Preferred pronoun: she/her. Astronomy PhD researcher at Kapteyn Astronomical Institute in Groningen with a big love for the oldest stars and structures in the universe. The Milky Way is my laboratory and metal-poor stars are my time machines!
Biography
Hello visitor!
I am an observational astronomer in the field of Galactic Archaeology and a final-year PhD research investigating the shenanigans of the infant Milky Way galaxy. I'm in this mission with the guidance of Else Starkenburg and Amina Helmi . I am specifically interested in the Milky Way halo where you have higher odds of finding these amazing metal-poor stars, being mostly ancient due to lack of metals in the early evolutionary phases of the Universe. My speciality lies in catalogue creation, distance derivation, isochrone fitting, stellar streams, spectral data reduction and analysis, photometry and spectroscopy of metal-poor stars and astrostatistics.
About me
I was born and raised in Chennai, India. I pursued my Bachelor in Engineering from Anna University. Transitioning from engineering to astronomy was quite the drama, but here I am! I pursued my Master in Astrophysics from University of Glasgow. Currently I am in the process of obtaining my doctrate in astronomy from the University of Groningen. I occasionally visit the Center for Computational Astrophysics, Flatiron Institute in New York to work on the origin of the Milky Way disk as a chapter of my PhD thesis. I spent my summers in 2017 and 2018 doing research in plasma physics in Institute for Plasma Research and astronomy in University of Victoria respectively. That being said, I have pursued research in five different countries over the course of six years in academic research life. My first name is pronounced as 'uh k sh uh r aa' and my last name is pronounced as 'v ih sh w uh n aa th uh n'.
Community goals
I believe in open (making all the data and codes public) and quality over quantity science with futuristic goals such as help building well-documented upcoming surveys to aid growing as a community with healthy competition and constructive criticism in understanding the most pristine episodes of our universe. All my codes, and data that go with my publications are public. Being a woman born and raised in a third world nation, I am also a huge advocate of "science for all" notion. After all, we are all made of star stuff!
Want to know more?
By the way, here you can check out short summary of some of my cool and awesome work in different sub-fields of astronomy and engineering.
A definitive merger-AGN connection at z~0 with CFIS: mergers have an excess of AGN and AGN hosts are more frequently disturbed. MNRAS. Ellison, Viswanathan et al., 2019
Detection of density variations and off-track features in stellar streams.
Dynamical Masses of Local Group Galaxies, Proceedings of IAU Symposium 379. Viswanathan, Starkenburg and Esselink 2023.
Low Profile Modified Loop Antenna for WBAN Applications. Proceedings of 5th National Conference on Information and Communication Technologies. Dinesh, Viswanathan et al., 2019
Full publication list: 12 papers with 152 citations and a h-index of 5
RESEARCH
My first observing experience in LA PALMA when the Cumbre Vieja Volcano was erupting! Three months later, I carried out more observations, and that went smoothly.
The fascinating field of galactic archaeology is what keeps me awake! In this field, we explore the history, formation, and evolution of our very own galaxy, the Milky Way and its neighbours - LMC, and SMC (Large and Small Magellanic Clouds) and few more galaxies in the Nearby Universe.
It's like being a cosmic detective, examining the ancient remnants of stars to reconstruct the story of our galactic origins.
The stars I am interested in are the metal-poor stars, often referred to as "living fossils" of our galaxy. These stars are relics from the early universe, formed when the Milky Way was still in its infancy. These stars also delve into the realms of the smallest, tiniest, and earliest galaxies that merged with our own. These ancient galactic entities, long since absorbed by the Milky Way, hold precious clues about the intricate dance of cosmic collisions over billions of years. By studying them, we can piece together the puzzle of how the Milky Way came into existence.
Unlike distant galaxies that are beyond our reach, studying our own cosmic backyard allows us to directly observe and analyze the remnants of the individual stars in these tiny galaxies that became part of our galactic family, complementing high-redshift analysis. It provides a level of spatial resolution on a star-by-star
basis and encompasses a mass range that is currently beyond the reach of direct high-redshift investigations. For this, we need chemical composition, kinematics, and distribution of these ancient galactic interlopers.
To unravel the kinematics of ancient stars, I harness the capabilities of the Gaia satellite, which provides us with precise measurements of stellar positions, distances, and motions for about 2 billion stars! To efficiently identify these intriguing stars amidst the vast stellar population, I utilize the Pristine survey, streamlining a remarkable photometric shortcut. I also use other spectroscopic surveys and catalogues that are publicly available. I don't stop there, like a true astronomer, I supplement my analysis with my own spectroscopic follow-up at the observatories in La Palma, meticulously analyzing the chemical composition and abundance patterns of these stars. This gives us a glimpse of the conditions in which these stars were born 10-13 billion years ago.
This multidimensional approach allows me to decipher the cosmic tales whispered by the most metal-poor and oldest stars, revealing the secrets of our galactic past.
But why does all of this matter? Understanding the evolution of our galaxy is not just an exercise in curiosity; it has profound implications for our broader understanding of the universe. We piece together the narrative of how small galaxies merged and merged again in fast and secular processes, eventually helping us refine our understanding of the universe.
Furthermore, this knowledge has practical applications. By exploring the unique tapestry of the Milky Way's history, we also gain insights into the conditions necessary for the emergence and sustainability of life. This research plays a vital role in determining the prevalence of habitable environments in the universe and the likelihood of finding life beyond our own planet.
Some of the elements we see in these stars are what life in Earth is made of - we are made of STAR STUFF!
In conclusion, as we delve into the secrets of galactic archaeology, our galaxy offers us a front-row seat to observe these ancient cosmic collisions, providing a unique opportunity to study the universe.
I study some of the first stars and the galaxies in the universe! See here some off my published works to know more.
Based on Viswanathan et al. 2023b. I take spectra from Gaia's Radial Velocity Spectrometer and look for very metal-poor stars in them. Want to know more?
Based on Viswanathan et al. 2023a. I select ~50 million stars with high tangential velocity from Gaia Data Release 3 using reduced proper motion parameter. Want to know more?
Based on Ellison, Viswanathan et al. 2019. Here I use a sample of AGN, non-AGN, galaxy mergers and non-mergers in different stages to understand if galaxy mergers can trigger AGN (active galactic nuclei) phenomena. Want to know more?
I was a contributing author for a lot of publications in the field of galactic archaeology. You can find these works here in my ADS
Gaia's brightest very metal-poor stars
I leverage the exceptional dataset from Gaia Data Release 3, featuring about one million spectra captured by the Radial Velocity Spec-
trometer (RVS) in the Calcium II triplet region.
I analysed and published a catalogue of approximately 1000 bright VMP stars across the entire sky.
This catalog is three times larger than the existing
collection of well-studied VMP stars in the literature within this magnitude range,
making it a valuable resource for high-resolution
spectroscopic follow-up and for exploring the properties of VMP stars across various regions of our
Galaxy.
In this work, I select halo main sequence stars using
Gaia DR3 proper motion and photometry information, the combination of which renders the
reduced proper motion parameter. This parameter allows us to pick out high tangential velocity
main sequence stars in halo orbits. Our sample reaches out until ~21 kpc thereby probing much
further out than would be possible using reliable Gaia parallaxes.
Binned velocity moments
on the star map of the reduced proper motion halo in the latitude, longitude and pseudo-azimuth directions pop up several known
and unknown tidal streams in the local halo. We find and characterise the stellar streams GD-1,
Jhelum, Phlegethon and part of Sagittarius and
characterise them in more detail. For these streams, we resolve the gaps, and density breaks
reported in the literature more clearly. As
an example case, we study the two components of the Jhelum stream in detail.
The narrow component is kinematically cold while the broad component is kinematically hot
suggesting that Jhelum may have originated from a globular cluster within a dwarf galaxy,
providing valuable insights into the Milky Way's merger history (Awad et al, submitted to A&A).
Thus, the faint signs of disequilibrium in the form of kinks and density variations in these thin
streams will paint a more detailed picture of the existence and properties of the dark matter
sub-haloes that perturb them and in turn, the mass distribution of our Galaxy.
AGN-MERGER Connection
My first research experience in observational astrophysics was focused on finding the possible connection between
the AGN and mergers using Canada France Imaging Survey (CFIS) and Sloan Digital Sky Survey (SDSS). This
can be broken down to two distinct questions: (i) Can galaxy mergers trigger AGN? (ii) Are galaxy mergers the
dominant AGN triggering mechanism? Starting from a list of optical AGN (~ 2000) and mid-IR AGN (~ 300 ), I
quantified the fraction of galaxies in on-going or recent mergers using CFIS images that are deeper than SDSS. The
same calculation was performed with a control sample. This could in future be repeated for other AGN selection
methods, e.g. in radio or X-ray. My major conclusion was that both mid-IR and optically selected AGN have
interacting fractions that are a factor of two greater than a mass and redshift matched non-AGN control sample, an
excess that increases with both AGN luminosity and host galaxy stellar mass
Physics and engineering research experiences
Indian Academy of Sciences Research Fellowship - Summer 2017:
Design of a high current, high frequency pulsar for the excitation of whistler waves with G. Ravi - Institute for Plasma Research,
India. My first research experience was the design of a direct current (DC) pulsar for the excitation of whistler waves. For my project, I
used a linear device, built in the laboratory, to simulate conditions similar to the upper ionosphere. I designed and developed a DC pulsar
to fire the antenna (also designed by me) for ~ 1 μs to 10 μs with high current inside the pulsed plasma that was used for a PhD project.
Bachelor thesis - Spring and Summer 2019:
Part 1: Low profile modified loop antenna for WMTS bands with K. Malati - Anna University, India. I published a conference
proceeding Dinesh, Viswanathan et al. (2019) during the first few months of my bachelor thesis on the design of a compact wearable
loop antenna in a wireless medical telemetry service (WMTS) band. This paper won the outstanding paper award at the conference.
Part 2: Design of frequency reconfigurable tri-band miniaturized antenna for WBAN applications. For the final thesis itself, I
designed a novel frequency reconfigurable wearable antenna for off-body communication that is published as MK, PS, GNAM, NMD,
MSM, Viswanathan et al. (2020) and up for a patent. This antenna utilizes switching characteristics of PIN diode to achieve frequency
reconfigurability. The antenna operates at GPS, ISM1 & ISM2 frequencies.
Outreach and Media
Here you can find some of the recorded talks and activities I organised. The talks are part of conferences or for outreach purposes. I have given a lot of in-person talks and outreach events, a record of which can be found in my CV.
GALAH Science meeting 2021 talk
Netherlands Astronomers Club 2021 talk
Interview about how I started the Astronomy Club at Anna University
Panel discussion about astronomy as a career in Kuala Lumpur
Astronomy offers a captivating entry into the mysteries of our Universe. However, the
scientific community often lacks diversity, falling short in terms of race, ethnicity, gender,
and LGBTQ+ representation. Traditional outreach can inadvertently exclude minority and
low-income communities, assuming prior knowledge and resources. During my PhD and
undergraduate studies, I tackled some of these disparities. As an EDI PhD representative at
Kapteyn Institute, Netherlands, I have been actively involved in fostering inclusive academic
environments. I have also organized "Women in Science" events through Young Minds, European
Physical Society and established the Astro Club of CEG in India to guide students, especially
those from underrepresented backgrounds, toward a career in astronomy. I was also on a panel
discussion about astronomy as a career for south-asian students. I am also a big supporter of open science.
My mentoring experiences include guiding a junior student on a successful graduate school
application and closely supervising three female students in completing their bachelor's theses.
As a postdoc, I am committed
to leading projects that support underrepresented STEM students. My approach aligns with
professional societies' recommendations, ensuring all voices are heard and talents nurtured.
International Day of Women and Girls in Science
Every year since 2021, I have organised an event for International Day of Women and Girls in science as the secretary and former treasurer of Young Minds Groningen, European Physical Society.
The event was publicized in Gopher article and event report featured in European Physical Society's Newsletter, both written by me.
Scientific movie night
In 2022, I organised a scientific movie night where we had scientists over talking and discussing about "How to build your own Iron Man suit?" and then we screened the movie Iron Man with Pizza and pop corn.
Astro Club of CEG - Founder and President (2019)
As part of astronomy club in my undergrad, I organised several works (such as Hands on Telescope and Observing Trip to Yelagiri) and space TED talks and Alumni talks, along with a python course, astronomy project all of which are summarised here
Zero shadow day 2019
During my undergraduate studies, I founded the astronomy club of my university, ASTRO CLUB OF CEG. As a part of our annual events, I organised a Zero Shadow Day demonstration for school and college students in the university. I organised this with SPACE INDIA company. Here is the media coverage of this event on The Hindu newspaper.
Mitacs Research Fellow 2018
Here is an interview that was taken to talk about my internship experiences and help juniors get into science.
Campus magazine - The Guindy Times
I was the head of interviews and deputy reporter of The Guindy Times, the campius magazine of Anna University. I wrote a lot of articles, poems and blogs. Find them here and here.
Vice president of Electronics Engineering Association
I organised a technical symposium called Vision for students across the state to participate and learn.
Conference dump!
Hobbies
I love rock climbing and mountain hiking and camping. And after living in the Netherlands, I am also into cycling and ice skating these days.
I also like to go on Park runs. I love cooking spicy Indian food - I have no mercy for my non-Indian friends with low-to-no spice tolerence.
I also love singing, I am very much into music and love training. I am learning ukulele, and preliminary level Dutch.
I love plants - I have 67 of them currently in my house with a growing outdoor plant collection in my roof. I also liking reading mystery and fantasy novels.
To destress, I do yoga every morning. I used to play chess, but not that much anymore. I occasionally blog when I have time. I hope to blog more often.
Here are some image dump of some of my hobbies.
About
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The blog is under construction. I aim to move all my articles from the many different blog pages I have had to this one page :) But there is one inaugral article to read over here. Happy reading!
Picture this: you're in a room full of chuckling folks, each delivering a witty one-liner after another. Laughter fills the air, and you're all having a grand time - unless, of course, you happen to be the punchline. Yes, welcome to the world of "jokes" about dark skin in India - where the humour comes at the expense of people who, surprise, just happen to be a shade darker.
Sometime back, a friend attempted to convey to me a perplexing viewpoint: they believed it was abhorrent when white people made remarks about Indians and our brown skin, yet strangely acceptable, even “funny”, when we, as Indians, cracked similar jokes about dark-skinned fellow Indians, mostly women, for that matter. This paradoxical viewpoint exposed a deeply ingrained mentality that it's acceptable to belittle our own people. As a woman of Indian descent with a dark skin colour, it rekindled memories of my childhood. During those years, I recall the discomfort of constantly hearing laughter at the expense of those of us with darker skin tones.
eauty standards upheld by the media serve as a driving force behind these biases. Advertisements inundate us with the message that lighter skin is more desirable, causing dark-skinned women to feel invisible and unrepresented. The impact is profound, with consequences that extend beyond mere jokes. Sometimes I look at Indian television, and if I didn't know better, I would say everyone in India is fair-skinned. The fair-skin privilege is in watching fair-skinned people on TV all the time.
Jokes targeting dark skin are not simply offensive because they imply a personal flaw. They highlight a systemic problem in our society where dark skin is unfairly devalued. This unfair treatment is palpable when we're bombarded with advertisements promoting things like “Fair & Lovely” face creams and rarely see dark-skinned women in lead roles on television.
Growing up, I experienced first-hand the weight of these biases. I remember a friend casually referring to me as a "black egg" - intended as a joke of course - we all laugh. But in the midst of the mirth, the line between a roast and bullying seemed elusive. Those words carried a hurtful declaration that I was an outlier, not quite fitting the mould of societal expectations for attractiveness.
And yet, that's not an isolated episode. I've been asked how, despite both my parents being Brahmins, I happened to be born with a complexion that defied the established norms. A close family member, undoubtedly with good intentions, has even referred to me as a "black pearl." It was meant to be a compliment, I understand that, just like the classic phrase "karuppa irundhalum kalaiya iruka,". But for me, it's become a subtle code - a way of saying, "Yes, you're dark, but don't worry, you're not too dark to be completely undesirable." A dark girl who is beautiful has to be an exception, right? It doesn't stop here, so many family functions where I have been called out to wear more whitening creams, and not to be in the sun, who will marry me? and what not! It's a shit show.
Few years have gone by, and with the vantage point of hindsight, I see the threads of colourism woven into every facet of my existence. Now, residing beyond the confines of India, the realization strikes me: I no longer endure the barbed humour centred around my skin tone. Being free from the necessity of participating in jokes that only emphasize my difference feels like a profound liberation.
As time distances me from those earlier interactions, I recognize that the foundation of deep friendships and relationships doesn't hinge upon my ability to endure being the punchline. It doesn't require me to cast myself as the comic relief to secure a place within the circle. Rather, it's the authentic connections, devoid of mockery, that have come to mean the most that I gathered the courage to write this piece. I'm very happy and proud of who I am and how I look!
Let's not be too hasty, though. While the world shifts, some folks still manage to make light (pun intended) of the whole situation. You know, the kind who suggests that our discomfort is a result of "sensitivity" rather than a genuine concern for dismantling oppressive behaviour. Because, surely, chuckling at deeply ingrained biases and casteism is an intellectual sport that we just don't appreciate.
Allies for a Better Tomorrow:
It's crucial to acknowledge that colorism isn't just a minor issue that can be overshadowed by seemingly more pressing concerns. Comparing various injustices doesn't diminish the significance of any of them. Rather, it's a reminder that we need to be allies for one another, recognizing that societal biases take various forms and contribute to a larger problem of discrimination.
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