In a significant discovery, astronomers have discovered one of the closest known multiple planetary systems to exist within our neighboring galaxy. The system is located about 10 parsecs or 33 light years from Earth and was identified by NASA’s Transiting Exoplanet Reconnaissance Satellite (TESS). The system was first observed in October 2021 when Michelle Kunimoto, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research and one of the lead discoverers, was analyzing data from TESS.
Adding to the fascination of astronomers, a star, HD 260655, was found at the heart of the system to host no fewer than two Earth-like planets.
Kunimoto observed a pair of periodic dips in starlight from the star HD 260655. It then took advantage of the mission’s science inspection pipeline to check for signals and were soon classified as TESS Objects of Interest (TOIs) or possible planets. While the process of such classification may take several years, the time has been shortened in the case of HD 260655 using archival data.
Kunimoto found that the star HD 260655 has been observed by the High Resolution Echelon Spectrometer (HIRES) as well. It is an instrument operating in Hawaii as part of the Keck Observatory. In addition, the same star was also included in an independent survey conducted by CARMENES, which operates as part of the Calar Alto Observatory in Spain.
Kunimoto and his team approached both HIRES and CARMENES and combined the data. After the collaboration, the existence of the two planets around HD 260655 was confirmed.
“Both planets in this system are among the best targets for studying the atmosphere because of the brightness of their star,” Kunimoto said.
By further studying the TESS data, astronomers determined that the inner planet, HD 260655b, orbits the star every 2.8 days while the outer planet, HD 260655c, orbits every 5.7 days. The inner planet was found to be twice the mass of Earth while the outer planet was three times larger than Earth.
By assessing the density of the two planets, the team concluded that they are terrestrial or rocky like Earth. However, the planets are unlikely to be habitable due to their high temperatures. “We consider this range outside the habitable zone to be too hot to allow liquid water to exist at the surface,” Kunimoto added.