Recent news articles about the habitability of a newly discovered world 35 light-years from Earth are overblown, Scientists made a much weaker claim in the published report. The planet is as likely to be another furnace-like Venus as another Earth.
Scientists at the European Southern Observatory (ESO) in Chile found that the star HD85512 (about 35 light-years from Earth) has a planet revolving about it that astronomers have named HD85512b. The news media have exaggerated the reports of the scientists. For example, The Guardian, a British newspaper whose science reporting has gone askew of late, titled an article published 13 September 2011 “Super-earth exoplanet found that could support life” (an exoplanet is a planet around a star other than the Sun), The article states: “[I]t is estimated that temperatures there range from 30C to 50C, and it is thought that the atmosphere is very humid.” These statements are typical of media coverage of HD85512b.
The scientific paper published by a team of scientists from the ESO (L. Kalteneggar, S. Udry, and F. Pepe) is titled “Habitable Planet around HD 85512?” The tentativeness and timidity of the title contrast sharply with The Guardian’s article. The scientific paper makes much weaker claims.
The paper asserts that the exoplanet HD85512b is within the habitable zone around its star. The habitable zone around a star is the area where liquid water can exist. If an earth-like planet is too close to a star, the only form of water that can exist there is steam and it is too hot to be habitable; if it is too far, then water can only exist as ice and it is too cold to be habitable. Planets in the habitable zone are said to be “just right” in temperature like the porridge in the story of Goldilocks. The habitable zone is sometimes called the Goldilocks zone. Thus the planet is said to be habitable given that water exists there, of which there is neither proof or even evidence in the case of HD85512b.
The Theoretical Habitable Zone Around HD85512. The green area is the most habitable.* Image Courtesy Wikipedia.
The authors of the scientific paper made a number of assumptions: (1) HD85512b is made of rock like Earth, (2) the exoplanet has an atmosphere of water vapor, carbon dioxide, and nitrogen, and (3) the planet is near the lower limit of its estimated mass. They note that the star HD85512 burns this planet with less radiation than the Sun puts out on Venus. They conclude, after considerable discussion and calculation, that if it is protected by enough cloud cover, “HD 85512 b is a planet on the edge of habitability.”
The ESO itself put out a much more accurate report than the Guardian’s, which may be found on its website as press release (http://www.eso.org/public/news/eso1134/) or a video:
*Wikimedia has the following legend for the color-coding of diagram of the habitable zone about HD85512b:
Red: Recent Venus (inner) – Runaway greenhouse (outer)
Yellow: Runaway greenhouse (inner) – Water loss (outer)
Green: Water loss (inner) – First CO2 condensation (outer)
Cyan: First CO2 condensation (inner) – Maximum greenhouse (outer)
Blue: Maximum greenhouse (inner) – Early Mars (outer)
Using this definition of the habitable zone, the most conservative habitable zone is the green region, the inner boundary corresponding to the start of water loss and the outer limit corresponding to the first condensation of carbon dioxide in the atmosphere.
“ESOcast 35: Fifty New Exoplanets.” September 12, 2011. (video) www.eso.org http://www.eso.org/public/news/eso1134/ (Accessed September 13, 2011).
“Fifty New Exoplanets Discovered by HARPS — Richest haul of planets so far includes 16 new super-Earths.” September 12, 2011. www.eso.org. http://www.eso.org/public/news/archive/year/2011/ (Accessed September 13, 2011).
Godfrey, Hannah. “Super-earth exoplanet found that could support life.” The Guardian. September 13, 2011. http://www.guardian.co.uk/science/2011/sep/13/super-earth-exoplanet-found-support-life. (Accessed September 13, 2011).
“HD85512b.” Wikipedia. (Accessed September 13, 2011).
Kalteneggar, L., S. Udry, and F. Pepe. “A Habitable Planet Around HD85512 b?” www.cfa.harvard.edu. https://www.cfa.harvard.edu/~lkaltenegger/Home_files/KalteneggerHD85512.pdf. (Accessed September 13, 2011.