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4001 Ptolemaeus, provisional designation 1949 PV, is a Florian asteroid from the inner regions of the asteroid belt, approximately 5 kilometers (3.1 miles) in diameter. It was discovered on 2 August 1949, by German astronomer Karl Reinmuth at the Heidelberg-Königstuhl State Observatory in Heidelberg, Germany. In 1991, the International Astronomical Union named the S-type asteroid after Greco-Roman astronomer Ptolemy.[1]

4001 Ptolemaeus
Orbit of 4001 Ptolemaeus.gif
Orbit of 4001 Ptolemaeus
Discovery [1]
Discovered byK. Reinmuth
Discovery siteHeidelberg Obs.
Discovery date2 August 1949
MPC designation(4001) Ptolemaeus
Named after
(Greco-Roman astronomer)
1949 PV · 1949 QD1
1982 BU9 · 1987 OE
main-belt[1][2] · (inner)
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc67.75 yr (24,744 d)
Aphelion2.6809 AU
Perihelion1.8940 AU
2.2874 AU
3.46 yr (1,264 d)
0° 17m 5.64s / day
Physical characteristics
Mean diameter
4.641±0.297 km[4]
5.0 km (est. at 0.24)[5]
SMASS = S[2]

Orbit and classificationEdit

Ptolemaeus is a member of the Flora family (402),[3] a giant asteroid family and the largest family of stony asteroids in the main-belt.[6] It orbits the Sun in the inner main-belt at a distance of 1.9–2.7 AU once every 3 years and 6 months (1,264 days; semi-major axis of 2.29 AU). Its orbit has an eccentricity of 0.17 and an inclination of 5° with respect to the ecliptic.[2]

The body's observation arc begins with its observations as 1949 QD1 at Lowell Observatory on 24 August 1949, or three weeks after its official discovery observation at Heidelberg.[1] On 24 April 1989, Ptolemaeus approached the asteroid 6 Hebe within 5.5 million kilometers at a relative velocity of 3.7 km/s.[2]

Physical characteristicsEdit

In the SMASS classification, Ptolemaeus is a common, stony S-type asteroid, which is in agreement with the overall spectral type for members of the Flora family.[6]:23

Diameter and albedoEdit

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Ptolemaeus measures 4.641 kilometers in diameter and its surface has a high albedo of 0.392.[4] Based on a generic magnitude-to-diameter conversion, assuming a Flora-type typical albedo of 0.24, the asteroid measures 5.0 kilometers for an absolute magnitude of 13.7.[5]

Rotation periodEdit

As of 2018, no rotational lightcurve of Ptolemaeus has been obtained from photometric observations. The body's rotation period, poles and shape remain unknown.[2]


This minor planet was named after 2nd-century Greco-Roman astronomer Ptolemy (Latin: "Ptolemaeus") by IAU's Minor Planet Names Committee. He is best known for his influential Almagest, a mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Its ideas dominated astronomy for 1200 years until Copernicus in the early Renaissance.[1] The official naming citation was published by the Minor Planet Center on 21 November 1991 (M.P.C. 19335).[7]


  1. ^ a b c d e f "4001 Ptolemaeus (1949 PV)". Minor Planet Center. Retrieved 16 March 2018.
  2. ^ a b c d e f g "JPL Small-Body Database Browser: 4001 Ptolemaeus (1949 PV)" (2017-05-01 last obs.). Jet Propulsion Laboratory. Retrieved 16 March 2018.
  3. ^ a b "Small Bodies Data Ferret". Nesvorny HCM Asteroid Families V3.0. Retrieved 16 March 2018.
  4. ^ a b c Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 16 March 2018.
  5. ^ a b "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 12 November 2017.
  6. ^ a b Nesvorný, D.; Broz, M.; Carruba, V. (December 2014). "Identification and Dynamical Properties of Asteroid Families" (PDF). Asteroids IV: 297–321. arXiv:1502.01628. doi:10.2458/azu_uapress_9780816532131-ch016. Retrieved 16 March 2018.
  7. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 16 March 2018.

External linksEdit