Goa PIO leads Nasa team to find the farthest group of galaxies

PANAJI: An international team of astronomers linked to Nasa, led by an Indian-origin Goa-born scientist, Vithal Tilvi, have discovered a never-before-seen group of galaxies, now labelled EGS77, which is the farthest group of galaxies to have ever been sighted.

In 2013, Tilvi was also part of a team that discovered the farthest single galaxy ever sighted by astronomers. The new group of galaxies, EGS77, is estimated to be over 13 billion light years away from the Earth. It took Tilvi and team over four years to make the findings.

This group of galaxies can now help astronomers see the universe directly in its infancy, and see what were the chemicals present when the universe was just born. “As we look farther and farther, we are looking back in time. This is because, the starlight which carries information about the galaxy group, is reaching the Earth now, after travelling for 13 billion years,” Tilvi told TOI.


“Usually, it is difficult to see galaxies as far as EGS77 because of the presence of neutral hydrogen fog in the universe, which blocks some of the galaxy light,” James Rhoads of Nasa, a team member, said.

Fortunately, intense heat from these same galaxies clears the surrounding hydrogen fog, allowing galaxy light to travel freely to the Earth. Galaxies and galaxy group such as EGS77 must have cleared all the hydrogen fog, leading to the transition from opaque to a transparent universe that we see today. “This is a tremendous achievement and will advance our knowledge about how the universe evolved,” Tilvi said.

In 2013, Tilvi’s team discovered farthest galaxy
The findings of the discovery of EGS77 are being presented for the first time on January 5, at the American Astronomical Society conference in Hawaii.

“While this is the first galaxy group identified as being responsible for clearing hydrogen fog, future Nasa missions will tell us much more,” said Sangeeta Malhotra at Nasa, co-author of the paper “Onset of Cosmic Reionization: Evidence of An Ionized Bubble Merely 680 Myr (million years) after the Big Bang”.

In 2013, Tilvi was part a team that discovered the farthest galaxy in the universe and, in 2017, he led a team of astronomers that discovered the earliest black hole candidate in the universe.

Currently, he is the project leader for a Nasa-funded project to study this black hole using observations taken by the Hubble Space Telescope. Tilvi is also part of the NASA’s Wide Field Infrared Survey Telescope (WFIRST) team, which is going to be launched in 2025.

The distance of EGS77 from the Earth means it is at the very edge of what can be observed using the current best technology on a platform like the Hubble Space Telescope.

“The current telescopes we have, like the Hubble Space Telescope, were not meant to discover galaxies this far. But we are pushing the limits. In another one and a half years, James Webb Telescope will be launched, which is much bigger than Hubble Space Telescope, and our plan is to use this new telescope to see groups like EGS77,” Tilvi said.

Tilvi is currently a visiting researcher at the School of Earth & Space Exploration, at the Arizona State University, US, and is contributing to State Higher Education Council of the government of Goa as a professor of research, development, and innovation.