Star profile
Phi Herculis
Hot blue starWhat is Phi Herculis
Phi Herculis is a chemically peculiar star of the mercury-manganese class: its atmosphere holds these heavy metals in concentrations thousands of times richer than the Sun's. To the eye it looks single, but spectrographs uncovered a hidden companion, an A8 star spinning far faster than the primary. It burns blue-white near 10,000 K at 204 light-years, owner of a strange chemistry that still puzzles astrophysicists.
Where it is and when to see it
Phi Herculis lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is May, when it culminates around midnight.
- From London it never sets and culminates about 83° up.
- From New York it culminates about 86° above the horizon.
- From Sydney it culminates about 11° above the horizon.
It can be seen from anywhere north of 45° S.
It ranks no. 19 in brightness among the 136 stars of Hercules in our catalogue. To find it, start from Kornephoros, the brightest: it lies about 24° away (a fist at arm's length covers about 10°).
The light you see today left it about 200 years ago.
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Astronomical data for Phi Herculis
- Constellation
- Hercules
- Apparent magnitude
- 4.23
- Distance
- 204.0 light years
- Coordinates (J2000)
- RA 242.192° · Dec 44.935°
- Catalogue
- HIP 79101 · HD 145389
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Other stars in Hercules
Hercules has 136 stars in Stelvia's catalogue. Here are a few of them.
- KornephorosBeta Herculis2.78
- RasalgethiAlpha 1 Herculis2.78
- Zeta Herculis2.81
- Rho Herculis4.15
- 110 Herculis4.19
- Sigma Herculis4.20
- 95 Herculis4.26
- 111 Herculis4.34