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'''Tau Ceti''' is a star similar in spectral type and mass to our [[sun]] that is located 11.9 light years away in the south central part of Constellation [[Cetus]].  The similarities to our own star have lead to widespread interest in the star in both [[astronomy]] and [[Science Fiction]] over the decades.  Interest in Tau Ceti has recently increased due to the large, dense debris disk discovered around the star in 2004.  

'''Tau Ceti''' is a star similar in spectral type and mass to our [[sun]] located 11.9 light years away in the south central part of Constellation [[Cetus]].  The similarities to our own star have lead to widespread interest in the star in both [[astronomy]] and [[Science Fiction]] over the decades.  Interest in Tau Ceti has recently increased due to the large, dense debris disk discovered around the star in 2004.  

==The Star==

==The Star==

Tau Ceti has an apparent magnitude of 3.50<ref name="tau">http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+ceti</ref>, allowing it to be easily seen in the night sky, in fact from a hypothetical planet around Tau Ceti, our [[sun]] being a similar G class star, would appear as a star of similar magnitude in the night sky.  Tau Ceti is the second closest class G star to us, with only Alpha Centauri A being closer, leading to much speculation and fiction about extraterrestrial life in the system.

Tau Ceti has an apparent magnitude of 3.50<ref name="tau">http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+ceti</ref>, allowing it to be easily seen in the night sky, in fact from a hypothetical planet around Tau Ceti, our [[sun]] being a similar G class star, would appear as a star of similar magnitude in the night sky.  Tau Ceti is the second closest class G star to us, with only Alpha Centauri A being closer, leading to much speculation and fiction about extraterrestrial life in the system.

Most of what we learned about the physical properties of Tau Ceti has been determined through spectroscopic measurements. The star is a yellow-orange, main sequence star of spectral type G8 V<ref name="tau">http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+ceti</ref>,  Tau Ceti though is both smaller and less massive then our sun, with around 81 to 82 percent of the mass, and around 77 percent of the diameter of Sol (our sun)<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003A%26A...406L..15P&db_key=AST&high=40d31b5ca015926</ref>.  The star is also significantly dimmer with only 59 percent of the luminosity of our [[sun|star]]<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1996ApJ...460..993S</ref>.

Most of what we learned about the physical properties of Tau Ceti has been determined through spectroscopic measurements. The star is a yellow-orange, main sequence star of spectral type G8 V<ref name="tau">http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+ceti</ref>,  though Tau Ceti is both smaller and less massive then our sun, with around 81 to 82 percent of the mass, and around 77 percent of the diameter of Sol (our sun)<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003A%26A...406L..15P&db_key=AST&high=40d31b5ca015926</ref>.  The star is also significantly dimmer with only 59 percent of the luminosity of our [[sun|star]]<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1996ApJ...460..993S</ref>.

Tau Ceti has a much lower [[Metallicity]] in comparison to stars of similar age to our sun.  Recent measurements show that Tau Ceti has only one-third of our sun’s abundance of iron.  Past measurements have produced a [[metallicity]] of 22 to 74 percent of Sol’s<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1992A%26AS...95..273C</ref>.  In all cases the [[metallicity]] is significantly lower, and using this data astronomers have estimated Tau Ceti to be around 10 billion years old<ref>http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.1731v1.pdf</ref>.

Tau Ceti has a much lower [[metallicity]] in comparison to stars of similar age to our sun.  Recent measurements show that Tau Ceti has only one-third of our sun’s abundance of iron.  Past measurements have produced a [[metallicity]] of 22 to 74 percent of Sol’s<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1992A%26AS...95..273C</ref>.  In all cases the [[metallicity]] is significantly lower, and using this data astronomers have estimated Tau Ceti to be around 10 billion years old<ref>http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.1731v1.pdf</ref>.

==Dust Disk==

==Dust Disk==

Thus far no large substellar companions such as a gas giant or a brown dwarf have been found around Tau Ceti, however the search was for such worlds that orbit very close to the star<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000AJ....119..906S&db_key=AST&high=38e0b7728711330</ref>.   

Thus far no large substellar companions such as a gas giant or a brown dwarf have been found around Tau Ceti, however the search was for such worlds that orbit very close to the star<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000AJ....119..906S&db_key=AST&high=38e0b7728711330</ref>.   

The [[habitable zone]] where any Earth-like terrestrial worlds where liquid water could exist are centered around 0.68 AUs, or the distance of Venus from the Sun<ref>http://www.exoplaneten.de/tauceti/english.html</ref>.  There is debate if such worlds could support complex life given the likelihood of heavy, frequent bombardment from Tau Ceti’s dense debris disk.  Others astronomers argue that a giant planet in the outer system could deflect comets and asteroids away from any world that may support life, much like [[Jupiter]] does for [[Earth]].

The [[habitable zone]] where any Earth-like terrestrial worlds where liquid water could exist is centered around 0.68 AUs, or approximately the distance of Venus from the Sun<ref>http://www.exoplaneten.de/tauceti/english.html</ref>.  There is debate if such worlds could support complex life given the likelihood of heavy, frequent bombardment from Tau Ceti’s dense debris disk.  Others astronomers argue that a giant planet in the outer system could deflect comets and asteroids away from any world that may support life, much like [[Jupiter]] does for [[Earth]].

Astronomers are hoping to use NASA's [[Terrestrial Planet Finder]] (TPF) and the ESA's Darwin to search for substellar companions, including smaller, terrestrial worlds.

Astronomers are hoping to use NASA's [[Terrestrial Planet Finder]] (TPF) and the ESA's Darwin to search for substellar companions, including smaller, terrestrial worlds.