• Question: how cold is Pluto's surface?

    Asked by the josh to Chris, Josh, Rebecca, Rob, Susan on 18 Jun 2015.
    • Photo: Rebecca Dewey

      Rebecca Dewey answered on 18 Jun 2015:

      The surface of pluto is at approximately -229 degrees C. Pluto is in an elliptical (oval-shaped) orbit, so its distance from the sun (which is the main thing that affects its surface temperature) varies quite a lot. So it can get as cold as -240 degrees C or it can reach a balmy -218 degrees C. Still pretty chilly!

    • Photo: Susan Cartwright

      Susan Cartwright answered on 18 Jun 2015:

      This varies quite a bit, because Pluto has a very non-circular (elliptical) orbit: its distance from the Sun varies from 29.7 times the Sun-Earth distance (that’s 4.44 billion kilometres) to 48.9 times (7.31 billion kilometres). Ut’s presently about 39.4 times the Sun-Earth distance, i.e. 5.89 billion kilometres, from the Sun, and moving outwards, so it is getting colder. At its coldest, it’s roughly 33 K, or -240 C; at its warmest, about 55 K, or -218 C; at present, about halfway between these (-229 C or 44 K).

      These are pretty much estimates at the moment. We will have much more information in about a month, when NASA’s “New Horizons” probe does a flyby of Pluto (it’s unfortunately travelling too fast to be able to go into orbit). This will be the first time we have ever observed Pluto from close up, and will probably tell us a lot more about surface conditions.

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