M91 (Galaxy)
The faintest of the Virgo galaxies on Messier's list, a barred spiral in Coma Berenices. For a long time it was considered the "lost" Messier object.
Galaxy in Coma Berenices. Magnitude 11.0.
Can you see it from Guyana?
From Georgetown (6.8° N) it climbs to 82° above the northern horizon at its highest; from Lethem (3.4° N), to 79° above the northern horizon. It is highest at midnight on the night of 29 Mar, 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 7.4° north-west of Vindemiatrix.
- 10x50 binoculars: Not visible in binoculars. M88 is 0.8° to the west.
- A small telescope (80 to 100 mm): A faint glow with a brighter bar across the middle under a dark sky; M88 is 0.8° to the west.
- 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: 5.5′ × 4.5′, 18% of the Moon's width (the Moon is about 31′ wide).
- Brightness: magnitude 11.0. Fainter than the faintest stars in Georgetown (4.3) and Lethem (6.0): binoculars or a telescope.
- Distance: 50 million light-years. The light reaching your eye left it about 50 million years ago.
- True size: 82,000 light-years across its catalogued outline; light crosses it in 82,000 years.
Apparent size from OpenNGC (Mattia Verga), CC-BY-SA-4.0.
What it is made of
- Type
- Barred spiral galaxy
- Notable
- Long considered the "lost" Messier object; its distance comes from Cepheid variable stars.
What is in it, not measured:
- Stars: an older central bulge and a disc of younger stars
- Gas and dust: in the spiral arms, where new stars form
- Dark matter: inferred from how fast it spins
How we know: Distance from Cepheid variable stars: NED-D (NASA/IPAC Extragalactic Database, redshift-independent distances), median of 22 Cepheids estimates: 15.60 Mpc, 14.74-16.10 Mpc (16th-84th percentile); e.g. 2008A&ARv..15..289T, 2006ApJS..165..108S, 2006A&A...452..423P; 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: M88 (Galaxy) · M90 (Galaxy) · M89 (Galaxy) · Virgo Galaxy (M87) · M86 (Galaxy) · M58 (Galaxy)