How many habitable planets are in our galaxy?

Ethan Siegel
Jan 7, 2015 · 10 min read
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Image credit: NASA.
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Image credit: NASA Ames.
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Image credit: Rachel Street of http://lcogt.net/spacebook/transit-method.
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Image credit: ESO.
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Image credit: Matt / The Zooniverse, via http://blog.planethunters.org/2010/12/20/transiting-planets/.
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Image credit: NASA.
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Image credit: NASA Ames/W Stenzel.
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Image credit: CoRoT exo-team, via http://sci.esa.int/corot/40952-transit-of-exoplanet-corot-exo-1b/.
  • around small stars, because they block a higher percentage of their parent star’s light,
  • that orbit very close to the star itself, because you’ll see transits far more frequently.
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Image credit: NASA / Kepler; slightly out of date.
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Image credit: ESA/NASA/SOHO, of the Mercury transit in 2006.
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Image credit: NASA / JPL-Caltech / Wikimedia Commons user Henrykus.
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Image credit: Jack J. Lissauer, Rebekah I. Dawson, & Scott Tremaine, via Nature 513, 336–344 (18 September 2014).
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Image credit: NASA, of WASP-43b, which is not lined up to ever transit its parent star! Via http://wasp-planets.net/2014/10/10/hubble-maps-the-atmosphere-of-wasp-43b/.
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Image credit: me.
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Image credit: NASA/JPL-Caltech/T. Pyle.
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Image credit: Exoplanets Data Explorer, via http://exoplanets.org/plots, of planetary candidate radius (y-axis) plotted against semimajor axis-to-star-radius ratio (x-axis). The Earth has about 1/11th the radius of Jupiter and the a/R* ratio for the Earth is just a little over 100. As you can see, we preferentially find planets closer to their stars than that!
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Image credit: Steve Jurvetson.

Starts With A Bang!

The Universe is out there, waiting for you to discover it.

Ethan Siegel

Written by

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.

Starts With A Bang!

The Universe is out there, waiting for you to discover it.

Ethan Siegel

Written by

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.

Starts With A Bang!

The Universe is out there, waiting for you to discover it.

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