2021 PH27
Discovery images of 2021 PH27 from the Dark Energy Camera in August 2021 | |
| Discovery | |
|---|---|
| Discovered by | S. S. Sheppard |
| Discovery site | Cerro Tololo Obs. |
| Discovery date | 13 August 2021 |
| Designations | |
| 2021 PH27 | |
| v13aug1 | |
| Atira · NEO | |
| Orbital characteristics | |
| Epoch 2025 May 05 (JD 2460800.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 6.63 yr (2,421 days) |
| Earliest precovery date | 16 July 2017 |
| Aphelion | 0.7903 AU |
| Perihelion | 0.1331 AU |
| 0.4617 AU | |
| Eccentricity | 0.7116 |
| 0.31 yr (114.60 days) | |
| 140.26° | |
| 3° 8m 28.02s / day | |
| Inclination | 31.941° |
| 39.396° | |
| 7 October 2021 @ 106 km/s | |
| 8.579° | |
| Earth MOID | 0.2254 AU |
| Mercury MOID | 0.1123 AU |
| Venus MOID | 0.0147 AU |
| Physical characteristics | |
| 1.2±0.5 km | |
| 3.49±0.01 h | |
| 0.098±0.081 (assumed for X-type asteroids) | |
| X | |
| 19.3 (discovery) 14 (unobservable) | |
| 17.67±0.24 | |
2021 PH27 is a kilometer-sized Atira-type near-Earth asteroid orbiting very close to the Sun. It was discovered by Scott Sheppard using the Dark Energy Camera (DECam) at Cerro Tololo Inter-American Observatory on 13 August 2021. 2021 PH27 has the smallest semi-major axis and shortest orbital period among all known asteroids as of 2026, with a velocity at perihelion of 106 km/s (240,000 mph). It also has the largest relativistic perihelion shift of any known object orbiting the Sun, 1.6 times that of Mercury. 2021 PH27 shares an identical orbit and color as 2025 GN1, which has led astronomers to believe that the two asteroids split apart from a parent body over 10,500 years ago.