Molėtai Astronomical Observatory contributes to the study of impressive asteroid

Molėtai Astronomical Observatory contributes to the study of one of the reddest asteroids – (269) Justitia

Photometry specialist Erika Pakštienė from the Faculty of Physics at Vilnius University are participating in an international team aiming to reveal the physical properties of one of the reddest objects in the main asteroid belt, (269) Justitia. These studies included photometric observations carried out at the Molėtai Astronomical Observatory using the 35/51 cm Maksutov telescope.

AI-generated interpretation of asteroid (269) Justitia based on the research model


(269) Justitia is a dark and unusually red asteroid orbiting between Mars and Jupiter. Its spectrum is so red that it resembles distant Solar System bodies (such as Centaurs or trans-Neptunian objects) than typical main-belt asteroids. It is thought that these colors are caused by complex organic compounds formed in cold regions of the early Solar System. It is therefore possible that Justitia formed far from the Sun and only later migrated into the main asteroid belt.
In one of the studies published in 2025, led by Anna Marciniak (Poland), a very interesting method “thermophysical modeling” was applied. This required the use of light curves (including observations from Molėtai) together with infrared data from space missions. Thermophysical modelling is a method used in planetary science in which models are compared with observations to describe how a celestial body’s surface absorbs, conducts, and re-emits heat as it rotates and orbits the Sun. This approach allowed the researchers to determine the asteroid’s shape, rotation parameters, size, and surface properties with high precision, and to better constrain its diameter to approximately 55–60 km.

Maksutov type 35/51 cm telescope, Molėtai AO

The second paper, published in Astronomy & Astrophysics and titled “Asteroid sizes determined with thermophysical model and stellar occultations,” was led by A. Choukroun and combined thermophysical modelling with stellar occultation results. The study also relied on international photometric observations, including contributions from Molėtai, and provided robust, independent constraints on asteroid sizes and shapes, strengthening the physical characterization of objects such as (269) Justitia.

Orbit of asteroid Justitia compared to the orbits of the planets. Credit: NASA JPL

📄 Key publications (2025):
• Thermophysical Model of (269) Justitia — Main Belt Asteroid Possibly Implanted from Trans-Neptunian Region, A. Marciniak et al., Planetary Science Journal, DOI: 10.3847/PSJ/adb28
• Asteroid sizes determined with thermophysical model and stellar occultations, A. Choukroun et al., Astronomy & Astrophysics, DOI: 10.1051/0004-6361/202554476
These studies clearly demonstrate how not necessarily the largest, but precise and well-used telescopes can find their own important niche in modern astronomy.