Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Detection of Earth-like planets around nearby stars using a petal-shaped occulter

Abstract

Direct observation of Earth-like planets is extremely challenging, because their parent stars are about 1010 times brighter but lie just a fraction of an arcsecond away1. In space, the twinkle of the atmosphere that would smear out the light is gone, but the problems of light scatter and diffraction in telescopes remain. The two proposed solutions—a coronagraph internal to a telescope and nulling interferometry from formation-flying telescopes—both require exceedingly clean wavefront control in the optics2. An attractive variation to the coronagraph is to place an occulting shield outside the telescope, blocking the starlight before it even enters the optical path3. Diffraction and scatter around or through the occulter, however, have limited effective suppression in practically sized missions4,5,6. Here I report an occulter design that would achieve the required suppression and can be built with existing technology. The compact mission architecture of a coronagraph is traded for the inconvenience of two spacecraft, but the daunting optics challenges are replaced with a simple deployable sheet 30 to 50 m in diameter. When such an occulter is flown in formation with a telescope of at least one metre aperture, terrestrial planets could be seen and studied around stars to a distance of ten parsecs.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Schematic showing how a starshade in position against a nearby star might appear.
Figure 2: Achieved stellar suppression.
Figure 3: Seeing Earth-like planets.

References

  1. Seager, S. The search for extra-solar Earth-like planets. Earth Planet. Sci. Lett. 208, 113–124 (2003)

    Article  ADS  CAS  Google Scholar 

  2. Henry, C. et al. Terrestrial planet finder interferometer: architecture, mission design, and technology development. Proc. Soc. Photo-Opt. Instrum. Eng. 5491, 265–274 (2004)

    Google Scholar 

  3. Marchal, C. Concept of a space telescope able to see the planets and even the satellites around the nearest stars. Acta Astronaut. 12, 195–201 (1985)

    Article  ADS  Google Scholar 

  4. Copi, C. J. & Starkman, G. D. The big occulting steerable satellite (BOSS). Astrophys. J. 532, 581–592 (2000)

    Article  ADS  Google Scholar 

  5. Schultz, A. B. et al. UMBRAS: a matched occulter and telescope for imaging extrasolar planets. Proc. Soc. Photo-Opt. Instrum. Eng. 4860, 54–61 (2003)

    Google Scholar 

  6. Jordan, I. J. E. et al. Apodized square aperture plus occulter concept for TPF. Proc. Soc. Photo-Opt. Instrum. Eng. 5487, 1391–1401 (2004)

    Google Scholar 

  7. Kasdin, N. J., Vanderbei, R. J., Spergel, D. N. & Littman, M. G. Extrasolar planet finding via optimal apodized and shaped pupil coronagraphs. Astrophys. J. 582, 1147–1161 (2003)

    Article  ADS  Google Scholar 

  8. Vanderbei, R. J., Spergel, D. N. & Kasdin, N. J. Circularly symmetric apodization via star-shaped masks. Astrophys. J. 599, 686–694 (2003)

    Article  ADS  Google Scholar 

  9. Cash, W., Kasdin, J., Seager, S. & Arenberg, J. Direct studies of exo-planets with the New Worlds Observer. Proc. Soc. Photo-Opt. Instrum. Eng. 5899, 274–285 (2005)

    Google Scholar 

Download references

Acknowledgements

I thank R. Vanderbei, J. Kasdin, M. Lieber, and J. Arenberg for advice, discussion and encouragement. I thank D. Feldkhun, A. Lo, N. Rajan, E. Schindhelm, and W. Simmons for investigating alternative approaches and verifying the results of this paper. I wish to thank R. Cassanova and the NASA Institute for Advanced Concepts for financial support and encouragement of the work from its early stages.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Webster Cash.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The author declares no competing financial interests.

Supplementary information

Supplementary Notes

This file contains Supplementary Information, including Supplementary Figures 1–3 and two references. (PDF 76 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Cash, W. Detection of Earth-like planets around nearby stars using a petal-shaped occulter. Nature 442, 51–53 (2006). https://doi.org/10.1038/nature04930

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature04930

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing