A recent
intergalactic discovery making headlines across
the world has an Indian connection. Earlier this week, it was widely reported that
scientists Richard D’Souza and Eric Bell of the University of Michigan had
deduced that the Milky Way once had a sibling, which was devoured by the
neighbouring galaxy of Andromeda about two billion years ago.
The findings were published
in the Nature Astronomy journal
on July 23 and have grabbed attention for their potential to change our
understanding of how galaxies merge and evolve over time.
When two galaxies are drawn together by gravitational pull, they
stand the risk of colliding. In such an event, the larger one usually subsumes
the smaller entity. Andromeda, the largest galaxy of the Local Group of which
Milky Way is also a part, was long believed to have gobbled up several small
galaxies over the years. Using computer simulations, D’Souza and Bell deduced
that one of the galaxies that Andromeda merged with was in fact a massive one,
the third-largest in the Local Group after the Milky Way.
The researchers have proposed
that the stars of this shredded galaxy ended up surrounding Andromeda, giving
it its outer faint stellar halo, and its intriguing satellite galaxy, M32.
Scientists have for long being trying to decipher how M32 was formed, as it is
a rare compact elliptical galaxy (unlike the Milky Way, which is spiral) that
is rich with stars. The new findings propose that the undestroyed core of the
cannibalised galaxy went on to form M32.
Described in media reports as Milky Way’s sibling or sister, the
lost galaxy has been named M32p. The findings are interesting not only because
they indicate that M32p’s core survived the collision, but also that the disk
of Andromeda remained intact despite merging with such a large galaxy. This
goes against traditional scientific belief that collisions between entities of
this size would dramatically impact the structure of the surviving galaxy.
D’Souza, the lead author of
the paper, comes from the Indian state of Goa, where his family still lives. He
is doing his post-doctoral research at the University of Michigan. D’Souza is
also a Jesuit priest and is a staff member of the Vatican Observatory, an
astronomical institution supported by the Roman Catholic Church.
D’Souza has had a long and illustrious academic record and
has studied an interesting mix of subjects. He was born in 1978 in Pune and
spent his early years in Kuwait. In 1990, he moved to Goa, where his family
still resides, and joined a Jesuit school. He did his BSc in Physics from St
Xavier’s College, Mumbai, followed by an MSc at the University of Heidelberg in
Germany. He then returned to Pune and got a second Bachelor’s degree in
Philosophy, followed by one in Theology. He got his PhD in Astronomy from the
Ludwig Maximilian University is now doing his post-doctorate from the
University of Michigan.
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