Definition
Celaeno is both the name of a star in the Pleiades open star cluster (designated η Tauri) and the name of one of the seven mythological daughters of the Titans Atlas and Pleione in Greek tradition.
Overview
- Astronomical designation: η Tauri, also catalogued as 27 Tauri.
- Location: Constellation Taurus, situated near the northeastern edge of the Pleiades (Messier 45).
- Apparent magnitude: Approximately 5.5, making it visible to the naked eye under good dark‑sky conditions.
- Spectral classification: B‑type (commonly listed as B6 IV or B8 III), indicating a hot, blue‑white star that has evolved off the main sequence.
- Distance: Roughly 440 light‑years (≈135 parsecs) from the Solar System, consistent with the measured distance to the Pleiades cluster.
- Cluster membership: As a confirmed member of the Pleiades, Celaeno shares the cluster’s estimated age of about 100 million years and its common motion through space.
- Multiplicity: Some studies suggest Celaeno may be a spectroscopic binary, but the presence of a companion has not been definitively established.
In mythology, Celaeno (Greek: Κελαίνη, “the dark one”) is one of the seven Pleiades, often associated with the theme of darkness or obscurity, contrasting with the brighter sisters such as Alcyone and Maia.
Etymology / Origin
The name derives from the ancient Greek Κελαίνη (Kelaínē), which is interpreted to mean “the dark one” or “the black‑haired.” The epithet likely reflects mythological attributes rather than any physical characteristic of the star.
Characteristics
| Property | Value / Description |
|---|---|
| Spectral type | B6 IV (subgiant) or B8 III (giant) – both classifications appear in different catalogues. |
| Effective temperature | Approximately 13,000 K, typical of B‑type stars. |
| Luminosity | About 200–300 times that of the Sun, inferred from its absolute magnitude and distance. |
| Radius | Roughly 4–5 solar radii, consistent with its evolved status. |
| Mass | Estimated at 3–4 solar masses. |
| Radial velocity | Near +5 km s⁻¹ relative to the Sun, matching the motion of the Pleiades. |
| Variability | No confirmed intrinsic variability; the star is considered photometrically stable. |
| Binary status | Possible spectroscopic binary; observational evidence is inconclusive. |
Related Topics
- Pleiades (Messier 45) – an open star cluster containing over a thousand stars, of which the seven brightest are traditionally identified as the Pleiades sisters.
- Other Pleiad stars – Alcyone (η Tauri’s brightest neighbor), Maia, Electra, Merope, Taygeta, and Sterope.
- Atlas and Pleione – the mythological parents of the Pleiades.
- Stellar evolution of B‑type stars – the process by which massive, hot stars leave the main sequence and become subgiants or giants.
- Spectroscopic binaries – binary star systems identified through periodic Doppler shifts in their spectral lines.
References
- SIMBAD astronomical database, entry for η Tauri.
- “The Pleiades” entry in The Handbook of Star Forming Regions (Bally, 2020).
- Classical sources: Hesiod’s Theogony and Apollodorus’s Bibliotheca for mythological background.