LL Pegasi
Variable star in the constellation Pegasus
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LL Pegasi (AFGL 3068) is a Mira variable star surrounded by a pinwheel-shaped nebula, IRAS 23166+1655, thought to be a preplanetary nebula. It is a binary system that includes an extreme carbon star. The pair is hidden by the dust cloud ejected from the carbon star and is only visible in infrared light.[8]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 23h 19m 12.607s[2] |
| Declination | +17° 11′ 33.13″[2] |
| Characteristics | |
| Evolutionary stage | Asymptotic giant branch[3] |
| Spectral type | C[4] |
| Variable type | Mira[5] |
| Astrometry | |
| Distance | 1,300[3] pc |
| Details | |
| A | |
| Mass | 3.5[6] M☉ |
| Radius | 1,100[7][a] R☉ |
| Luminosity | 10,900[7] L☉ |
| Temperature | 1,800[7] K |
| B | |
| Mass | 3.1[6] M☉ |
| Other designations | |
| LL Pegasi, IRAS 23166+1655, 2MASS J23191260+1711331, RAFGL 3068 | |
| Database references | |
| SIMBAD | data |
Variability
Nebula
The nebula displays an unusual Archimedean spiral shape. The shape is thought to be formed through the interaction between the stellar companion and the carbon star, as has been seen in other binary systems, although not with such a precise geometric form. The distance between the spiral arms and their rate of expansion is consistent with estimates of the pair's 810 year orbital period based on their apparent angular separation.[8]
Gallery
- Observed structure surrounding the binary star system.
Hubble Space Telescope image of IRAS 23166+1655, taken in the near-infrared. The bright object to the right is a star much closer to Earth. It was used as a guide star for adaptive optics corrections that allowed the Keck II telescope to resolve the LL Pegasi binary pair.
Notes
- Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
- .
