Coma Berenices
What is Coma Berenices?
Constellations· Spring evenings (N) · star haze between Leo's tail and Arcturus. The hair Queen Berenice of Egypt offered for her husband's safe return. Instead of bright stars its face is the Coma Star Cluster, a soft haze to the naked eye. It looks toward the galactic north pole, a window onto thousands of galaxies, including NGC 4889 and its giant black hole. Look east of Leo's tail in the Sky view.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Coma Berenices is in your sky right now: https://nowsky.org/solar/sky?sel=con:Coma Berenices — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Beta Comae Berenices | 4.3 |
| Diadem | 4.3 |
| Gamma Comae Berenices | 4.4 |
The 3 brightest of the 3 stars used in the figure (2 lines). Lower magnitude means brighter.
Deep-sky objects near this constellation
Constellation basics
| Season | spring evenings (N) |
|---|---|
| Brightest star | Beta Comae Berenices (4.3) |
| How to find | the faint star swarm between Denebola and Arcturus |
| Area rank | 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Coma Berenices?
- spring evenings (N).
- How do I find Coma Berenices?
- the faint star swarm between Denebola and Arcturus.
- What is the brightest star in Coma Berenices?
- Beta Comae Berenices, magnitude 4.3.
- Where is Coma Berenices in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The cluster where dark matter was first inferred, in 1933
Three hundred and twenty million light-years away in the direction of Coma Berenices lies the Coma Cluster, a gathering of more than a thousand galaxies. In 1933 Fritz Zwicky measured the speeds of galaxies within it and calculated that the mass of the visible stars alone could not hold galaxies moving that fast together. There had to be unseen mass hundreds of times the visible amount, and the term he used, dark matter, is still in use.
Zwicky's figure was exaggerated by the errors of the distance scale of his day, but the direction of his conclusion was right, and it was revived forty years later by observations of galaxy rotation curves. It is now established that most of a cluster's mass is dark matter, the next largest share is hot gas glowing in X-rays, and stars are only a few percent. Behind the faint star cluster of spring evenings is the place where the idea that most of the universe is invisible first arose.
The constellation in depth
Coma Berenices is one of the few constellations tied to a real person. In the 3rd century BC Queen Berenice II of Egypt cut off her hair as a vow when her husband Ptolemy III returned safely from war; when it vanished from the temple the next day, the court astronomer Conon pointed to this star haze and declared the gods had placed it in the sky. Tycho Brahe's 1602 catalogue made it a constellation in its own right.
At its heart the Coma Star Cluster (Melotte 111) is a nearby open cluster 280 light-years away — a soft patch to the eye, dozens of stars in binoculars. This is the direction of the galactic north pole, thin in stars and dust, so the deep universe shows through: the Black Eye Galaxy M64, the globular M53 and the Coma Cluster of galaxies some 300 million light-years off, whose central giant NGC 4889 gave the first direct measurement of a 21-billion-solar-mass black hole.
On April–June evenings look midway between Denebola, the tail of Leo, and Arcturus in Boötes; under a dark sky a faint smudge of stars appears. In town you will want binoculars. Switch on "More objects" in the Sky view to find NGC 4889.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.