NGC 5866 (often identified as M102)
M102 has no agreed identity: OpenNGC lists it as a repeat of M101, and many observers take it to be NGC 5866, the edge-on disc galaxy in Draco shown here. A crisp lane of dust splits NGC 5866 in two.
Galaxy in Draco. Magnitude 9.9.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 41° above the northern horizon at its highest; from Lethem (3.4° N), to 38° above the northern horizon. It is highest at midnight on the night of 6 May, in the middle of its season. The page works out tonight's rise, highest point and set for both towns in Guyana time (UTC-4), and where the Moon is.
What you'll see
- Your eyes: Not visible to the eye. It lies 11.5° west of Athebyne.
- 10x50 binoculars: Just detectable in binoculars from a dark site, as a faint smudge.
- A small telescope (80 to 100 mm): A bright, spindle-shaped glow 2.3 times as long as wide; the dust lane needs a larger telescope.
- A camera: Tiny on camera: it needs 2,000 mm or more of focal length on a tracking mount.
How big, how bright, how far
- Size on the sky: 6.3′ × 2.7′, 20% of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 9.9. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 46 million light-years. The light reaching your eye left it about 46 million years ago.
- True size: 84,000 light-years across its catalogued outline; light crosses it in 84,000 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Lenticular galaxy, seen edge-on
- Notable
- Messier's M102 is disputed: OpenNGC treats it as a duplicate of M101, and NGC 5866 is the usual candidate.
What is in it, not measured:
- Old stars: in a bulge and a smooth disc
- A little gas and dust: often in a thin lane
- Dark matter: inferred from how its stars move
How we know: Distance from the median of 11 published estimates by several methods (no two direct ones agree to combine): NED-D (NASA/IPAC Extragalactic Database, redshift-independent distances), median of 11 estimates: 14.00 Mpc, 8.67-15.30 Mpc (16th-84th percentile); e.g. 2013AJ....146...86T, 2007ApJ...668..209C, 2007A&A...465...71T; retrieved 2026-10-21. True size: the apparent size times the distance (apparent size: OpenNGC (Mattia Verga, CC BY-SA 4.0), commit 4e2398a2).
More deep-sky objects: Pinwheel Galaxy (M101) · Whirlpool Galaxy (M51) · Sunflower Galaxy (M63) · M94 (Galaxy) · Galaxy M106 · M109 (Galaxy)