91 Aquarii, also known as Psi1 Aquarii (ψ1 Aqr, ψ1 Aquarii), is the brightest star in a triple star system approximately 148 light-years away in the constellation of Aquarius. The system comprises three stars of which a fainter binary component is known under the name HD 219430. The primary star 91 Aqr is an orange giant star, around which an extrasolar planet is known to orbit with a mean distance from the central star slightly shorter than from Mercury to our Sun.
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The primary star, 91 Aquarii, is an orange giant star with an apparent magnitude of +4.22. At a separation of 49.6 arcseconds from the primary is a binary companion composed of two 10th magnitude stars (HD 219430 B and C). They are 0.3 arcseconds from each other.
| NAME | Apparent magnitude (V) | Spectral type |
|---|---|---|
| 91 Aqr (ψ¹ Aqr, HD 219449, Gliese 893.2) | 4.22 | K0III |
| HD 219430B | 9.62 | K3V |
| HD 219430C | 10.10 | D |
Another nearby binary system CCDM J23159-0905DE was listed to belong to the system according to the CCDM catalogue, but is listed as physically unconnected by the WDS catalogue. CCDM J23159-0905DE has two components, the 13th magnitude CCDM J23159-0905D 80.4 arcseconds from 91 Aquarii, and the 14th magnitude CCDM J23159-0905E 19.7 arcseconds from 91 Aquarii.
In 2003, the discovery of an extrasolar planet orbiting 91 Aquarii was announced.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | >2.9[3] MJ | 0.3[4] | 182[3] | 0 |
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