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.

Van Allen Probes: Giant Electric Fields Supercharge Particles In Radiation Belts

Huge electric fields in the radiation belts around Earth may help explain how electrons surrounding the planet can be accelerated to speeds near that of light, researchers have found in a new study.

These findings, detailed Dec. 2 in the journal Physical Review Letters, could help shed light on the radiation belts of planets such as Jupiter, Saturn, Uranus and Neptune, as well as the behaviour of the sun during flares and of bodies beyond the solar system, such as stellar nurseries, neutron stars and incredibly energetic black holes known as quasars.

After humanity began exploring space, the first major find made there were the Van Allen radiation belts, zones of magnetically trapped, highly energetic charged particles discovered in 1958.

The Van Allen Probes aka Radiation Belt Storm Probes (RBSP) Mission, part of NASA's Living With a Star program, will provide unprecedented insight into the physical dynamics of the radiation belts. 

Credit: NASA

These belts generally consist of two rings: 

• an inner zone with both high-energy electrons and very energetic positive ions that remains stable in intensity over the course of years to decades; and
• an outer zone made up mostly of high-energy electrons whose intensity swings over the course of hours to days, primarily depending on the influence from the solar wind, the deluge of radiation streaming from the sun. 

Earlier this year, scientists also detected a third radiation belt temporarily surrounding Earth.

The gigantic amounts of radiation the Van Allen belts generate can pose serious risks for satellites. To learn more about them, NASA launched twin spacecraft, the Van Allen probes, in the summer of 2012.

The satellites are armed with a host of sensors to comprehensively analyze the plasma, energetic particles, magnetic fields and plasma waves in these belts with unprecedented sensitivity and resolution.

Two giant swaths of radiation, known as the Van Allen Belts, surrounding Earth were discovered in 1958. In 2012, observations from the Van Allen Probes showed that a third belt can sometimes appear. 

The radiation is shown here in yellow, with green representing the spaces between the belts. 

Credit: NASA/Van Allen Probes/Goddard Space Flight Center.

Now, using the Van Allen probes, scientists have detected structures that pop in and out of existence in the outer belt that could help explain the high-energy electrons seen in that zone.

The structures in question are known as "double layers." They are each made up of a pair of parallel layers of particles with opposite electrical charge that move along Earth's magnetic field.

The probes saw huge numbers of double layers in the outer belt —7,000 in the course of a minute, each lasting on the order of seconds.

These double layers were discovered "sort of by accident as the Van Allen probes passed through this region of space, and only captured a snapshot," said study lead author Forrest Mozer, a physicist at the University of California, Berkeley.

"The spacecraft will get back to this region maybe eight months, maybe 10 months from now, and we're setting up our instruments to do what we now know they should — to collect data at that site then with a continuous view, to really get definitive information on what is going on there."