This is a rich cluster of galaxies 840 million light-years distant. Better known as Hydra A, Abell 780 has been thoroughly studied at X-ray wavelengths, but its fine-scale structure has largely remained a mystery to astronomers at optical wavelengths. Recent studies, however, show the cluster to have a gravitationally bound structure of 27 galaxies and a more strongly gravitationally bound structure of 14 galaxies. This GeMS/GSAOI image shows the cluster”s core in unprecedented detail.
“Our goal was to explore the structure of these galaxies at sub-kiloparsec scales,” said Rodrigo Carrasco, GeMS System Verification Team, Gemini Observatory. “This will allow us to compare the structure of these galaxies with similar objects found in the early universe.” The team selected Abell 780 because not only is it nearby but its center is dominated by a very powerful radio galaxy, known as Hydra A (also 3C 218), which has a prominent radio jet normally not detected in optical images.
“Thanks to the exquisite resolution (sharpness) provided by GeMS and GSAOI,” Carrasco said, “we can see some features of the jet, including at least two knots in the infrared, which are not visible in the optical images at similar resolution taken with the Hubble Space Telescope.”
The image also shows a number of globular star clusters surrounding this main galaxy. Such details are not seen in images that don't use adaptive optics. “We can see also several galaxies in the field that have compact morphologies,” Carrasco said, “and with details that normally are seen only from space.”