Cosmic Scale
Coma Cluster
Rich cluster of galaxies · 321 million light-years
How big is Coma Cluster?
Coma Cluster is about 20 million light-years across.
See Coma Cluster in 3D, at true scale
The Coma Cluster is a rich cluster of over 1,000 galaxies, most of them ellipticals. In 1933 Fritz Zwicky found its galaxies moving too fast to be held together by what can be seen — the first evidence of dark matter.
At a glance
| Diameter | 20 million light-years |
|---|---|
| Mass | 1.39 × 10⁴⁵ kg |
| Diameter compared with Earth | 1.5 × 10¹⁶ × Earth |
| Distance | 321 million light-years |
| Galaxies | Over 1,000 |
| Dark matter | About 90% of its mass |
Good to know
- At its centre are two giant ellipticals, NGC 4874 and NGC 4889.
- Hot gas between its galaxies glows in X-rays at around 100 million degrees.
- Zwicky called the missing mass 'dunkle Materie' — dark matter.
- Next smaller: Alcyoneus · 16 million light-years
- Next larger: Porphyrion · 23 million light-years