About NGC 2309
NGC 2309 is a trash cluster. It sits in the constellation Mon and shines at apparent magnitude 10.5.
An open cluster: a few hundred stars born together out of one collapsing cloud, still drifting along in loose formation.
Trash cluster 10 EP
NGC 2309
RA 104.0150° · Dec -7.1743° · openngc
Score breakdown
· 2 badgesTrash 15 pts → Common
- Star cluster +7
- Open cluster +3
Total score 10
5 more points to reach Common.
Badges
- Star cluster · +7
- Open cluster · +3
Trivia
What it actually is
- What it actually is. An open cluster: a few hundred stars born together out of one collapsing cloud, still drifting along in loose formation.
Sense of scale
- Sense of scale. Gravity is not strong enough to hold it. Within a few hundred million years these siblings will be scattered right around the galaxy.
Find it in the sky
- How to spot it. At magnitude 10.5 you'll want a small backyard telescope, over in Monoceros.
- Seen from everywhere. It sits almost on the celestial equator, so it can be seen from essentially anywhere on Earth.
- Best time of year. It stands highest in the middle of the night around January — that's when to go looking.
Its true colour
- Its true colour. Open clusters look blue-white because they are young — their hottest, bluest stars have not had time to die yet.
How we came to know it
- The New General Catalogue. Its NGC number comes from J. L. E. Dreyer's 1888 catalogue, itself built on decades of sky sweeps by William Herschel and his sister Caroline.
Properties
- constellation
- Mon
- dso type
- OCl
- mag
- 10.5
- name
- NGC 2309
- radial velocity kms
- 56
- redshift
- 0.0002
- size arcmin
- 5.4
How to see it
Look for NGC 2309 in the constellation Mon. At apparent magnitude 10.5, a small backyard telescope will bring it into view.
Like any astronomical target, NGC 2309 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 NGC 2309 is a trash cluster
NGC 2309 scores 10 points on Spacedle's rarity scale, which places it in the trash tier. Another 5 points would lift it into a rarer tier.
That score comes from 2 science badges — Star cluster and Open cluster — 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.