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Stellar occultations by asteroids: the contribution of Unistellar’s network of citizen astronomers

Presentation #312.04 in the session IDEA, Education, Public Engagement, Workforce Development and History (Poster + Lightning Talk)

Published onOct 23, 2023
Stellar occultations by asteroids: the contribution of Unistellar’s network of citizen astronomers

The Unistellar’s eVscopes and eQuinox telescope owners (>5,000) represent the largest network of potential citizen astronomers. These compact (9 kg) telescopes are equipped with a 114 mm mirror and an electronic eyepiece. Due to the unified design and user-friendly operation via a smartphone app, several types of scientific observations are enabled and supported by Unistellar. Any owner of an eVscope can receive notifications on its smartphone of transient events visible in the sky, such as comets, supernovae, asteroid flybys, stellar occultations by asteroids, or other targets of interest, perform the observations and upload the data to the Unistellar’s server.

In this contribution, we focus on a specific scientific mode: stellar occultations by asteroids. During the stellar occultation the asteroid is passing in front of a star, which is occulted, the duration of this event is directly related to the asteroids’ dimension. Various observers distributed on the ground can sample different parts of the asteroid, which can lead to an accurate size estimate, and possibly even to a shape model refinement. Stellar occultation observations are quite challenging and building its own set up from commercial pieces requires significant expertise. The essential component is a fast camera that allows image cadence of at least 100 ms. The eVscope telescopes represent a compact and easy-to-use alternative for general public. The Unistellar’s network of citizen astronomers then allows organization of observing campaigns.

Within the network, we are targeting stellar occultations by asteroids in order to estimate their dimensions with an accuracy non-achievable by commonly used techniques, and to improve the orbital properties, hence allow better predictions of future events. We will show several successful observations, including: (i) the Didymos-Dimorphos binary system (the target of the NASA’s DART space mission), we participated in the campaign organized by the ACROSS projects and obtained a double detection. (ii) The massive campaign of occultation by the NASA’s Lucy mission target Eurybates visible in Europe on October 23 2022 including 320 participants with 18 positive chords. One of the Unistellar’s chords is a grazing event revealing a concavity. Finally, (iii)

An occultation by the comet 29P Schwassmann-Wachmann on December 19 2022 with two positive chords revealing a projected size of 60-65 km when combined with 2 additional positive chords.

We will also illustrate several outreach activities that could be perform within the network.

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