Galaxy in Ursa Major
M108
A streak rather than a shape: edge-on, mottled with dust, and with no core showing at all. The Owl Nebula sits close enough that a single low-power field holds the two together.
The absence of a core is genuine rather than a matter of dust: it is a barred spiral that has almost no central bulge at all, which is unusual, and the mottling along its length is star formation seen through the disc it is happening in. Around 125 billion solar masses and roughly a hundred thousand light-years across.
- Catalogue
- M108
- Type
- Galaxy
- Constellation
- Ursa Major
- Distance
- 46 million light-years
- Apparent magnitude
- 10.0
- Surface brightness
- 21.6 mag/□″
- Apparent size
- 8′ × 2′
- Right ascension
- 11h 11m
- Declination
- +55.67°
- Found by
- Pierre Méchain, 1781
Small enough that its 10.0 magnitudes arrive concentrated rather than smeared: 21.6 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; with a 200mm from Bortle 5.
| 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 | Easy | Easy | Easy |
| 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
A thin, mottled streak with no core visible at all — an unusually strange-looking galaxy in a small telescope, and the mottling is genuine structure rather than noise. Half a degree from the Owl Nebula, and taking both in one low-power field is the way to do it.
When, and from where
Highest in the middle of the night in March. Well placed for the northern hemisphere and overhead for anyone near 56°N. South of 34°S it stays below the horizon.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 86° | Never sets |
| 51°N London, Calgary | 85° | Never sets |
| 40°N New York, Madrid | 74° | Never sets |
| 30°N Cairo, Houston | 64° | |
| 0°N the equator | 34° | |
| 33°S Sydney, Cape Town | 1° | Low — in the murk |
Nearby in the sky
The whole catalogue →One more of the catalogue sits within five degrees, close enough to take in on the same night without moving far. Everything below is measured from M108 itself, not from the middle of Ursa Major.
- M97 Owl Nebula 48′ apart Ursa Major · magnitude 9.9 · binoculars from Bortle 4 or darker
- M109 Galaxy 7.1° apart Ursa Major · magnitude 9.8 · binoculars from Bortle 4 or darker
- M40 Winnecke 4 10.0° apart Ursa Major · magnitude 8.4 · binoculars from Bortle 7 or darker
- M106 Galaxy 13° apart Canes Venatici · magnitude 8.4 · binoculars from Bortle 4 or darker
One of 110. Positions J2000; the sky is the final authority.