HD 161056

In 1985, the star was suggested as a standard for polarimetric observations via the Hubble Space Telescope, since the star's large distance from Earth produces a large interstellar polarization and its high luminosity makes it easily visible at such distances. In 1988, however, it was found that the star was slightly variable in polarization, and thus unsuitable as a standard star. Nevertheless, Hubble observed the star's ultraviolet interstellar polarization, thanks to it having been well-researched in the visible spectrum, presenting results consistent with Serkowski's law—an empirical formula regarding the dependency of interstellar polarization on wavelength. The extensive collected polarization spectrum showed a close match to what would be expected from an interstellar dust composition of pure amorphous forsterite. ==Spectroscopy==

In addition to polarimetry, spectroscopic observations have also been conducted on HD 161056 to provide insight into the interstellar medium. The ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) detected signatures of diatomic carbon and tricarbon molecules in interstellar clouds surrounding the star. Near-infrared spectroscopy has revealed signs of weak stellar emission lines of singly ionized magnesium and neutral helium (Mg II and He I in spectroscopic notation). ==Runaway star==

HD 161056 is a runaway star and a candidate for producing a bow shock observable in the infrared. Such stars commonly originate in multiple star systems, from which they were ejected due to gravitational interactions or supernovae of their companions, and indeed it is possible that the star could have been in a binary system with the pulsar PSR B1929+10 about 1.1 million years ago, when it was located in the vicinity of IC 4665. However, Zeta Ophiuchi is considered more likely to have been its binary companion, in which scenario the pair possibly split up around 900,000 years ago. ==See also==