescope has spotted 2,326 candidate planets outside our solar system with 139 of them potentially habitable ones. Even though the confirmed Kepler-22b is a bit big, it is still smaller than most of the other candidates. It is closest to Earth in size, temperature and star than either of the two previously announced planets in the zone.
Published in The Express Tribune, December 10th, 2011.
Kepler, named after the noted German astronomer Johannes Kepler who invented the Keplerian Telescope, is the first NASA mission capable of finding Earth-sized planets around other stars. Launched in 2009, its main goal is to generate a base estimate, or census, of the number of such planets orbiting within habitable zones, where conditions are right for liquid water to exist.
The instrument package doesn’t orbit the Earth in a satellite: It’s housed within a spacecraft 9 feet in diameter and 15.3 feet in height, that orbits the sun, trailing our home planet.
Kepler uses a very wide field telescope and a photometer — an instrument for measuring the intensity of light — to measure brightness variations in more than 156,000 stars simultaneously. It takes these readings every 30 minutes because transits can require from an hour to half a day, depending on the planet’s orbit and the type of star involved.
The Cygnus-Lyra neighbourhood (constellations in the Milky Way) was chosen as the study area because it is well-populated with stars and lies high enough above the Earth’s orbital plane that the sun, Earth and moon won’t get in the way of Kepler’s observations. The stars are between 600 and 3,000 light-years away. Kepler finds planets via the photometric or transit method, which entails detection of the small drop-off in a star’s brightness occurring when an orbiting planet passes between the star and the viewer. Once the data analysis identifies a dimming event, scientists look for further dips of the same magnitude, duration and period to confirm the planet’s existence.
This is no easy task: An Earth-sized planet crossing in front of a sun-sized star dims its light by a mere 0.01 percent. Scientists at NASA like to say that detecting such a tiny dip is like “spotting a flea crawling across a headlight from several miles away”. Bigger planets, like those of the size of Jupiter, cast a bigger shadow. Nevertheless, viewed from outside our solar system, Jupiter’s transit only reduces our sun’s brightness by 1 to 2 percent. So far the Kepler telescope has spotted 2,326 candidate planets outside our solar system with 139 of them potentially habitable ones. Even though the confirmed Kepler-22b is a bit big, it is still smaller than most of the other candidates. It is closest to Earth in size, temperature and star than either of the two previously announced planets in the zone.
Published in The Express Tribune, December 10th, 2011.