WASP-161b

Lore & Background

WASP-161b was discovered as part of the Wide Angle Search for Planets (WASP) survey. The discovery team, led by Khalid Barkaoui of Cadi Ayyad University, used additional telescopes including TRAPPIST-North at the Oukaïmeden Observatory, TRAPPIST-South, and SPECULOOS-South to confirm the planet initially detected by WASP. The discovery was announced in 2018 alongside two other planets around the stars WASP-163 and WASP-170.

The planet was later named Isli, and its host star Tislit, as part of the 2019 NameExoWorlds campaign during the 100th anniversary of the IAU. The system was assigned to Morocco, chosen because it hosts the first exoplanet with a discovery team led by a Moroccan astronomer. The names derive from the Tislit and Isli lakes in the Atlas Mountains of Morocco, near Imilchil, meaning bride and groom in the Amazigh language, referencing a local legend of a heartbroken couple.

A 2022 study reported evidence for transit-timing variations of WASP-161b, possibly due to orbital decay or precession, but this was not confirmed by a subsequent study in 2023.

Reader's Guide

WASP-161b holds significance as the first exoplanet discovered by a team led by a Moroccan astronomer, marking a milestone in the internationalization of exoplanet research. Its system was selected for naming in the 2019 NameExoWorlds campaign, with Morocco assigned the star and planet, resulting in the names Tislit and Isli after lakes in the Atlas Mountains. The names carry cultural meaning from Amazigh language and local legend, linking astronomical discovery to Moroccan heritage. The planet's discovery involved a collaboration of telescopes including TRAPPIST-North at the Oukaïmeden Observatory in Morocco, TRAPPIST-South, and SPECULOOS-South, demonstrating the use of multiple facilities to confirm WASP detections. The 2018 announcement placed WASP-161b among three planets announced together. Subsequent studies have examined transit-timing variations, with a 2022 study suggesting possible orbital decay or precession, though a 2023 study did not confirm this, leaving the dynamical behavior of the planet unresolved. As a massive hot Jupiter, it contributes to the population of close-in giant planets studied for atmospheric and orbital evolution.

Did You Know?

• The names mean bride and groom in the Amazigh language, from a local legend.
• A 2022 study suggested transit-timing variations possibly due to orbital decay, but a 2023 study did not confirm this.

The Host Star and Its Place in the Sky

WASP-161, now known as Tislit, is an F-type main-sequence star located roughly 1,162 light-years from Earth in the constellation Puppis. At 356 parsecs, it sits at a considerable distance, and with an apparent magnitude of 11.1, it is far too dim for any observer to spot without optical aid. Despite its modest brightness, the star serves as the anchor for a planetary system that has drawn international attention. It hosts one confirmed exoplanet, making it a single-planet system as of current knowledge. The star's designation traces back to the Wide Angle Search for Planets survey, which identified it as a candidate host for transiting worlds. Its F-type classification places it in a spectral category slightly hotter and more massive than the Sun, offering a distinct environment in which its giant planet orbits. The combination of its distance, faintness, and the survey pipeline that flagged it all contribute to the story of how a star invisible to the naked eye became part of a broader narrative about exoplanet discovery.

A Name Rooted in Moroccan Heritage

The naming of this system carries deep cultural significance. During the 2019 NameExoWorlds campaign, organized to mark the International Astronomical Union's centennial, each participating country was assigned a star-planet pair to christen. Morocco received WASP-161 because its planet was the first exoplanet discovered under the leadership of a Moroccan astronomer. The approved names—Tislit for the star and Isli for the planet—draw from two lakes nestled in the Atlas Mountains near the village of Imilchil. In the Amazigh language, these words translate to "bride" and "groom," evoking a local legend of a heartbroken couple. This choice transforms a catalog designation into a story tied to a specific landscape and oral tradition. The connection between the discovery team's national identity and the naming process highlights how exoplanet science can intersect with cultural heritage, giving a small country a permanent place in the sky through a name that resonates with its own mythology and geography.

Discovery and Multi-Telescope Confirmation

The planet now called Isli is a massive hot Jupiter whose existence was first flagged by the Wide Angle Search for Planets survey using the transit method. The discovery team, led by Khalid Barkaoui of Cadi Ayyad University, did not rely on a single instrument. To confirm the initial WASP detection, they turned to a network of other telescopes, including TRAPPIST-North stationed at the Oukaïmeden Observatory, TRAPPIST-South, and SPECULOOS-South. This multi-site, multi-instrument approach is characteristic of modern exoplanet validation, where a candidate signal must be corroborated across independent observatories before it is accepted as a genuine planetary transit. The announcement came in 2018, bundled with two additional newly confirmed planets orbiting the stars WASP-163 and WASP-170. The involvement of Moroccan-led science in a globally coordinated observing campaign underscores how discovery pipelines increasingly span continents and institutions, with a single team weaving together data from northern and southern hemispheres to establish a new world.

Orbital Mysteries and Unresolved Questions

Since its confirmation, Isli has attracted follow-up research probing the subtleties of its orbit. A 2022 study reported evidence of transit-timing variations in the planet's passage across Tislit's disk, suggesting the possibility of either a slow orbital decay or a gradual precession of its orbital plane. Such variations, if real, would hint at dynamical interactions—perhaps with an unseen companion or with the star's own gravitational field—that could reshape our understanding of the system's long-term stability. However, a subsequent study published in 2023 failed to confirm the earlier findings, leaving the question open. The planet's orbit thus remains an active area of investigation rather than a settled fact. For a hot Jupiter orbiting an F-type star at a distance of over a thousand light-years, the inability to definitively resolve whether its path is subtly shifting underscores the challenges of precision timing observations at such ranges and the importance of continued monitoring in exoplanet science.