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Posts Tagged ‘tau ceti f

[NEWS] Four science links, from water on the frontier to climate change to Tau Ceti exoplanets

  • At Wired, Matt Simon explores the remarkably wrong-headed theory of the 19th century US that “rain follows the plough.”
  • These National Geographic photos of the unexplored lakes in Angola that feed the Okavango are remarkable.
  • Rachel Brown examines billy burr, the Colorado hermit whose collection of decades of climate data is invaluable.
  • Universe Today notes a new study confirming the existence of Tau Ceti e and f, potentially habitable rocky exoplanets just 12 light years away.
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Written by Randy McDonald

August 9, 2017 at 10:59 pm

[LINK] The Tau Ceti system

A large part of me wants to making the posting of maps of planetary systems a daily feature. I’ll satisfy myself by reposting the below map, drawn up by the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo of the orbits of the five worlds discovered orbiting nearby Tau Ceti (Sol Station, Wikipedia), after Wednesday’s remarkable announcement. It turns out that a dense cloud of debris in-system might mean a planet would get heavily bombarded with cosmic detritus, but certainly doesn’t mean planets won’t form in the first place.

Chart of the Tau Ceti system

This came with this press release authored by Abel Mendez Torres, who made the point that Tau Ceti e (orbiting just inside the inner edge of the habitable zone, makred in blue) and Tau Ceti f (the outermost planet, orbiting just inside the outer edge of the habitable zone) are only marginally habitable.

Tau Ceti e doesn’t look very promising.

The planet Tau Ceti e orbits close to the inner edge of the habitable zone. It receives about 60% more light than Earth from the Sun making it a hot planet probably only habitable to simple thermophilic (heat-loving) life. Its mean global surface temperature should be near 70°C assuming a similar terrestrial atmosphere. However, it is likely that superterran planets have much denser and heat trapping atmospheres and Tau Ceti e might be instead dominated by a strong greenhouse effect making it more likely a super-Venus than a super-Earth. Without any knowledge of its atmosphere we are not able to tell if it is a mildly hot planet tolerable for simply life forms or a very hot non habitable Venus-like world. Tau Ceti e has an Earth Similarity Index of 0.77 assuming a more terrestrial-like atmosphere.

Tau Ceti f, now, might well be more promising.

The planet Tau Ceti f orbits close to the outer edge of the habitable zone. It only receives about 27% the light of Earth from the Sun making it a cold planet probably only habitable to simple psychrophilic (cold-loving) life. Its mean global surface temperature should be near -40°C assuming a similar terrestrial atmosphere. However, it is likely that as Tau Ceti e, it is also dominated by a strong greenhouse effect making it even acceptable for complex life, which requires temperatures from 0°C to 50°C. Without any knowledge of its atmosphere we are not able to tell if it is a frozen Mars-like planet tolerable for simply life forms or even an Earth-like world. Tau Ceti [f] has an Earth Similarity Index of 0.71 assuming a more terrestrial-like atmosphere.

It’s worth noting that there is a very large gap between e at ~0.55 AU and f at ~1.35 AU. Might there be other planets, smaller planets, squarely in Tau Ceti’s habitable zone? (0.7 AU seems to be the right distance.)

Written by Randy McDonald

December 21, 2012 at 9:21 pm