New Earth-sized exoplanet discovered near the Sun

Using NASA’s Kepler spacecraft and the Transiting Exoplanet Survey Satellite (TESS), astronomers have discovered a new Earth-sized exoplanet about 70 light-years from the Sun. The newly discovered exoworld, designated K2-415b, is at least three times as massive as Earth. The discovery was reported in a paper published on February 1 arXiv preprint server.

Kepler is the most prolific planet-hunting telescope, having discovered more than 2,600 exoplanets to date. After the failure of its two reaction wheels in 2013, the mission was renamed K2 to perform high-precision photometry of selected fields in the ecliptic. The revived Kepler spacecraft, operational until November 2018, has discovered hundreds of new extrasolar worlds.

As for TESS, the spacecraft is currently conducting a survey of about 200,000 of the brightest stars near the Sun, looking for passing exoplanets. So far, it has identified more than 6,100 possible exoplanets (TESS Objects of Interest or TOI), of which about 3,000 have been confirmed so far.

Now, an international team of astronomers led by Teruyuki Hirano of the Graduate University for Advanced Studies (SOKENDAI) in Japan reports that an exoplanet originally identified by the K2 mission in the light curve of the M dwarf star K2-415 confirmed by TESS observations.

“The candidate planet was first identified through analysis of the K2 mission’s light curve data and is detected here in the latest data from TESS,” the researchers wrote.

The observations indicated that K2-415b has a radius of approximately 1.015 Earth radii and its mass was calculated to be most likely 3.0 Earth masses. The planet orbits its parent star every 4.018 days at a distance of about 0.027 AU from it. The equilibrium temperature of K2-415b is estimated to be around 400 K.

The host K2-415 is of spectral type M5V and its effective temperature has been measured to be 3,173 K. The star has a radius of about 0.2 solar radii and its mass has been calculated to be about 0.16 solar masses.

Confirmation of the new exoplanet makes K2-415 the closest planet-hosting star from Earth identified by Kepler/K2 missions. In addition, K2-415 is also now one of the lowest-mass stars to host an Earth-like planet.

The paper’s authors emphasized that K2-415b’s proximity to Earth and moderate transit depth make it a potential target for future atmospheric characterization studies of Earth-like planets, particularly those with relatively low temperatures.

“The 22 pc distance and moderate transit depth make K2-415 a good target for future observations, including further RV monitoring (e.g. to search for additional planets) and transit spectroscopy,” the researchers concluded.

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