{
  "family": "variable-stars",
  "name": "Variable Stars",
  "generatedAt": "2026-10-14",
  "count": 6,
  "objects": [
    {
      "id": "star:betelgeuse",
      "slug": "betelgeuse",
      "canonicalName": "Betelgeuse (Alpha Orionis)",
      "aliases": [
        "α Orionis",
        "HD 39801",
        "HIP 27989",
        "58 Orionis"
      ],
      "constellation": "Orion",
      "path": "/objects/variable-stars/betelgeuse/",
      "coordinates": {
        "raHours": 5.919529,
        "raSexagesimal": "05h 55m 10.31s",
        "decDegrees": 7.407064,
        "decSexagesimal": "+07° 24′ 25.4″",
        "epoch": "J2000.0",
        "sourceId": "src:hipparcos-new"
      },
      "classification": {
        "primaryClass": "Semiregular red supergiant variable star",
        "spectralType": "M1–M2 Ia–Iab",
        "variableType": "SRc (Semiregular supergiant)"
      },
      "measurements": [
        {
          "id": "star:betelgeuse:dist-hip-vla",
          "entityId": "star:betelgeuse",
          "property": "distance_pc",
          "label": "Distance (Combined Hipparcos + radio + seismic solution)",
          "value": 168,
          "unit": "pc",
          "uncertainty": {
            "kind": "asymmetric",
            "plus": 27,
            "minus": 15
          },
          "method": "Combined astrometric & asteroseismic hydrodynamic modeling (Joyce et al. 2020)",
          "epoch": "J2016.0",
          "sourceId": "src:hipparcos-new",
          "datasetVersion": "2007 New Reduction",
          "qualityStatus": "disputed",
          "disagreementNote": "Betelgeuse's angular diameter (~42 mas) is 7× larger than its ~5–6 mas parallax, and giant convective surface plumes shift its optical photocenter, producing 15–25% discrepancies between combined optical/seismic solutions (168 +27/−15 pc) and pure radio/submillimeter solutions (222 +48/−34 pc)."
        },
        {
          "id": "star:betelgeuse:dist-radio",
          "entityId": "star:betelgeuse",
          "property": "distance_pc",
          "label": "Distance (VLA/ALMA radio continuum + Hipparcos solution)",
          "value": 222,
          "unit": "pc",
          "uncertainty": {
            "kind": "asymmetric",
            "plus": 48,
            "minus": 34
          },
          "method": "Submillimeter/radio astrometry combined with Hipparcos intermediate data (Harper et al. 2017)",
          "epoch": "J2000.0",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "disputed",
          "disagreementNote": "Radio continuum positions avoid optical TiO band photocenter jitter on the convective disk but carry larger per-epoch positional error bars."
        },
        {
          "id": "star:betelgeuse:vmag",
          "entityId": "star:betelgeuse",
          "property": "apparent_magnitude_v",
          "label": "Visual magnitude range (V)",
          "value": 0.5,
          "unit": "mag",
          "uncertainty": {
            "kind": "range",
            "min": 0,
            "max": 1.61
          },
          "method": "AAVSO & GCVS visual/photoelectric monitoring (reached V=1.61 in Feb 2020 Great Dimming)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:betelgeuse:period",
          "entityId": "star:betelgeuse",
          "property": "orbital_period_days",
          "label": "Fundamental radial pulsation period",
          "value": 416,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 24
          },
          "method": "Optical photometry & radial-velocity oscillation (plus ~2,100 d long secondary period)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:betelgeuse:radius",
          "entityId": "star:betelgeuse",
          "property": "radius_solar",
          "label": "Photospheric radius",
          "value": 764,
          "unit": "R☉",
          "uncertainty": {
            "kind": "asymmetric",
            "plus": 116,
            "minus": 62
          },
          "method": "Derived from ~42 mas limb-darkened diameter at 168 pc (scales to ~950–1,000 R☉ at 222 pc)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "model-dependent"
        },
        {
          "id": "star:betelgeuse:teff",
          "entityId": "star:betelgeuse",
          "property": "effective_temperature_k",
          "label": "Effective temperature",
          "value": 3600,
          "unit": "K",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 200
          },
          "method": "Near-IR & TiO band spectroscopy (dropped to ~3,450 K during 2020 dimming)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "high-confidence"
        }
      ],
      "sources": [
        "src:hipparcos-new",
        "src:gcvs-v5",
        "src:simbad-cds"
      ]
    },
    {
      "id": "star:polaris",
      "slug": "polaris",
      "canonicalName": "Polaris (Alpha Ursae Minoris)",
      "aliases": [
        "α Ursae Minoris",
        "North Star",
        "Pole Star",
        "HD 8890",
        "HIP 11767"
      ],
      "constellation": "Ursa Minor",
      "path": "/objects/variable-stars/polaris/",
      "coordinates": {
        "raHours": 2.530303,
        "raSexagesimal": "02h 31m 49.09s",
        "decDegrees": 89.264109,
        "decSexagesimal": "+89° 15′ 50.8″",
        "epoch": "J2000.0",
        "sourceId": "src:hipparcos-new"
      },
      "classification": {
        "primaryClass": "Classical Cepheid supergiant variable in a triple star system",
        "spectralType": "F7 Ib + F6 V + F3 V",
        "variableType": "DCEPS (First-overtone s-Cepheid)"
      },
      "measurements": [
        {
          "id": "star:polaris:vmag",
          "entityId": "star:polaris",
          "property": "apparent_magnitude_v",
          "label": "Mean apparent visual magnitude (V)",
          "value": 1.98,
          "unit": "mag",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.02
          },
          "method": "Space-based SMEI/TESS photometry (~0.03 mag peak-to-peak Cepheid amplitude)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:polaris:dist-pc",
          "entityId": "star:polaris",
          "property": "distance_pc",
          "label": "System distance (Gaia DR3 Polaris B)",
          "value": 137.2,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.6
          },
          "method": "Gaia DR3 parallax of physical companion Polaris B (7.289 ± 0.031 mas, 447.5 ly)",
          "epoch": "J2016.0",
          "sourceId": "src:gaia-dr3",
          "datasetVersion": "DR3 (2022-06-13)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:polaris:period",
          "entityId": "star:polaris",
          "property": "orbital_period_days",
          "label": "First-overtone Cepheid pulsation period",
          "value": 3.9696,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.0002
          },
          "method": "Radial-velocity & photometric pulsation tracking",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:polaris:mass",
          "entityId": "star:polaris",
          "property": "mass_solar",
          "label": "Cepheid primary mass (Polaris Aa)",
          "value": 5.13,
          "unit": "M☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.28
          },
          "method": "CHARA interferometric + HST astrometric 29.3-year binary orbit (Evans et al. 2024)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "high-confidence"
        },
        {
          "id": "star:polaris:radius",
          "entityId": "star:polaris",
          "property": "radius_solar",
          "label": "Photospheric radius",
          "value": 46.3,
          "unit": "R☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.9
          },
          "method": "CHARA interferometric angular diameter (3.123 ± 0.008 mas) at 137.2 pc",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        }
      ],
      "sources": [
        "src:gaia-dr3",
        "src:hipparcos-new",
        "src:gcvs-v5"
      ]
    },
    {
      "id": "star:algol",
      "slug": "algol",
      "canonicalName": "Algol (Beta Persei)",
      "aliases": [
        "β Persei",
        "Demon Star",
        "HD 19356",
        "HIP 14576",
        "26 Persei"
      ],
      "constellation": "Perseus",
      "path": "/objects/variable-stars/algol/",
      "coordinates": {
        "raHours": 3.136148,
        "raSexagesimal": "03h 08m 10.13s",
        "decDegrees": 40.955648,
        "decSexagesimal": "+40° 57′ 20.3″",
        "epoch": "J2000.0",
        "sourceId": "src:hipparcos-new"
      },
      "classification": {
        "primaryClass": "Semidetached eclipsing binary prototype in a hierarchical triple system",
        "spectralType": "B8 V + K0 IV + A7m",
        "variableType": "EA/SD (Algol-type eclipsing binary)"
      },
      "measurements": [
        {
          "id": "star:algol:vmag",
          "entityId": "star:algol",
          "property": "apparent_magnitude_v",
          "label": "Visual magnitude at maximum (out of eclipse)",
          "value": 2.12,
          "unit": "mag",
          "uncertainty": {
            "kind": "range",
            "min": 2.12,
            "max": 3.39
          },
          "method": "Photoelectric V-band photometry (primary eclipse drops to V = 3.39)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:algol:period",
          "entityId": "star:algol",
          "property": "orbital_period_days",
          "label": "Eclipsing orbital period (Aa1–Aa2)",
          "value": 2.867328,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.000005
          },
          "method": "O−C eclipse minimum timing (2d 20h 48m 56s; undergoes small secular shifts from mass transfer)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:algol:dist-pc",
          "entityId": "star:algol",
          "property": "distance_pc",
          "label": "Heliocentric distance",
          "value": 27.6,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.6
          },
          "method": "Hipparcos + VLBI + CHARA interferometric 3D orbit (89.9 ± 2.0 ly)",
          "epoch": "J2000.0",
          "sourceId": "src:hipparcos-new",
          "datasetVersion": "2007 New Reduction",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:algol:mass",
          "entityId": "star:algol",
          "property": "mass_solar",
          "label": "Primary B8V mass (Algol Aa1)",
          "value": 3.17,
          "unit": "M☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.21
          },
          "method": "CHARA interferometric + spectroscopic orbit (K0 IV secondary Aa2 = 0.70 ± 0.08 M☉)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        }
      ],
      "sources": [
        "src:hipparcos-new",
        "src:gcvs-v5",
        "src:simbad-cds"
      ]
    },
    {
      "id": "star:delta-cephei",
      "slug": "delta-cephei",
      "canonicalName": "Delta Cephei (δ Cephei)",
      "aliases": [
        "δ Cephei",
        "HD 213306",
        "HIP 110991",
        "27 Cephei"
      ],
      "constellation": "Cepheus",
      "path": "/objects/variable-stars/delta-cephei/",
      "coordinates": {
        "raHours": 22.486264,
        "raSexagesimal": "22h 29m 10.27s",
        "decDegrees": 58.415198,
        "decSexagesimal": "+58° 24′ 54.7″",
        "epoch": "J2000.0",
        "sourceId": "src:gaia-dr3"
      },
      "classification": {
        "primaryClass": "Prototype Classical Cepheid pulsating supergiant variable",
        "spectralType": "F5 Ib–G1 Ib",
        "variableType": "DCEP (Fundamental-mode Classical Cepheid)"
      },
      "measurements": [
        {
          "id": "star:delta-cephei:vmag",
          "entityId": "star:delta-cephei",
          "property": "apparent_magnitude_v",
          "label": "Visual magnitude range (V)",
          "value": 3.95,
          "unit": "mag",
          "uncertainty": {
            "kind": "range",
            "min": 3.48,
            "max": 4.37
          },
          "method": "Photoelectric V-band light curve (0.89-mag amplitude)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:delta-cephei:period",
          "entityId": "star:delta-cephei",
          "property": "orbital_period_days",
          "label": "Fundamental radial pulsation period",
          "value": 5.36627,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 0.00001
          },
          "method": "Two centuries of visual & photoelectric phase monitoring",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:delta-cephei:dist-pc",
          "entityId": "star:delta-cephei",
          "property": "distance_pc",
          "label": "Trigonometric distance (HST FGS + Gaia DR3)",
          "value": 290,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 8
          },
          "method": "HST Fine Guidance Sensor + Gaia DR3 parallax of δ Cep A & B (~946 ly)",
          "epoch": "J2016.0",
          "sourceId": "src:gaia-dr3",
          "datasetVersion": "DR3 (2022-06-13)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:delta-cephei:radius",
          "entityId": "star:delta-cephei",
          "property": "radius_solar",
          "label": "Mean photospheric radius",
          "value": 44.5,
          "unit": "R☉",
          "uncertainty": {
            "kind": "range",
            "min": 41.5,
            "max": 46.5
          },
          "method": "CHARA interferometric Baade-Wesselink angular diameter oscillation",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:delta-cephei:lum",
          "entityId": "star:delta-cephei",
          "property": "luminosity_solar",
          "label": "Mean bolometric luminosity",
          "value": 2000,
          "unit": "L☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 150
          },
          "method": "Period-luminosity zero point + trigonometric parallax",
          "sourceId": "src:shoes-2022",
          "datasetVersion": "2022 Baseline Cepheid + SN Ia",
          "qualityStatus": "definitive"
        }
      ],
      "sources": [
        "src:gaia-dr3",
        "src:gcvs-v5",
        "src:shoes-2022"
      ]
    },
    {
      "id": "star:mira",
      "slug": "mira",
      "canonicalName": "Mira (Omicron Ceti)",
      "aliases": [
        "ο Ceti",
        "Mira A & B",
        "VZ Ceti",
        "HD 14386",
        "HIP 10826"
      ],
      "constellation": "Cetus",
      "path": "/objects/variable-stars/mira/",
      "coordinates": {
        "raHours": 2.322458,
        "raSexagesimal": "02h 19m 20.79s",
        "decDegrees": -2.977639,
        "decSexagesimal": "-02° 58′ 39.5″",
        "epoch": "J2000.0",
        "sourceId": "src:hipparcos-new"
      },
      "classification": {
        "primaryClass": "Prototype long-period asymptotic giant branch variable + accreting white dwarf binary",
        "spectralType": "M5–M9 IIIe + DA",
        "variableType": "M (Mira-type long-period variable)"
      },
      "measurements": [
        {
          "id": "star:mira:vmag",
          "entityId": "star:mira",
          "property": "apparent_magnitude_v",
          "label": "Visual magnitude range (V)",
          "value": 3,
          "unit": "mag",
          "uncertainty": {
            "kind": "range",
            "min": 2,
            "max": 10.1
          },
          "method": "AAVSO & GCVS visual/CCD monitoring (~8-magnitude / 1,500× visual flux swing)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:mira:period",
          "entityId": "star:mira",
          "property": "orbital_period_days",
          "label": "Mean radial pulsation period",
          "value": 331.96,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 3
          },
          "method": "Four centuries of visual maximum timing (1596–2026)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:mira:dist-pc",
          "entityId": "star:mira",
          "property": "distance_pc",
          "label": "Heliocentric distance",
          "value": 100,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 11
          },
          "method": "Hipparcos New Reduction parallax (10.91 ± 1.22 mas) + VLBI water-maser astrometry",
          "epoch": "J2000.0",
          "sourceId": "src:hipparcos-new",
          "datasetVersion": "2007 New Reduction",
          "qualityStatus": "high-confidence"
        },
        {
          "id": "star:mira:radius",
          "entityId": "star:mira",
          "property": "radius_solar",
          "label": "Photospheric radius",
          "value": 370,
          "unit": "R☉",
          "uncertainty": {
            "kind": "range",
            "min": 330,
            "max": 450
          },
          "method": "Near-IR interferometry (strongly wavelength-dependent across TiO/H2O molecular layers)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "model-dependent"
        }
      ],
      "sources": [
        "src:hipparcos-new",
        "src:gcvs-v5",
        "src:simbad-cds"
      ]
    },
    {
      "id": "star:eta-carinae",
      "slug": "eta-carinae",
      "canonicalName": "Eta Carinae (η Carinae & Homunculus Nebula)",
      "aliases": [
        "η Carinae",
        "Homunculus Nebula",
        "HD 93308",
        "HR 4210"
      ],
      "constellation": "Carina",
      "path": "/objects/variable-stars/eta-carinae/",
      "coordinates": {
        "raHours": 10.750611,
        "raSexagesimal": "10h 45m 03.59s",
        "decDegrees": -59.684528,
        "decSexagesimal": "-59° 41′ 04.3″",
        "epoch": "J2000.0",
        "sourceId": "src:gaia-dr3"
      },
      "classification": {
        "primaryClass": "Colliding-wind Luminous Blue Variable (LBV) hypergiant binary",
        "spectralType": "LBV / B[e] + O/WR",
        "variableType": "SDOR (S Doradus / Luminous Blue Variable)"
      },
      "measurements": [
        {
          "id": "star:eta-carinae:vmag",
          "entityId": "star:eta-carinae",
          "property": "apparent_magnitude_v",
          "label": "Current visual magnitude (V, 2020s)",
          "value": 4,
          "unit": "mag",
          "uncertainty": {
            "kind": "range",
            "min": -0.8,
            "max": 7.9
          },
          "method": "Historical & modern photometry (peaked at −0.8 in 1843; faded to 7.9 by 1900; brightened to ~4.0 today)",
          "sourceId": "src:gcvs-v5",
          "datasetVersion": "v5.1 (2026 update)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:eta-carinae:dist-pc",
          "entityId": "star:eta-carinae",
          "property": "distance_pc",
          "label": "Distance (Homunculus 3D expansion & Trumpler 16 Gaia DR3)",
          "value": 2350,
          "unit": "pc",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 50
          },
          "method": "3D proper-motion/Doppler expansion of Homunculus Nebula + Gaia DR3 cluster parallax",
          "epoch": "J2016.0",
          "sourceId": "src:gaia-dr3",
          "datasetVersion": "DR3 (2022-06-13)",
          "qualityStatus": "definitive"
        },
        {
          "id": "star:eta-carinae:lum",
          "entityId": "star:eta-carinae",
          "property": "luminosity_solar",
          "label": "System bolometric luminosity",
          "value": 5000000,
          "unit": "L☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 500000
          },
          "method": "Mid/far-infrared thermal re-radiation by the Homunculus dust shroud",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "high-confidence"
        },
        {
          "id": "star:eta-carinae:mass",
          "entityId": "star:eta-carinae",
          "property": "mass_solar",
          "label": "Primary star mass (Eta Carinae A)",
          "value": 100,
          "unit": "M☉",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 20
          },
          "method": "Colliding-wind binary orbit + Eddington limit modeling (secondary B ≈ 30–40 M☉)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "model-dependent"
        },
        {
          "id": "star:eta-carinae:period",
          "entityId": "star:eta-carinae",
          "property": "orbital_period_days",
          "label": "Eccentric binary orbital period",
          "value": 2022.7,
          "unit": "d",
          "uncertainty": {
            "kind": "symmetric",
            "plusMinus": 1.3
          },
          "method": "X-ray & spectroscopic periastron eclipse cycle (5.538 yr, e ≈ 0.90)",
          "sourceId": "src:simbad-cds",
          "datasetVersion": "2026-10 release",
          "qualityStatus": "definitive"
        }
      ],
      "sources": [
        "src:gaia-dr3",
        "src:gcvs-v5",
        "src:simbad-cds"
      ]
    }
  ]
}