Galaxy in Coma Berenices
M99
Among the first galaxies in which anyone recognised spiral structure, drawn by Lord Rosse shortly after M51. Its arms are noticeably uneven, and it is leaving a long trail of gas behind it as the cluster pulls it away.
The trail behind it is hydrogen being stripped as it moves through the cluster, and the uneven arms are the same encounter seen from the other side — M98 shows the matching damage. Three supernovae since 1967, which for a galaxy this size is a high rate and probably a consequence of the same disturbance.
- Catalogue
- M99
- Type
- Galaxy
- Constellation
- Coma Berenices
- Distance
- 50 million light-years
- Apparent magnitude
- 9.9
- Surface brightness
- 22.0 mag/□″
- Apparent size
- 5′
- Right ascension
- 12h 19m
- Declination
- +14.42°
- Found by
- Pierre Méchain, 1781
Small enough that its 9.9 magnitudes arrive concentrated rather than smeared: 22.0 per square arcsecond, which is why it stands out from the sky better than its brightness alone suggests. Why surface brightness is the number that matters.
Could you see it?
Straightforward with 10×50 binoculars from Bortle 4.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 4 20.9 mag/□″ | No | Easy | Easy | Easy | Easy |
| Bortle 5 20.3 mag/□″ | No | No | Challenge | Challenge | Challenge |
| Bortle 6 19.3 mag/□″ | No | No | Challenge | Challenge | Challenge |
| Bortle 7 18.6 mag/□″ | No | No | No | No | No |
| Bortle 8 18.1 mag/□″ | No | No | No | No | No |
| Bortle 9 17.8 mag/□″ | No | No | No | No | No |
At the eyepiece
Round, face-on and evenly lit, with the arms only hinted at above 250mm. Sits close enough to M98 and M100 that all three can be worked in one session, and comparing a face-on spiral against an edge-on one in the same hour teaches more than either alone.
When, and from where
Highest in the middle of the night in March. Passes overhead at 14°N and rises from everywhere except the far south — below 76°S it never clears the horizon.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 44° | |
| 51°N London, Calgary | 53° | |
| 40°N New York, Madrid | 64° | |
| 30°N Cairo, Houston | 74° | |
| 0°N the equator | 76° | |
| 33°S Sydney, Cape Town | 43° |
Nearby in the sky
The whole catalogue →This is a busy patch. 4 more of the catalogue sit within five degrees, which is a binocular field or two — worth planning a session around rather than visiting once. Everything below is measured from M99 itself, not from the middle of Coma Berenices.
- M98 Galaxy 1.3° apart Coma Berenices · magnitude 10.1 · binoculars from Bortle 4 or darker
- M100 Galaxy 1.7° apart Coma Berenices · magnitude 9.3 · binoculars from Bortle 4 or darker
- M84 Galaxy 2.2° apart Virgo · magnitude 9.1 · binoculars from Bortle 5 or darker
- M86 Galaxy 2.3° apart Virgo · magnitude 8.9 · binoculars from Bortle 5 or darker
One of 110. Positions J2000; the sky is the final authority.