2020 HS7
2020 HS7 is a very small asteroid classified as a near-Earth object of the Earth-crossing Apollo group. When it was discovered by the Pan-STARRS 2 survey on 27 April 2020, the asteroid was initially calculated to have a 10% chance of impact with Earth before being ruled out by improved orbit determinations from additional observations. Although there is now no risk of impact with Earth, it did make a close approach 42,700 kilometres (26,500 mi) from Earth on 28 April 2020, with a flyby speed of 15.6 kilometres per second (9.7 mi/s) relative to Earth. The asteroid will not make any close encounters within 1 lunar distance (380,000 km; 240,000 mi) of Earth in the next 100 years.
| Discovery | |
|---|---|
| Discovered by | Pan-STARRS 2 |
| Discovery site | Haleakala Obs. |
| Discovery date | 27 April 2020 |
| Designations | |
MPC designation | 2020 HS7 |
Minor planet category | NEO · Apollo |
| Orbital characteristics | |
| Epoch 9 August 2022 (JD 2459800.5) | |
| Uncertainty parameter 6 | |
| Observation arc | 1 day |
| Aphelion | 2.904 AU |
| Perihelion | 0.793 AU |
Semi-major axis | 1.849 |
| Eccentricity | 0.5709 |
Orbital period (sidereal) | 2.51 yr (918 days) |
Mean anomaly | 308.988° |
Mean motion | 0° 23m 31.807s / day |
| Inclination | 4.732° |
Longitude of ascending node | 38.531° |
| 245.692° | |
| Physical characteristics | |
| Dimensions | a/b = ≥1.04 |
Mean diameter | 4–8 m |
Synodic rotation period | 2.9945±0.0002 s 2.9938±0.0002 s |
| 29.10±0.36 | |
Observations by Kiso Observatory in Nagano, Japan show that the asteroid rotates extremely rapidly with a rotation period of 3 seconds, making it the fastest-rotating asteroid known as of 2022. No other near-Earth asteroid of similar size is known to have a rotation period shorter than 10 seconds, which could be attributed to the tangential component of the YORP effect accelerating their rotation far beyond this period. The asteroid exhibits a very small light curve amplitude of 0.07 magnitudes, which either implies a nearly spherical shape or a pole-on rotation during observations.