Telescope link-up probes distant quasar

Astronomers have linked up three observatories to zoom in on a quasar marking the site of a monstrous black hole in unprecedented detail, two million times finer than can be seen with the eye.

An artist’s impression of the quasar 3C 279 which has been observed in unprecedented detail. Credit: ESO/M. Kornmesser

The huge distances between the observatories – in Arizona, Chile and Hawaii – meant that the instruments could work together like a single telescope thousands of kilometres across.

It is impossible to build a single telescope that big, of course, but the extremely high resolution it would offer can be achieved by combining the widely spaced smaller telescopes.

This “megascope” was able to peer into the heart of a distant galaxy called 3C 279 that shines brilliantly due to the presence of a supermassive black hole with a billion times the “weight” of the Sun and lying more than five billion light-years away in the constellation of Virgo.

The technique to simulate this single telescope is called Very Long Baseline Interferometry (VLBI) and it is an extended version of the e-Merlin link-up between radio telescopes in the UK that Skymania News described earlier this year.

Telescopes used were APEX – a European Southern Observatory (ESO) prototype of the dishes in the ALMA array – in Chile, the Submillimeter Array (SMA) in Hawaii, and the Submillimeter Telescope (SMT) in Arizona. This produced an interferometer, or “megascope”, measuring 9,447 km from Chile to Hawaii, 7,174 km from Chile to Arizona and 4,627 km from Arizona to Hawaii.

The observations were made in radio waves with the incredibly short wavelength of 1.3 millimetres. This allowed the astronomers to achieve a sharpness, or angular resolution, of about 8 billionths of a degree. To get a handle on what that means, the Moon is about half a degree across.

In the future, astronomers plan to link up even more telescopes, including ALMA, to create a virtual Event Horizon Telescope that will be able to make direct observations of the boundary between the normal Universe and whatever lies within the supermassive black hole at the centre of our own Milky Way galaxy.

I visited APEX last year on a tour of some of the ESO telescopes in Chile as well as the site for the future European Extremely Large Telescope (E-ELT). APEX lies close to ALMA on the 5,000-metre high plateau of Chajnantor in the Chilean Andes, where the altitude makes it a struggle to breathe.

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The positions of the telescopes used to observe the quasar. Credit: ESO/L. Calçada