Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Distance of GJ 436b to GJ 436 - doesn't work out.

  1. Jun 24, 2015 #1
    In an article on phys.org [http://phys.org/news/2015-06-red-dwarf-planet-hydrogen-massive.html] [Broken], it states that the exoplanet GJ 436b is 33x closer to its parent star than the earth is to our sun. It also states that the exoplanet is less than 2 million miles away from the star. If I assume an average distance of 93 million miles (earth-sun), then 1/33rd that yields nearly 3 million miles. Less than 2 million miles would yield a value approximately 48x closer than the earth-sun distance. What am I assuming incorrectly?
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Jun 25, 2015 #2

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    You are assuming the article is correct. That phys.org article is a word-for-word copy of http://www.nasa.gov/feature/goddard...h-bleeding-atmosphere-around-a-warm-exoplanet .

    When you look at other sites, and even better, in scientific journals (e.g., http://arxiv.org/abs/0707.2778), GJ 436b's orbit has a semi-major axis of 0.0291 au, or 2.7 million miles. The easiest explanation is that there's a typo in the NASA press release, and that this typo was copied over and over without question by sites such as phys.org.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook