26P/Grigg-Skjellerup
26P/Grigg–Skjellerup is a Jupiter-family comet that returns about every 5.3 years. On 10 July 1992 ESA's Giotto, six years after its encounter with Halley's comet, passed it about 200 km from the nucleus.
Key facts
Science
Physical
- Nucleus
- ≈ 2.6 km across — estimated (Lamy et al. 2004); never imaged
- Composition
- Its nucleus has never been imaged: Giotto's camera no longer worked. Giotto passed at 13.99 km/s, at 15:18:43 UT (Neubauer et al. 1993), about 200 km from the nucleus by one estimate (Grensemann and Schwehm 1993); another puts it nearer 100 km, and distances up to 300 km cannot be ruled out (McBride et al. 1997). The nucleus is estimated at about 2.6 km across (Lamy et al. 2004) and is drawn as a plain sphere of that size. Its mass has not been measured.
Orbital
- Semi-major axis
- 3.01 AU
- From catalogued orbital elements (MPC)
- Eccentricity
- 0.641
- From catalogued orbital elements (MPC)
- Inclination
- 22.45 °
- From catalogued orbital elements (MPC)
- Orbital period
- 5.23 years
- From catalogued orbital elements (MPC)
- Perihelion
- 1.08 AU
- Computed from the orbital elements
- Aphelion
- 4.95 AU
- Computed from the orbital elements
- Mean orbital velocity
- 17.2 km/s
- Computed from the orbital elements
Activity
- Perihelion distance
- 1.08 AU
- Becomes active within
- 5 AU of the Sun
Radiation & temperature
- Insolation
- 0.11 S⊕ · 11% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
Discovery & history
- Discovered
- July 23, 1902
- By
- John Grigg (Thames, New Zealand) and J. F. Skjellerup (Cape Town)
- Name
- Named after its two discoverers: John Grigg, who found it from New Zealand in 1902, and J. F. Skjellerup, who found it again from South Africa in 1922.
John Grigg found it at Thames, New Zealand, on 23 July 1902, and J. F. Skjellerup found it again at Cape Town on 17 May 1922; its return in 1927 confirmed that the two were the same comet. On 10 July 1992 Giotto passed it at 13.99 km/s, about 200 km from the nucleus. Its camera no longer worked, so the nucleus was never seen.
Passed at 13.99 km/s, about 200 km from the nucleus by one estimate (other analyses allow about 100 to 300 km); its camera no longer worked, so the nucleus was never seen.
Images
Images from open archives · credit shown per image