An international team of astronomers has reported the discovery of two exoplanets orbiting a nearby star known as HD 101581. The newfound alien worlds are slightly smaller than Earth and orbit their host very closely. The discovery was detailed in a paper published on December 12 on the pre-print server arXiv.
Introduction
Since the launch of NASA's Transiting Exoplanet Survey Satellite (TESS) in April 2018, the satellite has identified more than 7,300 candidate exoplanets, commonly referred to as TESS Objects of Interest (TOIs). Among these, 589 have been confirmed, marking significant progress in the quest for assessing the potential for life beyond Earth.
This article explores the findings regarding the two exoplanets discovered orbiting HD 101581, examining their characteristics, the star they orbit, and what their discovery means in the broader context of exoplanetary science.
Discovery of the Exoplanets
A recent study published by astronomers led by Michelle Kunimoto of the Massachusetts Institute of Technology (MIT) confirms the planetary nature of two TOIs. The team reports that transit signals identified by TESS in the light curve of TOI-6276, or HD 101581, are caused by two Earth-sized extrasolar worlds.
"Both planets were discovered in sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up," the researchers wrote. This rigorous validation process underscores the reliability of the findings.
Characteristics of HD 101581 b and c
The first exoplanet, designated as HD 101581 b, is located closer to the host star and has a radius of approximately 0.956 Earth radii. Its mass has been calculated to be no larger than 3.6 Earth masses. The exoplanet completes one orbit around HD 101581 every 4.47 days, at a distance of about 0.046 AU from the star. Its equilibrium temperature is estimated to be around 834 K.
The second exoplanet, referred to as HD 101581 c, is nearly the size of the Earth, with 0.99 Earth radii and a maximum mass of 4.2 Earth masses. It has a longer orbital period of 6.21 days, with a distance from its parent star of approximately 0.057 AU. The equilibrium temperature of HD 101581 c is lower, estimated to be around 747 K.
| Attribute | HD 101581 b | HD 101581 c |
|---|---|---|
| Radius (Earth radii) | 0.956 | 0.99 |
| Max Mass (Earth masses) | 3.6 | 4.2 |
| Orbital Period (days) | 4.47 | 6.21 |
| Distance from Host Star (AU) | 0.046 | 0.057 |
| Equilibrium Temperature (K) | 834 | 747 |
Potential Third Exoplanet
The astronomers have also identified a signal that possibly indicates the presence of a third planet transiting HD 101581. If confirmed, this outermost planet would have a radius of about 0.98 Earth radii and a maximum mass of 3.6 Earth masses, with an estimated orbital period of approximately 7.87 days. This potential additional exoplanet further adds to the intrigue surrounding HD 101581.
Characteristics of the Host Star HD 101581
HD 101581 is classified as a K dwarf star, which has several notable characteristics:
- Radius: Approximately 0.63 solar radii.
- Mass: Estimated at around 0.74 solar masses.
- Distance: Located about 41.7 light years away from Earth.
- Age: Nearly 7 billion years old.
- Effective Temperature: Approximately 4,634 K.
- Metallicity: -0.5 dex.
The bright apparent magnitude of HD 101581, recorded at 7.77 mag, makes it the brightest star currently known to host multiple transiting planets with radii below 1.5 Earth radii.
| Attribute | HD 101581 |
|---|---|
| Type | K Dwarf Star |
| Radius (solar radii) | 0.63 |
| Mass (solar masses) | 0.74 |
| Distance (light years) | 41.7 |
| Estimated Age (billion years) | 7 |
| Effective Temperature (K) | 4634 |
| Metallicity (dex) | -0.5 |
| V-band Magnitude | 7.77 mag |
Significance of the Discovery
The discovery of these two exoplanets is a noteworthy contribution to the study of planetary systems. Exoplanets that are Earth-sized and located in close proximity to their host stars are especially important because:
- They represent potential candidates for habitable conditions, depending on their atmospheres and other factors.
- They provide valuable data for understanding planetary formation and evolution, particularly in low-mass stars.
- Studying their atmospheres, if accessible, could reveal insights into their composition, weather patterns, and potential for hosting life.
Conclusion
The identification of HD 101581 b and c continues to advance our understanding of the universe and the possibilities of habitable worlds beyond our solar system. As researchers refine their methods and technologies, the exoplanetary landscape continues to expand, unveiling the mysteries of our cosmic neighborhood.
References
For more information, refer to the following additional sources:
- Kunimoto, Michelle et al. (2024). Two Earth-size Planets and an Earth-size Candidate Transiting the Nearby Star HD 101581. arXiv.
- NASA TESS Overview - An explanation of the satellite's mission and discoveries.
- The Exoplanet Archive - A rich resource for data and findings on exoplanets.
Additional citations and resources about exoplanetary research can be found through articles on Universe Today.
