Goan priest finds Milky Way's sibling

PANAJI: Around two billion years ago, Andromeda, the largest galaxy in our celestial neighbourhood, embarked on an ambitious merger and acquisition project, walloping M32p, a long-lost sibling of our own galaxy, the Milky Way, in an act of celestial cannibalism that left behind a rich trail of evidence - a halo of stars larger than the unimaginably large Andromeda itself, and a mysterious satellite galaxy.

This was recently discovered by a team of University of Michigan researchers led by Richard D'Souza from Pilerne, a small village 8km from Panaji. Growing up in Goa in the 90s, D'Souza couldn't have imagined that he would soon be solving celestial crimes involving astronomical distances that would make headlines around the world - and all this, as a Jesuit priest.

So, when not celebrating mass or ministering to the faithful, Fr D'Souza studies how galaxies grow through mergers. "Over the course of its lifetime, Andromeda is thought to have merged with hundreds of smaller galaxies," he told STOI from Michigan. "These smaller galaxies are destroyed in the process, leaving behind a trail of stellar debris around the main galaxy, called its stellar halo."

It has long been known that stellar halos comprise the remnants of small galaxies cannibalised by larger ones. But it has also long been thought it would be difficult to learn about any single one - that is, until D'Souza and his colleague Eric Bell, of the university's department of astronomy, used computer simulations to deduce most of the stars came from the shredding of one galaxy.

"It's similar to guessing what a small child has eaten after looking at the crumbs and mess scattered on the floor," D'Souza said. D'Souza and Bell published their findings in the peer-reviewed journal Nature Astronomy last week.

Pune-born D'Souza, 40, spent his initial years in Kuwait before studying at St Britto's High School and St Xavier's College in Mapusa. Later, amid the intellectual rigour of Jesuit training, which included degrees in philosophy and theology, he got a bachelor's degree in physics from St. Xavier's, Mumbai, a master's in physics from the University of Heidelberg, Germany, and a PhD in astronomy from Ludwig Maximilian University, Munich, before joining the Vatican Observatory and then the University of Michigan for post-doc research.

While many would wonder at the seeming dichotomy of a Catholic priest at the pinnacle of science, D'Souza sees no contradiction. In this, he follows in the footsteps of Jesuit scientists like Fr George Lemaitre, who proposed what came to be known as the Big Bang Theory.

"For me, science and faith are two very fundamental ways of knowing the same reality," D'Souza said. "It is important to realise science is based on assumptions and faith. Especially in astronomy, where it is very difficult to prove something precisely, it always surprises me how much really depends on assumptions and beliefs."

Not surprisingly for a Catholic priest, D'Souza, and his science, are fuelled by faith. "Science cannot offer us meaning in life," he said. "Only something that is totally transcendental can do that, like the divine."

"Science cannot provide us meaning. Religion and faith do, and it often gives us a pretty good reason to do good science, because it becomes an expression of reaching out to this transcendent, that is, God."