Cosmology

Triplet of ‘Ghostly’ Galaxies Hints at What Dark Matter Is — and Isn’t

Quanta's Robin George Andrews reports on DF2, DF4 and DF9, three diffuse galaxies with almost no dark matter. A June 2026 Astrophysical Journal paper proposes they formed after an ancient collision separated ordinary matter from dark matter, which many researchers say supports dark matter as a physical substance and spells trouble for modified-gravity theories like MOND.

Article · Astrophysics · Dark Matter · Cosmology