NGC 4889
What is NGC 4889?
Black holes & quasars· Distance 300 million ly. A supermassive black hole whose 21-billion-solar-mass weight was measured directly from stellar motions in 2011. It sits in the brightest galaxy of the Coma Cluster, once a blazing quasar and now quietly dormant.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where NGC 4889 is in your sky right now: https://nowsky.org/solar/sky?sel=ngc 4889 — location and time set automatically, no login.
Its place in the sky
A black hole, in the direction of Coma Berenices.
Mass, distance, nature
| Mass | ~21 billion Suns (from stellar motions) |
|---|---|
| Distance | ~300 million ly (Coma Cluster) |
| Event horizon | ~130 billion km, 14× Neptune's orbit |
| Apparent magnitude | 11.4 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
A giant elliptical in the Coma Cluster; its 21-billion-Sun black hole (2011) was then the record.
Frequently asked
- What is the mass of NGC 4889?
- ~21 billion Suns (from stellar motions).
- How far is NGC 4889 from Earth?
- ~300 million ly (Coma Cluster).
- How bright is NGC 4889 (apparent magnitude)?
- 11.4.
- Where in the sky is NGC 4889?
- In the direction of Coma Berenices.
- Where is NGC 4889 in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Measuring 21 billion Suns — the black hole's sphere of influence
The mass of NGC 4889's black hole was obtained by measuring how fast the stars at the galaxy's centre move, position by position. Close enough to the black hole, stellar speeds are set by its gravity rather than the galaxy's, and the radius of that "sphere of influence" in NGC 4889 is about 1,500 light-years. At 300 million light-years that spans barely an arcsecond, and the Gemini and Keck telescopes resolved the velocity distribution inside it with adaptive optics.
The measured velocity dispersion rises steeply toward the centre and demands 21 billion solar masses, but the error range is wide, from 6 to 37 billion, because the orientation of the stellar orbits is unknown and the value changes with the model. Even the lower bound exceeds a thousand times the Milky Way's central black hole, and it became the benchmark for how large the black hole of a cluster-central galaxy can grow.
The black hole in depth
NGC 4889 is the brightest giant elliptical galaxy in the Coma Cluster, about 300 million light-years away toward Coma Berenices. In 2011 velocity measurements of its central stars with the Gemini and Keck telescopes yielded a black-hole mass of roughly 21 billion Suns. It was the heaviest black hole directly measured at the time, and together with NGC 3842's 9.7 billion from the same paper it opened the era of ten-billion-solar-mass black holes.
Its event horizon spans about 130 billion kilometres, more than fourteen times the size of Neptune's orbit. The black hole probably blazed as a quasar in the early universe while devouring surrounding gas, but it has since run out of fuel and gone quiet. Finding such dormant giants nearby tells astronomers what the distant quasars they see eventually become.
The galaxy itself shines at magnitude 11.4, and on a clear spring night a 20-centimetre telescope shows it with its neighbour NGC 4874 as the twin smudges at the cluster's heart. Select NGC 4889 in the Sky view to find it in Coma Berenices east of Denebola, conveniently near the zenith on spring evenings.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.