TON 618
What is TON 618?
Black holes & quasars· Distance 10.4 billion ly. Among the heaviest black holes known, powering a quasar 10.4 billion light-years away toward Canes Venatici. Its event horizon is about 15 light-days across. Locate it in the Sky view and set it beside the solar system on the size ladder.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where TON 618 is in your sky right now: https://nowsky.org/solar/sky?sel=ton 618 — location and time set automatically, no login.
Its place in the sky
A black hole, in the direction of Canes Venatici.
Mass, distance, nature
| Mass | ~66 billion Suns |
|---|---|
| Distance | ~10.4 billion ly (z = 2.2) |
| Event horizon | ~390 billion km, ~15 light-days |
| Luminosity | 140 trillion Suns |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
Found as a faint dot on a 1957 Tonantzintla plate; among the most massive black holes known (40–66 billion Suns).
Frequently asked
- What is the mass of TON 618?
- ~66 billion Suns.
- How far is TON 618 from Earth?
- ~10.4 billion ly (z = 2.2).
- Where in the sky is TON 618?
- In the direction of Canes Venatici.
- Where is TON 618 in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
How 66 billion Suns was measured — the width of a broad line
The mass of a black hole 10.4 billion light-years away cannot be measured from stellar orbits. Instead the broad emission lines of the quasar's spectrum are used: the faster the gas clouds circling near the black hole, the wider the Doppler-broadened lines, and TON 618's hydrogen-beta line is more than 10,000 km/s wide. Putting that speed and the clouds' distance (estimated from brightness) into Newtonian mechanics gives the mass — about 66 billion Suns.
This "virial mass" can vary by a factor of several with assumptions about the clouds' geometry, so 66 billion is safest read as an order of magnitude. Under any assumption, though, it exceeds ten billion Suns, placing TON 618 among the heaviest supermassive black holes known. That a black hole this large already existed when the universe was three billion years old is itself a test for theories of black-hole growth.
The black hole in depth
TON 618 entered the catalogues in 1957 as a faint blue dot on photographic plates from Mexico's Tonantzintla Observatory. Radio and spectroscopic work in the 1970s revealed a quasar at redshift 2.2, and the width of its broad emission lines implied a central black hole of roughly 66 billion solar masses. The quasar alone shines with the light of 140 trillion Suns, thousands of times brighter than our whole galaxy.
At that mass the event horizon spans about 390 billion kilometres, a gulf light needs 15 days to cross, larger than the distance from the Sun to Voyager 1 and more than ten thousand times the size of Sagittarius A* at our galaxy's core. Line-width masses carry large error bars, and recent studies favour something nearer 40 billion Suns; either way it sits near the top of the list.
The light we receive left when the universe was about three billion years old, so what occupies that spot today is unknown. At magnitude 15.9 the quasar has been glimpsed as a star-like point in large amateur telescopes. Use the Sky view to find its position in southern Canes Venatici, then drop the horizon next to the solar system on the size ladder to feel the scale.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.