Access

Letters to Nature

Nature 407, 485-487 (28 September 2000) | doi:10.1038/35035015; Received 22 June 2000; Accepted 21 July 2000

Open Innovation Challenges

  • Methods to Analyze Consumer Emotions

    • Deadline: Jan 17 2010
    • Reward: $10,000 USD

    The Seeker is looking for methods to analyze consumer emotions. This Challenge requires only a writ...

  • Single-cell Analysis Platform

    • Deadline: Dec 02 2009
    • Reward: $5,000 USD

    This Challenge is looking for novel approaches to analyzing changes at a single-cell level. This is...

naturejobs

More science jobs
Post a job for free

Direct detection of pulsations of the Cepheid star zeta Gem and an independent calibration of the period–luminosity relation

B. F. Lane1, M. J. Kuchner1, A. F. Boden2, M. Creech-Eakman3 & S. R. Kulkarni1

  1. Palomar Observatory 105-24,
  2. Infrared Processing and Analysis Center,
  3. Jet Propulsion Laboratory 171-113, California Institute of Technology, Pasadena

Correspondence to: S. R. Kulkarni1 Correspondence and requests for materials should be addressed to B.F.L. (e-mail: Email: bfl@astro.caltech.edu).

Top

Cepheids are a class of variable (pulsating) stars whose absolute luminosities are related in a simple manner to their pulsational periods. By measuring the period and using the 'period–luminosity' relationship, astronomers can use the observed visual brightness to determine the distance to the star. Because these stars are very luminous, they can be observed in other galaxies, and therefore can be used to help determine the expansion rate of the Universe1 (the Hubble constant). Calibration of the period–luminosity relation is a necessary first step, but the small number of sufficiently nearby Cepheids has forced the use of a number of indirect means, with associated systematic uncertainties. Here we present a distance to the Cepheid zeta Geminorum, determined using a direct measurement (by an optical interferometer) of its changes in diameter as it pulsates. Within our uncertainty of 15 per cent, our distance is in agreement with previous indirect determinations. Planned improvements to the instrument will allow us to calibrate directly the period–luminosity relation to better than a few per cent.

  1. Palomar Observatory 105-24,
  2. Infrared Processing and Analysis Center,
  3. Jet Propulsion Laboratory 171-113, California Institute of Technology, Pasadena

Correspondence to: S. R. Kulkarni1 Correspondence and requests for materials should be addressed to B.F.L. (e-mail: Email: bfl@astro.caltech.edu).