Thursday, June 5, 2014

ESO ALMA upgrade to supercharge Event Horizon Telescope

ALMA's new hydrogen maser atomic clock arrives and is ready for installation at the ALMA high site. Supplemental oxygen is used due to the thin air at that altitude (5,000 meters, 16,500 feet).

The team includes Jay Blanchard, Univ. Concepcion (left); Christophe Jacques, NRAO (front); Jack Meadows, NRAO (back); and Enrique Garcia, ALMA Correlator Group (right, partly obscured). Credit: Carlos Padilla (NRAO/AUI/NSF)

Scientists recently upgraded the Atacama Large Millimeter/submillimeter Array (ALMA) by installing an ultraprecise atomic clock at ALMA's Array Operations Site, home to the observatory's supercomputing correlator.

This upgrade will eventually allow ALMA to synchronize with a worldwide network of radio astronomy facilities collectively known as the Event Horizon Telescope (EHT).

Once assembled, the EHT, with ALMA as the largest and most sensitive site, will form an Earth-sized telescope with the magnifying power required to see details at the edge of the supermassive black hole at the center of the Milky Way.

Before ALMA can lend its unmatched capabilities to this and similar scientific observations, however, it must first transform into a different kind of instrument known as a phased array.

This new version of ALMA will allow its 66 antennas to function as a single radio dish 85 meters in diameter. It's this unified power coupled with ultraprecise timekeeping that will allow ALMA to link with other observatories.

A major milestone along this path was achieved recently when the science team performed what could be considered a "heart transplant" on the telescope by installing a custom-built atomic clock powered by a hydrogen maser.

This new timepiece uses a process similar to a laser to amplify a single pure tone, cycles of which are counted to produce a highly accurate 'tick'.

ALMA's original time reference, a clock based on rubidium gas, will be retired and used as a spare after the maser is completely integrated with ALMA's electronics.

Shep Doeleman, the principal investigator of the ALMA Phasing Project and assistant director of the Massachusetts Institute of Technology's Haystack Observatory, participated during the maser installation via remote video link.

"Once the phasing is complete, ALMA will use the ultraprecise ticking of this new atomic clock to join the aptly named Event Horizon Telescope as the most sensitive participating site, increasing sensitivity by a factor of 10," he said.

Expanding the Frontiers of Astronomy
Supermassive black holes lurk at the center of all galaxies and contain millions or even billions of times the mass of our Sun. These space-bending behemoths are so massive that nothing, not even light, can escape their gravitational influence.

Understanding how a black hole devours matter, powers jets of particles and energy, and distorts space and time are leading challenges in astronomy and physics.

The black hole at the center of the Milky Way is a 4 million solar mass giant located approximately 26,000 light-years from Earth in the direction of the constellation Sagittarius.

It is shrouded from optical telescopes by dense clouds of dust and gas, which is why observatories like ALMA, which operate at the longer millimeter and submillimeter wavelengths, are essential to study its properties.

Supermassive black holes can be relatively tranquil or they can flare up and drive incredibly powerful jets of subatomic particles deep into intergalactic space; quasars seen in the very early Universe are an extreme example.

The fuel for these jets comes from in-falling material, which becomes superheated as it spirals inward.

Astronomers hope to capture our Galaxy's central black hole in the process of actively feeding to better understand how black holes affect the evolution of our Universe and how they shape the development of stars and galaxies.

ALMA maser installation team in front of a small portion of the ALMA antennas. Left to right: Jay Blanchard, Univ. Concepcion; Jack Meadows, NRAO; Neil Nagar, Univ. Concepcion; and Christophe Jacques, NRAO. Credit: Carlos Padilla (NRAO/AUI/NSF)

A phased ALMA will arrive just in time to observe a highly anticipated cosmic event, the collision of a giant cloud of dust and gas known as G2 with our Galaxy's central supermassive black hole.

It is speculated that this collision may awaken this sleeping giant, generating extreme energy and possibly fueling a jet of subatomic particles, a highly unusual feature in a mature spiral galaxy like the Milky Way. The collision is predicted to begin in 2014 and will likely continue for more than a year.

High resolution imaging of the event horizon also could improve our understanding of how the highly ordered Universe as described by Einstein meshes with the messy and chaotic cosmos of quantum mechanics – two systems for describing the physical world that are woefully incompatible on the smallest of scales.

Other independent research will target molecules in space to determine whether or not the fundamental constants of nature have changed over cosmic time.

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