NASA’s TESS Mission Discovers Ultra-Short-Period Super-earth Around M-Dwarf Star

Throughout the universe, planets with orbital periods shorter than one day are rare and have formation histories that are not completely understood. In a new study, an international team of astronomers has detected a new ultra-short-period exoplanet using NASA's TESS mission. Their findings are reported in the paper "Wolf 327b: A new member of the pack of ultra-short-period super-Earths around M dwarfs."

Goals of TESS Mission

The Transiting Exoplanet Survey Satellite (TESS) is a NASA mission designed to discover thousands of exoplanets that orbit around the brightest dwarf stars in the sky. It was officially launched in 2018 through a collaboration with the Massachusetts Institute of Technology (MIT).

TESS's prime mission involves a two-year survey of our Solar System. During this stage, the spacecraft focused on monitoring the brightness of stars for periodic drops brought by planet transits. It ended on July 4, 2020, and TESS is now on an extended mission. It currently aims to find planets that range from small, rocky worlds to giant planets, showcasing the diversity of planets in the Milky Way galaxy.

To date, the TESS mission has identified more than 7,000 candidate exoplanets, of which 415 have been confirmed. These celestial bodies are known as TESS Objects of Interest or TOI. Since its launch in April 2018, the space vehicle has been surveying almost 200,000 of the brightest stars near the sun.

New Wolf in the Pack

A team of astronomers led by Felipe Murgas of the University of La Laguna in Spain reports the confirmation of another TOI spotted by TESS. It was reported that a transit signal was identified in the light curve of Wolf 327 in a nearby M-dwarf star. Follow-up photometry, radial velocity (RV) measurements, and high-resolution imaging confirmed the planetary nature of this signal.

Wolf 327 is an exoplanet with a radius of 1.24 Earth radii and is about 2.5 more massive than our planet, yielding a bulk density at a level of 7.24 grams per cubic centimeter. This planet orbits its host star every 13.7 hours at a distance of approximately 0.01 AU. Meanwhile, its equilibrium temperature is estimated to be about 1,000 K.

From these observed properties, experts suggest that Wolf 327 b is a rocky planet with a Mercury-like internal composition. It is also assumed that this exoplanet has a substantial iron core at the center of a small mantle layer. It was also found to possess a negligible hydrogen/helium atmosphere.

Wolf 327's parent star, Wolf 327, is a 4.1-billion-year-old M dwarf of spectral type M2.5, located about 93 light years away from Earth. This star has size and mass that are only 40% of that of the sun, but it has an effective temperature of 3,542 K. Aside from this, its metallicity is estimated to be around -0.17 dex.

From all the results gathered, the researchers noted that this is an interesting addition to the known sample of ultra-short period (USP) planets that orbit M-dwarf stars. This is due to its interesting internal structure and favorable metrics for secondary transit detection with the James Webb Space Telescope (JWST). The research team also reported a high probability that other planets revolve around Wolf 327b since ultra-short-period planets are usually found in multi-planetary systems.