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Using one galaxy to look at another – Gravitational lenses map the space in detail

We have troubles mapping our own oceans, and as soon as someone sees a strange flying light or disc in the sky, we have troubles determining what we actually saw. Still, that doesn’t stop astronomers at that National Astronomical Observatory of Japan to create the most detailed image ever made of a galaxy that is 12 billion lightyears away.

By pulling a “magic trick” out of their sleeves, the astronomers noticed they were actually looking at the first galaxy through an intermediary galaxy and its gravitational field. The light curved around the gravity field, thereby enhancing the strength of the light, similar to how lenses in telescopes work.

However, this light that is transported through another galaxy comes out in a very distorted way, not exactly making it a precise reflection of the original light source. This meant the observing astronomers had to come up with a model to compensate for any changes. The result of the modeling calculations gave the image above this article, showing the extremely remote galaxy, called SDP.81.

Several observatories cooperated to complete the study, the model and its calculations, and one of the astronomers involved in the report, which was published in PASJ, Publications of the Astronomical Society of Japan, June 9, 2015, Dr. Rob Ivison, director of science at ESO, the European Southern Observatory, shares his perspective: Alma’s huge collecting area, the large separation of its antennas, and the stable atmosphere over the Atacama desert all lead to the exquisite detail in both images and spectra. That means that we get very sensitive observations, as well as information about how the different parts of the galaxy are moving.”

ALMA stands for Atacama Large Millimeter Array, and it consists of 66 separate high precision radio telescope antennas that together form an astronomical interferometer.

While observing SDP.81, it was also detected that the intermediary galaxy showed clear evidence of a central black hole, which had not been previously confirmed. The images of SDP.81 indicates that it’s in a star forming phase, with 5,000 light years of width, containing enormous gas clouds falling towards its center.

The phenomenon of curved light occurring when passing through gravitational lenses such as this one, is called Einstein rings, and Albert Einstein meant that light would follow the curved space-time curvatures of an object. This in turn has the effect of large “magnifying glasses” being created in space by both galaxies and galaxy clusters, helping astronomers to gain an even longer and more detailed viewing range through their telescopes.

Image: National Astronomical Observatory of Japan