2026-11-05 ワシントン大学（UW）
A skymap of stars in the Milky Way and its environment, using data from the Gaia satellite. The area of sky observed by Rubin during a test run is shaded in red. The positions of Rubin-GC1 and Aquarius IV appear in orange and blue, respectively. Rubin-GC1 stands out prominently as a collection of numerous resolved stars. Aquarius IV, which is much more distant, is only barely detectable by eye in the image, but was identified by automated search algorithms. Photo: NSF-DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA, ESA/Gaia/DPAC, W. Cerny
＜関連情報＞
- https://www.washington.edu/news/2026/11/05/rubin-observatory-milky-way-satellites/
- https://iopscience.iop.org/article/10.3847/2041-8213/aeb122
ルービン天文台がへびつかい座に塵に覆われたハロー球状星団を発見 Rubin Observatory Reveals a Dust-shrouded Halo Globular Cluster in Ophiuchus
Aashay Pai, William Cerny, Andrew B. Pace, Alex Drlica-Wagner, Peter S. Ferguson, Marla Geha, Chin Yi Tan, Sasha N. Campana, Burçin Mutlu-Pakdil, Alexander H. Riley,…
The Astrophysical Journal Letters Published: 2026 October 28
DOI:10.3847/2041-8213/aeb122
Abstract
We present the discovery of the Milky Way satellite Rubin-GC1 (Rubin J1628−1735) using data from the NSF-DOE Vera C. Rubin Observatory’s Early Data Preview 2. The system was discovered in the direction of the Galactic bulge with (l, b) ∼ (359°, 21°) in a region of high stellar density and a foreground reddening of E(B − V) ≈ 0.7. We simultaneously fit the morphology and isochrone parameters of Rubin-GC1, determining that it is a faint (Mv=-2.4+0.5-0.7) and compact (r1/2=5+1-1 pc) Milky Way satellite at a distance of D⦿=31+3-3 kpc; its stellar population is intermediate-age (τ=9.2+1.2-0.7 Gyr) and moderately metal-rich ([Fe/H]iso=-0.73+0.04-0.04). Together, these properties suggest Rubin-GC1 is most likely a star cluster in the faint tail of the luminosity function of globular clusters surrounding the Milky Way. We identify a distinct proper motion signature from Rubin-GC1 in Gaia DR3, and from a comparison of the system’s 5D phase space information to N-body models of the Sagittarius dwarf spheroidal galaxy’s tidal stream, we determine that Rubin-GC1 is likely an accreted cluster associated with the Sagittarius leading arm. The discovery of Rubin-GC1 highlights the potential of Rubin to uncover faint, resolved satellites in dust-shrouded regions of the Milky Way, including remnants of the accretion events that have shaped the Galaxy’s hierarchical assembly.
