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View Full Version : There's now a catalog of potentially habitable exoplanets



lpetrich
2014-Jul-07, 08:18 AM
I've discovered a catalog of potentially *habitable* ones. Those within their stars' habitable zones, where they can have liquid water on their surfaces.
The Habitable Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo (http://phl.upr.edu/projects/habitable-exoplanets-catalog)
It lists 22 confirmed planets, all super-Earths, and 67 Kepler candidates, mostly super-Earths. These are what's easiest to detect, it must be pointed out.

For exoplanets in general:
PHL's Exoplanets Catalog (http://phl.upr.edu/projects/habitable-exoplanets-catalog/data/database)
exoplanets.org - Exoplanet Orbit Database (http://exoplanets.org/)
exoplanets.eu - Extrasolar Planet Encyclopaedia (http://exoplanets.eu/)
NASA Exoplanet Archive (http://exoplanetarchive.ipac.caltech.edu/)
Open Exoplanet Catalogue (http://www.openexoplanetcatalogue.com/)

I've also found HEC: Periodic Table of Exoplanets - Planetary Habitability Laboratory @ UPR Arecibo (http://phl.upr.edu/projects/habitable-exoplanets-catalog/media/pte) It classifies planets by surface temperature:

Cold (water is solid)
Warm (water can be liquid) -- Habitable
Hot (water is gaseous)

Also by mass and size:

Mercurian: 10^(-5) - 0.1 ME, 0.03 - 0.4 RE
Subterran: 0.1 - 0.5 ME, 0.4 - 0.8 RE
Terran: 0.5 - 2 ME, 0.8 - 1.25 RE
Superterran: 2 - 10 ME, 1.25 - 2.6 RE
Neptunian: 10 - 50 ME, 2.6 - 6 RE
Jovian: > 50 ME, > 6 RE

The Solar System has 82 objects in this classification:

Planet SizeHotWarmCold
Mercurian1173
Subterran010
Terran110
Superterran000
Neptunian002
Jovian002

Hot ones: Mercury, -, Venus
Warm ones: Moon, Mars, Earth
Big cold ones: Uranus and Neptune, Jupiter and Saturn
Small cold ones: the larger asteroids, outer-planet moons, and Kuiper-Belt objects
No superterrans

1781 confirmed exoplanets:

Planet SizeHotWarmCold
Mercurian400
Subterran1500
Terran10910
Superterran501205
Neptunian3341215
Jovian469103183

The stats look very different, and this is almost certainly from the method used to detect many of them: radial velocity. Hot planets show up much more easily than cold ones, and big planets much more easily than small ones.

3845 Kepler candidates:

Planet SizeHotWarmCold
Mercurian400
Subterran13510
Terran55773
Superterran1730613
Neptunian892481
Jovian364361

Kepler's detectable-size threshold is subterran size, and its total observation time of 4 years made it hard to detect warm planets, let alone cold ones.

How many planets detected for each star:

#ConfirmedKepler
16412363
2310388
399134
43349
51218
643
710

This is also likely an artifact of what is easiest to detect. Hot Jupiters for radial velocity, and hot subterran-and-above planets for Kepler.

So the statistical properties of detected exoplanets are far from those of the Solar System's planets, meaning that we are still a long way from telling how typical or atypical the Solar System is.