Small Magellanic Cloud (SMC / NGC 292 / Nubecula Minor)
J2000 coordinates, eclipsing-binary distance (203,000 ly), magnitude 2.18, Henrietta Leavitt Cepheid law, Magellanic Bridge, and SMC observing guide.
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.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Integrated visual magnitude (V) | 2.18 mag | ± 0.06 mag | All-sky photoelectric & Gaia DR3 integrated photometry | definitive | ESA Gaia Archive — Data Release 3 |
| Distance in light-years | 203700 ly | ± 4200 ly | Late-type detached eclipsing binaries (62.44 ± 1.28 kpc — Graczyk et al. 2020) | definitive | SH0ES Local Distance Ladder Hubble Constant |
| Apparent major axis | 315 arcmin | ± 12 arcmin | Optical diameter (5.25° × 3.08°) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric radial velocity | 145.6 km/s | ± 0.6 km/s | Gaia DR3 & H I 21-cm systemic velocity | definitive | ESA Gaia Archive — Data Release 3 |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Small Magellanic Cloud (SMC / NGC 292) at RA 00h 52m 38.00s, Dec -72° 48′ 01.0″ within Tucana, 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.
Astrophysical Context & Structure
Located 20 degrees west of the Large Magellanic Cloud in the southern constellation Tucana, the Small Magellanic Cloud (SMC, NGC 292) is a dwarf irregular galaxy containing roughly 3 billion stars at a mean distance of 203,700 light-years (62.44 kiloparsecs). It was in photographic plates of the Small Magellanic Cloud taken at Harvard's Boyden Station in Peru that Henrietta Swan Leavitt examined 1,777 variable stars and, in 1912, discovered the Period-Luminosity Relation (Leavitt's Law) of Classical Cepheids—forging the yardstick that revealed the scale of the universe.
Because the SMC has a low heavy-element abundance (roughly one-fifth of solar metallicity, [Fe/H] ≈ −0.7), its interstellar medium and massive O-type stars closely mimic the primitive chemical conditions of star-forming galaxies in the early universe at redshift z ≈ 2–3. Within its northeastern 'Wing' sits NGC 346, a luminous H II region where the James Webb Space Telescope has imaged active protoplanetary disks forming around young low-metallicity stars.
Repeated gravitational collisions between the SMC and the larger LMC—most recently a near-head-on impact ~200 million years ago—have stretched the SMC along our line of sight and ripped out two colossal neutral-hydrogen structures: the Magellanic Bridge connecting both galaxies and the 600,000-light-year Magellanic Stream arching halfway across the southern sky.
Practical Visual Observing Guide
- Visible to the naked eye from the Southern Hemisphere (and tropical latitudes south of +15°N) as a 5° × 3° teardrop-shaped cloud shining at magnitude 2.18.
- Just off the western edge of the SMC sits the magnificent foreground Milky Way globular cluster 47 Tucanae (NGC 104, magnitude 4.0, only 14,500 light-years away), with a second bright globular cluster, NGC 362, positioned off the SMC's northern tip!
- In a 100–200 mm telescope at 60×–120×, sweep inside the SMC to resolve the bright knotty emission nebula NGC 346 and the rich open cluster NGC 330.
Catalog Cross-Identifications & Aliases
Common Aliases: SMC · NGC 292 · Nubecula Minor · PGC 3085
| Catalog Authority | Identifier |
|---|---|
| NGC | NGC 292 |
| SIMBAD | NAME SMC |
| WIKIDATA | Q49984 |
Related Objects, Comparisons & Guides
Large Magellanic Cloud (LMC / PGC 17223)
J2000 coordinates, eclipsing-binary distance (163,000 ly), magnitude 0.13, Tarantula Nebula (30 Doradus), SN 1987A, and observing guide for the LMC.
Sculptor Galaxy (NGC 253 Silver Coin)
J2000 coordinates, TRGB distance (11.4 Mly), magnitude 7.20, nuclear starburst superwind, mottled dust lanes, and observing guide for NGC 253.
Centaurus A (NGC 5128 Active Radio Galaxy)
J2000 coordinates, TRGB/Cepheid distance (12.4 Mly), magnitude 6.84, warped dust lane, relativistic radio lobes, and observing guide for Centaurus A.
Measurement Uncertainty & Optics in Astronomy
How random vs systematic errors, asymmetric error bars, model dependencies, and optical aperture/exit-pupil limits shape astronomical measurements.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
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)
- 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