Speaker
Description
The airburst event over Chelyabinsk, Russia in 2013 caused over 1,400 injuries and $30 million in property damage. This object was not tracked until it entered the Earth’s atmosphere, too late for any disaster response, partly because of its small (~20 meter-diameter) size, but also because it approached from interior to Earth’s orbit, obscured by the Sun’s brightness. The Chelyabinsk superbolide thus highlights an undersampled group of potentially hazardous asteroids: low-solar-elongation Aten-family (primarily) bodies whose orbits are largely interior to the Earth, and thus difficult to observe.
These “Sunward NEOs” (SNEOs) are high-risk due to the difficulty of confirming discoveries with subsequent same-night or multi-night observations, and their short impact warning times. It is thus critical to find and characterize SNEOs and predict their trajectories so that their long-term orbits can be tracked more carefully.
Studies in the last decade indicate that initial twilight observations (during the 10–45 min when the Sun has just set below the horizon in the evening or just before it rises above the horizon in the morning) on survey telescopes like ZTF and DECam have led to discoveries, and dynamical characterizations of potentially hazardous SNEOs. The Vera Rubin Observatory has published plans for a “low-solar-elongation twilight microsurvey,” which will capitalize on its wide field of view and large aperture to resolve even fainter objects and get better signal-to-noise—which could be critical for twilight observations, where the sky is not completely dark. Following initial identification from Rubin, other twilight-capable telescopes can perform observations to characterize orbits, compositions, and rotations, thus reducing threats.
Thus, for my winning planetary defense proposal for the B612 Foundation’s inaugural, 2024 Schweickart Prize for Planetary Defense, I proposed the SUnward NEO Surveillance and Early Twilight detection (SUNSET) community and observatory collaboration. SUNSET will, in the short term, advocate for and facilitate starting the Rubin twilight survey for SNEO detection in Year 1 of operations, and organize a follow-up characterization network of ground-based observatories–utilizing twilight time, when science observations are generally not taking place. As a first step in organizing follow-up, we aim to develop tools to prioritize objects for follow-up observations and provide relevant observing details, so that any observer with a twilight-capable telescope can be a part of SUNSET.
We hope to engage the broader community by incorporating amateur- and small-observatory follow-up observations and linking them to the data from primary discovery telescopes with novel orbit-recovery tools like THOR, from the B612 Foundation. THOR can derive orbits from disparate data sets or images from different nights in a way that de-emphasizes the observer’s relative position and relaxes the need to observe repeatedly in subsequent nights and form “tracklets,” meaning that anyone willing to do follow-up observations can help contribute to data sets and help SUNSET make Earth safer!