2026/07/24 by The Backyard Worlds, Planet 9 Collaboration, : +14
Physics and Astronomy · #astro-ph.SR #astro-ph.GA
accepted for publication in AJ
arxiv created 2026/07/24 · arxiv updated 2026/08/04
We present the discovery of SMDET-1, a red, fast-moving object (μ≈ 1.3"/yr) identified in time-resolved unWISE coadds using a pixel-level deep learning methodology called SMDET. Despite being relatively bright at 4.5 microns compared to many other recent WISE-based brown dwarf discoveries (m[4.5] ≈ 14.6 mag Vega), SMDET-1 had remained overlooked due to its location in a very crowded Galactic plane field (b ≈ 2.25∘) and contamination from brighter background objects. SMDET-1 is also serendipitously detected at 4.5 microns in late-2012 Spitzer Deep GLIMPSE survey imaging. SMDET-1 is undetected in UKIDSS and Palomar/WIRC near-infrared imaging, with the strongest constraint on its temperature (T\rm eff < 391 K) arising from its Deep GLIMPSE color limit of m[3.6] - m[4.5] > 2.81 mag, which also implies a very nearby photometric distance < 7.4 pc. The Spitzer color bound corresponds to a Y dwarf phototype. SMDET-1 illustrates the importance of continued searches for nearby brown dwarfs within archival datasets like WISE and Spitzer, as well as the potential of pixel-level deep learning to discover astronomical moving objects that challenge traditional data analysis approaches.