269 Justitia
 | This article or section is in a state of significant expansion or restructuring. You are welcome to assist in its construction by editing it as well. If this article or section has not been edited in several days, please remove this template. If you are the editor who added this template and you are actively editing, please be sure to replace this template with {{in use}} during the active editing session. Click on the link for template parameters to use.
This article was last edited by Nrco0e (talk | contribs) 0 seconds ago. (Update timer) |
 Shape of Justitia as seen by stellar occultation observations on 31 August 2023 | |
| Discovery[1] | |
|---|---|
| Discovered by | Johann Palisa |
| Discovery site | Vienna Obs. |
| Discovery date | 21 September 1887 |
| Designations | |
| (269) Justitia | |
| Pronunciation | /dʒʌˈstɪʃiə/[2] |
Named after | Justitia |
| A887 SA 1942 XY | |
| Main belt · (middle)[3] | |
| Orbital characteristics[4] | |
| Epoch 5 May 2025 (JD 2460800.5) | |
| Uncertainty parameter 0 | |
| Aphelion | 3.179 AU |
| Perihelion | 2.048 AU |
| 2.613 AU | |
| Eccentricity | 0.2164 |
| 4.22 yr (1,543 d) | |
| 244.365° | |
| 0° 13m 59.88s / day | |
| Inclination | 5.477° |
| 156.503° | |
| 120.144° | |
| Physical characteristics | |
| Dimensions | 32.30 × 29.17 × 23.30 km ± (1.43 × 1.32 × 1.30 km)[5] |
| 57.0–57.8 km (occultation)[6] 58±2 km (thermophysical)[7] | |
| 33.12962 ± 0.00001 h (1.38040083 ± 4.2×10−7 d)[7] | |
| 171°±15° (to ecliptic)[a] | |
Pole ecliptic latitude | −81°±15°[7] |
Pole ecliptic longitude | 73°±11°[7] |
| 0.072±0.007 (occultation)[6] 0.058±0.006 (thermophysical)[7] | |
| RR or IR (TNO classification)[3] Z-type asteroid[8] Ld-type (SMASS classification)[4][6] D-type (Bus–DeMeo classification)[6] | |
| 12–15[1] | |
| 9.82[6] | |
269 Justitia is an asteroid located in the middle main asteroid belt. It was discovered on 21 September 1887 by Austrian astronomer Johann Palisa at Vienna Observatory and was named after Justitia, the Roman goddess of justice. The asteroid is about 58 kilometres (36 mi) in diameter and rotates relatively slowly,[7]: 7 with a rotation period of 33.1 hours. Justitia is one of the targets of the United Arab Emirates' upcoming MBR Explorer mission, which will visit seven different asteroids in the asteroid belt during the 2030s. MBR Explorer is planned to enter orbit around Justitia via rendezvous in 2034 and will end its mission after dropping a lander to the surface of the asteroid.[5]
Justitia is unusual in that it has a much redder color compared to any other asteroid in the asteroid belt.[3] Spectroscopic observations show that Justitia's color and composition appears to resemble those of trans-Neptunian objects from the outer Solar System, whose surfaces are composed of ices and complex organic compounds (tholins). Hence, researchers believe that Justitia originated from the outer Solar System and then migrated inward to its present-day location in the asteroid belt. Only a few other main-belt asteroids have been identified to exhibit very red colors like Justitia, with 203 Pompeja being the largest known. The current sparsity of very red main-belt asteroids suggests that most of them were destroyed by asteroid collisions in the past.[3]
Orbit
[edit]
Justitia is located in the middle section of the main asteroid belt (2.50–2.82 AU), where it orbits the Sun at an average distance of 2.61 AU (0.390 billion km; 0.243 billion mi).[3]: 2 During its 4.2-year orbital period, Justitia's distance from the Sun varies from 2.05 AU at perihelion to 3.18 AU at aphelion due to its elliptical orbit, which has an eccentricity of 0.216.[4] Justitia has a low orbital inclination of 5.5° with respect to the ecliptic plane.[7]: 3
Physical characteristics
[edit]Shape and rotation
[edit]
On 31 August 2023, Justitia occulted a background star, with multiple observation teams successfully observing the event. This allowed for the direct determination of its size and shape. The occultation revealed that Justitia has a volume-equivalent diameter of 57.0 km (35.4 mi) or 57.8 km (35.9 mi), with the larger value being preferred by Marc Buie et al. Justitia was revealed to be highly irregular in shape, with at least three large facets 23–38 km (14–24 mi) in length being observed.[6]
Observations of Justitia's fluctuating brightness over time show that it has a relatively slow rotation period of about 33.1 hours, accurately measured to an uncertainty less than a tenth of a second.[7]: 4 Justitia has a retrograde rotation, meaning it rotates backwards relative to its orbit direction and has its rotational north pole pointed toward the ecliptic south.[7]: 3 Although observations based on light curves alone suggested two possible rotation pole orientations for Justitia, the August 2023 occultation by Justitia eliminated this ambiguity.[7][6]
Color and spectrum
[edit]
Spectroscopic observations of Justitia indicate that it is a spectrally red carbonaceous asteroid. Its surface is very dark, with a geometric albedo of 0.061±0.007.[6] Thermal modelling of the asteroid indicates that it is around 58 km (36 mi) in diameter, with a very rough surface.[7] In the Bus-DeMeo classification scheme, Justitia is categorized as a D-type asteroid; the Small Main-belt Asteroid Spectroscopic Survey, Phase II (SMASSII) classification scheme alternatively classifies it as an Ld-type asteroid. More recently, in 2022, a team of astronomers led by M. Mahlke proposed a new Z-type classification within which Justitia belongs to.[6] Z-type asteroids are similar to D-type asteroids, but are distinguished by their strong spectrally red colors and distinct orbital characteristics.[8]
Justitia's extreme redness is shared with the mid-sized asteroid 203 Pompeja. Spectroscopic analysis of the two asteroids suggests the presence of complex organic materials—tholins—and other undetermined and spectroscopically featureless materials on their surfaces. Based on their spectroscopic similarities to small outer Solar System objects—trans-Neptunian objects (TNOs) and centaurs—a team of astronomers led by Sunao Hasegawa argued that the two asteroids may have originated from the primordial Kuiper belt before later migrating to the main asteroid belt.[3]
Exploration
[edit]Justitia is planned to be the seventh and final target of the United Arab Emirates' MBR Explorer mission, which will attempt to land on its surface in 2034.[9][10]
Notes
[edit]- ^ Marciniak et al. (2025) give the ecliptic latitude of Justitia's rotational north pole direction, β) = −81°±15°.[7] Subtracting β from +90° (the ecliptic north pole latitude) gives Justitia's axial tilt with respect to the ecliptic: i = 90° – β = 171°±15°.
References
[edit]- ^ a b "(269) Justitia = 1887 SA = 1942 XY". Minor Planet Center. Retrieved 22 March 2025.
- ^ "justitium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ a b c d e f Hasegawa, Sunao; Marsset, Michaël; DeMeo, Francesca E.; Bus, Schelte J.; Geem, Jooyeon; Ishiguro, Masateru; et al. (July 2021). "Discovery of two TNO-like bodies in the asteroid belt". The Astrophysical Journal Letters. 916 (1): 8. arXiv:2106.14991. Bibcode:2021ApJ...916L...6H. doi:10.3847/2041-8213/ac0f05. S2CID 235669878. L6.
{{cite journal}}: CS1 maint: year (link) - ^ a b c "JPL Small-Body Database Lookup: 269 Justitia (A887 SA)" (2025-01-12 last obs.). Jet Propulsion Laboratory. Retrieved 22 March 2025.
- ^ a b Parker, Jeffrey S.; Al Hameli, Fatema S.; Knittel, Jeremy; Pilinski, Emily; Baskar, Sandeep; Imler, Paul; Almashjari, Mohamed H. (August 2024). Proximity Operations Strategy for the Emirates Mission to Explore the Asteroid Belt (EMA). AAS/AIAA Astrodynamics Specialist Conference. Broomfield, CO. p. 21. 269.
{{cite conference}}: CS1 maint: year (link) - ^ a b c d e f g h i Buie, Marc W.; AlMazmi, Hoor; Hayne, Paul; Marciniak, Anna; Keeney, Brian A.; Alawadhi, Fahad; et al. (March 2025). "Occultation-based Size and Shape of (269) Justitia". The Planetary Science Journal. 6 (3): 12. Bibcode:2025PSJ.....6...61B. doi:10.3847/PSJ/adb28c. S2CID 277163206. 61.
{{cite journal}}: CS1 maint: year (link) - ^ a b c d e f g h i j k l Marciniak, Anna; Choukroun, Antoine; Perła, Julia; Ogłoza, Waldemar; Szakáts, Robert; Antonini, Pierre; et al. (March 2025). "Thermophysical Model of (269) Justitia—Main Belt Asteroid Possibly Implanted from Trans-Neptunian Region". The Planetary Science Journal. 6 (3): 9. Bibcode:2025PSJ.....6...60M. doi:10.3847/PSJ/adb28b. S2CID 277186660. 60.
{{cite journal}}: CS1 maint: year (link) - ^ a b Mahlke, M.; Carry, B.; Mattei, P.-A. (September 2022). "Asteroid taxonomy from cluster analysis of spectrometry and albedo". Astronomy & Astrophysics. 665: 32. arXiv:2203.11229. Bibcode:2022A&A...665A..26M. doi:10.1051/0004-6361/202243587. S2CID 247597027. A26.
{{cite journal}}: CS1 maint: year (link) - ^ "UAE announces space mission to land MBR Explorer on asteroid 5 billion kilometres away". Arabian Business. 29 May 2023. Retrieved 14 June 2023.
- ^ "Touring Through the Asteroid Belt: United Arab Emirates Unveils Bold Mission". SpaceRef. 29 May 2023. Retrieved 14 June 2023.
External links
[edit]
- 269 Justitia at AstDyS-2, Asteroids—Dynamic Site
- 269 Justitia at the JPL Small-Body Database
- (269) Justitia shape model, Astronomical Institute of the Charles University
