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Pulsation timing variations

Some stars pulse like clocks; a planet makes the pulse arrive late.

2 planets found this way → Minimum mass Orbital period
An ordinary star that pulsates rhythmically; an orbiting planet shifts when each pulse arrives it swells and shrinks a clock — but one that wanders on its own far less steady than a pulsar

How the measurement works

Certain stars — subdwarf B stars, some white dwarfs, delta Scuti variables — oscillate with periods stable enough to serve as a clock, though far less precise than a pulsar.

An orbiting planet moves the star toward and away from us, and the pulsations arrive early and late by the light travel time across the star's own small orbit.

It is pulsar timing's logic applied to an ordinary star, with a clock several orders of magnitude worse — hence only two planets in the catalogue.

The arithmetic

Timing shift
Δt = (a* sin i / c) · sin(2πt / P)
Same relation as pulsar timing. Everything depends on how stable the star's pulsation actually is over years.

Why only two

Pulsar clock stability nanoseconds sub-lunar masses detectable
Pulsating star stability seconds, drifting giant planets at best
Planets found 2 against 8 by pulsar timing

The idea is sound; the clock is simply not good enough, and stellar pulsations wander for their own reasons.

What it does well
  • Works on evolved stars where other methods struggle
  • Can reuse long photometric archives
Where it cannot help
  • Pulsations are not stable enough to trust easily
  • Very few detections, some contested
  • Minimum mass only
Landmark discovery V391 Pegasi b — a giant planet that apparently survived its star's red-giant phase.
Instruments Ground-based photometry, Kepler
Archive name Pulsation Timing Variations — the value in NASA's discoverymethod field

Browse the 2 planets found by this method →

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