Ansky, a once-dormant black hole, is now emitting powerful X-ray bursts, giving scientists a rare chance to study its activity in real time.

A triple-galaxy merger is when three galaxies are colliding and will eventually combine into one larger galaxy. It happens through gravity, as tidal forces and dynamical friction drain orbital energy, funnel gas inward, and pull the galaxies and their central supermassive black holes together over hundreds of millions of years. In rare cases, all three black holes are active at once, producing radio jets that reveal a triple active galactic nucleus.

ESA/Hubble & NASA, M. J. Koss, A. J. Barth The light that the NASA/ESA Hubble Space Telescope collected to create this image reached the telescope after a journey of 250 million years. Its source was...