The Kepler space telescope discovered two Earth-sized planets for the first time

However, unlike the planet that NASA announced a few weeks ago that is 2.5 times the diameter of Earth, but is in the habitable zone - the two new planets are too hot to sustain life  

NASA's space telescope has discovered the first two Earth-sized planets orbiting a sun similar to ours. The planets, known as Kepler-20e and Kepler-20f, are too close to their star to be in the so-called "habitable zone," where water can exist in a liquid state on the planet's surface, but they are important anyway because they are the smallest planets that have been confirmed. So far, orbiting a star similar to our sun.
The discovery marks the next important milestone in the search for Earth-like planets. These planets are supposed to be rocky. Kepler-20e is slightly smaller than Venus, 0.87 Earth radii. Kepler-20f is slightly larger than the Earth - its radius is 1.03 Earth radii. The two planets together with three other planets orbit the planet Kepler 20, which is about a thousand light-years away from us in the direction of the Navel group.
Kepler-20e orbits its sun once every 6.1 days while Kepler-20f does so once every 19.6 days. These short years mean warm and unlivable worlds. Kepler-20f for example, whose surface temperature reaches 430 degrees Celsius is similar to the planet Mercury. The surface temperature of Kepler-20e is over 750 degrees Celsius, a temperature at which glass melts.
"Kepler's main goal is to find Earth-sized planets in the habitable zone," says François Persin of the Harvard-Smithsonian Center for Astrophysics in Massachusetts, lead researcher of a study published in the journal Nature. "This discovery demonstrates the first real Earth-sized planets around other stars that we are able to discover."
As mentioned, the Kepler 20 planetary system includes three more planets that are larger than Earth but smaller than Neptune (Neptune). Kepler 20b, the closest of them, the third Kepler 20c and the fifth Kepler 20d, orbit the star in orbits that are 3.7, 10.9 and 77.6 days respectively. All five planets are in an orbit similar to that of Mercury in our solar system. The parent star belongs to the same spectral type as our sun - type G, although it is slightly smaller and colder.
This solar system is arranged in an unexpected arrangement. In our solar system, the small rocky planets orbit close to the Sun, and the large - the gaseous planets, orbit it from a greater distance. For comparison, the planets of Kepler 20 are arranged in a different way: big, small, big, small, big.
"The Kepler data continue to reveal new insights about the variety and possibilities for arranging solar systems in our galaxy," says Jackel Leeser, a planetary scientist and member of the Kepler team at NASA's Ames Center in California.
The Kepler space telescope locates planets and planet candidates by measuring dimming in the brightness of over 150 stars in search of planets crossing in front of them (suggestion: creating an eclipse). The telescope team requires at least three passes to confirm the signal received from the telescope as a planet.
Kepler crew members are also using ground-based telescopes and the Spitzer Space Telescope to repeat observations of the candidate planets that the Kepler space telescope has detected. The field of stars is in the Cygnus and Harp constellations and is visible from ground-based observatories from spring to early fall (in the Northern Hemisphere). These observations also help the validity of the discovery of the planets. To discover these two planets, the astronomers used a computer program known as Blender, which runs a simulation to check that it is not another astronomical phenomenon that causes the deception that it is a planet.

Kepler crew members are also using ground-based telescopes and the Spitzer Space Telescope to repeat observations of the candidate planets the spacecraft has spotted. The field of stars is in the constellations Cygnus and Harp and is visible from ground observatories from spring to early autumn. These observations are also helpful for planetary attacks. To discover these two planets, the astronomers used a computer program known as Blender, which runs a simulation to check that it is not an astronomical phenomenon that misleads into thinking that it is a planet.
About two weeks ago on December 5, 2011, scientists announced the planet Kepler 22b which is in the habitable zone of its parent star, but is likely too large to have rocky ground. The two now discovered around Kepler 20 are the size of Earth but are too close to their sun to have liquid water on their surface. "In this game of hide and seek, finding planets of the right size and temperature is just a matter of time." says Natalie Bathela, Kepler's Deputy Chief of Science and Professor of Astronomy and Physics at the University of San Jose. "Kepler's most important discoveries are still ahead of us".

 For information on the NASA website