Credit: ESO/A. Merand

An interferometric observation of the quasar 3C 273 with the VLTI. The columns marked UT1, UT2, and UT4 show the data from the individual 8.2-metre Unit Telescopes, which were then combined interferometrically. The resultant fringes are shown in the column marked VLTI. The bright feature is the Paschen-α emission line from atomic hydrogen gas, redshifted to a wavelength of 2.17 µm due to the quasar’s distance of about two billion light-years. This image is a rare example of a five-second exposure that reveals the fringes. In real use, multiple much shorter 0.3-second observations must be made. It is thanks to the new “blind observation mode” that these shorter exposures can be successfully combined.

Provider: European Southern Observatory

Image Source: https://www.eso.org/public/images/ann11031a/

Curator: European Southern Observatory, Garching bei München, Germany

Image Use Policy: Creative Commons Attribution 4.0 International License