ALMA Extends Its Arms

The Atacama Large Millimeter/submillimeter Array (ALMA) has successfully tested an antenna in the most extended configuration of the array yet — the longest sub-millimetre baseline ever achieved. This advance became possible once the first of ALMA’s three extended arms was successfully powered up for the first time, and opens up the possibility of greatly extending ALMA’s capabilities. With longer baselines, the ability of a radio telescope to see fine detail increases, allowing astronomers to uncover much more information about objects observed in the Universe.

Lore, one of ALMA’s two tailor-made antenna transporters, made its first journey along the Pampa la Bola arm and for the first time relocated an antenna to a position more than seven kilometres away from its furthest neighbour. This marks a major new technical achievement in the Atacama Desert in Chile, at more than 5000 metres above sea level.

This new seven-kilometre antenna separation more than quadruples the longest ALMA baseline currently available to the scientific community. ALMA’s ability to reveal fine detail in astronomical sources now significantly exceeds that of the NASA/ESA Hubble Space Telescope.

Catherine Vlahakis, Lead Program Scientist for the ALMA Long Baseline Campaign says that: “successfully powering up an antenna for the first time over these long distances marks an important technical step towards increasing ALMA’s ability to see objects in the Universe in fine detail“.

Ed Fomalont, Lead Scientist for the ALMA Long Baseline Campaign, explains that “the combination of the signals from the antennas produces patterns called fringes. The fringes measured from the antenna seven kilometres away were as pure and strong as will be needed to obtain high quality images when additional antennas are moved to these long baselines.”

Catherine Vlahakis, adds that “this is the first step in a process of moving several antennas out to these longer distances. Once the rest of the antennas are also in place we will be able to begin test observations of astronomical objects at higher angular resolution, and therefore in more exquisite detail, than ALMA has yet achieved.“

Observations that will fully test extended configurations of the array will continue over the next three months. If all goes as intended, this process will provide astronomers with the knowledge needed to offer long-baseline observations to the scientific community.