A team of astronomers from the University of Hawaii Institute for Astronomy has made an astounding revelation: a planet that managed to survive an event that should have spelled its demise caused by its own sun.
In the distant future, our Sun will expand, consuming everything in its path, including Earth. Similarly, numerous planets in other star systems face an inevitable fate as their host stars age. However, a ray of hope shines through the findings of the University of Hawaiʻi Institute for Astronomy (IfA) astronomers who have stumbled upon a remarkable case of survival against all odds. Their groundbreaking study was recently published in the journal Nature on June 28.
Named Halla, the planet officially known as 8 UMi b, reminiscent of Jupiter in size, orbits a red giant star named Baekdu (8 UMi) at a mere half the distance separating Earth from the Sun. Utilizing the W. M. Keck Observatory and the Canada-France-Hawaiʻi Telescope (CFHT) situated on Hawaiʻi Island, the team, led by Marc Hon, a NASA Hubble Fellow at IfA, detected Halla’s persistence despite the typically treacherous evolutionary course of Baekdu. They accomplished this by analyzing Baekdu’s stellar oscillations through data gathered from NASA’s Transiting Exoplanet Survey Satellite, which revealed that the star had previously swelled into a red giant stage after burning helium in its core.
According to Hon, the lead author of the study, the process of planetary engulfment usually has catastrophic consequences for both the star and the planet. Therefore, Halla’s ability to survive in such close proximity to a giant star that should have engulfed it is nothing short of extraordinary.
The discovery of Halla dates back to 2015 when a team of Korean astronomers detected it using the radial velocity method, which measures the periodic movement of a star caused by the gravitational influence of an orbiting planet. After realizing that the star must have been larger than the planet’s orbit at some point, the IfA team embarked on additional observations between 2021 and 2022. Their investigations employed the High-Resolution Echelle Spectrometer from the Keck Observatory and the ESPaDOnS instrument from CFHT. The new data confirmed that Halla maintained a stable orbit for over a decade, completing its revolution in approximately 93 days.
Halla’s survival prompts several theories. One possibility is that it avoided engulfment by never facing the threat in the first place. Similar to Tatooine, the iconic planet from Star Wars, which orbits twin suns, Baekdu may have initially consisted of two stars that merged, preventing either of them from expanding enough to consume Halla.
Alternatively, Halla might be a relatively young planet, born from the violent collision of the two stars. In this scenario, the clash produced a gas cloud from which Halla eventually emerged—a “second generation” planet, so to speak.
Hon suggests that since most stars exist in binary systems, with two stars orbiting each other, the formation of planets in such systems remains a mystery. Therefore, the existence of planets around highly evolved stars, thanks to binary interactions, is a plausible possibility.
The findings of this study not only confirm the existence of Halla but also raise intriguing questions about the survival mechanisms of planets under extreme stellar conditions. Through the combined efforts of multiple telescopes on Maunakea, the team has shed light on a captivating astronomical phenomenon.
Reference: Hon, M., Huber, D., Rui, N. Z., Fuller, J., Veras, D., Kuszlewicz, J. S., … Weiss, L. M. (2023). A close-in giant planet escapes engulfment by its star. Nature. DOI: 10.1038/s41586-023-06029-0
Table of Contents
Frequently Asked Questions (FAQs) about Survival
What did the astronomers discover?
The astronomers discovered a planet named Halla that defied destruction by its own sun, leading to intriguing theories about planetary evolution and binary star origins.
How did Halla manage to survive the event that should have engulfed it?
Halla’s survival can be attributed to several possibilities. One theory suggests that the host star, Baekdu, may have originally been two stars that merged, preventing either of them from expanding enough to consume the planet. Another possibility is that Halla is a relatively young planet formed from the collision of the two stars, making it a “second generation” planet. Additionally, the findings raise the possibility that binary interactions between stars may play a role in the formation and survival of planets.
How was Halla’s survival confirmed?
Halla was initially discovered in 2015 using the radial velocity method by a team of Korean astronomers. The University of Hawaii team then conducted additional observations from 2021 to 2022 using telescopes at the W. M. Keck Observatory and Canada-France-Hawaii Telescope. These observations confirmed Halla’s stable orbit and existence, providing evidence of its survival.
What are the implications of Halla’s survival?
The discovery of Halla challenges existing theories of planetary evolution and expands our understanding of planet formation in binary star systems. It suggests that planets may have the potential to survive in close proximity to highly evolved stars, opening up new avenues for exploration in the field of exoplanet research.
More about Survival
- University of Hawaii Institute for Astronomy: Website
- W. M. Keck Observatory: Website
- Canada-France-Hawaii Telescope (CFHT): Website
- NASA Hubble Fellowship Program: Website
- Nature Journal: Article
