An international team, including University of Geneva researchers, discovered a super-Earth named TOI-512 b orbiting a star cooler than our Sun. The high-precision ESPRESSO spectrograph made this possible. The planet’s density is similar to Earth’s, at 1.02 times.
Astronomers detect exoplanets using two methods: the transit method and radial velocity. The transit method observes a star’s light dimming as a planet passes in front, while radial velocity tracks changes in a star’s movement caused by a planet.
Transit is faster and more efficient, as it can observe thousands of stars simultaneously, unlike radial velocity, which examines stars individually.
In recent years, the transit method has become the favored technique for detecting exoplanets. However, it often yields false positives, requiring confirmation through the radial velocity method to ensure the planet’s presence.
Additionally, while the transit method identifies potential planets, it cannot measure their mass, an essential detail for understanding their nature. The radial velocity technique is needed for this.
Together, these methods work in harmony: the transit method spots numerous candidates, which are then verified using global spectrographs, providing key data like planetary masses. This collaborative approach has revolutionized the study of exoplanets.
The TESS space telescope stands out as a highly productive transit program, identifying over 7,000 exoplanet candidates since its launch in 2018. Meanwhile, ESPRESSO, the world’s most precise spectrograph, excels in radial velocity measurements, with its design and construction led by the University of Geneva (UNIGE).
One of ESPRESSO’s key observation programs, “Working Group 3 (WG3): TESS follow-up,” is guided by the UNIGE Department of Astronomy. This program focuses on confirming the planetary nature of candidates discovered by TESS, aiming to deepen scientific understanding of the transition between rocky and gaseous planets.
Earth and Venus are the largest rocky planets in our solar system, while Uranus and Neptune are the smallest gaseous ones, with masses 14.5 and 17.1 times that of Earth. Interestingly, there’s no planet between these mass ranges in our system.
However, across the galaxy, planets with masses between 3 and 10 times that of Earth are very common. If their density resembles Earth’s, they’re called super-Earths and are likely rocky. If their density is closer to Neptune’s, they’re called mini-Neptunes and are probably gaseous.
Exoplanets are common, with most stars likely hosting their own planets, many of which are super-Earths or mini-Neptunes. However, discovering them is challenging and takes years. For example, finding TOI-512 b required over two years of TESS observations, 37 nights of ESPRESSO data collection, and months of detailed analysis by an international team.
TOI-512 b, a super-Earth, has a material density similar to Earth, with 1 cm³ weighing 5.62 grams compared to Earth’s 5.51 grams. It has a mass 3.5 times that of Earth and is 1.5 times larger in radius.
Orbiting a K-type star cooler than our Sun (5000°C), TOI-512 b completes its orbit in just over 7 Earth days. Its properties place it in the transition zone between rocky and gaseous exoplanets.
“The precision of ESPRESSO has been crucial in characterizing the composition of TOI-512 b. It’s a small addition to the already long list of known planets, but such discoveries are essential to improve our understanding of planet formation and evolution mechanisms.”
“Many more will be needed to transform our hypotheses into scientific certainties,” concludes José Rodrigues, a doctoral student at the Porto Institute of Astrophysics and the first author of the discovery.
Journal Reference
- J. ROdrigues, S.C. C. Barros et al. TOI-512: Super-Earth transiting a K-type star discovered by TESS and ESPRESSO★. Astronomy & Astrophysics. DOI: 10.1051/0004-6361/202452887
Source: Tech Explorist
