Xi Octantis
A faintly visible B-type variable star in Octans.
Xi Octantis, also known by its Latinized designation ξ Octantis, is a solitary variable star located in the southern circumpolar constellation Octans. With an apparent magnitude around 5.3, it is just barely visible to the naked eye, though its brightness fluctuates slightly. The star lies about 514 light-years from Earth and is moving away at a heliocentric radial velocity of 22 km/s.
Its stellar classification is B6 V, marking it as a typical B-type main-sequence star, though some sources assign it a subgiant luminosity class (IV) or an intermediate classification between a B5 and B7 dwarf. The star has roughly four times the Sun’s mass and three times its radius, shining with a luminosity of 360 times that of the Sun. Its photosphere has an effective temperature of 14,050 K, giving it a whitish-blue glow. At an age of 46 million years, Xi Octantis has completed about 64.8% of its short main-sequence lifetime, and it rotates modestly with a projected rotational velocity of 30 km/s.
Variability in its magnitude—ranging from 5.32 to 5.36—was first identified from data in the Hipparcos catalogue released in 1997, and it has since been classified as a slowly pulsating B-dwarf with a pulsation period of 1.78 days.
- Apparent magnitude range
- 5.32 to 5.36
- Distance
- 514 light-years
- Spectral classification
- B6 V (with some uncertainty: luminosity class IV subgiant per Hintler et al., intermediate B5-B7 dwarf per Houk and Cowley)
- Mass
- 4 solar masses
- Radius
- 3 solar radii
- Luminosity
- 360 L☉
- Effective temperature
- 14,050 K
- Age
- 46 million years
- Projected rotational velocity
- 30 km/s
- Variability type
- slowly pulsating B-dwarf
Lore & Background
Xi Octantis has a stellar classification of B6 V, indicating that it is an ordinary B-type main-sequence star. However, there is some dispute: Hintler et al. gives it a luminosity class IV (subgiant) while Houk and Cowley gives a classification intermediate between a B5 and B7 dwarf. Nevertheless, it has 4 times the mass of the Sun and is 3 times larger. It shines with a luminosity of 360 L☉ from its photosphere at an effective temperature of 14,050 K, giving it a whitish blue glow. Xi Octantis is 46 million years old—64.8% through its short main-sequence lifetime—and spins modestly with a projected rotational velocity of 30 km/s.
Reader's Guide
Xi Octantis is significant as a variable star whose variability was identified from the Hipparcos catalogue data. It has since been classified as a slowly pulsating B-dwarf with a period of 1.78 days, ranging in magnitude from 5.32 to 5.36. Its classification as a B-type main-sequence star is complicated by alternative luminosity class assignments, reflecting the ongoing refinement of stellar taxonomy. The star's age of 46 million years and its position 64.8% through its main-sequence lifetime provide context for its evolutionary stage. As a solitary variable in the southern circumpolar constellation Octans, it contributes to the study of pulsating B-type stars and their variability mechanisms.
Did You Know?
- The star is 46 million years old, about 64.8% through its main-sequence lifetime.
- Its spectral classification is disputed: B6 V, but also given as subgiant or intermediate B5-B7 dwarf.
More in Variable Stars 1-24
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