WR 16

WR 16 (HD 86161) is a Wolf-Rayet star located in the constellation Carina. It is a massive, luminous, and evolved star in a late stage of evolution, surrounded by a complex nebula formed by its strong stellar winds and past mass ejections. WR 16 is classified as a runaway star due to its high velocity through the interstellar medium.^[4]

WR 16

Observation data Epoch J2000      Equinox J2000
Constellation	Carina[1]
Right ascension	09h 54m 52.9034s[2]
Declination	+57° 43′ 38.2746″[2]
Apparent magnitude (V)	8.36[3]
Characteristics
Evolutionary stage	Wolf-Rayet[4]
Spectral type	WN8h[4]
Variable type	WR[5], ellipsoidal[6]
Astrometry
Proper motion (μ)	RA: −9.458[2] mas/yr Dec.: +5.054[2] mas/yr
Parallax (π)	0.438±0.0168 mas[2]
Distance	7,400 ± 300 ly (2,280 ± 90 pc)
Absolute magnitude (MV)	−5.6[7]
Details
Mass	19[8] M☉
Radius	11.56[8] R☉
Luminosity	525,000[8] L☉
Temperature	44,700[8] K
Other designations
Hen 3-342, V396 Carinae, HD 86161, HIP 48617, SAO 237491[9]
Database references
SIMBAD	data

Physical characteristics

A light curve for WR 16, plotted from TESS data^[10]

WR 16 is classified as a WN8h star,^[4] indicating a hydrogen-rich Wolf-Rayet star dominated by nitrogen emission lines.^[11] Its effective temperature of over 40,000 K^[8] is hotter than the Sun's typical value of 5,772 K,^[12] but cooler than many other WR stars.^[8]

WR 16 is a rotating ellipsoidal variable, meaning its brightness and shape change slightly due to rotation.^[6]

Runaway status

Motion measurements from the Gaia satellite show that WR 16 moves at about 61 km/s relative to its local interstellar medium, qualifying it as a runaway star. This rapid motion influences the shape of its surrounding nebula.^[4]

Nebular structure

WR 16 is surrounded by a bubble-like nebula formed by material ejected in previous evolutionary stages and shaped by its strong stellar winds. Observations reveal a round, bubble-shaped nebula visible in optical and infrared wavelengths. Multiple rings surround the star, likely from episodic mass ejections during its earlier Luminous Blue Variable (LBV) phase. Ionized hydrogen (H II regions) and nitrogen-enriched gas are present, indicating processed stellar material.^[4]

Bow shock

Due to its high velocity, WR 16 creates a bow shock—a curved front where its stellar wind collides with the interstellar medium, compressing gas and dust. Radio and infrared imaging confirms the bow shock’s presence.^[13][4]