Cosmic
ExtremesFour record-breaking objects

TON 618 is a hyperluminous, radio-loud quasar located 10.4 billion light-years away in the constellation Canes Venatici. At its core sits one of the most massive black holes ever directly measured, weighing in at 40–66 billion solar masses — so large that its event horizon alone is wider than our entire solar system.

The quasar's accretion disk blazes with the energy of 140 trillion Suns. Gas near the black hole moves at 10,500 km/s. It is surrounded by an enormous Lyman-alpha nebula stretching over 330,000 light-years. First catalogued in 1957 as a "faint blue star," its true nature as a quasar wasn't confirmed until 1970.

Holmberg 15A* is the central galaxy of the Abell 85 cluster, located about 700 million light-years away. It hosts one of the largest directly measured black holes: a mass of 40 billion solar masses, confirmed through stellar dynamics — earning it the informal designation "Holm 15A*" (echoing Sgr A*).

Its core is defined by a remarkably flat, depleted stellar density — the largest cored galaxy known — extending 15,000 light-years across. This core is thought to have been excavated by two merging supermassive black holes in the galaxy's past, creating a gravitational slingshot that ejected stars outward. Its velocity dispersion of ~320 km/s hints at an even larger dark matter halo.