TON 618 (abbreviation of Tonantzintla 618) is a hyperluminous, broad-absorption-line, radio-loud quasar, and Lyman-alpha blob[2] located near the border of the constellations Canes Venatici and Coma Berenices, with the projected comoving distance of approximately 18.2 billion light-years from Earth.

[3] As quasars were not recognized until 1963,[4] the nature of this object was unknown when it was first noted in a 1957 survey of faint blue stars (mainly white dwarfs) that lie away from the plane of the Milky Way.

[7] As a quasar, TON 618 is believed to be the active galactic nucleus at the center of a galaxy, the engine of which is a supermassive black hole feeding on intensely hot gas and matter in an accretion disc.

[14] Observations made by the Atacama Large Millimeter Array (ALMA) in 2021 revealed the apparent source of the Lyman-alpha radiation of TON 618: an enormous cloud of gas surrounding the quasar and its host galaxy.

These enormous, galaxy-sized clouds are some of the largest nebulae known to exist, with some identified LABs in the 2000s reaching sizes of at least hundreds of thousands of light-years across.

The extreme radiation from TON 618 excites the hydrogen in the nebula so much that it causes it to glow brightly in the Lyman-alpha line, consistent with the observations of other LABs driven by their inner galaxies.