Eta Carinae (η Carinae & Homunculus Nebula)
Coordinates, Gaia/expansion distance (2.35 kpc), 5 million L☉ luminosity, 1843 Great Eruption Homunculus, and observing guide for Eta Carinae.
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 |
|---|---|---|---|---|---|
| Current visual magnitude (V, 2020s) | 4 mag | -0.8 to 7.9 mag | Historical & modern photometry (peaked at −0.8 in 1843; faded to 7.9 by 1900; brightened to ~4.0 today) | definitive | General Catalogue of Variable Stars (GCVS) & AAVSO VSX |
| Distance (Homunculus 3D expansion & Trumpler 16 Gaia DR3) | 2350 pc | ± 50 pc | 3D proper-motion/Doppler expansion of Homunculus Nebula + Gaia DR3 cluster parallax (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| System bolometric luminosity | 5000000 L☉ | ± 500000 L☉ | Mid/far-infrared thermal re-radiation by the Homunculus dust shroud | high-confidence | SIMBAD Astronomical Database (CDS) |
| Primary star mass (Eta Carinae A) | 100 M☉ | ± 20 M☉ | Colliding-wind binary orbit + Eddington limit modeling (secondary B ≈ 30–40 M☉) | model-dependent | SIMBAD Astronomical Database (CDS) |
| Eccentric binary orbital period | 2022.7 d | ± 1.3 d | X-ray & spectroscopic periastron eclipse cycle (5.538 yr, e ≈ 0.90) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Eta Carinae (Luminous Blue Variable Binary) at RA 10h 45m 03.59s, Dec -59° 41′ 04.3″ within Carina, 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
Eta Carinae (η Carinae), embedded inside the Trumpler 16 cluster at the heart of the Carina Nebula 2.35 ± 0.05 kiloparsecs (7,660 light-years) away, is the most luminous and massive stellar system within 10,000 light-years of Earth, radiating an astonishing 5 million solar luminosities. In March 1843, Eta Carinae underwent its famous 'Great Eruption'—a non-terminal supernova impostor event in which the star briefly shone at apparent magnitude −0.8 (second only to Sirius) while ejecting 10 to 20 solar masses of gas and dust at ~650 km/s without destroying its core.
That ejected material formed the bipolar Homunculus Nebula ('Little Man'), a twin-lobed hourglass now spanning ~18 arcseconds across that absorbs most of the central stars' fierce ultraviolet and visual light and re-radiates it in the mid-infrared, making Eta Carinae the brightest extrasolar object in the sky at wavelengths of 10 to 20 microns. As the Homunculus dust condensed after 1850, Eta Carinae faded to magnitude 7.9, but over the past 70 years the expanding dust shroud has thinned out, allowing Eta Carinae to brighten back into naked-eye visibility around magnitude 4.0.
In 1996 Augusto Damineli proved that Eta Carinae is a highly eccentric (e ≈ 0.90) colliding-wind binary with a period of 5.538 years (2,022.7 days): a ~100-solar-mass Luminous Blue Variable primary (blowing a dense 500 km/s wind) is orbited by a hot ~30-to-40 solar-mass O or Wolf-Rayet companion (blowing a 3,000 km/s wind). At periastron the two stars pass within 1.5 AU of each other, collapsing the X-ray shock cone.
Practical Visual Observing Guide
- Visible to the naked eye from the Southern Hemisphere inside the bright central lobe of the Carina Nebula (NGC 3372).
- In a 150–250 mm telescope at 200×–350× under steady seeing, Eta Carinae does not look like a point star at all: you can visually resolve the 18-arcsecond peanut-shaped orange-amber lobes of the expanding Homunculus Nebula!
Catalog Cross-Identifications & Aliases
Common Aliases: η Carinae · Homunculus Nebula · HD 93308 · HR 4210
| Catalog Authority | Identifier |
|---|---|
| HD | HD 93308 |
| SIMBAD | * eta Car |
| WIKIDATA | Q12174 |
Related Objects, Comparisons & Guides
Carina Nebula (NGC 3372 Star-Forming Cloud)
Coordinates, Gaia DR3 distance (2.35 kpc), Keyhole Nebula, Trumpler 14/16 OB clusters, and observing guide for NGC 3372 in Carina.
Betelgeuse (Alpha Orionis Red Supergiant)
Coordinates, competing optical vs radio distances (168 vs 222 pc), radius, Great Dimming physics, and observing guide for Betelgeuse.
Rigel (Beta Orionis Blue Supergiant)
Coordinates, Hipparcos distance (264 pc), luminosity (120,000 L☉), Rigel BC companion, and observing guide for Rigel in Orion.
Crab Nebula (Messier 1 Supernova Remnant)
Coordinates, Gaia DR3 distance (1.96 kpc), SN 1054 history, pulsar wind physics, and observing guide for the Crab Nebula (M1) in Taurus.
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
- 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
- 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