Galaxy in Cetus
Cetus A (M77)
The nearest bright Seyfert: a galaxy whose centre is lit by a black hole actively feeding, brightly enough to outshine everything else in it at some wavelengths. At the eyepiece that comes out as a fuzzy star with a halo, which is exactly what it means.
Seyfert galaxies were the first evidence that some galaxies have an engine at the centre rather than merely a crowd of stars, and this was among the six Carl Seyfert listed in 1943. The black hole is around ten million solar masses, and the reason we see the core at all is that this one happens to be pointed our way.
- Catalogue
- M77
- Type
- Galaxy
- Constellation
- Cetus
- Distance
- 47 million light-years
- Apparent magnitude
- 8.9
- Surface brightness
- 21.6 mag/□″
- Apparent size
- 7′ × 6′
- Right ascension
- 2h 43m
- Declination
- −0.02°
- Found by
- Pierre Méchain, 1780
Small enough that its 8.9 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 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 | Easy | Easy | Easy | Easy |
| Bortle 6 19.3 mag/□″ | No | Challenge | 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 bright, almost stellar core inside a small faint halo — which looks like a fault in the optics until you realise it is the point. That concentrated middle is a black hole feeding, and the reason this galaxy looks unlike every other one here.
When, and from where
Highest in the middle of the night in October. Close enough to the celestial equator to rise from almost anywhere on Earth, and to pass overhead for anyone near 0°S.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 30° | |
| 51°N London, Calgary | 39° | |
| 40°N New York, Madrid | 50° | |
| 30°N Cairo, Houston | 60° | |
| 0°N the equator | 90° | |
| 33°S Sydney, Cape Town | 57° |
Nearby in the sky
The whole catalogue →Nothing else in the catalogue is especially close; the nearest is 23° apart, which is a separate trip rather than a nudge of the tube. Everything below is measured from M77 itself, not from the middle of Cetus.
- M74 Phantom Galaxy 23° apart Pisces · magnitude 9.4 · binoculars from Bortle 3 or darker
- M45 Pleiades 29° apart Taurus · magnitude 1.2 · binoculars from Bortle 9 or darker
- M33 Triangulum Galaxy 35° apart Triangulum · magnitude 5.7 · binoculars from Bortle 3 or darker
- M34 Open cluster 43° apart Perseus · magnitude 5.5 · binoculars from Bortle 9 or darker
One of 110. Positions J2000; the sky is the final authority.