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IN RETROSPECT

30 years of exoplanet detections

Nature Reviews Physics volume 4, page 290 (2022)Cite this article

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Until 30 years ago, the idea of finding planets outside our Solar System was a dream. It made sense that such exoplanets should exist — why should our Solar System be unique in the whole Universe, after all? — but actually detecting such small, far-away, objects that produce no visible light of their own posed a huge technical challenge. There had been previous suspected exoplanet discoveries, but it was in 1992 that Aleksander Wolszczan and Dale Frail announced that they had discovered at least two exoplanets, and theirs was the first discovery to be confirmed. Over the next few years, dozens more exoplanets were discovered, until the rate of discovery really took off with the launch of NASA’s dedicated exoplanet-hunting mission, Kepler, in 2009; there are now nearly 5,000 confirmed exoplanets.

Although planets orbiting pulsars were the first confirmed detections, such planetary systems are unlikely to be common. But to detect ‘normal’ exoplanets required new techniques that didn’t rely on exquisite details of the systems under observation. Fortunately, technological advances were making other methods possible, and in 1995, Michel Mayor and Didier Queloz announced that they had detected a Jupiter-mass planet orbiting a solar-type star. They did so by monitoring the radial velocity of the star as it moved in response to the planet’s gravitational pull. The motion of the star results in shifts in its measured spectral lines, because of the Doppler effect. Such shifts are tiny, and the method works best if the planet is large and close to a small star, so that the motion of the star is as large as possible. However, despite this drawback, the technique has found hundreds of candidate exoplanets.

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References

Original article

  • Wolszczan, A. & Frail, D. A. A planetary system around the millisecond pulsar PSR1257 + 12. Nature 355, 145–147 (1992)

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Related article

  • Mayor, M. & Queloz, D. A Jupiter-mass companion to a solar-type star. Nature 378, 355–359 (1995)

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  • Udalski, A. et al. The Optical Gravitational Lensing Experiment. Search for planetary and low-luminosity object transits in the Galactic Disk. Results of 2001 campaign — supplement. Acta Astron. 52, 115–128 (2002)

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  1. Nature Reviews Physics https://www.nature.com/natrevphys/

    Zoe Budrikis

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  1. Zoe Budrikis
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Correspondence to Zoe Budrikis.

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Budrikis, Z. 30 years of exoplanet detections. Nat Rev Phys 4, 290 (2022). https://doi.org/10.1038/s42254-022-00459-x

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