Mira (Omicron Ceti)
Coordinates, Hipparcos distance (100 pc), 332-day pulsation cycle (mag 2.0 to 10.1), white dwarf companion, and observing guide for Mira.
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) | 3 mag | 2 to 10.1 mag | AAVSO & GCVS visual/CCD monitoring (~8-magnitude / 1,500× visual flux swing) | definitive | General Catalogue of Variable Stars (GCVS) & AAVSO VSX |
| Mean radial pulsation period | 331.96 d | ± 3 d | Four centuries of visual maximum timing (1596–2026) | definitive | General Catalogue of Variable Stars (GCVS) & AAVSO VSX |
| Heliocentric distance | 100 pc | ± 11 pc | Hipparcos New Reduction parallax (10.91 ± 1.22 mas) + VLBI water-maser astrometry (J2000.0) | high-confidence | Hipparcos New Reduction Catalog |
| Photospheric radius | 370 R☉ | 330 to 450 R☉ | Near-IR interferometry (strongly wavelength-dependent across TiO/H2O molecular layers) | model-dependent | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Mira (Omicron Ceti Pulsating Giant) at RA 02h 19m 20.79s, Dec -02° 58′ 39.5″ within Cetus, 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
Mira (Omicron Ceti—named 'the Wonderful' by Polish astronomer Johannes Hevelius in 1662) was the first non-supernova variable star ever discovered. On August 13, 1596, Frisian pastor and astronomer David Fabricius noted a 3rd-magnitude red star in Cetus that faded completely from naked-eye view by October, only to reappear in February 1609—shattering the Aristotelian dogma of an immutable celestial sphere.
Located ~100 ± 11 parsecs (326 light-years) away, Mira A is a cool ~1.2-solar-mass red giant on the thermally pulsing asymptotic giant branch (AGB) that expands and contracts every 331.96 days. Although its total bolometric luminosity changes by only a factor of ~2 over each cycle (mostly in the near-infrared), its visual brightness swings by up to 8 magnitudes (a factor of 1,500!) between magnitude 2.0–3.5 at maximum and magnitude 8.5–10.1 at minimum: as the photosphere cools from ~3,200 K to ~2,600 K, titanium oxide (TiO) molecules condense in its atmosphere and absorb almost all visible light while shifting the star's energy peak deeper into the infrared.
Plowing through the interstellar medium at an supersonic 130 km/s, Mira sheds ~3 × 10^-7 solar masses per year, leaving behind a dramatic 13-light-year-long ultraviolet bow-shock and turbulent cometary tail discovered by NASA's GALEX space telescope in 2007. A portion of this wind is also captured into an accretion disk around Mira B (VZ Ceti), a white dwarf companion orbiting ~70 AU away with a period of ~500 years.
Practical Visual Observing Guide
- Because Mira's pulsation period is 332 days (about 11 months), its peak brightness shifts roughly one month earlier on the calendar each year.
- During the 6 to 8 weeks around maximum light, Mira shines at magnitude 2.5–3.5 in the neck of Cetus and is conspicuous to the naked eye; during the 6 months around minimum (magnitude 9–10), you need a 70–100 mm telescope to spot its deep crimson ember.
Catalog Cross-Identifications & Aliases
Common Aliases: ο Ceti · Mira A & B · VZ Ceti · HD 14386 · HIP 10826
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 10826 |
| HD | HD 14386 |
| SIMBAD | * omi Cet |
| WIKIDATA | Q13026 |
Related Objects, Comparisons & Guides
Betelgeuse (Alpha Orionis Red Supergiant)
Coordinates, competing optical vs radio distances (168 vs 222 pc), radius, Great Dimming physics, and observing guide for Betelgeuse.
Algol (Beta Persei Eclipsing Binary)
Coordinates, Hipparcos distance (90 ly), 2.8673-day eclipse cycle, Algol Paradox mass transfer, and visual timing guide for Algol.
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.
Tau Ceti (HD 10700 Nearby Solar Analog)
Coordinates, Gaia DR3 parallax (273.81 mas, 11.91 ly), magnitude 3.50, debris disk, and observing guide for G8V star Tau Ceti.
Tracking Bright Variable Stars Observing Guide
How to estimate visual magnitudes and light curves of naked-eye and binocular variable stars: Algol, Delta Cephei, Betelgeuse, Mira, and Eta Carinae.
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.
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
Scientific Sources & Dataset Provenance
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- General Catalogue of Variable Stars (GCVS) & AAVSO VSX (v5.1 (2026 update)): Samus, N. N., et al. 2017, Astronomy Reports, 61, 80 (General Catalogue of Variable Stars: Version GCVS 5.1) — Sternberg Astronomical Institute / AAVSO
- 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