PZ Telescopii

PZ Telescopii, also known as HD 174429 or simply PZ Tel, is a young star in the constellation Telescopium. Based on parallax measurements, it is located at a distance of 154 light years from the Sun. The star is drifting closer with a radial velocity of −4 km/s.[6] It is too faint to be visible to the naked eye and is classified as a BY Draconis variable that ranges in apparent visual magnitude from 8.33 down to 8.63 over a period of 22.581 hours (0.94088 days).[3] It is one of the closest and hence brightest pre-main-sequence stars to Earth.[7]

PZ Telescopii

Visual band light curves for PZ Telescopii, adapted from Innis et al. (1990)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Telescopium
Right ascension	18h 53m 05.87338s[2]
Declination	−50° 10′ 49.9014″[2]
Apparent magnitude (V)	8.33 - 8.63[3]
Characteristics
Spectral type	G9 IV[4] + M7±1[5]
B−V color index	+0.784±0.021[6]
Variable type	BY Dra[3]
Astrometry
Radial velocity (Rv)	−4.2±0.2[6] km/s
Proper motion (μ)	RA: +16.348±0.084[2] mas/yr Dec.: −85.254±0.084[2] mas/yr
Parallax (π)	21.2186 ± 0.0602 mas[2]
Distance	153.7 ± 0.4 ly (47.1 ± 0.1 pc)
Absolute magnitude (MV)	4.88[6]
Orbit[5]
Period (P)	622.2 yr
Semi-major axis (a)	1.504″
Eccentricity (e)	0.755
Inclination (i)	92.05°
Longitude of the node (Ω)	58.43°
Periastron epoch (T)	2000.0
Argument of periastron (ω) (secondary)	264.38°
Details[7]
Mass	1.13±0.03 M☉
Radius	1.23±0.04 R☉
Luminosity	0.993+0.004 −0.005[2] L☉
Surface gravity (log g)	4.41±0.10 cgs
Temperature	5,338±200 K
Metallicity [Fe/H]	+0.05±0.20 dex
Rotation	0.943±0.002[5]
Rotational velocity (v sin i)	69.0±0.1[4] km/s
Age	24±3 Myr
B
Mass	38–72[5] MJup
Surface gravity (log g)	< 4.5[5] cgs
Temperature	2,700±100 K
Other designations
PZ Tel, CD−50°12190, HD 174429, HIP 92680, SAO 245781, PPM 347231, WDS J18531-5011AB[8]
Database references
SIMBAD	data

PZ Telescopii has an effective surface temperature of around 5,338 K (the Sun has an approximate surface temperature of 5,778 K), a mass around 1.13 times, and diameter 1.23 times that of the Sun.[7] The star has a high rate of spin, showing a projected rotational velocity of 69 km/s[4] and a rotation period of 22.6 h.[5] It is radiating about the same luminosity as the Sun. PZ Telescopii was originally considered to be a member of the Beta Pictoris moving group; however in a 2012 paper, James Jenkins of Universidad de Chile and colleagues used three methods to calculate its age and came up with a figure of around 24 million years—significantly older than the 12 million years of the association.[7]

This star has an orbiting debris disk calculated to span from a radius of 35 to 165 astronomical units (AU), as well as a substellar companion with 36 times the mass of Jupiter orbiting at a distance of 16 AU, discovered in 2008. The companion, currently known as PZ Tel B, is thought to be a brown dwarf; however it is possible (though very unlikely) that it is an extremely large Jupiter-like planet, in which case it would be PZ Tel b, and the first such planet to be directly imaged.[7] Preliminary orbital elements give a best fit orbital period of 622.2 years with an eccentricity of 0.755.[5]