NASA finds 2 Earth-sized rocky planets 195 light-years away
What's the story
NASA's Transiting Exoplanet Survey Satellite (TESS) has found two rocky exoplanets orbiting a nearby K-type star, TOI-2322. The newly found planets are comparable in size to Earth, with one being Earth-sized and the other larger, and both have short orbital periods. The discovery was detailed in a paper published on the arXiv pre-print server.
TESS's journey
TESS's mission and observations of TOI-2322
Launched in 2018, TESS has been surveying some 200,000 of the brightest stars near the Sun for transiting exoplanets. So far, it has found over 7,600 candidate exoplanets (TESS Objects of Interest or TOI), with 686 confirmed. TOI-2322 is a K4-type star located about 195 light-years away from Earth. It was observed by TESS multiple times between 2018 and 2023.
Exoplanet confirmation
Confirmation of exoplanets around TOI-2322
The presence of exoplanets around TOI-2322 was confirmed by follow-up observations from a team led by Melissa Hobson at the University of Geneva. The planets were first identified as candidates by TESS. They were then confirmed and characterized using radial velocities and activity indicators from the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO).
Planet profiles
Characteristics of TOI-2322 b and c
The inner planet, TOI-2322 b, is Earth-sized with a mass less than 2.03 times that of Earth. It orbits its host every 11.3 days at a distance of about 0.09 AU and has an equilibrium temperature of around 329.95 degree Celsius. The outer planet, TOI-2322 c, is larger with a radius nearly 1.87 times that of Earth and an estimated mass about 18 times greater than Earth's.
Composition analysis
Notable features of TOI-2322 c and host star
TOI-2322 c has a density of 14.69g/cm3, suggesting it is rocky with an Earth-like internal structure. This makes it the largest known planet with an Earth-like composition. The host star, TOI-2322, is about 30% smaller and less massive than the Sun, with an effective temperature of 4,390 degree Celsius. Its age is estimated to be around 3.9 billion years.