Cosmic recycling strengthens stellar Spiderweb theory

Eight years ago Dr Nina Hatch , an astronomer at The University of Nottingham , identified a thin haze around a distant galaxy known as the Spiderweb galaxy. She suggested this haze was made up of rapidly forming young stars. But the problem with this research, published in the academic journal Royal Astronomical Society , was that no one knew where this young stellar population could be coming from.

Over the intervening years, and with a lack of additional evidence, Dr Hatch, from the School of Physics and Astronomy , began to get increasingly worried about her theory. But no longer.

Fellow astronomers, led by Dr Bjorn Emonts from the Centro de Astrobiología in Spain, have observed the first clue suggesting she was right all along. They have identified a giant reservoir of molecular gas that is replenishing the fuel supply to this young galaxy - feeding the development of new stars. In light of her discovery Dr Hatch was asked to write an article for Science giving her insight into this latest twist in the Spiderweb galaxy story.

The Spiderweb galaxy is so distant we are seeing it when the universe is only a quarter of its current age – just three billion years after the big bang. It is one of the most massive galaxies in the universe and has all the hallmarks of a galaxy caught in the act of forming. Its morphology resembles a spider’s web with a mature galaxy at the centre surrounded by a web of diffuse ultraviolet light with tens of smaller galaxies that resemble flies caught in the web.

Dr Hatch said: “I was beginning to wonder if I had made a mistake as there were several other things this haze could have been, but here is the information that was missing. It’s so rewarding to know that my theory has finally been confirmed.”

Closing the gap in our understanding of galaxies

There is still a lot to learn about how young galaxies end up being so big so early so Dr Hatch’s original theory was a bold one.

Dr Hatch says: “The gap in our understanding is how to feed the galaxies with enough raw material to form. A constant supply of cold gas is required to fuel the rapid formation of stars. Cold primordial gas is prevented from simply streaming through to fuel star formation in massive galaxies. When gas falls towards the galaxies it is heated by shocks to a few million degrees, forming hot halos that identified a giant reservoir of molecular gas that is replenishing the fuel supply to this young galaxy - feeding the development of new stars."

Dr Hatch hopes the detection of this vast cloud of recycled molecular gas may help solve the mystery of how massive galaxies grow. But she warns it also throws up new questions. You can read the full Insight article here.