UGC 12591: The Fastest Rotating Galaxy Known
Model: gpt-4.1-mini
Prompt version: 1.0
Why does this galaxy spin so fast?
To start, even identifying which type of galaxy UGC 12591 is difficult — featured on the lower left, it has dark dust lanes like a spiral galaxy but a large diffuse bulge of stars like a lenticular.
Surprisingly observations show that UGC 12591 spins at about 480 km/sec, almost twice as fast as our Milky Way, and the fastest rotation rate yet measured.
The mass needed to hold together a galaxy spinning this fast is several times the mass of our Milky Way Galaxy.
Progenitor scenarios for UGC 12591 include slow growth by accreting ambient matter, or rapid growth through a recent galaxy collision or collisions — future observations may tell.
The light we see today from UGC 12591 left about 400 million years ago, when trees were first developing on Earth.