Epsilon Draconis (ε Dra) is a solitary star in the northern constellation Draco. It is identified by several catalogue designations, the most common being HD 16458, HR 777, and HIP 12323. The star is also listed in the Bayer system as ε Draconis.
Basic Properties
| Property | Value |
|---|---|
| Apparent magnitude (V) | 3.53 mag |
| Spectral type | G8 III (yellow‑giant) |
| B‑V colour index | +0.92 |
| Parallax | 31.37 ± 0.25 mas (milliarcseconds) |
| Distance | ≈ 104 light‑years (≈ 32 parsecs) |
| Absolute magnitude (V) | +0.61 mag |
| Radius | ≈ 7 R☉ (solar radii) |
| Mass | ≈ 2.3 M☉ (solar masses) |
| Luminosity | ≈ 68 L☉ (solar luminosities) |
| Effective temperature | ≈ 5,050 K |
| Radial velocity | –13.2 km s⁻¹ (approaching) |
| Proper motion | RA: +84.26 mas yr⁻¹, Dec: +53.41 mas yr⁻¹ |
The parallax measurement from the Hipparcos mission (and confirmed by Gaia DR2) yields the distance quoted above. Its spectral classification G8 III indicates it has evolved off the main sequence and expanded into a giant star.
Nomenclature
- Bayer designation: ε Draconis, where the Greek letter “epsilon” follows the traditional order of brightness within Draco, though ε Draconis is not the brightest star in the constellation.
- Flamsteed number: None assigned; the star is generally referred to by its Bayer designation.
- Traditional name: The star does not possess a widely recognised traditional Arabic or Latin name in major catalogues. Some historical sources have occasionally referred to it as “Al Haik,” but this usage is rare and not standardized.
Observational Information
Epsilon Draconis is visible to the naked eye under dark‑sky conditions and appears as a yellowish point of light near the centre of Draco. Its celestial coordinates (epoch J2000.0) are:
- Right Ascension: 02ʰ 31ᵐ 23.79ˢ
- Declination: +68° 57′ 36.2″
Because of its moderate apparent magnitude and relatively high declination, it is observable from most northern latitudes throughout the year.
Physical Characteristics
As a G‑type giant, ε Draconis has exhausted hydrogen in its core and is now fusing helium or heavier elements in shells surrounding an inert carbon‑oxygen core. Its expanded envelope accounts for the large radius and increased luminosity compared with a main‑sequence star of similar mass. The estimated age is on the order of 1 billion years, consistent with evolutionary models for a star of ~2.3 M☉.
Multiplicity and Planetary Companions
Current high‑resolution surveys (e.g., speckle interferometry and radial‑velocity monitoring) have found no evidence of stellar companions or exoplanets orbiting ε Draconis. The star is therefore classified as a single (isolated) object.
Cultural and Historical Notes
Epsilon Draconis does not play a major role in mythological or historical star lore compared with brighter Draco members such as Thuban (α Draconis) or Errai (γ Draconis). Its lack of a prominent traditional name reflects this relatively minor cultural significance.
All data are drawn from peer‑reviewed astronomical catalogues and databases such as the Hipparcos and Gaia missions, the SIMBAD astronomical database, and standard stellar reference works.
