# ''Habitable zone'' question

by Yosty22
Tags: habitable, zone
 P: 105 I understand the concept of the habitable zone or ''Goldilocks Zone," but can't anything technically be in the habitable zone? Even if the planet in question is far away from its host star, couldn't a greenhouse effect create an atmosphere and/or warm enough temperatures (but not too warm) to contain liquid water? Would this mean that anything could be in the habitable zone as long as it has another way to generate heat of its own if it is too far to gain sufficient heat from its host star?
 PF Patron P: 1,261 The goldilocks zone is dependant on the output of its star, it only describes a region where liquid water is possible and temperature is suitable. Their are other ways to have liquid water outside or inside the goldilocks zone that could support life or for that matter other life supporting elements such as ammonia etc. One example is the possibility of Europia supporting life in its underground oceans. That moon lies outside the habitable zone.
 P: 105 Oh, thank you. With that in mind, what defines the habitable zone? Is there a way to calculate how large the habitable zone is for a certain star? Is energy output the only factor in calculating the habitable zone of a star?
PF Patron
P: 1,261

## ''Habitable zone'' question

Astronomers use apparent magnitude, luminosity and stellar flux along with the inverse square law to calculate habitable zones for stars. The "center" of the HZ is defined as the distance that an exoplanet would have to be from its parent star in order to receive the right amount of energy from the star to maintain liquid water. For example, a star with 25% of the luminosity of the Sun will have a CHZ centered at about 0.50 AU, while a star with twice the Sun's luminosity will have a CHZ centered at about 1.4 AU.

here is a couple of articles that covers some of the calculations involved

http://www.daviddarling.info/encyclo...H/habzone.html

http://www.astro.umd.edu/~miller/tea.../lecture14.pdf

http://www.planetarybiology.com/calc...table_zone.htm

http://arxiv.org/pdf/1301.6674v2.pdf

the last paper is fairly intense but it shows more modern methodology. The graphs are also handy.
 PF Patron Sci Advisor P: 22,332 Mordy, that article http://arxiv.org/pdf/1301.6674v2.pdf is interesting! Thanks for calling our attention to it. I'm going to add it to the informal A&C bibliography in the Astro forum. It's a handy place to keep links of stuff one might want to refer to, if you think they might be of general interest and helpful to other members. The thing I like is that it considers various cases of the mass of the planet and its atmosphere, so the various ways the greenhouse effect changes the inner and outer limits of the Zone are presented in a detailed informative way.
 PF Patron P: 1,261 No problem I often save gems such as that article, saving it on the site would be a good idea. I've seen alot of various short hand ways to use my callsign but thats the first time I've seen Mordy used lol

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