[1] It is classified as a gigahertz peaked-spectrum quasar (GPS)[2] with a flat-spectrum radio source[3] and a blazar, a type of active galaxy shooting an astrophysical jet towards Earth.

First identified by astronomers in 1977 who were studying an optical follow-up of flat-spectrum sources from the Parkes 2700 MHz surveys,[4] and subsequently by the Imaging Proportional Counter by the Einstein Observatory in 1981,[5] PKS 2126-158 was only the fifth radio quasar with z > 3 to have its redshift measured.

[6] PKS 2126−158 is a notable bright object emitting radio signals of S2.7 GHz= 1.17 Jy, optical with near-infrared rays of V= 16.92, H= 14.89[7] and X-ray (F0.1−2.4 keV= 2 × 10−12 erg s-1 cm −2) frequencies.

Notably, an optical/near-infrared spectrum showed PKS 2126−158 has a blue power-law shape for longer wavelengths compared to V bands where the Lyα line falls.

[7] The flux drops off at shorter wavelengths due to its absorption by the intervening gas of the Lyman α forest.

Although, there is no soft excess and low energy absorption have been detected, the thermal bremsstrahlung model is found to fit with the spectrum of PKS 2126 - 158, with a rest-frame temperature of 6.4_-4_^+40^ keV.

[10] These observations confirms the presence of a low energy absorption unrelated from the continuum model adopted, at a high confidence level.