Astronomers using NASA’s TESS satellite and the historic 1.93-meter telescope at the Observatoire de Haute-Provence have discovered two mini-Neptunes and a massive super-Jupiter. The findings include TOI-2141 b in a primitive 7.5-billion-year-old system and TOI-1736 c, a gas giant ninety-nine times wider than Earth.
Re-aiming the very instrument that first detected an exoplanet orbiting a Sun-like star has yielded a fresh bounty of distant worlds. Researchers leveraging a mix of space-based transit data and ground-based spectroscopy have identified planetary systems that challenge our understanding of how giant planets form and evolve around mature stars. These observations were conducted using the Transiting Exoplanet Survey Satellite (TESS) of NASA and the 1.93-meter telescope at the Observatoire de Haute-Provence (OHP), in France.
TOI-2141: A Mini-Neptune Around an Ancient Sun-like Star
The first system, named TOI-2141, is located about 250 light-years from Earth. The central star, although similar in size to ours, appears to be older due to a lack of heavier chemical elements than hydrogen and helium. Indeed, this characteristic generally means that a star has a more primitive chemical composition, similar to that of the oldest stars. These stars formed from primordial gas composed mainly of hydrogen and helium. Over time, successive generations of stars enriched the interstellar medium with heavier elements. Here, the team estimates that this star is about 7.5 billion years old. For comparison, our star is about 4.6 billion years old.
The main planet of this system, TOI-2141 b, is a mini-Neptune, about three times larger than Earth, with a mass 24 times greater. It orbits very close to its star at a distance of 19 million kilometers. Moreover, its temperature reaches 450 degrees Celsius. TOI-2141 b also seems to be composed of a rocky core surrounded by a water vapor atmosphere.
TOI-1736: A Binary System Hosting a Massive Super-Jupiter
The second system, TOI-1736, is located about 290 light-years from Earth. It stands out because it is a binary system. Although the main star is similar to the Sun in terms of size, temperature, and age (about 4.9 billion years), it has a smaller companion star.
Two planets have been discovered in this system: TOI-1736 b, a mini-Neptune about 2.5 times larger than Earth with a mass thirteen times greater, and TOI-1736 c, a massive “super-Jupiter.” This world, 99 times larger and about 2,800 times more massive than Earth, would be located in the habitable zone of its star. TOI-1736 c could also potentially have moons with atmospheres conducive to life. For comparison, Jupiter is about eleven times larger than Earth in terms of equatorial diameter.
Tracing Exoplanets from Haute-Provence to Modern Space Surveys
Incidentally, it was with this instrument that astronomers Michel Mayor and Didier Queloz identified 51 Pegasi b in 1995. This was the first exoplanet discovered orbiting a star similar to the Sun.
Researchers plan to further investigate by examining an indicator suggesting the presence of a third planet around TOI-1736 using the OHP’s SOPHIE spectrograph. These discoveries offer a fascinating glimpse into the diversity of planetary systems and contribute to expanding our understanding of the formation and evolution of planets around stars similar to the Sun.
