Spotlight: Interesting facts about most-like-Earth exoplanet Kepler-452b

Kepler-452b, the first near-Earth-size planet in the "habitable zone" around a sun-like star confirmed by the U.S. National Aeronautics and Space Administration (NASA), has drawn worldwide attention. The following are a package of interesting facts about it:

1. What is Kepler-452b?

Kepler-452b is 1,400-light-year away within the constellation Cygnus, the Swan. The newly discovered planet is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet.

According to NASA, while Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star Kepler-452 than Earth is from Sun.

Kepler-452 is 6 billion years old, 1.5 billion years older than our Sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.

2. Is Kepler-452b an Earth 2.0?

"This exciting result brings us one step closer to finding an Earth 2.0," said John Grunsfeld, associate administrator of NASA's Science Mission Directorate at the space agency's headquarters in Washington.

Are we alone in the universe? Thanks to Kepler's latest finding, we're taking "one small step in answering that question today," said Grunsfeld.

Scientists say Kepler-452b is like an "older, bigger cousin" to Earth, providing an opportunity to understand and reflect upon Earth's evolving environment. While its mass and composition are not yet determined, previous research suggests that planets with a size of Kepler-452b have a good chance of being rocky.

3. Why is Kepler-452b so special?

Kepler-452b excites scientists because it is the most similar to the Earth-Sun system found yet: a planet at the right temperature within the habitable zone, and only about one-and-a-half times the diameter of Earth, circling a star very much like our own Sun. The planet also has a good chance of being rocky, like Earth, NASA said.

It is the smallest planet to date discovered orbiting in the habitable zone -- the area around a star where liquid water could pool on the surface of an orbiting planet -- of a G2-type star, like our Sun.

Kepler-452b is more similar to Earth than any system previously discovered. And the timing is especially fitting: 2015 marks the 20th anniversary of the first exoplanet confirmed to be in orbit around a typical star.

4. Is there anybody out there?

Ever since the dawn of science, human beings have wondered if there are other earth-like worlds in the universe, which support lives like us. We have looked up into space to try to find such worlds.

"It's awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; longer than Earth. That's a substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet," said Jon Jenkins, Kepler data analysis head at NASA's Ames Research Center in Moffett Field in the western U.S. state of California, who led the team that discovered Kepler-452b.

The Earth-like planet Kepler-452b is located at just the right distance where liquid water could exist. Since liquid water is critical to life on Earth, many scientists believe the search for extra-terrestrial life should focus on planets where liquid water occurs.

Kepler-452b "almost certainly has an atmosphere," Jenkins said, although scientists can't say what it's made of.

5. Is the discovery of Kepler-452b the first of its kind?

The discovery of Kepler-452b is substantial but it's not the first of its kind. Last year, astronomers announced the first Earth-sized exoplanet, Kepler-186f, found orbiting in a star's habitable zone. The main difference between Kepler-186f and Kepler-452b is their host stars. Kepler-186 is a red dwarf whereas Kepler-452b is much more closely related to our Sun.

The first exoplanet orbiting another star like our Sun was discovered in 1995. Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago.

Before Kepler-186f, Kepler-62f and Kepler-22b also were hailed in their days as the most like Earth. Kepler-22b was the first of the Kepler planets found within the habitable zone, and it orbits a star much like our Sun. But Kepler-22b is about 2.4 times Earth's size. And no one knows if it is rocky, gaseous or liquid.

Not all the planets considered to be most like Earth were discovered by using Kepler. Gliese 667C also came to light in 2011, discovered by astronomers combing through data from the European Southern Observatory's 3.6-meter telescope in Chile. Endi