.png) Lightcurve-based 3D-model ofNysa | |
| Discovery | |
|---|---|
| Discovered by | H. Goldschmidt |
| Discovery date | 27 May 1857 |
| Designations | |
| (44) Nysa | |
| Pronunciation | /ˈnaɪsə/[1] |
Named after | Nysa |
| 1977 CE | |
| Main belt (Nysa) | |
| Adjectives | Nysian/ˈnɪsiən/[2][3] |
| Orbital characteristics[4] | |
| Epoch 2008-05-14 (JD 2454600.5) | |
| Aphelion | 2.78291235 AU (416.3 Gm) |
| Perihelion | 2.06469721 AU (308.9 Gm) |
| 2.42380478 AU (362.6 Gm) | |
| Eccentricity | 0.148158617 ± 5.7499e-08 |
| 3.77 yr | |
| 118.743236 ± 2.4281e-05° | |
| Inclination | 3.7028885 ± 6.2628e-06° |
| 131.59519 ± 1.0657e-04° | |
| 342.52066 ± 1.0904e-04° | |
| Physical characteristics | |
| Dimensions | 113±10 × 67±10 × 65±12 km[5] |
| Mass | (7.72 ± 3.92/1.52)×1017 kg[6] |
Meandensity | 3.405 ± 1.727/0.672 g/cm3[6][a] |
| 6.421417 ± 0.000001[7] | |
| 98 ± 2°[7] | |
| +58 ± 3°[7] | |
| 0.44 ± 0.10 (vis.)[5] 0.19 ± 0.06 (rad.)[5] | |
| E[7] | |
| 8.83 to 12.46 | |
| 7.03[4] | |
| 0.09" to 0.026" | |
44 Nysa is a large and very brightmain-beltasteroid, and the brightest member of theNysian asteroid family. It is classified as a rareclass E asteroid and is the largest asteroid of this type.
It was discovered byHermann Goldschmidt on May 27, 1857, and named after the mythical land ofNysa inGreek mythology.
In 2002Kaasalainenet al. used 63lightcurves from the Uppsala Asteroid Photometric Catalog (UAPC) to construct a shape model of 44 Nysa. The shape model is conical, which they interpreted as indicating the asteroid may actually be a contactbinary.[7]
In 2003, Tangaet al. published results obtained from theFine Guidance Sensor on theHubble Space Telescope in which high-precision interferometry was performed on Nysa with the goal of a more accurate shape determination. Due to Hubble's orbit around the Earth, hours-long photometry sessions, as are normally used to resolve the asteroid's shape, were not possible. Instead, the team used interferometry on the asteroid at the time in its rotation when it would have its longest axis perpendicular to the Earth. Ellipsoidal shape models were then fit to the resulting data to determine an estimate of the asteroid's shape. Both single and double ellipsoid models were fit to the data with both providing approximately the same goodness of fit; leaving the team unable to differentiate between a single elongated object and the contact binary model put forth by Kaasalainenet al.[8]An observation of an occultation by 44 Nysa of TYC 6273-01033-1 from the Dutch amateur astronomer Harrie Rutten showed a two-phase reappearance on March 20, 2012. This confirms the conical shape or the binary nature of Nysa.
In December 2006, Shepardet al. performed three days ofradar observations on Nysa with theArecibo radio telescope. The asteroid was found to have a high radarpolarization value (μc) of 0.50 ± 0.2, a radar albedo () of 0.19 ± 0.06, and a visual albedo (pv) of 0.44 ± 0.10.[5] The albedo measurements were based on a shape model worked out at Arecibo. The best fit shape model as measured by the Arecibo team has parameters a/b = 1.7 ± 0.1, a/c = 1.6–1.9, with an a-axis of 113 ± 10 km; this gives an effective diameter of 79 ± 10 km, which is in agreement with the HST study by Tangaet al. in 2003.[5] The data gathered also showed signs of significant concavity in Nysa's structure, but the dip in the radar curves is not pronounced enough to indicate bifurcation, calling into question whether or not Nysa really is a contact binary.[5]
Nysa has so far been reportedocculting astar three times.
44 Nysa was in a study of asteroids using the HubbleFGS.[9] Asteroids studied include63 Ausonia,15 Eunomia,43 Ariadne, 44 Nysa, and624 Hektor.[9]
