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ALMA captures sharpest ever view of star formation in the distant universe

ALMA captures sharpest ever vi...
Lensed image of galaxy SDP.81 as taken by ALMA
Lensed image of galaxy SDP.81 as taken by ALMA
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Lensed image of galaxy SDP.81 as taken by ALMA
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Lensed image of galaxy SDP.81 as taken by ALMA
Star-forming regions present in SDP.81
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Star-forming regions present in SDP.81
Hubble Space Telescope image of the region – SDP.81 is faintly visible as an Einstein ring behind the central galaxy
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Hubble Space Telescope image of the region – SDP.81 is faintly visible as an Einstein ring behind the central galaxy

The Atacama Large Millimeter/submillimeter Array (ALMA) has succeeded in imaging star formation regions in adistant galaxy, with a resolution six times greater than thatachievable by the Hubble Space Telescope. The galaxy, dubbed HATLASJ090311.6+003906 or SDP.81, would ordinarily be far too distant to beobserved in such impressive detail. However, thanks to an amazingcosmic coincidence, it has fallen foul of a phenomenon known asgravitational lensing, which essentially grants astronomers theopportunity to gaze into the distant past.

First predicted byAlbert Einstein as an element of his theory of general relativity,gravitational lensing occurs when a nearby galaxy is perfectlyaligned between a more distant galaxy and Earth. This nearby galaxyhas the effect of warping spacetime, and any light emitted from themore distant galaxy would pass through this lensing effect, becominggreatly magnified, but also heavily distorted in the process.

Hubble Space Telescope image of the region – SDP.81 is faintly visible as an Einstein ring behind the central galaxy
Hubble Space Telescope image of the region – SDP.81 is faintly visible as an Einstein ring behind the central galaxy

Thankfully, astronomersnow have tools that allow them to heavily minimize the detrimentaleffects of gravitational lensing. This particular class ofgravitational lens is known as an Einstein ring.The faintness of the center of the image acts as an indicator for themass of the celestial object that eclipses it. Based on the fact thatthe center of SDP.81's image is essentially invisible, it is believedthat the foreground galaxy hosts a supermassive black hole at itsheart, 200 - 300 million times the mass of the Sun.

In order to make themost of the lensing effect, the 66 high-precision antennas that makeup ALMA were separated by 15 km (9.3 miles), providing the greatest possibledetail.

These factors workingin concert have allowed astronomers to view the distant galaxy as itwas 2.4 billion years after the Big Bang, when the Universe was only15 percent its present age. It is estimated that the light fromSDP.81 took 11.4 billion years to reach us, allowing astronomers toobserve instances of ancient star formation.

Star-forming regions present in SDP.81
Star-forming regions present in SDP.81

By examining thespectral characteristics of SND.81, astronomers have been able toestimate the galaxy's mass and rotation. We can see vast clouds ofgas collapsing inward, ready to explode into regions of fierce starformation. Furthermore, the clarity of the data returned by ALMA issuch that astronomers were able to pick out a number of massive,active stellar formation regions down to a scale of 200 light-yearsthat share many characteristics with the famous Orion Nebula.

"The reconstructed ALMAimage of the galaxy is spectacular," states Rob Ivison, ESO’sDirector for Science and co-author of two of the papers on thefindings. "ALMA’s huge collecting area, the largeseparation of its antennas, and the stable atmosphere above theAtacama desert all lead to exquisite detail in both images andspectra. That means that we get very sensitive observations, as wellas information about how the different parts of the galaxy aremoving. We can study galaxies at the other end of the Universe asthey merge and create huge numbers of stars. This is the kind ofstuff that gets me up in the morning."

The video below courtesy of ESO displays how light from a distant background galaxy is distorted by the foreground galaxy.

Source: ESO

Gravitational lensing of distant star-forming galaxies (schematic)

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