Omicron Serpentis

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Omicron Serpentis is a single star in the Serpens constellation, visible to the naked eye with an apparent magnitude of about 4.26. It lies in the Serpens Cauda region and is roughly 173 light-years away from Earth.

This star is an A-type main-sequence star (spectral type A2 Va), meaning it is white-hot and still fusing hydrogen in its core. Omicron Serpentis is also a Delta Scuti variable, so its brightness changes very slightly over time. Its brightness ranges from magnitude 4.26 to 4.27 with a period of about 76 minutes (0.053 days).

Physical properties include:
- Mass: about 2.1 solar masses
- Radius: about 2.2 solar radii
- Luminosity: about 42.6 times the Sun
- Surface temperature: around 8,970 K
- Rotational velocity: about 113 km/s (projected)
- Age: roughly 500 million years

The star has several other names, including ο Ser, 56 Ser, BD −12°4808, FK5 3405, HD 160613, HIP 86565, HR 6581, and SAO 160747. It is not known to be part of a binary system. A historical note: in 1909, a symbiotic nova called RT Ser appeared near Omicron Serpentis, reaching a maximum brightness of about magnitude 10.