30 Piscium (HIP 154) is a solitary[9] variable star in the zodiac constellation of Pisces. It is visible to the naked eye with an apparent visual magnitude of 4.37.[7] Its calculated mid-value of antiposed parallax shift as the earth moves around the sun of very roughly 7.8859 mas, makes it around 410 light years away. Its net movement in the present epoch is one of moving closer – radial velocity (speed away from our star system) is −12 km/s.[6]

30 Piscium

Location of 30 (also called YY) Piscium (circled). It presents in a narrow triangle with two other stars of similar brightness, 27 and 33 Piscium.
Observation data Epoch J2000      Equinox J2000
Constellation	Pisces
Right ascension	00h 01m 57.61523s[1]
Declination	−06° 00′ 50.6684″[1]
Apparent magnitude (V)	4.31 – 4.41[2]
Characteristics
Spectral type	M3 III[3]
B−V color index	1.631±0.011[4]
Variable type	LPV,[5] LB?[2]
Astrometry
Radial velocity (Rv)	−11.7±0.5[6] km/s
Proper motion (μ)	RA: +51.158[1] mas/yr Dec.: −39.551[1] mas/yr
Parallax (π)	7.8859 ± 0.4358 mas[1]
Distance	410 ± 20 ly (127 ± 7 pc)
Absolute magnitude (MV)	−1.20[5]
Details
Radius	73.66+16.69 −6.79[1] R☉
Luminosity	1,148.5±71.1[1] L☉
Surface gravity (log g)	2[7] cgs
Temperature	3,647[7] K
Other designations
30 Psc, YY Psc, BD−06° 6345, FK5 1630, HD 224935, HIP 154, HR 9089, SAO 147042[8]
Database references
SIMBAD	data

This is an aging red giant star with a stellar classification of M3 III,[3] indicating it has exhausted the hydrogen at its core and evolved off the main sequence. It is a candidate long-period variable star[5] and has been given the designation YY Psc.[11] It varies in brightness between magnitudes 4.31 and 4.41 with no clear period. Possible periods of 23.1, 32.0, 53.6, and 167.8 days have been identified.[10] The star has 74 times the Sun's radius and is radiating 1,148.5[1] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,647 K.[7]

References