ABSTRACTS OF ORAL PRESENTATIONS

    Determining the size distribution of asteroids is key for understanding the collisional history and evolution of the inner Solar System - PABLO GARCÍA MARTÍN

    Aims. We aim at improving our knowledge on the size distribution of small asteroids in the Main Belt by determining the parallaxes of newly detected asteroids in the Hubble Space Telescope (HST) Archive and hence their absolute magnitudes and sizes.
    Methods. Asteroids appear as curved trails in HST images due to the parallax induced by the fast orbital motion of the spacecraft. Taking into account its trajectory, the parallax effect can be computed to obtain the distance to the asteroids by fitting simulated trajectories to the observed trails. Using distance, we can obtain the object’s absolute magnitude and size estimation assuming an albedo value, along with some boundaries for its orbital parameters.

    Results. In this work we analyse a set of 632 serendipitously imaged asteroids found in the ESA HST Archive. These objects were obtained from instruments ACS/WFC and WFC3/UVIS. An object-detection machine learning algorithm (trained with the results of a citizen science project) was used to perform this task during previous work. Our raw data consists of 1,031 asteroid trails from unknown objects, not matching any entries in the Minor Planet Center (MPC) database using their coordinates and imaging time. We also found 670 trails from known objects (objects featuring matching entries in the MPC). After an accuracy assessment and filtering process, our analysed HST asteroid set consists of 454 unknown objects and 178 known objects. We obtain a sample dominated by potential Main Belt objects featuring absolute magnitudes (H) mostly between 15 and 22 mag. The absolute magnitude cumulative distribution logN(H > H0) ∝ α log(H0) confirms the previously reported slope change for 15 < H < 18, from α ≈ 0.56 to α ≈ 0.26, maintained in our case down to absolute magnitudes around H ≈ 20, hence expanding the previous result by approximately two magnitudes.

    Conclusions. HST archival observations can be used as an asteroid survey since the telescope pointings are statistically ran- domly oriented in the sky and they cover long periods of time. They allow to expand the current best samples of astronomical objects at no extra cost on telescope time.

    Article: https://arxiv.org/abs/2401.02605

     

     Presentation PDF

     

    View »