Professor Sukanya Chakrabarti, School of Physics and Astronomy,
Rochester Institute of Technology
I occasionally check with astrophysicist Sukanya Chakrabarti what she has been up to since I last interviewed her a couple of years ago. Then she was busy studying what was called Galaxy X located 260,000 light years away. In particular, she was studying gravitational perturbations caused by the galaxy at the outer edge of our own Milky Way.
This is how I had explained what Dr. Chakrabarti was engaged in:
Dealing with structures of the Milky Way that seem to exist more by their gravitational signature than by actually observational fact, Dr. Chakrabarti of the University of California, Berkeley (now she is a professor at the Rochester Institute of Technology), has perfected a technique that could give scientists some key answers to deeply troubling questions. The most baffling of them relates to dark matter, which forms over 80 percent of the universe. Dark matter is a mysterious matter that cannot be seen because it does not interact with light. Its presence is inferred by the gravitational forces it exerts on matter that can be seen.
When an object that is hundreds of thousands of light years away from the earth and happens to be dimly lit the way Galaxy X is, scientists do not have much choice except to look for what they call gravitational perturbations. Dr. Chakrabarti deployed a method to predict Galaxy X that is similar to the way Neptune was discovered 160 years ago. Then Neptune was called Planet X, and hence the name Galaxy X for now.
At the heart of Dr. Chakrabarti’s work as a theoretical physicist is the conundrum arising from a major gap between what theory predicts should be the number of galaxies, known as satellite galaxies around the Milky Way, and what is actually observed. What can be seen is way less than what theory predicts.
Two years hence she has moved on to another satellite galaxy called Sagittarius or Sgr. which is about 92,630 light years from the earth. I have done an updated interview with her for an upcoming Indian Diaspora portal. I will publish it here once it has been published on the portal.
For me, conversations with someone of Sukanya’s caliber are a thrilling escape from the humdrum existence one is forced to lead. Physics in all its glory has provided an escape for me since I was in my teens. Of course, I do not understand the subject in all its complexities the way Dr. Chakrabarti obviously does but one has a broad intuitive feel for what is going on.
For instance, the idea that a satellite galaxy such as Galaxy X or Sgr., whose existence can be inferred from the gravitational perturbations they cause at the edges of the Milky Way is rather easy for me to visualize. I can actually picture in my mind’s eye the galactic gas and dust being disturbed on a scale that is truly mindboggling. It is not mindboggling in the manner that Himesh Reshamiya might describe a contestant’s singing on an Indian reality show.
Picture if you can a satellite galaxy weighing 10 billion Suns as Galaxy X does passing at its pericenter, which is the closest approach point of 22, 831 light-years of the Milky Way, and causing gravitational perturbations. That is mindboggling. The rest is just stamp collecting (with apology to Ernest Rutherford).*
Her latest paper, Dr. Chakrabarti says, shows that “the masses implied by our eccentricity-mass relation indicate that galaxies do indeed have dark matter halos. Dark matter is of course inferred from its gravitational effects.” If dark matter halos are not cool, what is?
* Rutherford’s exact quote was “All science is either physics or stamp collecting.”