NASA announced on Thursday that a planet near the size of the Earth has been discovered via the planet-hunting Kepler space telescope. It's been hailed as "the Earth's closest twin".
It's been estimated that the planet has 98 percent of similarity to the Earth.
Many netizens say that the Earth's "closest cousin" has been found, while many scientists also say they've found Earth 2.0.
Confirmation of the discovery also brings the total number of planets found by to 1,030.
Profile of Kepler-452b
Kepler-452b, located in the constellation Cygnus which is 1,400 light years from the Earth, is one of the 12 exoplanet candidates discovered with diameters between 1 to 2 times that of the Earth.
All of those candidates orbit in the so-called habitable zones of their host stars, where conditions are not too hot or cold, enabling them to potentially support life.
NASA experts have predicted that there might be liquid water and air atmosphere on the planet's surface, and the temperature might be suitable for aminimals similar to humans to survive.
Kepler 452b accompanies a star with characteristics very similar to those of the Sun - it is 4 percent larger in mass and 10 percent brighter. Kepler-452b orbits its star at the same distance as the Earth orbits the Sun.
It takes 385 days for Kepler-452b to travel around its parent star, which means a year on the planet is 5 percent longer than that on Earth.
Still a Long Way to Go
However, the new breakthrough does not mean another "Earth" has been discovered, since the Kepler space telescope could only measures the planet's size and its distance from its parent star. The mass and the density of Kepler 452b has yet to be measured.
Therefore, scientists can't determine whether the planet is a rocky planet like the Earth, making the label "another Earth" pre-mature.
But NASA still believes that the discovery is a milestone, taking us one step closer to "finding another Earth".
The Road to Exploring Habitable Planets
NASA's Kepler space telescope was launched in March 2009. It has accumulated a list of accomplishments in the past six years.
In December 2011, two planets similar to the Earth were found - the Kepler-20e and the Kepler-22b.
Kepler-20e, smaller than the Earth, orbits a Sun-like star slightly cooler and smaller than the Sun. But the surface temperature on the planet reaches 726 degrees Celsius, making the existence of life, atmosphere and liquid water unlikely.
Kepler-22b is more than twice the size of the Earth and 600 light years from it. The surface temperature is only 22 degrees Celsius. But it's still not known whether it's a rocky star like the Earth.
Kepler-186f was discovered in April 2014, and it's 492 light years away from the Earth.
It is the first Earth-size planet found in the habitable zone of a small, cool M dwarf about half the size and mass of our Sun.
Kepler-186 is a miniature solar system that would fit entirely inside the orbit of Mercury. The habitable zone of Kepler-186 is very small compared to that of Kepler-452 or the Sun because it is a much smaller and cooler star.
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