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Monthly Space Topic
Join university faculty, graduates, and students as we explore space history, technology, astronomy, planetary geology, and exciting new space missions. A new topic will be selected each month, and a member of the APUS Space Studies Research Group will present a short paper. In addition to their insight, additional links will be provided for further investigation. So, buckle up and join us as we explore the vast wonders of space.
Goldilocks is not just a character from a storybook; in astronomy, the Goldilocks zone refers to the "sweet spot" around a star where conditions are just right for a planet to be habitable. For many years, scientists believed a habitable planet could only exist around a star similar to our Sun. However, recent research has expanded the possibilities to include other types of stars. This month's topic, presented by Emma Follis, explores the parameters of habitable zones around these stars that could support life on other planets.
A little more about Emma...
Emma is a graduate student at APUS pursuing a master's degree in Space Studies with a concentration in Earth & Planetary Science. Her space interests revolve around exoplanets, atmospheric science, and astrobotany. When Emma is not deep-diving into a space topic of interest (and excitedly giving new random space facts to her husband when he least expects it), she is either spending time with her family, reading a book, trying to recreate her favorite restaurant dishes, or identifying plants and collecting rocks while hiking.
Stellar Environments and Life: A Study of Habitability Metrics in M-, K-, and G-Dwarf Systems
by Emma Follis
The discovery of exoplanets has significantly transformed our understanding of planetary systems and the potential for extraterrestrial life, focusing on the concept of the habitable zone (HZ) where liquid water may exist.
Often called the "Goldilocks Zone," this idea is not set in stone and varies
considerably based on the star's luminosity, temperature, and size.
Differences Between M-, K-, & G-Dwarfs
Three stellar types are relevant to habitability:
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M-dwarfs offer many potentially habitable planets because they are the most common
stars but have small habitable zones vulnerable to stellar flares. -
K-dwarfs are intermediate in size and temperature and are stable and long-lived.
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G-dwarfs, like our Sun, have wider habitable zones but are less common.
Who's the Best Target for Exoplanets?
The analysis of habitable zone boundaries and occupancy differences among these stellar types is achieved using the NASA Exoplanet Archive. These boundaries define the range where liquid water could exist, and their variations provide critical insights into the diversity of planetary environments. Building on previous research, the following trends are recognized below:
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Habitable Zone (HZ) Boundaries: G-dwarfs have the widest HZs, K-dwarfs have moderately wide HZs, and M-dwarfs have the narrowest, all influenced by their luminosities.
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Fraction of HZ Planets: K-dwarfs host 40% of their planets within their HZ,
M-dwarfs 33%, and G-dwarfs 25%. K-dwarfs provide a better balance of
habitability with stable, long-lived stellar environments. Despite their wide
HZs, G-dwarfs have a lower fraction of HZ planets, likely due to their
relative scarcity compared to M- and K-dwarfs. -
Statistical Significance: ANOVA tests indicate statistically significant
differences in HZ size and the fraction of HZ planets among these stellar
types. This offers strong support for the trends that have been observed,
prioritizing certain stellar types in the hunt for habitable exoplanets. -
Best Candidates for Habitability: K-dwarfs are presented as optimal
candidates due to their intermediate HZ size, high percentage of HZ planets,
and longer lifetimes. M-dwarfs face challenges from high stellar activity levels having the potential to remove planetary atmospheres. In contrast, G-dwarfs, though having wider HZs, are less favorable due to their rarity and shorter lifespans. -
Implications for Exoplanet Exploration: Focusing on K-dwarfs for future research and missions, and emphasizing the importance of considering stellar characteristics and HZ size alongside quantitative measures of habitability.
Improving our knowledge of stellar environments advances the larger effort to find planets that could sustain life and, eventually, provide an answer to the fundamental question of whether or not we are the only species in the universe.
Read the details of Emma's paper to explore the methods, analyses, and discussions she used to reach her conclusions.
*First image, Credit: NASA via Unsplash
