Concepts
Habitable Zone
Also Known As Goldilocks zone
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The range of orbital distances around a star within which a planet could plausibly maintain liquid water on its surface given adequate atmospheric pressure, used in astrobiology as a first order proxy for potential habitability. The modern quantitative concept was developed by astrophysicist Su-Shu Huang in a series of papers in the 1950s and 1960s; exact boundary distances remain model dependent rather than fixed.
Facts
Disputed
Formulated YearMultiple researchers converged on the idea independently rather than one person formulating it: Hubertus Strughold introduced the related 'ecosphere' concept in 1953, the same year Harlow Shapley wrote about a 'liquid water belt'; the modern circumstellar habitable zone concept was then developed and formalized by Su-Shu Huang across a series of papers in the 1950s and 1960s. Proposed ByHubertus Strughold and Harlow Shapley (1953); formalized as the modern circumstellar habitable zone by Su-Shu Huang in the 1950s-1960s 1 Multiple researchers converged on the idea independently rather than one person formulating it: Hubertus Strughold introduced the related 'ecosphere' concept in 1953, the same year Harlow Shapley wrote about a 'liquid water belt'; the modern circumstellar habitable zone concept was then developed and formalized by Su-Shu Huang across a series of papers in the 1950s and 1960s. Concept Domain Cross-Tradition Connections
Associated With
Exoplanet, Concepts The habitable zone concept is a central tool for assessing exoplanet habitability.
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCircumstellar habitable zone, lead paragraph sectionQuote, Circumstellar habitable zone, lead paragraph section
The alternative name, Goldilocks zone, is a metaphor, allusion and antonomasia of the children's fairy tale of 'Goldilocks and the Three Bears'.
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationCircumstellar habitable zone, History sectionQuote, Circumstellar habitable zone, History section
Su-Shu Huang, an American astrophysicist developed the modern concept of circumstellar habitable zones in a series of papers in the 1950s and 60s.
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Exoplanet
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Exoplanet
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Drake Equation
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Fermi Paradox
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Drake Equation
Dissenting Readings (1 dissenting reading)
Description
Heller and Armstrong (2014, 'Superhabitable Worlds') argue that the classic circumstellar habitable zone, defined mainly by where liquid surface water can exist on an Earth-like planet, is not the same question as where life or even more hospitable conditions than Earth's are most likely; they propose that some planets orbiting outside the traditional zone, around long-lived K-dwarf stars for example, could be more broadly habitable than Earth itself, and that subsurface ocean worlds can host liquid water entirely outside any circumstellar habitable zone.
A dissenting reading, from Rene Heller and John ArmstrongWikipedia (space and spaceflight articles), Wikimedia Foundation
Frequently Asked Questions
Does a planet in the habitable zone guarantee it can support life?
No; the habitable zone marks where liquid water COULD exist, not where life is guaranteed.
No. The circumstellar habitable zone identifies where a planet could hold liquid water on its surface given an Earth-like atmosphere, but it does not by itself guarantee habitability. A planet inside the zone can still be uninhabitable for other reasons, such as a runaway greenhouse atmosphere, no atmosphere at all, or a lack of a protective magnetic field, and some researchers argue that worlds outside the traditional zone, including subsurface ocean moons and planets around certain long-lived stars, may be just as habitable or more so.
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