Pick spin-up or spin-down and scrub or play elapsed years to watch sunlight torque on two asymmetric asteroid facets speed up or slow down its rotation, then read the real measured spin-up rate on asteroid 54509 YORP.
An irregularly-shaped asteroid reflects and re-emits sunlight unevenly across its asymmetric facets. That imbalance creates a net torque about the spin axis - not a net force on the orbit - so the rotation rate itself speeds up or slows down over years to decades. Asteroid 54509 YORP (formerly 2000 PH5) is a measured spin-up case: four years of photometry plus a radar shape model found its already-fast 12.174-minute rotation period shortening at a real, published rate.
Drag to orbit and scroll or pinch to zoom. For the sibling non-gravitational, orbit-shifting mechanism see the Yarkovsky Effect 3D Explorer; for gravitational maneuvers see the Gravitational Slingshot 3D Explorer.
YORP Effect 3D Explorer
This browser explorer shows sunlight torque on an irregular asteroid's asymmetric facets speeding up or slowing down its spin, then lets you compare that against asteroid 54509 YORP's real measured spin-up rate.
The YORP effect (Yarkovsky-O'Keefe-Radzievskii-Paddack effect) is a net torque, not a net force: sunlight reflected and thermally re-emitted off an irregularly-shaped body's asymmetric facets pushes unevenly around the spin axis, so the rotation rate itself changes over years to decades. Four years of precise optical photometry (2001-2005) plus a radar shape model of near-Earth asteroid (54509) YORP - discovered 2000-08-03 by the LINEAR survey and about 150 x 128 x 93 meters across - found its spin rate steadily increasing: domega/dt = (2.0 +/- 0.2) x 10^-4 degrees per day squared (Taylor et al. 2007, Science 316, 274-277), independently confirmed the same year by a separate photometric study (Lowry et al. 2007, Science 316, 272-274). Gravitational perturbations from the asteroid's close Earth approaches during that window were modeled and shown unable to explain the spin-up, confirming the non-gravitational YORP cause - together the first direct observational confirmation that sunlight measurably changes an asteroid's spin, and why the International Astronomical Union later named the asteroid "YORP" for the discovery's significance.
- Pick spin-up (54509 YORP, measured) or spin-down (teaching mirror)
- Scrub or play elapsed years (0-100) to watch the rotation speed change
- Read the period-change readout alongside 54509 YORP's real measured rate
- Compare with the Yarkovsky-effect sibling and the gravitational-maneuver pages
- Drag to orbit, scroll or pinch to zoom
- Runs fully in the browser with the vendored three.js engine - no account, no upload
| Figure | Value |
|---|---|
| 54509 YORP measured spin-up rate | domega/dt = (2.0 +/- 0.2) x 10^-4 deg/day^2 (Taylor et al. 2007, Science) |
| Current rotation period | 12.174 minutes (730.4 s) |
| Derived period change | about 1.25 ms/year shorter (commonly rounded to "about 1 ms/year") |
| Long-term projection | dynamical simulations project ~20 s by the end of its dynamical lifetime (Taylor et al. 2007) |
| Size (radar shape model) | about 150 x 128 x 93 meters |
Every asteroid with a directly-measured YORP rotation-rate change to date - including 1862 Apollo, 1620 Geographos, 3103 Eger, 25143 Itokawa, 1685 Toro, 161989 Cacus, and 1992 SK alongside 54509 YORP - has measured as spinning up, a documented observational asymmetry (Durech et al. 2022, Astronomy & Astrophysics). YORP-driven spin-up is also implicated in forming small asteroid binary and pair systems once a rubble-pile body reaches its structural breakup spin limit (Walsh, Richardson & Michel 2008, Nature). For the sibling non-gravitational, orbit-shifting mechanism, open the Yarkovsky Effect 3D Explorer; for impulsive gravity-assist maneuvers, open the Gravitational Slingshot 3D Explorer.
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached.
This is an educational approximation - the on-screen spin speed and the wedge-bump/arrow geometry are exaggerated for teaching, not a to-scale simulation. The Spin-down option mirrors 54509 YORP's real measured magnitude with the sign flipped to teach the general rule; it is not a second measured asteroid.
Frequently Asked Questions
What is the YORP effect?
A net torque from sunlight reflected and thermally re-emitted off an irregularly-shaped asteroid's asymmetric facets. Unlike a net force, a torque acts about the spin axis, so it changes the body's rotation rate rather than its orbit.
How was it measured on asteroid 54509 YORP?
Four years of precise optical photometry (2001-2005) plus a radar shape model found the spin rate steadily increasing at domega/dt = (2.0 +/- 0.2) x 10^-4 degrees per day squared (Taylor et al. 2007, Science), independently confirmed the same year by a separate photometric study (Lowry et al. 2007, Science).
Is the Spin-down option a second real measured asteroid?
No. It mirrors 54509 YORP's real measured magnitude with the sign flipped, to teach the general rule that YORP torque direction depends on shape and obliquity - it is a teaching mirror, not a second measured object. No asteroid has yet had a directly-measured YORP spin-down confirmed.
How is the YORP effect different from the Yarkovsky effect?
Yarkovsky is a net force from a spinning body's thermal-lag re-emission that shifts its orbit (semimajor axis). YORP is a net torque from an irregular shape's asymmetric facets that changes the body's spin rate instead - the orbit itself is not directly altered by YORP. See the Yarkovsky Effect 3D Explorer.
Could YORP also change an asteroid's spin-axis direction?
Yes - over much longer timescales than the spin-rate change shown here, theory shows YORP also drives a body's spin-axis obliquity toward 0, 90, or 180 degrees (Capek and Vokrouhlicky 2004). This page visualizes only the spin-rate change, not obliquity evolution.
Why does this matter for asteroid pairs and binaries?
YORP-driven spin-up is implicated in forming small asteroid binary and pair systems once a rubble-pile body spins fast enough to reach its structural breakup limit (Walsh, Richardson and Michel 2008, Nature).
Is the on-screen spin change real physics?
The direction (sunlight torque can speed up or slow down rotation) and 54509 YORP's cited rate are real. The on-screen spin speed and the wedge-bump/arrow geometry are exaggerated for teaching, not a to-scale simulation.
How is this different from the gravitational-slingshot page?
That page teaches an impulsive gravity-assist maneuver. This page is a slow, continuous, sunlight-powered torque - the only rotation-rate-changing mechanism among the space visualizers on this site.