The Hubble Space Telescope pushed beyond its limits observing a distant galaxy through a gravitational lens

The galaxy SGAS J111020.0+645950.8 (Image NASA, ESA, and T. Johnson (University of Michigan))
The galaxy SGAS J111020.0+645950.8 (Image NASA, ESA, and T. Johnson (University of Michigan))

Three articles published in “The Astrophysical Journal Letters” describe various aspects of the observation of the galaxy SGAS J111020.0+645950.8, 11 billion light years away from Earth, with the Hubble Space Telescope. So much attention is due to the fact that the team of astronomers who conducted this study had to use a gravitational lens to conduct the observations and use a very sophisticated analysis to sharpen the images, which also show star formation areas.

The use of gravitational lenses has become a routine in the field of astronomy, so much that the galaxy SGAS J111020.0+645950.8 is one of more than 70 galaxies studied using the Hubble Space Telescope by exploiting this possibility. It was among the targets of follow-up observations selected by the Sloan Giant Arcs Survey (SGAS), which discovered hundreds of galaxies visible with gravitational lenses looking among the data from another survey, the Sloan Digital Sky Survey (SDSS).

In this case between the target of the observations and the Earth there was in the middle, almost literally being about 6 billion light away from Earth, the galactic cluster SDSS J1110+6459. It bends the light coming from the galaxies behind it with the force of gravity of the hundreds of galaxies that compose it, a phenomenon predicted by Einstein’s general relativity.

This type of observation normally produces bright arcs such as the one visible on the left side of the image because the gravitational lens has as its effect a distortion of the galaxy’s light. For this reason, it’s necessary to apply computer algorithms to reconstruct the target’s real appearance, visible in the center-right inset of the image. The distortion caused on the light from a distant galaxy such as SGAS J111020.0+645950.8 forced the astronomers to develop a computer analysis more sophisticated than normal to achieve that reconstruction.

The result was excellent, with images 10 times sharper than the Hubble Space Telescope could get on its own. This allowed to discover a couple of dozen star formation areas that look like gas and dust lumps. Their structure was surprising for the researchers.

So far the models of star formation in the early universe indicated that the areas where they took place had sizes in the order of 3,000 light years. Instead, the ones detected in the galaxy SGAS J111020.0+645950.8, which appears to us as it was when the universe was “only” 2.7 billion years old, have sizes between 200 and 300 light years.

Traci Johnson of the University of Michigan, the lead author of two of the three articles, explained that star formation areas are visible thanks to the gravitational lens and without it the astronomers would see very different images of the areas where new stars are forming. Models are developed by scientists based on observations so the observations’ quality influences the models’ quality.

This research pushed the possibilities of the Hubble Space Telescope beyond its limits forcing the scientists to improve the processing techniques of the image obtained through gravitational lenses. The galaxy SGAS J111020.0+645950.8 was added to the already very long list of objects to be observed with the James Webb Space Telescope, which will allow to see older stars that formed earlier and through the dust inside the galaxy.

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