Space: the final frontier... More than being immortalised as the opening monologue of Star Trek by William Shatner, these four words also describe one of the fiercest battlegrounds between the worlds of faith and reason. The unknown expanse of the cosmos and its origins have long fascinated, intrigued and terrified mankind and often pitted the clergyman against the rationalist.

However, lost in the din of rationalist criticism of religion is the fact that several clergymen have taken lead roles in furthering research into the unknown. For instance, Belgian Catholic priest and astronomer Georges Lemaitre was the first to propound what later became known as the ‘Big Bang Theory’ when he was pursuing his PhD at the Massachusetts Institute of Technology in the 1920s. And one of the people who initially opposed Lemaitre’s theory of the universe expanding was a certain Albert Einstein!

Now, a Jesuit priest-scientist, Richard D'Souza, could well be the next to follow the path of Lemaitre. D'Souza, a post-doctoral researcher at the University of Michigan, made headlines recently as he was the lead author of a study that sheds light on our galaxy, the Milky Way, having a “long-lost sibling” galaxy. This sibling galaxy was “devoured” by Andromeda, the major galaxy that is nearest to the Milky Way, about 2 billion years ago. The study, led by D'Souza, is expected to alter our understanding of how a galaxy evolves.

Forty-year-old D'Souza has an Indian connection. He hails from Goa and grew up in Kuwait. After joining the Jesuits, he began his college education at St Xavier’s College in Mumbai, which eventually led him to earn his PhD in astronomy from Ludwig Maximilian University, Munich, in 2016. D'Souza, who works with the Vatican Observatory, is currently pursuing his post-doctoral studies in Michigan. In a conversation with THE WEEK, D'Souza gave insights into his work, what motivates him and the science-faith debate:

Can you explain what the nature of your research in astronomy is?

I study the growth and evolution of galaxies. Galaxies grow either by forming their own stars or by merging with other smaller galaxies. In the last few years, I have been focusing on the latter process. In particular, I am interested in studying what mergers do to galaxies. Do the properties of the main galaxy change after an impact with a smaller galaxy? By using a combination of computer models and observations, I tried to reconstruct the merger history of a particular galaxy.

... As a Catholic priest, what made you choose astronomy? Is it to show faith and science can be harmonious and prove God does exist?

I have always been interested in science, and as a person of faith, I believe in God and in his creation. For me studying the universe helps me learn more about its creator. Hence for me, studying astronomy, the stars and the galaxies is a form of worship. My Jesuit superiors have always encouraged me to pursue the study of astronomy and have destined me to work for the Vatican Observatory. Ultimately, I hope that my scientific research demonstrates that the Catholic Church is not against science, and that science and faith can mutually coexist and help each other.

A Vatican observatory was first established in 1774; would you argue that its work in astronomy has helped change the image of the Catholic Church, which has often been associated with the hounding of the likes of Galileo, Copernicus and Kepler?

In re-founding the Vatican Observatory in 1891, Pope Leo XIII wanted a scientific organisation that demonstrated that everyone might see clearly that the Church and her pastors are not opposed to true and solid science ... but that they embrace it, encourage it and promote it.

Over the years, the Vatican Observatory tries to do this—not only in doing frontier research, but to demonstrate through our research that the Catholic Church is not opposed to good and true science. It is rather unfortunate how things played out in the life of Galileo; most of the happenings were connected with power struggles within the church. It must be emphasised that Galileo, till the end of his life, remained a good Catholic and one of his daughters was a nun.

What impact do you think your recent finding—the discovery of a long-lost sibling galaxy of the Milky Way—will have in boosting our understanding of the universe?

First, it is just cool to realise that there was a large galaxy, the third-largest member of the Local Group after the Andromeda and the Milky Way galaxies, and we did not know anything about it. Furthermore, this finding gives us the confidence that if we could solve part of the merger history of the Andromeda galaxy (for which we have the best data because of its proximity to us), then we could begin to unravel the merger history of more distant galaxies.

Finally, we have learned some important lessons from this finding: the disk of the Andromeda galaxy survived this massive merger and probably thickened in the process. We are confident that our own galaxy, the Milky Way, will survive the eventual collision with its satellite galaxy, the Large Magellanic Cloud, in about 1-2 billion years. In the future, we are confident that we will eventually unravel what mergers do to other galaxies.

What are the areas of astronomy you would like to venture into?

I would like to carry on with my current research into understanding what mergers do to galaxies. Eventually, I would also like to study our own Milky Way galaxy, and understand which of the properties of the Milky Way are due to mergers and which are due to its own evolution. Finally, I also would like to study the various physical processes that shape the growth and evolution of galaxies.

Being a Catholic priest, how 'different' do you feel while among fellow scientists, who are almost always perceived to be rationalists/sceptics?

Most scientists are often pleasantly surprised that I am a Catholic priest. This is because the members of the Vatican Observatory have set a good precedent in this academic field. Everywhere I go, I find that scientists know who they [Vatican Observatory researchers] are, and that they are well loved and accepted. Sometimes, I do encounter a few “younger” rationalists and sceptics, but these initial feelings soon go away once we start talking about science!

And how would you answer the 'believers/creationists'? Would people who believe the earth was formed in six days be comfortable to hear a priest talk of galaxies formed billions of years ago?

Before starting my PhD in astronomy, I taught biblical theology for about two years in Goa, catering towards the educated laity! Most people misunderstand the Catholic Church’s teaching on creation, or the Church’s position on Genesis, the first book of the Bible.

In fact, the first few chapters of Genesis are one of my favourite portions of the Bible and are a rich theological resource of the Christian understanding of the human person and the world. Much of our Christian ideas come from those chapters! I wish, in general, Christians and, in particular, these ‘creationists’ would learn some more theology, beyond what is taught to children. This is why Pope Leo XIII insisted way back in 1891 that through the research and work of the members of the Vatican Observatory, we educate both the clergy and the laity about the Catholic Church’s teaching!

And finally, you spent years in India ministering as a priest before leaving for pursuing doctoral studies. Any plans to return?

I would love to come back to India; I always enjoy visiting, especially my parents in Goa. Some of my happiest years were the initial ones where I taught biblical theology for the laity in Goa. However, I am at the disposal of my Jesuit superiors. If there is an urgent need, they will mission me back to India.