“Understanding the past is the pathway to understand our future…

… by observing how galaxies, stars, planets, dark matter, dark energy have evolved over time, astronomers are able to build models that allow us to predict the future evolution of our own galaxy, human civilization…”

Encounter

Dr Shardha Jogee, Professor of Astronomy, University of Texas

(the journey of science exploration belongs to everyone, and we get the best far-reaching results by having diverse teams – where does this fit?)

After over twenty years of planning and 10 billion US dollars in expenses, NASA launched the James Webb Space Telescope (JWST) — the most powerful space telescope every built and launched – in December 2021. The first science data are transforming our views of the Universe, says Dr Shardha Jogee, Professor and holder of the Rex G. Baker, Jr. and McDonald Centennial Professorship on the Department of Astronomy at the University of Texas (UT) at Austin. Her research group in the USA has led some of the early important discoveries with JWST in the last few months. This month the results have been shared with the public by over 60 media outlets (written or TV) all over the USA and in countries across six continents

At UT Austin, Dr Jogee leads a scientific research program to explore how galaxies and their constituent stars, black holes and dark matter grow across cosmic time, and she also teaches undergraduate and PhD students. Her research uses NASA’s space telescopes, McDonald Observatory and other ground telescopes, as well as the Texas Advanced Computing Centre. Dr Jogee is a member of several international science teams, has won over $3.4 millions in grant funding from NASA, the National Science Foundation, the Department of Defense and published 190+ papers with over 7,750 citations.

Dr Jogee credits the power of education for enabling her to pursue her dream of becoming an astrophysicist. She is a proud member of Leadership Texas 2014, a public voices fellow with the OpEd Project, and strongly supports a broader participation of women and under-represented groups in STEM and the essential partnership between universities, federal agencies, and philanthropists in advancing society.

* The wellspring of astronomy and astrophysics is said to be basic human curiosity about the universe, and our place within it. Was it that same curiosity that brought you to the USA and to the world of astronomy and astrophysics?

Science and the quest to understand the universe have no geographical boundaries. When I was around 15 years old, I fell in love with the field of Physics, its objectivity and elegance, and how it tries to explain the diverse phenomena around us. I was fascinated by how science constantly questions and re-evaluates itself when faced with new facts on new scales. Thanks to the excellent high school education I received in Mauritius and my amazing parents who infused me with the idea that nothing is outside our reach if we work hard and aim high, I won a full scholarship to pursue a Bachelor’s degree in Physics at Cambridge University in England, and later a scholarship to pursue a PhD in Astronomy at Yale University in the USA.

Of all the possible sub-fields of physics, I picked astronomy (also called astrophysics) as it applies the laws of physics on the largest scales to address the most fundamental questions about our universe and our place in it. How did stars, planets, galaxies, black holes, and the chemical elements for life form and evolve? What are the opportunities for life outside our solar system? What is the nature of the dark matter and dark energy that make up most of the universe? What is the ultimate fate of the Universe?

After my PhD, I conducted scientific research at Caltech and the Space Telescope Science Institute, which oversees the scientific operations of NASA’s space missions. In 2004, I was honoured to join the faculty in the Department of Astronomy at the University of Texas at Austin (UT Austin), which is ranked as one of the top programs in space science in the USA.

* What is the nature of your work as a faculty member in the Department of Astronomy at UT Austin?

I teach and supervise students at the Bachelor and PhD levels, serve on different national committees, and lead a research program that explores how galaxies and their constituent stars, black holes and dark matter grow across cosmic time. My research program uses NASA’s space telescopes such as the Hubble Space Telescope and the James Webb Space Telescope, ground-based telescopes, as well as the Texas Advanced Computing Center (TACC).

While conducting research, I tremendously enjoy simultaneously training the next generation of young scientists. I believe that the journey of science exploration belongs to everyone, and we get the best far-reaching results by having diverse teams. I am passionately committed to advancing inclusive excellence and a broader participation of women and other groups traditionally under-represented in STEM. I also believe it is essential for scientists to tell the public at large what we do, how we do it and why we do it.

*Billions of US dollars are being spent in space telescopes and other equipment in the US alone for such research programs. Why is it important to understand galaxies? Are they important to our existence?

Galaxies are the fundamental building blocks of our universe.An individual massive galaxy can contain trillion of stars like our sun, as well as hydrogen gas, and dark matter. Most of the mass of a galaxy is in the form of dark matter, which refers to matter that does not emit light and manifests itself through the force of gravity.

The galaxy where our sun resides is called the Milky Way (“La Voielactée”), and astronomers have discovered over a billion other galaxies in the universe.Astronomers conduct observations to probe how galaxies formed more than thirteen billion years ago evolved to their present-day state, and they use these observations to refine the laws of physics and build better models of galaxies and the universe. These models in turn allow us to predict the future evolution of our own galaxy, and future pathways for human civilization.

For example, we know that in about 4 to 5 billion years, our Milky Way galaxy will merge with the neighbouring M31 (Andromeda) galaxy. This merger will change the orbits of stars in our galaxy and have other important consequences.

* We understand that your recent work with the James Webb Space Telescope has attracted a lot of media attention in the USA, especially in space research circles. What are the new discoveries that have been made and do they challenge the existing theoretical model(s) about the universe?

On December 25, 2021, after two decades of planning, NASA launched the James Webb Space Telescope (JWST) — the most power space telescope ever built. JWST aims to provide the deepest eyes on the universe and inform the quest to understand our origins.

When the first JWST data started to arrive in summer 2022, I was blown away by the sheer power of the JWST high-resolution infrared images. And I was stunned to see that the JWST images were revealing galaxies with stellar bars at early cosmic epochs.

I immediately redirected my research program to focus on this important discovery. My research group conducted an in-depth quantitative analysis, and we were the first team to report the discovery of barred galaxies like our own Milky Way at early cosmic epochs when the young universe was a mere 20% of its present age.

Our paper, led by my PhD student, was accepted for publication in the high-impact peer reviewed journal The Astrophysical Journal Letters in November 2022. Our JWST image, press release (https://news.utexas.edu/2023/01/05/james-webb-telescope-reveals-milky-way-like-galaxies-in-young-universe/), and KXAN/NBC science coverage(https://www.youtube.com/watch?v=uRQA0BDuvd4) garnered worldwide interest, receiving over 198 million views in January 2023.

This result on barred galaxies like our own Milky Way in the young universe is important for several reasons.

First, stellar bars solve the supply chain problem in galaxies by transporting gas from the outer parts of the galaxy into the central regions where the gas is very rapidly converted into new stars. Second, bars also partially help to grow central supermassive black holes in galaxies by driving gas part of the way it needs to go on its journey toward the black hole. Third, observations of young, barred galaxies can effectively stress test and improve theoretical model of galaxy evolution because these models cannot reproduce such barred galaxies unless they correctly model the gas, stars, and dark matter in the galaxy.

Right now, there are several models that cannot reproduce our observations and therefore have to go back to the drawing board and see which aspects of the physics they may be getting wrong.

* A report by Fox News quotes theoretical physicist Dr Michio Kaku explaining the significance of new images provided by NASA’s Webb Space Telescope (WST) saying that JWST allows us to ‘look into the past’. Will the understanding of our past enlighten us about how our future will evolve?

As I explain in the KXAN/NBC science coverage, JWST images of distant galaxies act as time-machines and allow us to look back in time. This happens because the light we are collecting today with JWST from a distant galaxy took several billions of years to travel from that distant galaxy to us, and therefore the JWST images tell us how the galaxy looked like billions of years ago when the Universe was much younger.

Yes, understanding the past is the pathway to understand our future. By observing how the constituents of our universe (e.g., galaxies, stars, planets, dark matter, dark energy) have evolved over time, astronomers are able to refine the laws of physics and build models that predict how the Universe, and its constituents evolve. These models in turn allow us to predict the future evolution of our own galaxy, human civilization, and ultimately the universe.

* Is the Big Bang followed by an unlimited expansion, slow cooling and ultimate death of our galaxy and, later, the Universe itself still the accepted model of the Universe?

Essentially yes, the Big Bang model is still part of the main paradigm of cosmology.The Universe is observed to have an accelerating expansion, which is believed to be caused by dark energy dominating over gravity from matter.

Different theories have been put forward on the nature of dark energy, including a vacuum energy related to Einstein’s cosmological constant, a new field called quintessence, and the possible breakdown of the laws of gravity and general relativity on the largest scales in the Universe.

At the moment, no one really knows which of these theories, if any, is correct.Ongoing surveys to shed light on the nature of dark energy could determine the fate of the Universe and confirm or rule out scenarios, such as a Big Rip or Big Freeze.

Mauritius Times ePaper Friday 24 March 2023