Betelgeuse (Alpha Orionis Red Supergiant)
Coordinates, competing optical vs radio distances (168 vs 222 pc), radius, Great Dimming physics, and observing guide for Betelgeuse.
Aliases: α Orionis, HD 39801, HIP 27989, 58 Orionis
Variable Stars Catalog & Light Curve Guide
Stars whose apparent brightness varies measurably over hours, days, or years due to radial pulsation, binary eclipses, or eruptive mass loss.
Cataloged Profiles6 Objects
ClassificationVariable Stars
Machine-Readable DataJSON Shard (variable-stars.json)
Physical & Observational Overview
Variable stars are foundational to astrophysical measurement: pulsating Classical Cepheids (anchored by prototype Delta Cephei and nearest Cepheid Polaris) obey the Leavitt Period–Luminosity law that calibrates extragalactic distances, while eclipsing binaries like Algol reveal stellar radii and mass transfer.
At the extremes of stellar evolution, AGB long-period variables (Mira) and massive supergiants (Betelgeuse, Eta Carinae) shed dust-rich circumstellar envelopes that enrich the interstellar medium.
Classification Criteria: Classified by the General Catalogue of Variable Stars (GCVS) and AAVSO VSX into pulsating variables (Classical Cepheids like Delta Cephei and Polaris, Mira AGB variables, SRC red supergiants like Betelgeuse), eclipsing binaries (EA/Algol), and eruptive luminous blue variables (Eta Carinae).
Visual Observing Regime: Bright naked-eye and binocular variables allow amateur observers to record calibrated visual or CMOS light curves, timing Algol's 10-hour eclipses or Delta Cephei's 5.37-day sawtooth pulsation.
Variable Stars Comparison Table
| Object | Constellation | Classification | RA (J2000) | Dec (J2000) | Min. Instrument | Best Season |
|---|---|---|---|---|---|---|
| Betelgeuse (Alpha Orionis Red Supergiant) | Orion | Semiregular red supergiant variable star | 05h 55m 10.31s | +07° 24′ 25.4″ | Naked eye | Winter (December–March) |
| Polaris (Alpha Ursae Minoris North Star) | Ursa Minor | Classical Cepheid supergiant variable in a triple star system | 02h 31m 49.09s | +89° 15′ 50.8″ | Naked eye (50–60 mm telescope at 60×+ to split Polaris B) | Year-round (circumpolar across the entire Northern Hemisphere) |
| Algol (Beta Persei Eclipsing Binary) | Perseus | Semidetached eclipsing binary prototype in a hierarchical triple system | 03h 08m 10.13s | +40° 57′ 20.3″ | Naked eye | Autumn to Winter (September–March) |
| Delta Cephei (Cepheid Distance Ladder Anchor) | Cepheus | Prototype Classical Cepheid pulsating supergiant variable | 22h 29m 10.27s | +58° 24′ 54.7″ | Naked eye for variable light curve; 50 mm telescope for 41″ companion | Summer to Late Autumn (July–December) |
| Mira (Omicron Ceti Pulsating Giant) | Cetus | Prototype long-period asymptotic giant branch variable + accreting white dwarf binary | 02h 19m 20.79s | -02° 58′ 39.5″ | Naked eye at maximum; 70–100 mm telescope at minimum | Autumn to Early Winter (September–January) |
| Eta Carinae (Luminous Blue Variable Binary) | Carina | Colliding-wind Luminous Blue Variable (LBV) hypergiant binary | 10h 45m 03.59s | -59° 41′ 04.3″ | Naked eye; 150 mm+ telescope at 200×+ to resolve the 18″ Homunculus Nebula | Southern Autumn (March–June) |
Detailed Variable Stars Profiles
Polaris (Alpha Ursae Minoris North Star)
Coordinates, Gaia/HST distance (137 pc), 3.97-day Cepheid pulsation, Polaris B companion, and pole-alignment guide for Polaris.
Aliases: α Ursae Minoris, North Star, Pole Star, HD 8890, HIP 11767
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.
Aliases: β Persei, Demon Star, HD 19356, HIP 14576, 26 Persei
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.
Aliases: δ Cephei, HD 213306, HIP 110991, 27 Cephei
Mira (Omicron Ceti Pulsating Giant)
Coordinates, Hipparcos distance (100 pc), 332-day pulsation cycle (mag 2.0 to 10.1), white dwarf companion, and observing guide for Mira.
Aliases: ο Ceti, Mira A & B, VZ Ceti, HD 14386, HIP 10826
Eta Carinae (Luminous Blue Variable Binary)
Coordinates, Gaia/expansion distance (2.35 kpc), 5 million L☉ luminosity, 1843 Great Eruption Homunculus, and observing guide for Eta Carinae.
Aliases: η Carinae, Homunculus Nebula, HD 93308, HR 4210
Related Astrometric & Optical Reference Guides
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.
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.
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.