HD 1185 is a visual double star located in the northern constellation of Andromeda. The system is catalogued in the Henry Draper (HD) Catalogue and is also known by other identifiers such as HIP 1302, HR 56, and SAO 36221.
System components
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Primary (HD 1185 A) – A white main‑sequence star of spectral type A2VpSi, indicating it is an chemically peculiar Ap star with enhanced silicon absorption lines. It has an apparent visual magnitude of 6.15, making it faintly visible to the naked eye under dark skies. Its physical parameters are approximately: mass 2.4 M☉, radius 2.1 R☉, effective temperature ≈ 9,100 K, luminosity ≈ 38 L☉, surface gravity log g ≈ 4.02, and a projected rotational velocity of about 128 km s⁻¹.
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Secondary (HD 1185 B) – A fainter companion with an apparent visual magnitude of 9.76. It lies about 9.08 arcseconds from the primary and shares a common proper motion and parallax, confirming it as a gravitationally bound companion. Its estimated properties are: mass ≈ 1.0 M☉, radius ≈ 0.90 R☉, effective temperature ≈ 5,700 K, luminosity ≈ 0.76 L☉, surface gravity log g ≈ 4.50, and an age of roughly 224 million years.
Astrometric data
- Equatorial coordinates (J2000): Right ascension 00ʰ 16ᵐ 21.53ˢ, declination +43° 35′ 42.2″.
- Parallax: 10.23 ± 0.03 mas, corresponding to a distance of about 320 light‑years (≈ 98 parsecs).
- Proper motion: +35.4 mas yr⁻¹ in right ascension, –23.0 mas yr⁻¹ in declination.
- Radial velocity: ≈ +3 km s⁻¹.
Historical and catalogue information
HD 1185 appears in several astronomical catalogues, including the Henry Draper Catalogue, the Bright Star Catalogue (HR 56), the Hipparcos Catalogue (HIP 1302), and the Durchmusterung (BD +42° 41). Its binary nature has been confirmed by astrometric surveys such as Gaia Data Release 3, which provide precise parallaxes and proper motions for both components.
Observational notes
The primary’s spectral peculiarities classify it as an Ap star, a subgroup of chemically peculiar A‑type stars characterized by strong magnetic fields and abnormal surface abundances of certain elements (e.g., silicon). The secondary is not visible to the naked eye but can be resolved with modest telescopic equipment due to its separation from the primary.
References
- Wikipedia, “HD 1185.” Retrieved from the Wikipedia article on HD 1185.
- SIMBAD Astronomical Database entry for HD 1185.
- Gaia Collaboration (2023), Gaia Data Release 3 – astrometric parameters.
This entry summarizes the currently documented astronomical data for the star system HD 1185.