Galaxies · Constellation Leo

Messier 65 (NGC 3623)

J2000 coordinates, distance (34.6 Mly), magnitude 9.31, tightly wound SA(rs)a arms, prominent eastern dust lane, and observing guide for Messier 65.

Right Ascension (J2000.0)11h 18m 55.90s
Declination (J2000.0)+13° 05′ 32.0″
Primary ClassificationEarly-type intermediate spiral galaxy in the interacting Leo Triplet (Arp 317)
Best Observing SeasonSpring (February–June)

Provenance-Backed Scientific Measurements

Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.

Astrometric, Photometric, and Physical Parameters for Messier 65 (NGC 3623)
ParameterValueUncertaintyMethod & EpochQuality StatusSource Archive
Integrated visual magnitude (V)9.31 mag± 0.08 magIntegrated CCD aperture photometrydefinitiveRevised New General Catalogue and Index Catalogue (RNGC/IC)
Distance in light-years34600000 ly± 2000000 lyTip of the Red Giant Branch (TRGB) & Type II-P SN 2013am distance (10.6 ± 0.6 Mpc)definitiveSH0ES Local Distance Ladder Hubble Constant
Apparent major axis9.8 arcmin± 0.4 arcminOptical 25 mag/arcsec² isophotal dimensions (9.8′ × 2.9′)definitiveRevised New General Catalogue and Index Catalogue (RNGC/IC)
Heliocentric recession velocity807 km/s± 3 km/sH I 21-cm and optical absorption spectroscopydefinitiveSIMBAD Astronomical Database (CDS)
Measurement Uncertainties & Competing Solutions: TRGB star counts and standardized photospheric modeling of Type II-P supernova SN 2013am place M65 at 10.6 ± 0.6 Mpc (34.6 ± 2.0 Mly) within the M66 Group (Leo II subgroup).

J2000 Equatorial Sky Chart & Culmination Altitude

The chart below plots Messier 65 (NGC 3623 Leo Triplet Spiral) at RA 11h 18m 55.90s, Dec +13° 05′ 32.0″ within Leo, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.

J2000 Equatorial Sky Position (Leo) +90° 0° −90° 24h 12h RA 0h Peak Meridian Altitude 63° 40°N Lat 47° 30°S Lat RA: 11h 18m 55.90s Dec: +13° 05′ 32.0″ Epoch: J2000.0 · V = 9.31 mag First-party vector diagram derived from IAU / CDS SIMBAD / Gaia DR3 astrometry.

Astrophysical Context & Structure

Discovered by Charles Messier on March 1, 1780, Messier 65 (NGC 3623) is the westernmost member of the famous Leo Triplet (Arp 317)—a tight gravitational grouping of three large spiral galaxies (M65, M66, and NGC 3628) packed inside a 35-arcminute circle roughly 34.6 million light-years away under the hindquarters of Leo. Inclined 74 degrees from face-on and oriented nearly north-south, M65 spans ~98,000 light-years across its elegant SAB(rs)a disk.

In sharp contrast to its turbulent neighbor M66 just 20 arcminutes to the east, M65 emerged comparatively unscathed from the Leo Triplet's gravitational encounter ~800 million years ago. It retains a quiescent, low-gas-fraction early-type spiral structure dominated by an old, golden central bulge and smoothly wound arms, though high-resolution radio and optical imaging detects a subtle S-shaped warp at the northern and southern tips of its disk and a prominent opaque dust lane running along its eastern (near) rim.

Although M65 has a relatively modest current star-formation rate concentrated along the inner edge of its dust lane, a massive progenitor star in its southern spiral arm exploded in March 2013 as the low-velocity Type II-P supernova SN 2013am.

Practical Visual Observing Guide

Minimum Instrument70–80 mm telescope (frames M65 + M66 together)
Recommended Magnification45×–70× for Leo Triplet; 120×–160× for M65 dust lane
Best Evening SeasonSpring (February–June)
  • Located halfway between Chertan (θ Leonis) and Iota (ι) Leonis, just 20′ west of M66.
  • A wide-field eyepiece (40×–65×) in any 100–200 mm telescope frames all three members of the Leo Triplet (M65, M66, and the edge-on Hamburger Galaxy NGC 3628) in a single stunning view.
  • In a 200–300 mm telescope at 120×–160×, M65 appears as a sleek 9′×2.5′ silver-white spindle with a bright oval bulge and a crisp eastern edge cut off by its foreground dust lane.

Catalog Cross-Identifications & Aliases

Common Aliases: M65 · NGC 3623 · UGC 6328 · PGC 34612

Cross-Catalog Identifiers for Messier 65 (NGC 3623)
Catalog AuthorityIdentifier
MESSIERM 65
NGCNGC 3623
SIMBADM 65
WIKIDATAQ13988
Related Object · Leo

Messier 66 (NGC 3627 Asymmetric Spiral)

J2000 coordinates, Cepheid/TRGB distance (31.3 Mly), magnitude 8.92, tidally warped arms, five supernovae, and observing guide for Messier 66 in Leo.

Related Object · Leo

Messier 95 (NGC 3351 Theta-Shaped Spiral)

J2000 coordinates, HST Cepheid distance (32.6 Mly), magnitude 9.73, textbook SB(r)b bar and ring, circumnuclear knots, and observing guide for Messier 95.

Related Object · Leo

Messier 96 (NGC 3368 Leo I Group Anchor)

J2000 coordinates, HST Cepheid distance (34.9 Mly), magnitude 9.25, asymmetric dusty spiral arms, double bar, and observing guide for Messier 96 in Leo.

Reference Guide

Angular Size, Separation & Field of View

How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.

Scientific Sources & Dataset Provenance

  • Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC
  • SH0ES Local Distance Ladder Hubble Constant (2022 Baseline Cepheid + SN Ia): Riess, A. G., et al. 2022, ApJL, 934, L7 (A Comprehensive Measurement of the Local Value of the Hubble Constant) — SH0ES Collaboration (HST / JWST)
  • SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg