Open Clusters · Constellation Taurus

Pleiades (Messier 45)

Coordinates, Gaia DR3 distance (136.2 pc), magnitude 1.6, reflection nebulosity, and observing guide for the Pleiades (M45) in Taurus.

Right Ascension (J2000.0)03h 47m 00.00s
Declination (J2000.0)+24° 07′ 00.0″
Primary ClassificationOpen star cluster with dusty reflection nebulosity
Best Observing SeasonLate Autumn to Winter (November–February)

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 Pleiades (Messier 45)
ParameterValueUncertaintyMethod & EpochQuality StatusSource Archive
Integrated visual magnitude (V)1.6 mag± 0.1 magIntegrated wide-field photometrydefinitiveRevised New General Catalogue and Index Catalogue (RNGC/IC)
Mean cluster distance (Gaia DR3)
Resolved the historic 'Pleiades distance controversy' where Hipparcos reported ~120.2 ± 1.9 pc due to correlated small-scale attitude residuals, whereas VLBI, HST FGS, and Gaia DR3 all confirm 136.2 ± 1.2 pc.
136.2 pc± 1.2 pcGaia DR3 trigonometric parallax of 1,000+ co-moving cluster members (J2016.0)definitiveESA Gaia Archive — Data Release 3
Cluster age0.115 Gyr± 0.01 GyrLithium depletion boundary in substellar brown dwarfs + B-star turnoffhigh-confidenceESA Gaia Archive — Data Release 3
Apparent core diameter110 arcmin± 10 arcminVisual and photographic cluster core extenthigh-confidenceRevised New General Catalogue and Index Catalogue (RNGC/IC)
Measurement Uncertainties & Competing Solutions: For nearly two decades the Pleiades was the center of an astrometric controversy when the Hipparcos satellite derived 120.2 ± 1.9 pc against 133–137 pc from main-sequence fitting and VLBI; Gaia DR3 decisively settled the distance at 136.2 ± 1.2 pc (444 light-years).

J2000 Equatorial Sky Chart & Culmination Altitude

The chart below plots Pleiades (Messier 45 Open Cluster) at RA 03h 47m 00.00s, Dec +24° 07′ 00.0″ within Taurus, 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 (Taurus) +90° 0° −90° 24h 12h RA 0h Peak Meridian Altitude 74° 40°N Lat 36° 30°S Lat RA: 03h 47m 00.00s Dec: +24° 07′ 00.0″ Epoch: J2000.0 · V = 1.6 mag First-party vector diagram derived from IAU / CDS SIMBAD / Gaia DR3 astrometry.

Astrophysical Context & Structure

The Pleiades (Messier 45, or the Seven Sisters) is the most famous naked-eye open cluster in the night sky, lying 136.2 ± 1.2 parsecs (444 light-years) away in the constellation Taurus. Dominated by nine luminous B-type hot blue stars—led by Alcyone (η Tauri, magnitude 2.87), Atlas, Electra, Maia, Merope, Taygeta, Pleione, Celaeno, and Asterope—the cluster contains over 1,200 gravitationally bound stars and brown dwarfs totaling roughly 800 solar masses.

Lithium-depletion boundary measurements in the cluster's low-mass brown dwarfs place the age of the Pleiades at 115 ± 10 million years. Contrary to early 20th-century assumptions, the lacy blue reflection nebulae draping Merope (NGC 1435) and Maia (NGC 1432) are not leftover placental gas from the cluster's birth; proper-motion vectors show M45 is currently passing at ~11 km/s through an unrelated interstellar dust cloud in the Taurus-Auriga complex, where sub-micron dust grains preferentially scatter blue starlight.

In observational astrophysics, the Pleiades played a historic role in testing space astrometry: when the original Hipparcos catalog yielded an anomalously short 120 pc distance, follow-up VLBI radio interferometry, Hubble Fine Guidance Sensor parallaxes, and ESA's Gaia mission proved the true distance is 136.2 pc.

Practical Visual Observing Guide

Minimum InstrumentNaked eye; best in 7×50 or 10×50 binoculars
Recommended Magnification7×–25× wide-field
Best Evening SeasonLate Autumn to Winter (November–February)
  • Unmistakable to the naked eye on autumn and winter evenings as a miniature dipper-shaped knot of 6 to 9 stars northwest of Aldebaran in Taurus.
  • Because M45 spans nearly 2° across, 7×50 or 10×50 binoculars or a rich-field telescope with a 2.5°–3.5° true field of view frame the entire cluster far better than high-power telescopes.
  • Under transparent dark skies (Bortle 1–3) with clean optics, look for the faint fan-shaped Merope Nebula (IC 349 / NGC 1435) extending south-southwest from 4th-magnitude Merope.

Catalog Cross-Identifications & Aliases

Common Aliases: M45 · Seven Sisters · Melotte 22

Cross-Catalog Identifiers for Pleiades (Messier 45)
Catalog AuthorityIdentifier
MESSIERM 45
SIMBADM 45
WIKIDATAQ13423
Related Object · Taurus

Hyades (Melotte 25 Nearest Cluster)

Coordinates, Gaia DR3 distance (47.0 pc), age 650 Myr, moving-group kinematics, and observing guide for the Hyades cluster in Taurus.

Related Object · Cancer

Beehive Cluster (Messier 44 Praesepe)

Coordinates, Gaia DR3 distance (186.2 pc), magnitude 3.1, exoplanet hosts, and observing guide for the Beehive Cluster (M44 / NGC 2632).

Related Object · Taurus

Aldebaran (Alpha Tauri Orange Giant)

Coordinates, Hipparcos distance (66.6 ly), 45.1 R☉ radius, Hyades foreground alignment, and observing guide for Aldebaran in Taurus.

Side-by-Side Comparison

Pleiades (M45) vs Beehive (M44) Comparison

Compare the two brightest Messier open clusters—the Pleiades (M45) in Taurus and Beehive Cluster (Praesepe, M44) in Cancer—in age, distance, and stars.

Reference Guide

Trigonometric Parallax, Parsecs & Gaia DR3

How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.

Reference Guide

Stellar Spectral Classification (OBAFGKM)

Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.

Catalog · Gaia DR3 / Melotte / Messier / NGC

Galactic Open Clusters Reference Catalog

Cross-reference catalog of nearby galactic disk open star clusters—Hyades, Pleiades (M45), Beehive (M44), and Double Cluster (NGC 869/884)—with Gaia DR3 data.

Scientific Sources & Dataset Provenance

  • ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
  • Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
  • 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