Results 1 to 3 of 3

Thread: Major error in February 2019 Sky and Telescope

  1. #1
    Join Date
    Mar 2007
    Location
    Falls Church, VA (near Washington, DC)
    Posts
    8,355

    Major error in February 2019 Sky and Telescope

    On p. 49 in the article "Echoes from a Variable Star" the author asserts that RS Puppis, a Cepheid variable, culminates at different altitudes on different dates over a few weeks during the winter, over a range of a few degrees. We all know that the declination of a star, and thus its altitude at culmination, is virtually constant over such a short time, with only vanishingly small changes from precession and proper motion. Unless I am missing something, this is a ghastly error. I have written to them, saying just what I am saying here.

  2. #2
    Join Date
    Mar 2007
    Location
    Falls Church, VA (near Washington, DC)
    Posts
    8,355
    Quote Originally Posted by Hornblower View Post
    On p. 49 in the article "Echoes from a Variable Star" the author asserts that RS Puppis, a Cepheid variable, culminates at different altitudes on different dates over a few weeks during the winter, over a range of a few degrees. We all know that the declination of a star, and thus its altitude at culmination, is virtually constant over such a short time, with only vanishingly small changes from precession and proper motion. Unless I am missing something, this is a ghastly error. I have written to them, saying just what I am saying here.
    Another one for the “Oops”! file. In a December 2017 article about the Geminids the author asserted that the meteors are relatively slow because of the shallow angle of entering the atmosphere. As I understand it that is not why they are slow. They are in a direct orbit and are converging at a somewhat low relative velocity. In contrast the Leonids, in a retrograde orbit, meet the Earth in nearly head-on collisions and thus are extremely fast. This holds regardless of whether the entry is grazing when the radiant is at the horizon or nearly vertical when the radiant is high.

  3. #3
    Join Date
    Jul 2005
    Posts
    17,190
    Yeah, that makes no sense - the angle should be everywhere from grazing to vertical for all meteor showers, according to whether the meteors strike the edge or centre of the Earth's disc. (From an Earth observer's point of view, depending on whether the radiant is on the horizon or overhead.) What's strikingly different, as you say, is the relative velocity of different showers.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •