Quasars

At a glance

Key points

3C 273, the first identified, is 2.5 billion light-years away.

• Outshine their host galaxies
• First identified in 1963
• 3C 273's jet spans more than 100,000 light-years

A puzzle solved in 1963

Radio surveys of the 1950s found strong sources that, through optical telescopes, looked like faint bluish stars with baffling emission lines. In 1963 Maarten Schmidt realised that the lines of 3C 273 were ordinary hydrogen lines shifted far to the red: the 'star' was receding at about a tenth of the speed of light and so lay far beyond the Milky Way. To look that bright from so far away, it had to outshine an entire galaxy.

Engines

Gas spiralling into the black hole heats to millions of degrees in a disc surrounded by a dusty torus. Some quasars launch jets at nearly the speed of light.

Why a black hole

Quasars change brightness over months or less, so most of their light must come from a region tiny by galactic standards. No cluster of stars could pack that much power into so small a space; gas falling onto a supermassive black hole, which turns a far larger share of its mass into radiation than nuclear fusion does, can. In 2024 Hubble's coronagraph blocked 3C 273's glare and revealed blobs and an L-shaped filament within 16,000 light-years of the black hole.

Early giants

Quasars are seen when the universe was less than a billion years old. J0313-1806, which held the distance record from 2021, shines from 670 million years after the Big Bang, already powered by a black hole of more than 1.6 billion Suns. How such black holes grew so large so quickly is one of the questions Webb is now probing.

Seeing one yourself

3C 273 in Virgo is the brightest quasar in our sky, around magnitude 13, so it appears as a faint star in a 150 mm telescope on spring evenings. The light reaching your eye left it about two and a half billion years ago, long before the first animals appeared on Earth.

Missions

1. 1990–

   Hubble Space Telescope

   NASA / ESAActive

   Ultraviolet to near-infrared imaging from low Earth orbit.

   Mission page (opens in a new tab)

Related entries

• Centaurus AThe nearest active galaxy
• Messier 87Giant elliptical with the first imaged black hole
• Sagittarius A*The black hole at the centre of the Milky Way

Sources

1. NASA Science: Hubble: closest look at a quasar (opens in a new tab)
2. Chandra: 3C 273 (opens in a new tab)
3. Schmidt 1963, Nature 197:1040 (opens in a new tab)
4. ESO: eso2402: the brightest known quasar (opens in a new tab)
5. W. M. Keck Observatory: earliest quasar (opens in a new tab)

Last reviewed 10 Oct 2026 against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.