Phoenix Planet: A New Discovery That Defies Atmospheric Loss Theories

Key Takeaway

Phoenix, a newly discovered exoplanet, retains a thick atmosphere despite being close to a red giant star, challenging existing theories on planetary evolution and atmospheric retention. This discovery, led by researchers from Johns Hopkins University, provides fresh insights into how planets can defy expectations in extreme environments.

Summary

Discovery: Phoenix is a rare exoplanet that retains a thick atmosphere close to its red giant star.
Significance: Challenges existing theories about planetary evolution and atmospheric retention in harsh stellar environments.
Characteristics: Smaller, older, and hotter than expected; 6.2 times the size of Earth and 60 times less dense than the densest “hot Neptune.”
Research Techniques: Utilized NASA’s Transiting Exoplanet Survey Satellite and the W.M. Keck Observatory to filter and combine data for precise measurements.
Implications: Provides new insights into planetary system evolution, particularly for Earth’s future atmospheric changes.
Future Discoveries: The research team has identified a dozen potential candidates for similar studies.
Publication: Findings published in The Astronomical Journal on June 5, 2024.

An artist’s concept shows TIC365102760 b, nicknamed Phoenix. This planet can survive intense radiation from a nearby red giant star. Credit: Roberto Molar Candanosa/Johns Hopkins University.

Introduction

In a groundbreaking discovery, astronomers have identified an exoplanet, named Phoenix, that defies conventional expectations of planetary evolution and atmospheric retention. This planet, orbiting a red giant star, should have been stripped of its atmosphere due to intense radiation, yet it maintains a thick, puffy atmosphere. This finding, published by Johns Hopkins University researchers, challenges existing theories and opens new avenues for understanding planetary behavior in extreme environments.

Characteristics of Phoenix

Phoenix, officially designated TIC365102760 b, belongs to the rare category of “hot Neptunes.” Despite being situated close to its host star, Phoenix has retained a substantial atmosphere. This discovery is particularly surprising given the planet’s characteristics:

Size and Mass: Phoenix is 6.2 times larger than Earth and exhibits significantly lower density, being 60 times less dense than the densest known hot Neptune.
Orbit and Proximity: The planet completes an orbit around its red giant star every 4.2 days, at a distance six times closer than Mercury is to the Sun.
Age and Temperature: Phoenix is notably older and hotter than anticipated for planets in such proximity to a red giant star.

Unusual Atmospheric Retention

“This planet isn’t evolving the way we thought it would,” said Sam Grunblatt, the lead researcher from Johns Hopkins University. “It appears to have a much bigger, less dense atmosphere than we expected for these systems.” This phenomenon challenges our understanding of how atmospheres can persist in harsh stellar environments where intense radiation is expected to strip them away.

Table 1: Characteristics of Phoenix

Characteristic	Detail
Size	6.2 times the size of Earth
Density	60 times less dense than the densest hot Neptune
Orbital Period	4.2 days
Proximity to Star	6 times closer than Mercury to the Sun
Age and Temperature	Older and hotter than expected

Research Techniques

The discovery of Phoenix was made possible through innovative research techniques. Grunblatt and his team utilized NASA’s Transiting Exoplanet Survey Satellite (TESS) and the W.M. Keck Observatory to obtain precise measurements. TESS detects low-density planets by observing the dimming of their host stars’ brightness as they pass in front. The team enhanced this data by filtering out unwanted light and combining it with measurements of the stars’ wobbles caused by orbiting planets, observed by the Keck Observatory.

Implications for Planetary Evolution

The persistence of Phoenix’s atmosphere, despite its proximity to a red giant star, has significant implications for our understanding of planetary evolution. The slow atmospheric stripping observed in Phoenix suggests that other factors may influence atmospheric retention. This insight is crucial for predicting the future of Earth’s atmosphere as our Sun evolves into a red giant.

“We don’t understand the late-stage evolution of planetary systems very well,” Grunblatt noted. “This is telling us that maybe Earth’s atmosphere won’t evolve exactly how we thought it would.”

Potential for Future Discoveries

Phoenix’s discovery highlights the potential for finding other unusual exoplanets. Puffy planets like Phoenix are rare, with scientists estimating that only about 1% of stars host such planets. Their smaller size makes them challenging to detect, but Grunblatt’s team has already identified a dozen potential candidates for further study using their refined techniques.

Conclusion

Phoenix’s discovery marks a significant milestone in astrophysics, challenging existing theories and providing new insights into planetary evolution. The planet’s ability to retain a thick atmosphere despite intense stellar radiation prompts a re-evaluation of our understanding of atmospheric loss and planetary decay in extreme environments. As researchers continue to uncover more about these rare puffy planets, we can expect to learn even more about the diverse and complex nature of solar systems.

Table 2: Future Research Directions

Research Area	Description
Atmospheric Retention	Investigate factors influencing atmospheric persistence in extreme environments.
Late-Stage Planetary Evolution	Study how planetary systems evolve as their host stars enter late stages of life.
Detection Techniques	Refine methods for detecting small, low-density exoplanets.
Comparative Planetology	Compare atmospheric characteristics across different types of exoplanets.

Reference

“TESS Giants Transiting Giants. IV. A Low-density Hot Neptune Orbiting a Red Giant Star” by Samuel K. Grunblatt et al., The Astronomical Journal, June 5, 2024. DOI: 10.3847/1538-3881/ad4149
Johns Hopkins University Press Release, June 8, 2024.

Hashtags

#Astronomy, #Astrophysics, #Exoplanets, #PhoenixPlanet, #JohnsHopkinsUniversity, #NASA, #TESS, #KeckObservatory, #PlanetaryScience, #RedGiantStar