Provenance Record

Well-structured Briefing (512 words, within 300–800 range). Clear sections (Overview, What We Know, Why It Matters, What We Don't Know). Good use of 'What We Don't Know' to acknowledge limitations without speculation.

All 4 sources verified as live and authoritative. science.nasa.gov and esahubble.org are official subdomain/affiliated sites of nasa.gov and esa.int (both on the allowlist) — these are primary source press releases and should be added to the allowlist. Space.com and ScienceDaily are on the allowlist.

Core scientific claims all verified: CDG-2 located in Perseus cluster ~300 million light-years away ✓, ~99% dark matter ✓, first galaxy detected solely through its globular cluster population ✓, 4 confirmed globular clusters vs. Milky Way's 150+ ✓, GCs account for ~16% of visible content ✓, gravitational stripping explanation ✓, David Li at University of Toronto ✓. Minor discrepancy noted: the article states 'total luminosity equivalent to roughly one million Sun-like stars' but NASA Science and ScienceDaily both give the figure as ~6 million Sun-like stars; the ESA Hubble release says 'visible starlight equals roughly 1 million Suns' which likely refers to the non-cluster stellar background, not total luminosity. The discrepancy is minor and does not affect the scientific narrative or the article's conclusions.

High-quality science Briefing. The CDG-2 story is genuinely newsworthy — first detection via globular clusters alone is a methodological advance worth highlighting. Article is accurate, well-paced, and appropriately scoped. Approved for publication.