Star profile
Pi Aquarii
Variable starWhat is Pi Aquarii
It is one of the most studied Be stars in the sky: a blue point spinning at dizzying speeds, surrounded by a disc of gas that appears and fades across the decades. Since the early 20th century astronomers have documented its outbursts, its double-peaked, triple-peaked and almost flat-topped spectral profiles, and an invisible companion — likely a white dwarf — that crosses it every 84 days and triggers an X-ray flare. At 782 light-years away, its light pulses with a story that is never quite the same twice.
Where it is and when to see it
Pi Aquarii lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is September, when it culminates around midnight.
- From London it culminates about 40° above the horizon.
- From New York it culminates about 51° above the horizon.
- From Sydney it culminates about 55° above the horizon.
It can be seen from anywhere north of 89° S.
It ranks no. 28 in brightness among the 99 stars of Aquarius in our catalogue. To find it, start from Sadalsuud, the brightest: it lies about 15° away (a fist at arm's length covers about 10°).
The light you see today left it about 780 years ago.
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Astronomical data for Pi Aquarii
- Constellation
- Aquarius
- Apparent magnitude
- 4.80
- Distance
- 782.3 light years
- Coordinates (J2000)
- RA 336.319° · Dec 1.377°
- Catalogue
- HIP 110672 · HD 212571
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Other stars in Aquarius
Aquarius has 99 stars in Stelvia's catalogue. Here are a few of them.
- SadalsuudBeta Aquarii2.90
- SadalmelikAlpha Aquarii2.95
- SkatDelta Aquarii3.27
- 89 Aquarii4.71
- Mu Aquarii4.73
- Omicron Aquarii4.74
- Sigma Aquarii4.82
- 104 Aquarii4.82