Nebula in Serpens
Eagle Nebula (M16)
The Eagle Nebula, and the site of the Pillars of Creation — the Hubble photograph that did more than any other to make people care what a telescope was pointed at. Visually the cluster is easy and the nebula is not. The pillars themselves are about four light-years tall and are being eaten away from the outside by the same starlight that makes them visible.
Infrared images have been read as showing a shock front already passing through the region, which would mean the structure was destroyed thousands of years ago and the light has not reached us yet — suggestive rather than settled.
- Catalogue
- M16
- Type
- Nebula
- Constellation
- Serpens
- Distance
- 7,000 light-years
- Apparent magnitude
- 6.0
- Surface brightness
- 22.3 mag/□″
- Apparent size
- 35′
- Right ascension
- 18h 19m
- Declination
- −13.78°
- Found by
- Philippe Loys de Chéseaux, 1745
Magnitude 6.0 sounds comfortable and is spread over 35′, which brings it down to 22.3 per square arcsecond — the number that actually decides whether there is anything to see. Why surface brightness is the number that matters.
Could you see it?
Straightforward from a Bortle 2 sky or darker, and aperture makes almost no difference to that — spread this thinly, an object is limited by how bright the sky behind it is rather than by how much light the telescope collects. A darker site beats a bigger telescope.
| Sky | Eye | 10×50 | 80mm | 130mm | 200mm |
|---|---|---|---|---|---|
| Bortle 1 21.9 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 2 21.7 mag/□″ | Easy | Easy | Easy | Easy | Easy |
| Bortle 3 21.4 mag/□″ | Challenge | Challenge | Challenge | Challenge | Challenge |
| Bortle 4 20.9 mag/□″ | Challenge | Challenge | Challenge | Challenge | Challenge |
| Bortle 5 20.3 mag/□″ | No | No | No | No | No |
| Bortle 6 19.3 mag/□″ | No | No | No | No | No |
| 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
Two objects sharing a name, and only one of them is easy. The cluster is a straightforward scattering in any telescope; the nebula around it needs a dark sky and a narrowband filter before it amounts to more than a suspicion, and the Pillars themselves are photographic only.
When, and from where
Highest in the middle of the night in June. Overhead at 14°S and southerly enough to sit low from northern Europe, though never out of reach there — only north of 76°N does it stop rising at all.
| Latitude | Highest it gets | |
|---|---|---|
| 60°N Oslo, Anchorage | 16° | Low — in the murk |
| 51°N London, Calgary | 25° | |
| 40°N New York, Madrid | 36° | |
| 30°N Cairo, Houston | 46° | |
| 0°N the equator | 76° | |
| 33°S Sydney, Cape Town | 71° |
Nearby in the sky
The whole catalogue →This is a busy patch. 3 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 M16 itself, not from the middle of Serpens.
- M17 Omega Nebula 2.4° apart Sagittarius · magnitude 6.0 · needs more than binoculars
- M18 Open cluster 3.4° apart Sagittarius · magnitude 7.5 · binoculars from Bortle 9 or darker
- M24 Sagittarius Star Cloud 4.7° apart Sagittarius · magnitude 2.5 · binoculars from Bortle 9 or darker
- M25 Open cluster 6.3° apart Sagittarius · magnitude 4.6 · binoculars from Bortle 9 or darker
One of 110. Positions J2000; the sky is the final authority.