Astronomy:44 Nysa

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44 Nysa
A blurry black-and-white photograph of Nysa taken by the Large Binocular Telescope on 15 February 2026. The asteroid resembles a jagged triangular shard bent at an angle, resembling the upside-down letter V.
Nysa photographed by the Large Binocular Telescope on 15 February 2026
Discovery[1]
Discovered byH. Goldschmidt
Discovery date27 May 1857
Designations
(44) Nysa
Pronunciation/ˈnaɪsə/[3]
Named afterNysa
A857 KA · 1977 CE
Minor planet categoryMain belt (inner) · Nysa–Polana complex[2]
AdjectivesNysian /ˈnɪsiən/[4][5]
Orbital characteristics[6]
Epoch 9 June 2026 (JD 2461200.5)
Uncertainty parameter 0
|{{{apsis}}}|helion}}2.785 AU
|{{{apsis}}}|helion}}2.060 AU
2.422 AU
Eccentricity0.1497
Orbital period3.77 yr (1,377 d)
Mean anomaly41.457°
Mean motion0° 15m 41.046s / day
Inclination3.713°
Longitude of ascending node131.476°
343.893°
Known satellites1
Proper orbital elements[7]
Proper semi-major axis2.423 AU
Proper eccentricity0.174
Proper inclination3.06°
Proper mean motion95.4524 deg / yr
3.77151 yr
(1377.545 d)
Precession of perihelion41.2913 arcsec / yr
Precession of the ascending node−46.3579 arcsec / yr
Physical characteristics[2]
Mean diameter75+3
−1 km (volume equivalent)[2]
Mass
Mean density> 3 g/cm3[lower-alpha 2]
Sidereal rotation period6.4214175±0.0000005 h[2]
Pole ecliptic latitude+55.3°±0.5°[2]
Pole ecliptic longitude102.7°±0.5°[2]
Geometric albedo0.48 (average)[9][2]
Absolute magnitude (H)6.75[6][1]


44 Nysa is a binary asteroid located in the Solar System's inner main asteroid belt. It is one of the largest and brightest known E-type asteroids, a rare type of asteroid with a highly reflective and enstatite-rich surface.[2] It was discovered by Hermann Goldschmidt on 27 May 1857 and was named after the mythical land of Nysa in Greek mythology.[1]

High-resolution imaging in 2026 revealed that Nysa has an elongated and highly irregular shape, with three apparent lobes carved by several massive valleys and craters. The asteroid has a uniform surface color and rotates relatively rapidly with a period of 6.42 hours. The origin of Nysa's shape is uncertain, as it does not resemble those of other asteroids with similar properties. Astronomers have suggested that Nysa's shape may have resulted from either asteroid impacts or the slow agglomeration of three smaller asteroids.[10][11] Nysa has one known moon, which is unnamed and was discovered in 2026. The moon has a diameter of 1.0 ± 0.5 km (0.6 ± 0.3 mi) and is estimated to orbit Nysa at a distance of at least 180 km (110 mi).[2]

Nysa shares similar orbital properties with numerous other main-belt asteroids, making it a member of an asteroid family. Nysa specifically belongs to the Nysa–Polana complex, one of the largest known asteroid families. The asteroids of the Nysa–Polana complex have a variety of compositions ranging from carbonaceous (C-type) to silicaceous (S-type), but are rarely found as E-type like Nysa.[2][9] While the Nysa–Polana complex is believed to have formed from the destruction of a differentiated parent body to a collision, the rarity of E-type asteroids in this family suggests that Nysa may be an interloper with an unrelated origin.[9]

Discovery

It was discovered by Hermann Goldschmidt on 27 May 1857 and was named after the mythical land of Nysa in Greek mythology.[1][2]

Orbit

Nysa is located in the inner region of the main asteroid belt between the orbits of Mars and Jupiter. It follows an elliptical orbit around the Sun, with an average distance (semi-major axis) of 2.42 astronomical units (AU) and an orbital period of 3.77 Earth years.[6] It has an eccentricity of 0.15 and an inclination of 3.7° with respect to the ecliptic,[6] although over long periods of time they can change and average out to 0.17 and 3.1°.[7] Throughout its elliptical orbit, the asteroid's distance from the Sun varies from 2.1 AU at perihelion to 2.8 AU at aphelion.[6]

Physical characteristics

Size and shape

Shape model of Nysa as seen from three different views. This model was constructed from imaging observations from 2026.

Nysa is one of the largest known E-type asteroids in the Solar System.[2] Radar observations from 2006 suggest that the asteroid has overall dimensions of 113 km × 67 km × 65 km (70 mi × 42 mi × 40 mi) (15% uncertainty for each axis),[12] while optical imaging from 2026 indicates that it has a volume-equivalent diameter of 75+3
−1 km (47+2
−1 mi).[2] Long-term measurements of perturbations in Nysa's trajectory indicate that it has a mass of (5.76±1.43)×1017 kg.[lower-alpha 1] The asteroid is expected to have a density of at least 3 g/cm3, since it has an enstatite-rich composition and a highly battered shape indicating a sturdy structure.[lower-alpha 2] Nysa's bulk density is higher than that of a typical main-belt asteroid, which may indicate an internal structure consisting of compact (low porosity) rock or a metal-rich core.[12][2]

Nysa has an elongated and highly irregular shape carved by numerous indentations.[2] It appears bent at a 110-degree angle[15] and has three distinct lobes separated by two deep valleys wrapping around the asteroid's circumference.[2][16] These valleys make the lobes appear connected by narrow necks, called "colli".[2][16]

Surface and composition

Satellite

During the February 2026 observation of the asteroid from the Large Binocular Telescope, it was discovered that Nysa has a moon orbiting it, roughly 1.0 ± 0.5 km (0.6 ± 0.3 mi) in diameter, and at an estimated distance of 180 km (110 mi).[17][2] It is estimated that the moon takes 0.96 days to orbit around Nysa.[18]

Origin

See also

Notes

  1. ↑ 1.0 1.1 Fuentes-Muñoz et al. (2025) give Nysa's mass in terms of the standard gravitational parameter GM = 0.038444658±0.009560725 km3 s−2 (or after converting to SI units, (3.8444658±0.9560725)×107 m3 s−2).[13] This can be converted into mass (M) by dividing GM (in SI units) by the gravitational constant G = 6.6743×10−11 m3⋅kg−1⋅s−2[14]. The resulting mass of Nysa is approximately M = (5.76±1.43)×1017 kg.
  2. ↑ 2.0 2.1 Minker et al. (2026) says that Nysa's density is at least 3 g/cm3.[2] Given Nysa's volume-equivalent sphere diameter of D = 75+3
    −1     km     from Minker et al. (2026)[2] and mass of M = (5.76±1.43)×1017 kg from Fuentes-Muñoz et al. (2025),[13] the density formula gives ρ=MV=M43π(D/2)3≈(2600±700) kg/m3≈(2.6±0.7) g/cm3.

References

  1. ↑ 1.0 1.1 1.2 1.3 "(44) Nysa = 1857 KA = 1977 CE". Minor Planet Center. http://www.minorplanetcenter.net/db_search/show_object?object_id=44. 
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 Minker, Kate; Berdeu, Anthony; Causi, Gianluca Li; Hanuš, Josef; Marsset, Michaël; Conrad, Al; et al. (July 2026). "Unmasking (44) Nysa: Evidence for a trilobate structure". arXiv:2607.25786 [astro-ph.EP].
  3. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
  4. ↑ Katz (2004) The complete elegies of Sextus Propertius
  5. ↑ Stein (2004) Persephone Unveiled
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 "44 Nysa (A857 KA)". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=20000044. 
  7. ↑ 7.0 7.1 "(44) Nysa – Proper Elements". Asteroids Dynamic Site. https://newton.spacedys.com/astdys2/index.php?pc=1.1.6&n=44.  For more information about proper orbital elements, go to the "Proper Elements" tab and then click "[Help]" at the upper right corner.
  8. ↑ Fienga, A.; Avdellidou, C.; Hanuš, J. (February 2020). "Asteroid masses obtained with INPOP planetary ephemerides". Monthly Notices of the Royal Astronomical Society 492 (1): 589–602. doi:10.1093/mnras/stz3407. Bibcode: 2020MNRAS.492..589F.  Mass of Nysa is shown in Table A1 of the paper's Supplementary Material.
  9. ↑ 9.0 9.1 9.2 9.3 Tatsumi, Eri; de León, Julia; Popescu, Marcel M. (May 2026). "Hayabusa2# enstatite-like target 1998 KY26 originating from the Nysa family". Astronomy & Astrophysics 709: A105. doi:10.1051/0004-6361/202659046. Bibcode: 2026A&A...709A.105T. 
  10. ↑ Whitt, Kelly Kizer (2026-08-02). "Does asteroid Nysa have 3 lobes and a moon?". https://earthsky.org/space/asteroid-nysa-3-lobes-moon/. Retrieved 2026-08-02. 
  11. ↑ Cooper, Keith (2026-07-30). "1st three-headed asteroid found in our solar system — and it has a little moon". https://www.space.com/astronomy/asteroids/1st-three-headed-asteroid-found-in-our-solar-system-and-it-has-a-little-moon. Retrieved 2026-08-02. 
  12. ↑ 12.0 12.1 Shepard, M. (May 2008). "Radar observations of E-class Asteroids 44 Nysa and 434 Hungaria". Icarus 195 (1): 220–225. doi:10.1016/j.icarus.2007.12.018. Bibcode: 2008Icar..195..220S. 
  13. ↑ 13.0 13.1 Fuentes-Muñoz, Oscar; Farnocchia, Davide; Giorgini, Jon D.; Park, Ryan S. (December 2025). "Asteroid Mass Estimation by Mutual Perturbations During Close Encounters After Gaia Focused Product Release". The Astronomical Journal 170 (6): 353. doi:10.3847/1538-3881/ae0cc9. Bibcode: 2025AJ....170..353F.  GM of Nysa is shown in Table 5 of the Appendix (A.1. List of Perturber Asteroids).
  14. ↑ "2018 CODATA Value: Newtonian constant of gravitation". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. http://physics.nist.gov/cgi-bin/cuu/Value?bg. Retrieved 2019-05-20. 
  15. ↑ Minker, K.Expression error: Unrecognized word "etal". (2026-02-23). Green, Daniel W. E.. ed. "CBET 5664: (44) NYSA". Central Bureau Electronic Telegrams (Central Bureau of Astronomical Telegrams) (5664): 1. Bibcode: 2026CBET.5664....1M. http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET005664.txt. Retrieved 2026-07-29. 
  16. ↑ 16.0 16.1 Schindler, Kevin (2026-07-29). "Press Release: Asteroid (44) Nysa May Be the First-Known Three-Lobed World". Lowell Observatory. https://lowell.edu/press-release-asteroid-44-nysa-may-be-the-first-known-three-lobed-world/. Retrieved 2026-07-29. 
  17. ↑ Berdeu, A.Expression error: Unrecognized word "etal". (2026-05-26). Green, Daniel W. E.. ed. "CBET 5693: (44) NYSA". Central Bureau Electronic Telegrams (Central Bureau of Astronomical Telegrams) (5693): 1. Bibcode: 2026CBET.5664....1M. http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET005693.txt. Retrieved 2026-07-29. 
  18. ↑ "(44) Nysa". https://johnstonsarchive.net/astro/astmoons/am-00044.html. 



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