{
  "family": "supernova-remnants",
  "name": "Supernova Remnants",
  "generatedAt": "2026-10-14",
  "count": 3,
  "objects": [
    {
      "id": "obj:messier-1",
      "slug": "crab-nebula-m1",
      "canonicalName": "Crab Nebula (Messier 1)",
      "aliases": [
        "M1",
        "NGC 1952",
        "Taurus A",
        "SN 1054 Remnant"
      ],
      "constellation": "Taurus",
      "path": "/objects/supernova-remnants/crab-nebula-m1/",
      "coordinates": {
        "raHours": 5.575539,
        "raSexagesimal": "05h 34m 31.94s",
        "decDegrees": 22.0145,
        "decSexagesimal": "+22° 00′ 52.2″",
        "epoch": "J2000.0",
        "sourceId": "src:ngc-ic-steinicke"
      },
      "classification": {
        "primaryClass": "Pulsar wind nebula (plerion) and core-collapse supernova remnant"
      },
      "measurements": [
        {
          "id": "obj:messier-1:vmag",
          "entityId": "obj:messier-1",
          "property": "apparent_magnitude_v",
          "label": "Integrated visual magnitude (V)",
          "value": 8.4,
          "unit": "mag",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.1
          },
          "method": "Integrated optical continuum + line photometry",
          "sourceId": "src:ngc-ic-steinicke",
          "datasetVersion": "2024/2026 edition",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:messier-1:dist-pc",
          "entityId": "obj:messier-1",
          "property": "distance_pc",
          "label": "Distance (Gaia DR3 pulsar + kinematic expansion)",
          "value": 1960,
          "unit": "pc",
          "uncertainty": {
            "kind": "asymmetric",
            "plus": 510,
            "minus": 350
          },
          "method": "Gaia DR3 pulsar parallax (0.51 ± 0.08 mas) combined with 3D filament kinematics",
          "epoch": "J2016.0",
          "sourceId": "src:gaia-dr3",
          "datasetVersion": "DR3 (2022-06-13)",
          "qualityStatus": "high-confidence",
          "disagreementNote": "Because the central pulsar is faint (V ≈ 16.5) and embedded in bright synchrotron nebulosity, its Gaia parallax has ±15% error, combining with 3D expansion models around 1.96 +0.51/−0.35 kpc (~6,390 ly)."
        },
        {
          "id": "obj:messier-1:ang-size",
          "entityId": "obj:messier-1",
          "property": "angular_size_arcmin",
          "label": "Apparent major axis",
          "value": 6,
          "unit": "arcmin",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.3
          },
          "method": "Optical synchrotron and [O III] boundary (6.0′ × 4.0′)",
          "sourceId": "src:ngc-ic-steinicke",
          "datasetVersion": "2024/2026 edition",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:messier-1:vrad",
          "entityId": "obj:messier-1",
          "property": "radial_velocity_km_s",
          "label": "Filament expansion velocity",
          "value": 1500,
          "unit": "km/s",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 150
          },
          "method": "Doppler splitting of [O III] and H-alpha emission filaments",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        }
      ],
      "sources": [
        "src:ngc-ic-steinicke",
        "src:gaia-dr3",
        "src:jwst-archive"
      ]
    },
    {
      "id": "obj:veil-nebula",
      "slug": "veil-nebula",
      "canonicalName": "Veil Nebula (Cygnus Loop / NGC 6960 & NGC 6992)",
      "aliases": [
        "Cygnus Loop",
        "NGC 6960",
        "NGC 6992",
        "Witch's Broom Nebula",
        "Caldwell 33 & 34"
      ],
      "constellation": "Cygnus",
      "path": "/objects/supernova-remnants/veil-nebula/",
      "coordinates": {
        "raHours": 20.76,
        "raSexagesimal": "20h 45m 36.00s",
        "decDegrees": 30.71,
        "decSexagesimal": "+30° 42′ 36.0″",
        "epoch": "J2000.0",
        "sourceId": "src:ngc-ic-steinicke"
      },
      "classification": {
        "primaryClass": "Evolved shell-type core-collapse supernova remnant"
      },
      "measurements": [
        {
          "id": "obj:veil-nebula:vmag",
          "entityId": "obj:veil-nebula",
          "property": "apparent_magnitude_v",
          "label": "Integrated visual magnitude (V)",
          "value": 7,
          "unit": "mag",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.3
          },
          "method": "Integrated emission across NGC 6960 + NGC 6992/6995",
          "sourceId": "src:ngc-ic-steinicke",
          "datasetVersion": "2024/2026 edition",
          "qualityStatus": "high-confidence"
        },
        {
          "id": "obj:veil-nebula:dist-pc",
          "entityId": "obj:veil-nebula",
          "property": "distance_pc",
          "label": "Distance (Gaia DR3 background/absorber stars)",
          "value": 735,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 25
          },
          "method": "Gaia DR3 parallaxes of stars showing high-velocity interstellar absorption from the SNR shell",
          "epoch": "J2016.0",
          "sourceId": "src:gaia-dr3",
          "datasetVersion": "DR3 (2022-06-13)",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:veil-nebula:ang-size",
          "entityId": "obj:veil-nebula",
          "property": "angular_size_arcmin",
          "label": "Full Cygnus Loop angular diameter",
          "value": 180,
          "unit": "arcmin",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 10
          },
          "method": "Optical and soft X-ray blast wave diameter (~3.0°)",
          "sourceId": "src:ngc-ic-steinicke",
          "datasetVersion": "2024/2026 edition",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:veil-nebula:age",
          "entityId": "obj:veil-nebula",
          "property": "age_gyr",
          "label": "Remnant expansion age",
          "value": 0.000015,
          "unit": "Gyr",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.000005
          },
          "method": "Sedov-Taylor shock deceleration modeling (~10,000–20,000 yr)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "model-dependent"
        }
      ],
      "sources": [
        "src:ngc-ic-steinicke",
        "src:gaia-dr3",
        "src:simbad-cds"
      ]
    },
    {
      "id": "obj:cassiopeia-a",
      "slug": "cassiopeia-a",
      "canonicalName": "Cassiopeia A (Cas A / 3C 461)",
      "aliases": [
        "Cas A",
        "3C 461",
        "SNR G111.7-02.1"
      ],
      "constellation": "Cassiopeia",
      "path": "/objects/supernova-remnants/cassiopeia-a/",
      "coordinates": {
        "raHours": 23.390556,
        "raSexagesimal": "23h 23m 26.00s",
        "decDegrees": 58.815,
        "decSexagesimal": "+58° 48′ 54.0″",
        "epoch": "J2000.0",
        "sourceId": "src:simbad-cds"
      },
      "classification": {
        "primaryClass": "Young core-collapse (Type IIb) supernova remnant & brightest extrasolar radio source"
      },
      "measurements": [
        {
          "id": "obj:cassiopeia-a:dist-pc",
          "entityId": "obj:cassiopeia-a",
          "property": "distance_pc",
          "label": "Kinematic expansion distance",
          "value": 3400,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 100
          },
          "method": "3D proper motion vs. Doppler velocity of optical ejecta knots",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:cassiopeia-a:ang-size",
          "entityId": "obj:cassiopeia-a",
          "property": "angular_size_arcmin",
          "label": "Apparent shell diameter",
          "value": 5,
          "unit": "arcmin",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.2
          },
          "method": "Radio, X-ray, and infrared blast-wave shell",
          "sourceId": "src:jwst-archive",
          "datasetVersion": "Cycle 1–4 Public Releases (2022–2026)",
          "qualityStatus": "definitive"
        },
        {
          "id": "obj:cassiopeia-a:vrad",
          "entityId": "obj:cassiopeia-a",
          "property": "radial_velocity_km_s",
          "label": "Fast optical knot expansion velocity",
          "value": 5500,
          "unit": "km/s",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 500
          },
          "method": "Optical/NIR spectroscopy of oxygen- and sulfur-rich ejecta knots",
          "sourceId": "src:jwst-archive",
          "datasetVersion": "Cycle 1–4 Public Releases (2022–2026)",
          "qualityStatus": "high-confidence"
        }
      ],
      "sources": [
        "src:simbad-cds",
        "src:jwst-archive"
      ]
    }
  ]
}