Habitability of K-type main-sequence star systems

Short description: Overview of the habitability of K-type main-sequence star systems

K-type main-sequence stars, also known as orange dwarfs, may be candidates for supporting extraterrestrial life. These stars are known as "Goldilocks stars" as they emit enough radiation in the non-UV ray spectrum[1] to provide a temperature that allows liquid water to exist on the surface of a planet; they also remain stable in the main sequence longer than the Sun by burning their hydrogen slower,[2] allowing more time for life to form on a planet around a K-type main-sequence star.[3] The planet's habitable zone, ranging from 0.1–0.4 to 0.3–1.3 astronomical units (AU),[4][better source needed] depending on the size of the star, is often far enough from the star so as not to be tidally locked to the star, and to have a sufficiently low solar flare activity not to be lethal to life. In comparison, red dwarf stars have too much solar activity and quickly tidally lock the planets in their habitable zones, making them less suitable for life. The odds of complex life arising may be better on planets around K-type main-sequence stars than around Sun-like stars, given the suitable temperature and extra time available for it to evolve.[5] Some planets around K-type main-sequence stars are potential candidates for extraterrestrial life.[2]

## Contents

* 1 Habitable zone
* 2 Radiation hazard
* 3 Potentially habitable planets
* 4 See also
* 5 References

## Habitable zone

A K-type star's habitable zone approximately ranges between 0.1–0.4 to 0.3–1.3 AU from the star. Here, exoplanets will receive only a relatively small amount of ultraviolet radiation, especially so towards the outer edge. This is favorable to support life, as it means that there is enough radiated energy to allow liquid water to exist on the surface, but not so much, especially ionizing radiation, as to destroy life.[4]

The habitable zone is also very stable, lasting for most of the K-type main-sequence star's main sequence phase and with little instability of luminosity during that phase.[6]

## Radiation hazard

61 Cygni, a binary K-type star system

Despite K-stars' lower total UV output, in order for their planets to have habitable temperatures, they must orbit much nearer to their K-star hosts, offsetting or reversing any advantage of a lower total UV output. There is also growing evidence that K-type dwarf stars emit dangerously high levels of X-rays and far ultraviolet (FUV) radiation for considerably longer into their early main sequence phase than do either heavier G-type stars or lighter early M-type dwarf stars.[7] This prolonged radiation saturation period may sterilise, destroy the atmospheres of, or at least delay the emergence of life for Earth-like planets orbiting inside the habitable zones around K-type dwarf stars.[7][8]

## Potentially habitable planets

The super-Earth HD 40307 g around the K2.5V star HD 40307 orbits in the CHZ, although it has a reasonably elliptical orbit (e=0.22). There may be many more, and the Kepler space telescope (now retired) was one of the main sources of information of these exoplanets.[9] Kepler-62 and Kepler-442 are examples of discoveries by Kepler of systems consisting of a K-type dwarf with potentially habitable planets orbiting it. A super-Earth orbiting a K-type main-sequence star called HD 85512 b was originally thought to have habitability potential,[10][11] but it is now considered too hot to be potentially habitable.

## See also

* Astrobiology
* Circumstellar habitable zone
* Habitability of neutron star systems
* Habitability of red dwarf systems
* Habitability of yellow dwarf systems
* Planetary habitability

## References

1. ↑ Grossman, Lisa. "Sun may not be a 'Goldilocks' star". Science News. https://www.sciencenews.org/article/sun-may-not-be-goldilocks-star.
2. ↑ 2.0 2.1 Shiga, David. "Orange stars are just right for life". New Scientist. https://www.newscientist.com/article/dn17084-orange-stars-are-just-right-for-life.html.
3. ↑ Vieru, Tudor. "Life Could Easily Develop Around Orange Dwarfs". Softpedia. http://news.softpedia.com/news/Life-Could-Easily-Develop-Around-Orange-Dwarfs-111006.shtml.
4. ↑ 4.0 4.1 Merchant, David (18 June 2009). "Orange Dwarf Stars and Life – Common?". http://alienrealities.blogspot.co.uk/2009/06/orange-dwarf-stars-and-life-common.html.
5. ↑ Loeb, Abraham (2017). "Reduced biodiversity of life around Proxima Centauri and TRAPPIST-1". The Astrophysical Journal Letters 846 (L21): L21. doi:10.3847/2041-8213/aa8860. Bibcode: 2017ApJ...846L..21L.
6. ↑ "Kepler's Hunt for Earths Shows Progress at Space Conference" Hadhazy, Adam March 9, 2010 12:00 AM
7. ↑ 7.0 7.1 Richey-Yowell, Tyler; Shkolnik, Evgenya L.; Loyd, R.O. Parke et al. (2022-04-26). "HAZMAT. VIII. A spectroscopic analysis of the ultraviolet evolution of K stars: Additional evidence for K dwarf rotational stalling in the first gigayear". The Astrophysical Journal (American Astronomical Society) 929 (2): 169. doi:10.3847/1538-4357/ac5f48. Bibcode: 2022ApJ...929..169R.
8. ↑ Toubet, Georgina (22 April 2022). "What UV radiation from the 'Goldilocks' stars could really mean". https://www.slashgear.com/841058/what-uv-radiation-from-the-goldilocks-stars-could-really-mean/.
9. ↑ Adam Hadhazy Kepler's Hunt for Earths Shows Progress at Space Conference, Popular Mechanics, March 9, 2010
10. ↑ Kaltenegger, L; S. Udry; F. Pepe (2011). "A Habitable Planet around HD 85512?". arXiv:1108.3561v1 [astro-ph.EP].
11. ↑ Pepe, F.; Lovis, C.; Ségransan, D.; Benz, W.; Bouchy, F.; Dumusque, X. et al. (3 October 2011). "The HARPS search for Earth-like planets in the habitable zone". Astronomy & Astrophysics 534: A58. doi:10.1051/0004-6361/201117055. Bibcode: 2011A&A...534A..58P.

* v
* t
* e

Astrobiology

Disciplines|

* Astrochemistry
* Astrophysics
* Atmospheric sciences
* Biochemistry
* Evolutionary biology
* Exoplanetology
* Geomicrobiology
* Microbiology
* Paleontology
* Planetary science

Main topics|

* Abiogenesis
* Allan Hills 84001
* Biomolecule
* Biosignature
* Drake equation
* Earliest known life forms
* Earth analog
* Extraterrestrial life
* Extraterrestrial sample curation
* Extremophiles
* Hypothetical types of biochemistry
* List of microorganisms tested in outer space
* Molecules detected in outer space
* Ocean planet
* Origin of life
* Panspermia
* Planetary protection
* Search for extraterrestrial intelligence (SETI)
* Yamato meteorite

Planetary
habitability|

* Habitability of binary star systems
* Habitability of K-type main-sequence star systems
* Habitability of natural satellites
* Habitability of red dwarf systems
* Circumstellar habitable zone
* Earth analog
* List of potentially habitable exoplanets
* Tholin
* Extraterrestrial liquid water
* Galactic habitable zone
* Superhabitable planet

Space
missions|

| Earth orbit|

* BIO
* BIOCORE
* Biolab
* Bion
* BIOPAN
* Biosatellite program
* E-MIST
* ERA
* CROPIS
* EXOSTACK
* EXPOSE
* Lunar Micro Ecosystem
* O/OREOS
* OREOcube
* Tanpopo
* VEGGIE

|

Mars|

* Beagle 2
* ExoMars Trace Gas Orbiter
* Fobos-Grunt
* Mars Science Laboratory
* Curiosity
* Phoenix
* Viking

Comets and
asteroids|

* Hayabusa2
* OSIRIS-REx
* Rosetta

Planned|

* BioSentinel
* Dragonfly
* Europa Clipper
* ExoMars
* Rosalind Franklin rover
* Kazachock lander
* Mars 2020 rover
* HX-1

Proposed|

* CAESAR
* Enceladus Explorer
* Enceladus Life Finder‎
* Enceladus Life Signatures and Habitability
* Europa Lander
* ExoLance
* Explorer of Enceladus and Titan
* Icebreaker Life
* Journey to Enceladus and Titan
* Laplace-P
* Life Investigation For Enceladus
* Mars sample return mission
* Oceanus
* THEO
* Trident

Cancelled and
undeveloped|

* Astrobiology Field Laboratory
* Beagle 3
* Biological Oxidant and Life Detection
* Living Interplanetary Flight Experiment
* Mars Astrobiology Explorer-Cacher
* MELOS
* Northern Light
* Red Dragon
* Terrestrial Planet Finder

Institutions
and programs|

* Astrobiology Society of Britain
* Astrobiology Science and Technology for Exploring Planets
* Breakthrough Initiatives
* Breakthrough Listen
* Breakthrough Message
* Breakthrough Starshot
* Carl Sagan Institute
* Center for Life Detection Science
* European Astrobiology Network Association
* NASA Astrobiology Institute
* Nexus for Exoplanet System Science
* Ocean Worlds Exploration Program
* Spanish Astrobiology Center‎

* Category
* Commons
* Portal: Astronomy
* Biology

* v
* t
* e

Extraterrestrial life

Events and objects|

* ALH77005
* ALH84001
* Cells in the stratosphere
* CI1 fossils
* Murchison meteorite
* Nakhla meteorite
* Polonnaruwa meteorite
* Red rain in Kerala
* Shergotty meteorite
* Viking lander biological experiments
* Yamato 000593

Signals of interest|

| Misidentified|

* CP 1919 (misidentified pulsar)
* CTA-102 (misidentified quasar)

|

Stars|

* KIC 8462852 (unusual light fluctuations)
* EPIC 204278916 (unusual light fluctuations)
* VVV-WIT-07 (unusual light fluctuations)
* HD 164595 signal (unknown origin)

Other|

* SHGb02+14a (radio source)
* Wow! signal (inconclusive)
* Fast radio burst (unknown origin)

Life in the Universe|

* Earliest known life forms
* Habitability of Enceladus
* Habitability of Europa
* Habitability of Mars
* Habitability of Titan
* Habitability of Venus

Planetary
habitability|

* Catalog of Nearby Habitable Systems
* Circumstellar habitable zone
* Earth analog
* Extraterrestrial liquid water
* Galactic habitable zone
* Habitability of binary star systems
* Habitability of orange dwarf systems
* Habitability of red dwarf systems
* Natural satellite habitability
* Planetary habitability

Space missions|

* Beagle 2
* Biological Oxidant and Life Detection
* BioSentinel
* Curiosity rover
* Darwin
* Dragonfly
* Enceladus Explorer
* Enceladus Life Finder
* Europa Clipper
* ExoMars
* Rosalind Franklin rover
* ExoLance
* EXPOSE
* Foton-M3
* Icebreaker Life
* Journey to Enceladus and Titan
* Laplace-P
* Life Investigation For Enceladus
* Living Interplanetary Flight Experiment
* Mars Geyser Hopper
* Mars sample-return mission
* Mars 2020
* Northern Light
* Opportunity rover
* SpaceX Red Dragon
* Spirit rover
* Tanpopo
* Titan Mare Explorer
* Venus In Situ Explorer
* Viking 1
* Viking 2

Interstellar
communication|

* Active SETI
* Allen Telescope Array
* Arecibo message
* Arecibo Observatory
* Berkeley SETI Research Center
* Bracewell probe
* Breakthrough Initiatives
* Breakthrough Listen
* Breakthrough Message
* Communication with extraterrestrial intelligence
* Gauss's Pythagorean right triangle proposal
* Lincos language
* NIROSETI
* Pioneer plaque
* Project Cyclops
* Project Ozma
* Project Phoenix
* SERENDIP
* Search for extraterrestrial intelligence
* SETI@home
* setiQuest
* Voyager Golden Record
* Water hole
* Xenolinguistics

Exhibitions|

* The Science of Aliens

Hypotheses|

* Ancient astronauts
* Aestivation hypothesis
* Cosmic pluralism
* Directed panspermia
* Drake equation
* Extraterrestrial hypothesis
* Fermi paradox
* Great Filter
* Hypothetical types of biochemistry
* Interplanetary contamination
* Kardashev scale
* Mediocrity principle
* Neocatastrophism
* Panspermia
* Planetarium hypothesis
* Rare Earth hypothesis
* Zoo hypothesis

Related topics|

* Astrobiology
* Astroecology
* Biosignature
* Brookings Report
* Planetary protection
* Potential cultural impact of extraterrestrial contact
* Exotheology
* Extraterrestrials in fiction
* Extremophile
* Nexus for Exoplanet System Science
* Noogenesis
* San Marino Scale
* Technosignature
* UFO religion
* Xenoarchaeology

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Habitability of K-type main-sequence star systems. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:Habitability_of_K-type_main-sequence_star_systems&oldid=680122"
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template