RR Lyrae (HD 182989)
Coordinates, Gaia DR3 distance (264 pc), 13.60-hour pulsation cycle, Blazhko effect, and cosmic distance ladder guide for RR Lyrae.
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 |
|---|---|---|---|---|---|
| Visual magnitude range (V) | 7.76 mag | ± 0.45 mag | Kepler/TESS & AAVSO V-band light curve (oscillates from 7.06 at peak to 8.12 at minimum) | definitive | SIMBAD Astronomical Database (CDS) |
| Fundamental radial pulsation period | 0.5668678 d | ± 0.000001 d | Kepler space photometry (13 hours 36 minutes 17 seconds; 39.1-day Blazhko cycle) | definitive | SIMBAD Astronomical Database (CDS) |
| Trigonometric distance (Gaia DR3) | 264.4 pc | ± 1.8 pc | Gaia DR3 parallax (3.782 ± 0.026 mas / 862.4 ± 5.9 ly) + HST FGS (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Mean bolometric luminosity | 49 L☉ | ± 3 L☉ | Horizontal-branch standard candle zero point (M_V ≈ +0.61 ± 0.03) | definitive | ESA Gaia Archive — Data Release 3 |
| Metallicity [Fe/H] | -1.39 dex | ± 0.05 dex | High-resolution Population II halo spectroscopy (~4% of solar iron abundance) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots RR Lyrae (Horizontal-Branch Standard Candle) at RA 19h 25m 27.93s, Dec +42° 47′ 03.7″ within Lyra, 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
RR Lyrae (HD 182989), discovered on Harvard College Observatory photographic plates by Scottish astronomer Williamina Fleming in 1899 and published by Edward C. Pickering in 1901, is the brightest and closest prototype of the RR Lyrae variable stars—the indispensable 'Population II standard candles' used to measure distances to globular clusters, the Galactic bulge, and dwarf satellite galaxies across the Local Group. Located 264.4 ± 1.8 parsecs (862 light-years) away in northeastern Lyra, it is an ancient (>10-billion-year-old), metal-poor ([Fe/H] = −1.39 dex) halo star racing past the solar neighborhood at over 230 km/s.
Having exhausted core hydrogen, ascended the red giant branch, and ignited helium fusion in its core via the helium flash, RR Lyrae now resides on the horizontal branch of the Hertzsprung-Russell diagram (~0.65 solar masses, ~5.2 solar radii, 49 solar luminosities) right inside the radial instability strip. Every 13 hours 36 minutes (0.56687 days), the helium-ionization kappa mechanism drives a supersonic radial pulsation: the star's brightness surges by a full magnitude from 8.12 to 7.06 in less than two hours as its spectral class heats from F7 to A5, followed by a gradual 11-hour decline.
Because RR Lyrae happens to lie inside the original Cygnus-Lyra field of NASA's Kepler space telescope, Kepler recorded its light curve at sub-millimagnitude precision, revealing period doubling and the mysterious 39.1-day 'Blazhko effect'—a long-term modulation of the pulsation amplitude and phase discovered by Sergei Blazhko in 1907.
Practical Visual Observing Guide
- At magnitude 7.06 to 8.12 (located ~4.5° northeast of Vega and Epsilon Lyrae near the Cygnus border), RR Lyrae is easily visible in 10×50 binoculars or any small 50–80 mm finder scope.
- Because its rising branch takes less than 90 minutes to double in brightness by ~1.0 magnitude, you can watch RR Lyrae brighten in real time over a single two-hour evening session using nearby 7th- and 8th-magnitude comparison stars!
Catalog Cross-Identifications & Aliases
Common Aliases: HD 182989 · HIP 95497 · BD+42 3338
| Catalog Authority | Identifier |
|---|---|
| GAIADR3 | 2125982599343482624 |
| HIP | HIP 95497 |
| HD | HD 182989 |
| SIMBAD | V* RR Lyr |
| WIKIDATA | Q1146685 |
Related Objects, Comparisons & Guides
Delta Cephei (Cepheid Distance Ladder Anchor)
Coordinates, Gaia/HST distance (290 pc), 5.366-day pulsation period, Leavitt law calibration, and observing guide for Delta Cephei.
W Virginis (Type II Cepheid Prototype)
Coordinates, Gaia DR3 distance (~1.84 kpc), 17.27-day pulsation period, Baade's 1952 doubling of the universe scale, and guide for W Virginis.
Vega (Alpha Lyrae Zero-Point Star)
Coordinates, distance (25.04 ly), magnitude 0.03 photometric zero point, rapid oblate rotation, and observing guide for Vega in Lyra.
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.
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
- 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
- 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