An extrasolar planet larger than the Earth has been discovered orbiting a nearby cool star, thanks to data gathered by NASA’s Kepler/K2 mission.
Artist’s impression of the exoplanet Wolf 503b and its host star. Image credit: Sci-News.com.
The newly-discovered exoplanet, named Wolf 503b, has a radius two times that of Earth and represents one of the best opportunities to date to conduct a detailed study of a planet in the 1-4 Earth radii range.
“The majority of close-in planets found by NASA’s Kepler satellite throughout the past decade are smaller than Neptune, but larger than Earth,” explained Merrin Peterson, an astronomer in the Department of Physics and the Institute for Research on Exoplanets at the University of Montreal, Canada, and co-authors.
“However, recent studies of the distribution of planets within the 1-4 Earth radii range have revealed a significant drop in the population — called the Fulton gap — between 1.5 and 2 Earth radii. The origin of this division is not well understood.”
“With its measured radius near the gap in the planet radius and occurrence rate distribution, Wolf 503b offers a key opportunity to better understand the origin of the Fulton gap as well as the nature of the intriguing populations of super-Earths and sub-Neptunes as a whole.”
Wolf 503b orbits its parent star once every 6 days at a distance of only 0.057 AU (astronomical units).
Peterson and colleagues estimate the planet’s temperature to be about 990 degrees Fahrenheit (532 degrees Celsius).
Its host star, Wolf 503 (also known as HIP 67285, 2MASS J13472346-0608121, and EPIC 212779563), is a bright, high proper motion star with a spectral type of K3.5V.
The star is located 145 light-years from Earth and is approximately 11 billion years old, whereas the Sun is only 4.6 billion years old.
It has a radius about 69% that of our Sun, a mass 68.8% that of the Sun, and a surface temperature of 8,029 degrees Fahrenheit (4,443 degrees Celsius).
According to the team, the Wolf 503 system is an ideal target for detailed characterization with both current telescopes and the forthcoming James Webb Space Telescope (JWST).
“The brightness of the host star makes Wolf 503b a prime target for prompt radial velocity follow-up, Hubble Space Telescope transit spectroscopy, as well as detailed atmospheric characterization with JWST,” the astronomers said.
A paper describing the discovery is publicly available at arXiv.org.
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Merrin S. Peterson et al. 2018. A 2 Earth Radius Planet Orbiting the Bright Nearby K-Dwarf Wolf 503. arXiv: 1806.03494
