AstronomyMilky Way

Kepler has found Earth’s older, larger cousin

This artist's concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun. Kepler-452b orbits its star every 385 days. The planet's star is about 1,400 light-years away in the constellation Cygnus. It is a G2-type star like our sun, with nearly the same temperature and mass. This star is 6 billion years old, 1.5 billion years older than our sun. Credit: NASA Ames/JPL-Caltech/T. Pyle
This artist’s concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun. Kepler-452b orbits its star every 385 days. The planet’s star is about 1,400 light-years away in the constellation Cygnus. It is a G2-type star like our sun, with nearly the same temperature and mass. This star is 6 billion years old, 1.5 billion years older than our sun. Credit: NASA Ames/JPL-Caltech/T. Pyle

Some of the very fundamental questions about our existence – why we are here, what is out there, if we will ever find another planet similar enough to ours to live on – have come another step closer to being solved, today. The latest exciting Kepler Space Telescope planet-hunting discovery was announced by NASA this afternoon. We now know that Earth has a very close cousin – an Earth 2.0 – since Kepler has discovered a new planet that is very similar to Earth, Kepler-452b. It was found in the habitable zone, orbiting its star, Kepler-452, which is similar in size and temperature to our own G2-type star – the Sun. This is the first time the combination has been found.

Sometimes referred to as the “Goldilocks Zone”, the habitable zone is a range of distance where a planet resides that is not too far from and not too close to the star it orbits. This would keep its temperature in the perfect range allowable for water to remain in a liquid state and possibly collect over the surface of the planet. Previously, Earth-like planets had been discovered in the zone, but the combination of factors surrounding Kepler-452b’s existence had yet to be found, until now.

This size and scale of the Kepler-452 system compared alongside the Kepler-186 system and the solar system. 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, cooler star. The size and extent of the habitable zone of Kepler-452 is nearly the same as that of the sun, but is slightly bigger because Kepler-452 is somewhat older, bigger and brighter. The size of the orbit of Kepler-452b is nearly the same as that of the Earth at 1.05 AU. Kepler-452b orbits its star once every 385 days. Credit: NASA/JPL-CalTech/R. Hurt
This size and scale of the Kepler-452 system compared alongside the Kepler-186 system and the solar system. 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, cooler star. The size and extent of the habitable zone of Kepler-452 is nearly the same as that of the sun, but is slightly bigger because Kepler-452 is somewhat older, bigger and brighter. The size of the orbit of Kepler-452b is nearly the same as that of the Earth at 1.05 AU. Kepler-452b orbits its star once every 385 days. Credit: NASA/JPL-CalTech/R. Hurt

There are some interesting facts that have already been uncovered about this new cousin of Earth. The planet resides in the constellation of Cygnus, a mere 1,400 light-years in distance. It takes 385 days to orbit its star – only 5 percent longer than our own orbit of our star, despite it being 60 percent larger in diameter than Earth. Due to its size in comparison with Earth, it is classified as a “super-Earth-size”. The composition and mass of the planet have yet to be known, but if we look at research done on planets of similar size, we can infer that it has a good chance of being rocky in its make-up.

Kepler-452b’s parent star, Kepler-452 is 5 percent further away than the Sun is from Earth, and  at 6 billion years old, it is 1.5 years older than the Sun. While its temperature is the same as that of the Sun, it is 20 percent brighter and has 10 percent larger in diameter.

Since Kepler launched in 2009, twelve planets less than twice the size of Earth have been discovered in the habitable zones of their stars. These planets are plotted relative to the temperature of their star and with respect to the amount of energy received from their star in their orbit in Earth units. The light and dark shaded regions indicate the conservative and optimistic habitable zone. The sizes of the blue disks indicate the sizes of these exoplanets relative to one another and to the image of Earth, Venus and Mars, placed on this diagram for reference. Note that all the exoplanets discovered up until now are orbiting stars which are somewhat to significantly cooler and smaller than the sun. Kepler-452b is the first planet less than twice the size of Earth discovered in the habitable zone of a G-type star. Credit: NASA Ames/N. Batalha and W. Stenzel
Since Kepler launched in 2009, twelve planets less than twice the size of Earth have been discovered in the habitable zones of their stars. These planets are plotted relative to the temperature of their star and with respect to the amount of energy received from their star in their orbit in Earth units. The light and dark shaded regions indicate the conservative and optimistic habitable zone. The sizes of the blue disks indicate the sizes of these exoplanets relative to one another and to the image of Earth, Venus and Mars, placed on this diagram for reference. Note that all the exoplanets discovered up until now are orbiting stars which are somewhat to significantly cooler and smaller than the sun. Kepler-452b is the first planet less than twice the size of Earth discovered in the habitable zone of a G-type star. Credit: NASA Ames/N. Batalha and W. Stenzel

It is not yet known if the planet has the ability to sustain life, but more information about this world will be learned as time goes on. Jon Jenkins, Kepler data analysis lead for NASA’s Ames Research Center in Moffett Field, California, led the team that is credited with the discovery of Kepler-452b. According to Jenkins, “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 substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

John Grunsfeld, Associate Administrator for NASA’s Science Mission Directorate in Washington, mentioned today that when he was growing up, he would look up at the sky and ask himself if there are planets around the stars. Today, we know factually, that many exist, and some are probably like our own blue marble. This is just the beginning of many more thrilling discoveries that will happen in the years to come!

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