3C 380

3C 380 is a radio-loud quasar located in the constellation of Draco.^[1][2] First discovered in 1965 and identified with a starlike object,^[3][4] it is one of the luminous and powerful radio sources in Third Cambridge Catalogue, with a redshift of (z) 0.692 and a compact steep spectrum (CSS) source.^[5][6][7]

3C 380
The quasar 3C 380.
Observation data (J2000.0 epoch)
Constellation	Draco
Right ascension	18h 29m 31.7809s
Declination	+48° 44′ 46.161″
Redshift	0.6920000
Heliocentric radial velocity	207,456 km/s
Distance	6.074 Gly
Apparent magnitude (V)	16.81
Apparent magnitude (B)	17.05
Characteristics
Type	Opt. var, Sy 1.5, LPQ
Other designations
CTA 79, NRAO 565, LEDA 2817708, QSO B1828+4842, 4C +48.46, S4 1828+487, WK 396, WMAP 46,

Description

3C 380 contains a complex radio structure. Radio images produced by the very long baseline interferometry (VLBI) at 5 GHz, showed the source is mainly extended, containing several components including a compact radio core and a ridge of extended radio emission.^[8][9] In additional, the quasar also has a diffused halo with a spectral index of 1.0 ± 0.2 which represents a common feature of the radio lobes in Fanaroff-Riley class II quasars.^[6] An extended radio lobe was also discovered in 3C 380, having a low spectral index when compared to those at decimeter wavelengths.^[10] There are also two hotpots located in northwest direction.^[11]

The radio jet of 3C 380 on parsec-scales is known to be bent. Based on VLBI observations, it is shown to be resolved when travelling in a transverse direction, however it also shows signs of rapid brightness variations unlike other nuclear jets indicating phase effects play a role in causing these changes. Apart from that, the jet shows superluminal motion^[12] and a Faraday rotation gradient measuring 70-200 parsecs in width across it.^[13] Radio imaging Very Long Baseline Array (VLBA) also finds the jet is extending in a northwest direction.^[14]

According to Hubble Space Telescope (HST) and VLBA, the jet has two knots. These knots are respectively named as knot 1, located 0.73 arcseconds from the core and knot 2 which is located 0.4 arcseconds away from the former. Together, these knots are found laid over lobelike emission which in turn, is stretched out in both east and northeast directions.^[15]

Multifrequency polarization have also been found in 3C 380. Based on observations, both the core and jet contains polarization by 6 percent, while the other component has 16 percent polarization.^[16] Enhanced flux density at 24 GHz from the object was also detected in September 2020.^[17]