About IC 1747
IC 1747 is a rare nebula. It sits in the constellation Cas and shines at apparent magnitude 12.
A planetary nebula: the shed outer atmosphere of a dying Sun-like star, lit from within by the naked stellar core left behind.
Rare nebula 46 EP
IC 1747
RA 29.3989° · Dec 63.3218° · openngc
Score breakdown
· 5 badgesRare 50 pts → Epic
- Planetary nebula (a dying star's shell) +12
- Its dying star is still visible +12
- Coming towards us +10
- Nebula +8
- Never sets (northern circumpolar) +4
Total score 46
4 more points to reach Epic.
Badges
- Nebula · +8
- Planetary nebula (a dying star's shell) · +12
- Never sets (northern circumpolar) · +4
- Coming towards us · +10
- Its dying star is still visible · +12
Trivia
What it actually is
- What it actually is. A planetary nebula: the shed outer atmosphere of a dying Sun-like star, lit from within by the naked stellar core left behind.
Find it in the sky
- How to spot it. At magnitude 12 it is far too faint for the eye: this one belongs to cameras and long exposures, over in Cassiopeia.
- Never sets. So far north that from Britain, Canada or northern Europe it never dips below the horizon — it is up every clear night of the year.
- Best time of year. It stands highest in the middle of the night around October — that's when to go looking.
Its true colour
- Its true colour. Its teal-green comes from doubly-ionised oxygen at 501 nanometres, and its red from hydrogen at 656 — colours no ordinary object on Earth produces.
What's in a name
- A misleading name. 'Planetary nebula' is a 240-year-old mistake. William Herschel coined it in the 1780s because these round greenish discs resembled the planet Uranus he had just discovered. There are no planets involved whatsoever.
How we came to know it
- The Index Catalogue. The IC was the 1895 and 1908 supplement to the NGC — the first catalogue in history to be filled largely with objects found on photographic plates rather than by eye.
Properties
- central star mag
- 15.4
- constellation
- Cas
- dso type
- PN
- mag
- 12
- name
- IC 1747
- radial velocity kms
- -63
- size arcmin
- 0.22
How to see it
Look for IC 1747 in the constellation Cas. At apparent magnitude 12, a small backyard telescope will bring it into view.
Like any astronomical target, IC 1747 is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. The visibility panel above works out tonight's viewing window for your saved location.
Why IC 1747 is a rare nebula
IC 1747 scores 46 points on Spacedle's rarity scale, which places it in the rare tier. Another 4 points would lift it into a rarer tier.
That score comes from 5 science badges — Nebula, Planetary nebula (a dying star's shell), Never sets (northern circumpolar), Coming towards us and Its dying star is still visible — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.