Phoenix A
What is Phoenix A?
Black holes & quasars· Distance 5.7 billion ly. A colossal black hole about 5.7 billion light-years from Earth, hidden at the centre of the Phoenix Cluster. The rate at which the cluster's hot gas cools suggests a mass approaching 100 billion Suns, placing it among the most massive black hole candidates known.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Phoenix A is in your sky right now: https://nowsky.org/solar/sky?sel=phoenix a — location and time set automatically, no login.
Its place in the sky
A black hole, in the direction of Phoenix.
Mass, distance, nature
| Mass | ~100 billion Suns (indirect estimate) |
|---|---|
| Distance | ~5.7 billion ly (z = 0.6) |
| Host | central galaxy of the Phoenix Cluster |
| Star formation | ~740 solar masses per year |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
Center of the Phoenix Cluster (2012); its black hole may reach 100 billion Suns, near the theoretical limit.
Frequently asked
- What is the mass of Phoenix A?
- ~100 billion Suns (indirect estimate).
- How far is Phoenix A from Earth?
- ~5.7 billion ly (z = 0.6).
- Where in the sky is Phoenix A?
- In the direction of Phoenix.
- Where is Phoenix A 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 the South Pole Telescope found the cluster — a cluster seen as a shadow
The Phoenix Cluster was found not by its light but by its shadow. The hot gas filling a cluster scatters the microwaves of the cosmic background so that at certain wavelengths the cluster appears darker than the background (the Sunyaev–Zeldovich effect), and the South Pole Telescope, surveying the sky for such shadows, caught Phoenix in 2010. Because the shadow's depth scales with the total gas regardless of distance, the method counts massive clusters across the distant universe without missing them.
X-ray and optical follow-up then showed the cluster to be among the most massive known, with stars forming in its central galaxy at 740 solar masses a year. The hot gas at a cluster's centre is normally kept from cooling by the central black hole's jets, but in Phoenix that feedback is weak, so the gas cools, sinks and makes stars. The enormous estimated mass of the central black hole is the value that comes from calculations trying to explain that cooling flow.
The black hole in depth
The Phoenix Cluster, found in 2010 by the South Pole Telescope, is a massive galaxy cluster about 5.7 billion light-years away toward Phoenix. Its tens-of-millions-of-degrees gas glows brightly in X-rays, and at the centre that gas is cooling and forming stars at around 740 solar masses per year. In most clusters the central black hole heats the gas and throttles star birth; here the brake is unusually weak.
The central galaxy's black hole, Phoenix A, has not been weighed from stellar motions. Its mass is inferred from the relation between the cluster's cooling rate and the brightness of the central galaxy, and the estimate comes out near 100 billion solar masses, raising the possibility that it outweighs TON 618 as the heaviest known. The method carries large uncertainties, but at that mass the event horizon would span some 600 billion kilometres, about 23 light-days.
The cluster lies deep in southern skies and is far too faint for amateur telescopes. Select Phoenix A in the Sky view to see its position within Phoenix, a constellation that skims the southern horizon on autumn evenings from Korea. Treat it as a way to learn where it sits and how large it is rather than as an observing target.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.