Propus
Eta Geminorum
Scientific overview
Propus is a red giant in the constellation Gemini (Geminorum), lying about 384.6 light-years from Earth.
Class M. Cool red stars. The most common type in the galaxy, ranging from red dwarfs to red giants. Such stars have surface temperatures around 2,400–3,700 K and appear red to the eye.
Physical properties
| Spectral type | M3III |
| Luminosity class | III |
| Apparent magnitude | 3.31 |
| Absolute magnitude | -2.05 |
| Luminosity (Sun = 1) | 574 |
| Colour index (B−V) | 1.6 |
| Distance | 384.6 ly (117.92 pc) |
Values are real catalogue data; fields without a reliable value are omitted, never estimated.
Precision measurements
Astrometry and astrophysics from SIMBAD
| Parallax | 4.7312 ± 1.0207 mas | SIMBAD · measured |
| Proper motion (RA) | -59.53 mas/yr | SIMBAD · measured |
| Proper motion (Dec) | -7.766 mas/yr | SIMBAD · measured |
| Radial velocity | 22.39 ± 0.36 km/s | SIMBAD · measured |
| Spectral type | M2IIIa | SIMBAD · catalogued |
| Right ascension (ICRS) | 93.7194 deg | SIMBAD · measured |
| Declination (ICRS) | 22.5068 deg | SIMBAD · measured |
Full field-level provenance
- Parallax: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · plx_value · 2018yCat.1345....0G · direct catalogue measurement · retrieved 2026-07-11
- Proper motion (RA): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmra · 2018yCat.1345....0G · direct catalogue measurement · retrieved 2026-07-11
- Proper motion (Dec): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmdec · 2018yCat.1345....0G · direct catalogue measurement · retrieved 2026-07-11
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 2005A&A...430..165F · direct catalogue measurement · retrieved 2026-07-11
- Spectral type: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · sp_type · 1989ApJS...71..245K · catalogue identifier/value · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2018yCat.1345....0G · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2018yCat.1345....0G · direct catalogue measurement · retrieved 2026-07-11
measured = direct catalogue value · estimated = Bayesian inference (Bailer-Jones distance) · modeled = model output (Gaia GSP-Phot). Fields a source did not provide are omitted, never invented.
Evolution
A red giant is an evolved star that has exhausted core hydrogen and expanded enormously, cooling at its surface as it fuses heavier elements in shells.
Location in the sky
Knowledge connections
- In constellationGemini
Related stars in Gemini
Sources
The primary and reference sources this topic draws on.
- HYG DatabaseHYG Database (Hipparcos + Yale Bright Star + Gliese), by D. Nash / astronexus
Aggregated, openly-licensed star catalogue combining Hipparcos, the Yale Bright Star Catalogue, and the Gliese Catalogue of Nearby Stars.
- HipparcosESA Hipparcos space astrometry mission
High-precision parallax, magnitude, and position for ~118,000 stars.