Rho Hydrae
Scientific overview
Rho Hydrae is a main-sequence star in the constellation Hydra (Hydrae), lying about 354.1 light-years from Earth.
Class A. White stars with strong hydrogen lines. Many of the brightest stars in the sky are class A. Such stars have surface temperatures around 7,500–10,000 K and appear white to the eye.
Physical properties
| Spectral type | A0Vn |
| Luminosity class | V |
| Apparent magnitude | 4.35 |
| Absolute magnitude | -0.83 |
| Luminosity (Sun = 1) | 187 |
| Colour index (B−V) | -0.044 |
| Distance | 354.1 ly (108.58 pc) |
Values are real catalogue data; fields without a reliable value are omitted, never estimated.
Precision measurements
Astrometry and astrophysics from SIMBAD and Gaia DR3 · Gaia DR3 582791194797052416 · elevated RUWE
| Parallax | 10.4431 ± 0.1778 mas | SIMBAD · measured |
| Distance | 95.5552 pc | Gaia · estimated |
| Proper motion (RA) | -18.871 mas/yr | SIMBAD · measured |
| Proper motion (Dec) | -29.454 mas/yr | SIMBAD · measured |
| Radial velocity | 30.85 ± 0.63 km/s | SIMBAD · measured |
| Spectral type | A0Vn | SIMBAD · catalogued |
| Effective temperature | 9833.6 K | Gaia · modeled |
| Radius | 4.9263 R_sun | Gaia · modeled |
| Surface gravity (log g) | 3.5752 log(cm/s^2) | Gaia · modeled |
| Metallicity [M/H] | 0.2875 dex | Gaia · modeled |
| Right ascension (ICRS) | 132.1 deg | SIMBAD · measured |
| Declination (ICRS) | 5.8378 deg | SIMBAD · measured |
Full field-level provenance
- Parallax: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · plx_value · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Distance: ESA Gaia astrometric survey · Gaia EDR3 · Bailer-Jones (2021) · external.gaiaedr3_distance · r_med_geo · row 582791194797052416 · Bayesian estimate · retrieved 2026-07-11
- Proper motion (RA): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmra · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Proper motion (Dec): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · pmdec · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Radial velocity: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · rvz_radvel · 2022yCat.1355....0G · direct catalogue measurement · retrieved 2026-07-11
- Spectral type: Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · sp_type · catalogue identifier/value · retrieved 2026-07-11
- Effective temperature: ESA Gaia astrometric survey · Gaia DR3 · gaiadr3.astrophysical_parameters · teff_gspphot · row 582791194797052416 · model output · retrieved 2026-07-11
- Radius: ESA Gaia astrometric survey · Gaia DR3 · gaiadr3.astrophysical_parameters · radius_gspphot · row 582791194797052416 · model output · retrieved 2026-07-11
- Surface gravity (log g): ESA Gaia astrometric survey · Gaia DR3 · gaiadr3.astrophysical_parameters · logg_gspphot · row 582791194797052416 · model output · retrieved 2026-07-11
- Metallicity [M/H]: ESA Gaia astrometric survey · Gaia DR3 · gaiadr3.astrophysical_parameters · mh_gspphot · row 582791194797052416 · model output · retrieved 2026-07-11
- Right ascension (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · ra · 2020yCat.1350....0G · direct catalogue measurement · retrieved 2026-07-11
- Declination (ICRS): Centre de données astronomiques de Strasbourg (CDS) · SIMBAD · basic · dec · 2020yCat.1350....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 main-sequence star fuses hydrogen into helium in its core. It will remain on the main sequence for most of its life before evolving into a giant.
Location in the sky
Knowledge connections
- In constellationHydra
Related stars in Hydra
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.