Key Takeaways:

  1. Kepler 438b, located in the Lyra constellation, could be the most Earth-like exoplanet ever found.
  2. It’s slightly larger than Earth, orbits an orange dwarf star, and receives 40% more heat than Earth from its star.
  3. Positioned in the habitable zone, it may possess crucial factors for life: a rocky surface and conditions for liquid water.
  4. Completing an orbit every 35 days, a year on Kepler 438b is 10 times shorter than on Earth.
  5. Detected by NASA’s Kepler telescope, it’s one of eight newly identified planets in their star’s habitable zones.

In a breakthrough astronomical discovery, Kepler 438b, an exoplanet situated in the Lyra constellation, emerges as a potential mirror of Earth. This distant world, approximately the size of our own planet, orbits an orange dwarf star, basking in 40% more radiant heat than Earth receives from the sun. What makes Kepler 438b particularly intriguing is its positioning within the “Goldilocks” zone, where conditions are ideal for the existence of liquid water. These elements—rocky terrain and flowing water—stand as critical indicators for a planet’s potential habitability.

Situated some 470 light years away, Kepler 438b boasts a swift orbital cycle, completing a full revolution around its star every 35 days. This rapid pace translates to a year on Kepler 438b being a mere fraction of the duration on Earth. The planet’s relatively small size, only 12% larger than Earth, significantly raises the likelihood of it being predominantly rocky, a probability researchers estimate at about 70%.

This groundbreaking discovery, along with seven other planets also residing in their star’s habitable zones, was announced by scientists from the Harvard-Smithsonian Center for Astrophysics at a meeting of the American Astronomical Society in Seattle. These findings effectively double the count of small planets—those less than twice Earth’s size—thought to orbit within their parent stars’ habitable zones.

The identification of these planets was facilitated by NASA’s Kepler space telescope, which discerns planets through the periodic dimming of starlight as they transit across their stars’ surfaces. Among these newly found exoplanets, Kepler 442b, located 1,100 light years away in the same constellation, stands out. About a third larger than Earth, it receives roughly two thirds of the starlight Earth enjoys, presenting a 60% probability of being rocky.

Kepler-186f is part of five-planet system 795 lights years away. The find is described in the journal Science as ‘a landmark on the road to discovering habitable planets’. Photograph: Nasa Ames/SETI Institute/JPL-Cal/PA

Lead author Guillermo Torres emphasizes that the combination of size and received light makes Kepler 438b and 442b the most Earth-like exoplanets known beyond our solar system. Their conditions surpass previous contenders, such as Kepler 186f and Kepler 62f, in terms of similarity to Earth. While the presence of atmospheres remains unknown, if they exist, estimated mean temperatures for Kepler 438b and 442b are approximately 60 and zero degrees Celsius, respectively.

To ensure the authenticity of the planets spotted by Kepler, the Harvard-Smithsonian team employed a computer program named Blender. This tool minimizes the likelihood of false sightings that can occur when pairs of stars in the background eclipse one another, mimicking a planetary transit. Out of the 12 suspected planets assessed, 11 were confirmed with over 99.7% certainty.

In the meantime, scientists plan to look for other, indirect signs, that a planet may be well-suited for life. Kipping is searching through the Kepler data for hints that some planets have moons, which can improve their odds of being habitable. Our own moon stabilises Earth’s tilt, making the temperatures far less erratic than they would be otherwise. Alien planets that share a solar system with a gas giant like Jupiter are also interesting, because the vast size of the planet acts as a shield against devastating asteroid and comet impacts.

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