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Topic: Habitable zone

In the News (Tue 18 Dec 18)

  Habitable zone - Wikipedia, the free encyclopedia
In astronomy a habitable zone (HZ) is a region of space where conditions are favorable for the creation of life.
The circumstellar habitable zone (or ecosphere) is a notional spherical shell of space surrounding stars where the surface temperatures of any planets present might maintain liquid water.
On the other hand, the solar system must be far enough from the galaxy center to avoid hazards such as impacts from comets and asteroids, close encounters with passing stars, and outbursts of radiation from supernovae and from the fl hole at the center of the galaxy.
en.wikipedia.org /wiki/Habitable_zone   (752 words)

 Habitable Zone   (Site not responding. Last check: 2007-10-14)
About 4 billion years ago, Venus was located near the inner edge of the habitable zone; today it lies closer to the Sun than the inner edge of the habitable zone.
is proportional to the stellar luminosity, the area of the habitable zone, and the likelihood of finding planets in it, is largest for the massive O, B, and A stars on the upper main sequence.
In the figure at left, the habitable zone (yellow) is plotted as a function of spectral type for main sequence stars.
www.ess.sunysb.edu /fwalter/AST101/habzone.html   (557 words)

 habitable zone (HZ)
The idea of galactic habitable zones, and of preferred regions within the Galaxy to search for intelligent life, has also been discussed.
If all of the complicating factors discussed above are ignored and the habitable zone is defined simply as the distance from a star where the effective temperature is in the range 0° to 100°C then it is straightforward to calculate the radii of the HZ's inner and outer bounds.
Circumstellar Habitable Zones, Proceedings of the First International Conference on Habitable Zones, San Francisco, Menlo Park, Calif.: Travis House (1996).
www.daviddarling.info /encyclopedia/H/habzone.html   (1305 words)

 Dying Stars Could Make Frozen Planets Habitable
The zone extends from just within Earth's orbit to nearly the orbit of Mars (or 0.95 to 1.37 astronomical units, with 1 AU being the distance between the Earth and Sun).
The habitable zone sweeps outward, extending from 2 to 9 AU.
The inner edge of this zone remains habitable for several billion years while the outer extreme, where Saturn currently orbits, is habitable for a few hundred million years.
www.rense.com /general63/habo.htm   (623 words)

 Centauri Dreams » Blog Archive » Ultraviolet Limits on Habitable Worlds
In defining the UV habitable zone, Andrea Buccino (Instituto de Astronomía y Física del Espacio, Buenos Aires) and colleagues try to establish both an inner limit (not so close to the star as to damage DNA) and an outer (beyond which there is not sufficient UV for biogenesis to occur).
Intriguingly, in most cases the ultraviolet habitable zone is closer to the star than the traditional habitable zone.
The authors find seven cases where the traditional habitable zone and the UV zone overlap at least partially, allowing the presence of a habitable planet.
www.centauri-dreams.org /?p=636   (794 words)

 The habitable zone of Earth-like planets around 47 UMa
Clearly, the ultimate quest of extra-solar planet research is to identify Earth-like planets located in the habitable zones (HZs) of their host stars, which however at the present time is still beyond technical feasibility.
In particular, habitability is linked to the photosynthetic activity of the planet, which in turn depends on the planetary atmospheric CO concentration, and is thus strongly influenced by the planetary geodynamics.
In principle, this leads to additional spatial and temporal limitations of habitability, as the stellar HZ (defined for a specific type of planet) becomes narrower with time due to the persistent decrease of the planetary CO concentration.
www.pik-potsdam.de /~bloh/extrasolar/47uma.html   (1810 words)

The habitable zone of a planetary system is defined to be the circumstellar region (or annulus) in which liquid water can exist on a planet with certain atmospheric and geologic properties.
The intersection of these regions defines the continues habitable zone, in which planets are habitable throughout the total life-time of the host star.
Hence, the habitable zone is an annulus with increasing inner and outer radius.
www.astro.ku.dk /~tobiash/HD4208/hd4208.html   (3110 words)

 Space.com articles - Author - SETI Institute   (Site not responding. Last check: 2007-10-14)
In our circumstellar habitable zone, Venus was a bit too close, and likely experienced a moist runaway greenhouse effect thereby losing its oceans.
The small, cooler M-type red stars we say might allow a habitable zone, but the planets there would be tidally locked in their rotation.
We also saw that the larger, hotter F-type white stars could also have circumstellar habitable zones since their production of ultraviolet light would actually create much more ozone than needed, apparently making planets in the circumstellar habitable zone around these hotter stars even safer from ultraviolet light than Earth is around our G-type yellow star.
www.seti.org /site/apps/nl/content2.asp?c=ktJ2J9MMIsE&b=191981&ct=221043   (1432 words)

 Stars and Habitable Planets
In general, the conditions needed to support Earth-type life may exist for rocky planets (or sufficiently large moons) that are orbiting a star in its so-called "habitable zone" or "HZ" (James F. Kasting; and Kasting et al, 1993).
Such zones are bounded by the range of distances from a star for which liquid water can exist on a planetary surface, depending on such additional factors as the nature and density of its atmosphere and its surface gravity.
The habitable zone around a star was first developed for roughly circular planetary orbits, where the eccentricity of the orbit is close to zero (e~ 0).
www.solstation.com /habitable.htm   (3213 words)

There exists a meta-stable figure-8 orbit around two stars, but this is likely to range in and out of the habitable zones of the two stars in a single orbit, and long-term stability in the presence of other stars or planets would be very doubtful.
While we might compare volumes of habitable zones, it probably makes more sense to compare areas on the star's equatorial plane, as it appears that most planets will be found in such planes.
Here is a table of habitable zones for various star types, from big, hot O stars to small, relatively cool M stars.
exobio.ucsd.edu /Space_Sciences/zones.htm   (876 words)

 sciforums.com - Galactic Habitable Zone
Habitable in the standards that we are used means that the place must have a minimum of heat, so any planet around a star is potentially a place for the flourishment of life, and stars are distributed throughout the disk, and there are also stars in the halo.
The research, by Australian astronomers and published in Friday's issue of the journal Science, determined that a ring-shaped habitable zone opened in the galaxy 25,000 light-years from its core eight billion years ago.
The zone's size and location is based on a number of factors, including the presence of heavy elements needed to form planets and stars located a safe distance from supernovae.”
www.sciforums.com /showthread.php?t=44683   (427 words)

 Plotting A Habitable Zone For 47 Ursae Majoris
The habitable zone is the region surrounding a star where liquid water could exist on the surface of a planet -- a region roughly equivalent to the space between the orbits of Venus and Mars in the solar system.
On the other hand, the embryos that started inside the habitable zone were always able to consolidate into several Earth-sized planets, all having an orbital period of half a year or less.
The researchers' assessment of habitable planet formation was part of a larger theoretical investigation of the two planets orbiting 47 UMa, in which the team narrowed the range of possible orbital configurations that the planets might occupy.
www.spacedaily.com /news/extrasolar-02a.html   (1030 words)

 The number of habitable planets in the Milky Way over cosmological time scales
The ultimate quest of extrasolar planet research is to identify Earth-like planets located in the habitable zone of their host stars.
The habitable zone (HZ) is defined a s the region around a star within which a planet might enjoy moderate surface temperatures required for higher life forms.
To estimate the planet formation rate, PFR, of Earth-like planets in the Milky Way an approach by Lineweaver (2001) has been followed- The PFR is derived from the star formation rate and star metallicity as an ingredient for the formation of Earth-like planets.
www.pik-potsdam.de /~bloh/extrasolar/milkyway.html   (1372 words)

 Media Release: The Galactic Habitable Zone
In the early stages of galaxy formation (lower panel) there were not enough heavy elements to form terrestrial planets except in the most central regions of the Galaxy, where the danger due to nearby supernovae was very high (shown in red).
As heavy elements spread through the Galaxy, terrestrial planets formed and a habitable zone emerged and broadened (shown in green in the upper panels).
Known as the Galactic Habitable Zone, it is an area of space whose boundaries are set by its calm and safe environment, and access to the chemical materials necessary for building terrestrial planets similar to the Earth.
astronomy.swin.edu.au /GHZ   (584 words)

 UFPDOCA Planetary Classifications Table
Class C - Reducing Planets of this class are usually found in a star's "habitable zone".
Class H - Geo-Thermal Planets of this class are usually found in a star's "habitable zone" or "cold zone".
Class L - Geo-Inactive Planets of this class are usually found in a star's "habitable zone" or "cold zone".
members.tripod.com /~asrpages/doca/planets.html   (753 words)

 USATODAY.com - The growing habitable zone: Locations for life abound   (Site not responding. Last check: 2007-10-14)
Traditionally, this zone has been defined as a narrow disk around a star where temperatures are moderate enough that water on the surface of a planet can exist in a liquid form.
One of the main objections was that the habitable zones of red dwarfs would be very narrow and very close to the stars.
As for the criticism that a red dwarf's habitable zone is very narrow, Todd Henry, an astronomer at Georgia State University, has an interesting view.
www.usatoday.com /tech/science/space/2006-02-07-life-universe_x.htm   (1264 words)

 OSETI III: Can Terrestrial Planets Exist in the Habitable Zones of Known Exoplanetary Systems?
Most of the known exoplanetary systems have giant planets closer to the star than the inner boundary of the habitable zone - the range of distances from the star within which water at the surface of a terrestrial planet would be in the liquid phase.
The 47 Ursae Majoris system is unusual in having the known giant planet beyond the habitable zone, which is the case for the giant planets in the Solar System.
It is therefore of interest to see whether such planets could exist in them, and in particular whether they could survive in the habitable zones for times long enough to allow the emergence of intelligent species.
www.coseti.org /4273-04.htm   (341 words)

 Star Light, Star Bright...Any Oxygen Tonight? :: Astrobiology Magazine ::
The habitable zone - or the orbital region around a star where water can remain in a liquid state - is seen as the most promising target in the search for life in the universe.
Habitable zones for hotter stars will be further away than the habitable zone in our own solar system (which lies roughly between the orbits of Venus and Mars).
Red stars, meanwhile, are so much cooler than our sun that their habitable zones would have to be much closer.
www.astrobio.net /news/modules.php?op=modload&name=News&file=article&sid=404   (1756 words)

 Challenger Learning Center   (Site not responding. Last check: 2007-10-14)
They will investigate how the size of the model "habitable zone" around the light bulbs depends on the wattage of the bulb, and transfer this information to discuss habitable zones around real stars.
The limits on the distance from the star where a planet could maintain liquid water mark the boundaries of what is called the “habitable zone.” The region that could have liquid water is the region that could have life- at least, the kind of life that we understand.
So to retain liquid water within the habitable zone, a planet must be big enough for its gravity to hold onto these gases and liquids formed at its surface.
www.lasm.org /stage/html/mn_clc_demo_dec05.html   (2947 words)

 Star Trek: Odyssey | Planetary Classifications
Class H planets are typically the size of Earth and are in their sun's habitable zone.
Class K planets are typically 1 to 1/10 the size of Earth, and are in their sun's habitable zone.
Class L planets are typically the size of Earth and are in their sun's habitable zone.
www.geocities.com /ussodyssey2003/planetclass.html   (928 words)

 Life Beyond the Earth
The life zone, or habitable zone, is the distance from the star where the temperature is between the freezing point (0° C) and boiling point (100° C) of water.
The life zone of a hotter main sequence star will be farther out and wider because of the hotter star's greater luminosity.
At the outer boundary of the life zone the temperature is 0° C for all of the stars and the inner boundary is at 100° C for all of the stars.
www.astronomynotes.com /lifezone/s2.htm   (660 words)

However, in relation to the SIM mission, a "zone of interest" should be considered where a moderate definition be used to calculate the HZ such as using an effective albedo of -0.7.
The distances for most close by stars is found by measuring the parallax of the star, the angular displacement relative to background stars over the course of a year as the earth revolves around the sun.
Habitable Zone Inner edge, HZIE, determined by loss of water due to photolysis and hydrogen escape.
www.physics.sfsu.edu /~ebierman/research/HZ.html   (4720 words)

 Universe Today - How Many Habitable Earths Are Out There?   (Site not responding. Last check: 2007-10-14)
In order to determine which of the gas giants located within habitable zones could possess a life-friendly moon, the computer models search for systems where the orbits of Earth-sized satellites would be stable and confined within the habitable zone for at least the one billion years needed for life to emerge.
The OU team's method of determining whether any putative 'Earths' or Earth-sized satellites in habitable zones can offer suitable conditions for life to evolve can be applied rapidly to any planetary systems that are newly announced.
The remaining planet was discovered as the result of a slight dimming of starlight caused by its regular passage across the disk of its parent star.
www.universetoday.com /am/publish/how_many_habitable_earths.html?142004   (958 words)

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