Optics underpins astronomy Nobel

Graydon, Oliver

doi:10.1038/s41566-019-0565-5

News & Views
Published: 22 November 2019

AWARDS

Optics underpins astronomy Nobel

Oliver Graydon¹

Nature Photonics volume 13, page 827 (2019)Cite this article

814 Accesses
Metrics details

Subjects

Access through your institution

Buy or subscribe

In October 1995, in a landmark paper in Nature¹, the duo reported a Jupiter-mass companion around the star 51 Pegasi in the constellation of Pegasus. Notably, this observation was made by measuring tiny Doppler frequency shifts in the spectral absorption lines of a star that occur when the presence of an orbiting planet slightly perturbs the star’s motion as seen from Earth. Such measurements, usually quoted in terms of variation in the star’s radial velocity, are very small and thus highly demanding. In the 1990s, Mayor and Queloz from the University of Geneva in Switzerland decided to build a custom-designed, highly sensitive echelle spectrograph in order to improve the precision of measurements and expand observations to dimmer stars.

The resulting ELODIE instrument was installed at the Haute-Provence Observatory in France (pictured) and was able to make radial velocity measurements with an accuracy of 13 m s^–1 for stars of up to magnitude 9 in brightness in an exposure time of within 30 min. ELODIE was novel in that instead of using an absorption cell and a slit to measure spectral shifts in stellar absorption lines it used a dual optical fibre delivery system, an echelle grating and a charge-coupled device (CCD) camera (https://go.nature.com/2NqzPCx). One fibre delivered the starlight and the other reference light from a thorium–argon calibration lamp, while the echelle grating performed high-order diffraction and the CCD camera digitally recorded the resulting spectrum between 390 to 680 nm. The result was a spectrograph with a resolving power of 42,000, and, importantly, the radial velocity accuracy of just 13 m s^–1 was precise enough to detect the 59 m s^–1 variation associated with the 51 Pegasi exoplanet. The exoplanet was determined to have a mass of about half of Jupiter and an orbital period of about 4 days.

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

Access options

Access through your institution

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

References

Mayor, M. & Queloz, D. Nature 378, 355–359 (1995).
Article ADS Google Scholar
Obrzud, E. et al. Nat. Photon. 13, 31–35 (2019).
Article ADS Google Scholar
Suh, M.-G. et al. Nat. Photon. 13, 25–30 (2019).
Article ADS Google Scholar
Nat. Photon. 11, 677 (2017).