An international team led by the Instituto de Astrofísica de Canarias (IAC) identified a “super-Earth” orbiting the star HD 176986, located about 91 light-years from the solar system.
With this discovery, there are now three known planets around this K-type orange dwarf star, slightly smaller than the Sun.
Background
In 2018, the first two planets of the system were discovered:
- HD 176986 b, with an orbital period of 6.5 days.
- HD 176986 c, with an orbital period of 16.8 days.
After years of observations with state-of-the-art instruments, researchers managed to detect the signal of a third planet, named HD 176986 d.
Characteristics of the new super-Earth
- Minimum mass: less than seven times that of Earth.
- Classification: super-Earth, more massive than our planet but much smaller than gas giants.
- Orbital period: 61.4 days around its star.
- Rarity: only a dozen planets are known with periods longer than 50 days and masses less than seven times that of Earth, making it an exceptional find.
Complexity of the discovery
Detecting planets with such weak signals is a challenge. Scientists had to rule out that the signal came from stellar activity.
- Exhaustive tests were conducted that confirmed its planetary nature.
- Innovative techniques were applied to refine the star’s light spectra and separate the effects of stellar activity.
- The tool Yarara, developed at the University of Oxford, stands out for correcting noise sources that can mimic or hide planetary signals.
Detection method
The planet was discovered using the radial velocity (RV) method, which measures the movement of the star induced by the gravitational pull of the orbiting planets.
- More than 350 nights of observations were collected with different spectrographs.
- One of them is installed at the Telescopio Nazionale Galileo at the Roque de los Muchachos Observatory in La Palma.
Scientific importance
The discovery of HD 176986 d highlights the relevance of prolonged observation campaigns and the use of advanced techniques to detect worlds that are difficult to identify. Moreover, it expands the catalog of known super-Earths and offers new opportunities to study the diversity of planetary systems in the galaxy.
The detection of this new super-Earth reinforces the role of the IAC and Spanish astronomy in the exploration of exoplanets. HD 176986 d adds to a system that already arouses great scientific interest and could provide clues about the formation and evolution of Earth-like planets in environments close to ours.
