Evidence of interstellar Na I structure at scales down to 15 AU in low-density gas

J. T. Lauroesch*, David M. Meyer, J. C. Blades

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


We present high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph and multiepoch KPNO coudé feed observations of multiple interstellar lines toward the binary system HD 32039/40. Comparisons of the Na I profiles observed over a period of 4.25 yr reveal significant temporal variation in the Na I column in at least one component, implying that there is structure at scales on the order of the proper motion (~15-21 AU). Large differences are also observed among multiple components in the profiles of the neutral species between the binary sight lines (5060 AU separation). In addition, significant differences in the S II profile are seen between the stars - the first optical/UV detection of small-scale variations in a dominant ion. Measurements of the C I fine-structure excitation in the variable components suggest that the densities in these components are ~20-200 cm-3, significantly lower than the densities inferred in past H I 21 cm and Na I studies.

Original languageEnglish (US)
Pages (from-to)L43-L47
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - Nov 1 2000


  • ISM: Clouds
  • ISM: Structure
  • Stars: Individual (HD 32039, HD 32040)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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