W49B Supernova Remnant (SNR G043.3−00.2 / 3C 398)
Coordinates, H I kinematic distance (10.0 kpc / 32,600 ly), Chandra bipolar iron jet rings, black-hole birth candidate, and data for W49B in Aquila.
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 |
|---|---|---|---|---|---|
| Near-infrared [Fe II] 1.64 μm integrated magnitude | 14.5 mag | ± 0.8 mag | Palomar/JWST near-IR shocked [Fe II] & H₂ barrel photometry (A_V > 30 mag optically) | model-dependent | SIMBAD Astronomical Database (CDS) |
| Heliocentric distance | 32600 ly | ± 3900 ly | 21-cm H I & 13CO molecular absorption velocity profile (10.0 ± 1.2 kpc) (J2016.0) | high-confidence | SIMBAD Astronomical Database (CDS) |
| Apparent barrel diameter | 4 arcmin | ± 0.3 arcmin | Chandra X-ray, VLA radio, and IR [Fe II] shell (4.0′ × 3.5′) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots W49B Supernova Remnant (Jet-Driven Barrel SNR) at RA 19h 11m 11.00s, Dec +09° 06′ 00.0″ within Aquila, 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
W49B (SNR G043.3−00.2, 3C 398) is one of the most luminous X-ray, gamma-ray, and radio supernova remnants in the Milky Way, located ~32,600 light-years (10.0 ± 1.2 kiloparsecs) away in Aquila, just 12 arcminutes east of the hyper-luminous star-forming region W49A. First cataloged in 1958 by Dutch radio astronomer Gart Westerhout, W49B spans 4.0 × 3.5 arcminutes (~35 light-years physically) and exploded roughly 1,000 to 3,000 years ago behind 30+ magnitudes of interstellar dust that blocked any historical sighting from Earth.
Unlike virtually every other supernova remnant in our Galaxy—where iron is mixed symmetrically or distributed in a spherical shell—Chandra X-ray Observatory and NuSTAR mapping of W49B discovered that its iron and nickel are concentrated inside a dense, 25-light-year central axial jet, surrounded by five coaxial rings of infrared [Fe II] (1.64 μm) emission and an outer cocoon of shocked molecular hydrogen (H₂ at 2.12 μm) shaped like a ribbed barrel.
This striking bipolar jet morphology—combined with an anomalously high manganese-to-chromium and iron-to-silicon abundance ratio and the complete absence of any central neutron star down to ultra-deep Chandra X-ray limits—makes W49B the premier candidate in the Milky Way for a 'jet-driven' (bipolar/collapsar-like) core-collapse supernova that gave birth to one of the youngest stellar-mass black holes in our Galaxy.
Practical Visual Observing Guide
- Situated on the Galactic equator in Aquila at RA 19h 11.2m, Dec +09°06′, about 4.3° north-northeast of Lambda Aquilae and 2.5° southeast of Zeta Aquilae.
- Because ~32 magnitudes of foreground dust absorb 99.9999999999% of its visible light, W49B cannot be seen through an optical eyepiece of any aperture; it is a classic multi-wavelength benchmark studied in radio (VLA 20 cm), near-infrared ([Fe II] 1.64 μm and H₂ 2.12 μm), X-rays (Chandra/XMM), and GeV/TeV gamma rays (Fermi/H.E.S.S.).
- Visual observers sweeping the rich Aquila Milky Way Rift can locate its exact coordinates against the dark Barnard dust lanes that obscure this hidden cataclysm.
Catalog Cross-Identifications & Aliases
Common Aliases: W49B · SNR G043.3-00.2 · 3C 398 · Westerhout 49B
| Catalog Authority | Identifier |
|---|---|
| SIMBAD | W 49B |
| WIKIDATA | Q2537758 |
Related Objects, Comparisons & Guides
Cassiopeia A (3C 461 Young Supernova Remnant)
Coordinates, kinematic distance (3.4 kpc), JWST/Chandra ejecta knots, and high-aperture observing guide for Cassiopeia A (3C 461).
Tycho's Supernova Remnant (SN 1572 / 3C 10)
Coordinates, distance (2.8 kpc / 9,100 ly), SN 1572 Type Ia light-echo spectrum, Chandra X-ray stripes, and data for Tycho's SNR in Cassiopeia.
Kepler's Supernova Remnant (SN 1604)
Coordinates, kinematic distance (5.1 kpc / 16,600 ly), SN 1604 history, circumstellar bow-shock knots, and data for Kepler's SNR in Ophiuchus.
Bortle Dark-Sky Scale & Sky Brightness Guide
Reference guide to the 9-class Bortle Dark-Sky Scale, zenith Sky Quality Meter (SQM) readings in mag/arcsec², naked-eye limiting magnitude, and light pollution.
Measurement Uncertainty & Optics in Astronomy
How random vs systematic errors, asymmetric error bars, model dependencies, and optical aperture/exit-pupil limits shape astronomical measurements.
Scientific Sources & Dataset Provenance
- 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
- 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
- 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