The Atacama Large Millimeter/submillimeter Array (ALMA) recently came online, becoming the world’s most powerful ground based observatory. One of the first examples of its awesome power is the image of an almost-perfect Einstein ring, which shows general relativity in action, writes Ian O’Neill for Discovery.
ALMA: Scientists profit from wide-baseline collection
The ALMA Long Baseline Campaign took place at the end of 2014, and saw the antennae take up their widest separation of some 9.3 miles. Scientists spotted the ancient galaxy known as SDP.81 during this time, and its light had been bent around warped spacetime thanks to the presence of a massive galaxy between it and the Earth.
This phenomenon is known as gravitational lensing, and relates to distant sources of light which are warped by massive objects. They are commonly spotted by Hubble, but ALMA stole the show this time. A gravitational lens allows scientists to see further into the cosmos than was previously possible, and bright arcs of light are usually observable.
It is possible for these arcs to join together and form rings if the conditions are just right, and the ALMA image is one of the best Einstein rings we have seen. Scientists can even de-warp the light and put it back together again in order to look at galaxies that would usually be too far away for existing equipment to see.
Largest ground-based telescope proves its power
ALMA improved the resolution of the ring in order to reveal new levels of detail in the young galaxy SDP.81. Long-baseline interferometers such as ALMA provide a wider collecting area than even the biggest space-based telescope mirrors.
As well as capturing this amazing image of SDP.81, the ALMA Long Baseline Campaign also studied Mira, a star, an asteroid known as Juno, quasar 3C138 and the protoplanetary disk which surrounds HL Tauri. The capabilities of ALMA allow for detailed study of distant space objects that was never possible before, and the observatory could lead to major advances in the field.