NGC40 · Bow-Tie Nebula
| Chinese name | 蝴蝶结星云 |
|---|---|
| Type | Planetary nebula |
| Constellation | Cep |
| RA | 00h13m |
| Dec | +72° |
| Apparent magnitude | 11.4ᵐ |
| Hemisphere | Northern |
| Best season | Autumn |
| Difficulty | Hard |
| Focal length | 长焦 1500mm+ |
About
The Bow-Tie Nebula (NGC 40, Caldwell 2) lies about 3,500 light-years away in Cepheus and is a small planetary nebula. At its center sits a bright dying star around 50,000 degrees, wrapped in a warm red gas shell that the star expelled earlier and now heats to a glow with its intense radiation. Curiously, the nebula's gas is actually hotter than the central star itself, making it an interesting case for planetary-nebula physics. Hubble imagery indicates that in roughly 30,000 years this shell will cool and disperse into interstellar space. It shows a distinctive warm red-orange hue at long focal lengths, a small challenging target in the late autumn Cepheus sky.