TOI-1685 b: A Remarkable Super-Earth Orbiting Close to Its Star
Astronomers continuously push the boundaries of exoplanetary science, revealing worlds that challenge our understanding of planetary systems. One such fascinating discovery is TOI-1685 b, a super-Earth orbiting an M-dwarf star located approximately 123 light-years from Earth. Unveiled in 2021 through the transit method, this exoplanet boasts unique characteristics that make it an intriguing subject for researchers.
General Characteristics of TOI-1685 b
TOI-1685 b is classified as a super-Earth, a type of exoplanet that is larger in size and mass than Earth but smaller than ice giants like Uranus and Neptune. Its mass is 3.78 times that of Earth, and its radius is approximately 1.7 times larger than Earth’s radius, leading to a density that may provide clues about its composition. These attributes suggest a predominantly rocky world with potential traces of volatiles in its atmosphere, although direct observations are necessary to confirm this hypothesis.
The host star of TOI-1685 b has a stellar magnitude of 13.378, making it relatively faint and requiring advanced instruments for detailed studies. As a red dwarf star, it is cooler and smaller than the Sun, providing a dim and less energetic environment, yet exerts significant gravitational influence on its closely orbiting planet.
Orbital Dynamics and Proximity to the Star
One of the most striking features of TOI-1685 b is its incredibly close proximity to its host star. With an orbital radius of just 0.011557 AU (about 1.7 million kilometers), it lies much closer to its star than Mercury does to the Sun. This results in an orbital period of only 0.0019164955 years—roughly 16.6 hours. Such an extreme proximity places TOI-1685 b in a category of ultra-short-period (USP) planets.
The orbit of TOI-1685 b is nearly circular, with an eccentricity of 0.0, indicating a stable gravitational interaction with its star. Despite this stability, its closeness subjects it to intense stellar radiation, which could lead to atmospheric erosion if the planet possesses a gaseous envelope.
Discovery and Detection Method
TOI-1685 b was discovered using the transit method, a widely used technique in exoplanetary research. This method involves monitoring the dimming of a star’s light as a planet passes in front of it. The periodic dips in brightness allow astronomers to calculate the planet’s size, orbital period, and other essential parameters. The data for TOI-1685 b were obtained from NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission dedicated to identifying exoplanets around nearby stars.
The precision of the transit method enables the detection of planets with extremely short orbital periods, such as TOI-1685 b, which would be challenging to identify using other techniques.
Implications for Atmospheric Studies
Although TOI-1685 b’s close proximity to its star likely exposes it to intense stellar radiation, the planet may still retain a thin atmosphere, depending on its initial composition and evolutionary history. Ultra-short-period planets like TOI-1685 b are valuable candidates for atmospheric studies because their short orbits allow frequent opportunities for observations during transits.
Researchers are particularly interested in determining whether such planets can maintain atmospheres despite the potential for atmospheric stripping caused by stellar winds and high-energy radiation. Spectroscopic observations, using instruments like the Hubble Space Telescope or the upcoming James Webb Space Telescope, could provide insights into the chemical composition of the planet’s atmosphere, if present.
Comparative Analysis
When compared to other known super-Earths, TOI-1685 b stands out for its ultra-short orbital period and extreme proximity to its host star. While planets with similar characteristics have been discovered, the specific properties of TOI-1685 b, such as its mass, radius, and circular orbit, contribute valuable data to the growing catalog of USP planets.
Table 1 highlights a comparison of TOI-1685 b with Earth and another notable super-Earth, 55 Cancri e:
| Property | TOI-1685 b | Earth | 55 Cancri e |
|---|---|---|---|
| Mass (Earth units) | 3.78 | 1 | 8.08 |
| Radius (Earth units) | 1.7 | 1 | 2.0 |
| Orbital Radius (AU) | 0.011557 | 1 | 0.01544 |
| Orbital Period (days) | ~0.69 | 365.25 | ~0.74 |
| Eccentricity | 0.0 | 0.0167 | ~0.02 |
| Detection Method | Transit | — | Transit/RV |
The comparison underscores the extreme conditions under which TOI-1685 b exists, particularly its orbital radius and period, which are significantly smaller than those of both Earth and 55 Cancri e.
Challenges and Future Research Directions
The study of TOI-1685 b poses several challenges due to the faintness of its host star and the potential difficulty in distinguishing atmospheric signals from stellar noise. However, these obstacles also present opportunities to refine observational techniques and improve models of planetary atmospheres and interiors.
Future observations with ground-based telescopes, as well as space-based missions, will aim to better constrain the planet’s mass and radius, determine its density, and explore any potential atmosphere. Additionally, studying the star itself, including its magnetic activity and stellar wind properties, will be crucial to understanding the long-term evolution of TOI-1685 b.
Conclusion
TOI-1685 b exemplifies the diversity of planetary systems and expands our understanding of ultra-short-period planets. As a super-Earth with unique orbital characteristics, it serves as a valuable target for ongoing and future research. Its discovery not only highlights the capabilities of missions like TESS but also underscores the importance of exploring the myriad planetary systems in our galaxy.
The study of such exoplanets continues to inspire curiosity about the mechanisms of planetary formation, the conditions necessary for habitability, and the potential for finding life beyond Earth. TOI-1685 b, with its extreme environment and intriguing properties, stands as a testament to the richness of the cosmos.