File:128_Nemesis_VLT_(2021),_deconvolved.pdf · Wikimedia Commons · See Wikimedia Commons
Picture of the Day · NASA
Pathfinder on Mars
2026-07-04
On July 4th, 1997, using its own array of fireworks, a parachute, and a cocoon of airbags, the Mars Pathfinder spacecraft bounced like a giant beach ball at least 15 times before it came to rest on the surface of Mars at 10:07 AM Pacific Daylight Time. After its then novel airbag-assisted landing sequence was completed, Pathfinder transmitted this color mosaic to mission operators on Earth. In the scene from another world, the Mars Sojourner robot rover is visible in the foreground, crouched on top of the unfolded Pathfinder. About the size of a large house cat, the six-wheeled, solar-powered Sojourner became the first successful Martian rover. Surrounding Pathfinder are deflated airbags and the rock-strewn terrain of the Ares Vallis floodplain. In the distance Martian hills appear against a dusty brownish sky. The Pathfinder lander was subsequently renamed the Carl Sagan Memorial Station.
via NASA APOD
Key facts
- Discovered by
- James Craig Watson
- Discovery date
- 25 November 1872
- Pronunciation
- / ˈ n ɛ m ɪ s ɪ s /
- Named after
- Nemesis
- Alternative designations
- A872 WA; 1952 HW 1
- Minor planet category
- main-belt · Nemesis
- Adjectives
- Nemesian / n ə ˈ m iː ʒ ( i ) ə n /
- Observation arc
- 144.93 yr (52,934 d)
- Aphelion
- 3.10 AU (463.69 Gm )
- Perihelion
- 2.40 AU (359.00 Gm)
- Semi major axis
- 2.75 AU (411.35 Gm)
- Orbital period sidereal
- 4.56 years (1,665 d)
- Mean anomaly
- 345.49 °
- Mean motion
- 0° 12 58.32 / day
- Inclination
- 6.2453°
- Longitude of ascending node
- 76.243°
- Argument of perihelion
- 303.82°
- Mean diameter
- 163 ± 5 km , 162.5 ± 1.3 km , 184.2 ± 5.2 km
via Wikipedia infobox
Wikidata facts
- Instance of
- asteroid
- Named after
- Nemesis
- Followed by
- 129 Antigone
- Follows
- 127 Johanna
- Parent body
- Sun
- Minor-planet group
- asteroid belt
- Diameter
- 162.515
- Orbital period
- 1665.678187935098
- Image
- 128 Nemesis (orbit).gif
Show 20 more facts
- discoverer or inventor
- James Craig Watson
- site of astronomical discovery
- Detroit Observatory
- provisional designation
- A872 WA
- time of discovery or invention
- 1872-11-25
- asteroid spectral type
- C-type asteroid
- orbital inclination
- 6.246829388245652
- albedo
- 0.067
- different from
- Nemesis
- Commons category
- 128 Nemesis
- rotation period
- 38.9325
- absolute magnitude
- 7.67
- orbital eccentricity
- 0.1270063895583919
- semi-major axis of an orbit
- 2.74997311430276
- periapsis
- 2.400708957672519
- apoapsis
- 3.099237270933
- longitude of ascending node
- 76.16029676552017
- argument of periapsis
- 302.8129137024323
- mean anomaly
- 231.8896520770643
- time of periapsis
- 2461593.251700511
- epoch
- November 21, 2025
Sources (3)
via Wikidata · CC0
~1 min read
Encyclopedic overview
128 Nemesis is a large 180 km main-belt asteroid, of carbonaceous composition. It rotates rather slowly, taking about 78 hours to complete one rotation. Nemesis is the largest member of the Nemesian asteroid family bearing its name. It was discovered by J. C. Watson on 25 November 1872, and named after Nemesis, the goddess of retribution in Greek mythology.
Diagram of Nemesis's orbit This object is orbiting the Sun with a period of 4.56 years and an eccentricity (ovalness) of 0.13. The orbital plane is inclined by 6.2° to the plane of the ecliptic. It is categorized as a C-type asteroid, indicating a primitive carbonaceous composition. Based on IRAS data Nemesis is about 188 km in diameter and is around the 33rd largest main-belt asteroid, while WISE measurements yield a size of ~163 km. The 77.81‑hour rotation period is the second longest for an asteroid more than 150 km in diameter.
Excerpted from Wikipedia’s “128 Nemesis” article, available under the CC BY-SA 4.0 licence.