By Ilana MacDonald, Dunlap Institute for Astronomy & Astrophysics
University of Toronto Scarborough student Aishani Chaudhuri, who just started her third year specializing in Physics and Astrophysics, is this year’s recipient of the Mercedes T. Richards Award for Excellence in Summer Undergraduate Research.
This past summer, Chaudhuri participated in the Astronomy & Astrophysics 2025 Summer Undergraduate Research Program (SURP) under the supervision of David A. Dunlap Department of Astronomy & Astrophysics (DADDAA) postdoctoral fellows Dr. Nathan Sandford and Dr. Gustavo Medina, as well as DADDAA Assistant Professor Ting Li. Her research involved identifying binary star systems using the Dark Energy Spectroscopic Instrument, or DESI.
“I’m very grateful to have had such an incredible first research experience, and it was a great honour to receive the Mercedes T. Richards award for my work,” said Chaudhuri. “My supervisors, Dr. Nathan Sandford, Dr. Gustavo Medina, and Prof. Ting Li, have been incredibly supportive and encouraging, and I loved being around other students doing so much fascinating research.”
Since stars form in clusters, most of them tend to be found with at least one companion. Binary stars, where two stars are bound gravitationally, are sometimes so close that they cannot be resolved as separate objects. Some of these are called spectroscopic binaries, as one or both stars’ spectra are Doppler-shifted as the stars move toward or away from us due to their orbital motion.
Chaudhuri’s research focused on single-lined spectroscopic binaries, or SB1s, where only the shift in spectrum from the brighter star is measured. Finding and categorizing these binaries is essential to understanding stellar evolution as most stars are thought to exist in binaries. Interactions between stars in binary systems also lead to a lot of fascinating phenomena, including spectacular events like supernova explosions, stellar mergers, and the birth of black holes and neutron stars.
Credit: Dunlap Institute.
“This past summer,” said Sandford, “Aishani took on the ambitious task of searching for and characterizing binary stars within the DESI survey, which has observed millions of stars in and around our Galaxy.”
DESI is the most powerful multi-object survey spectrograph in the world. It is attached to the 4-meter Mayall Telescope, located in the Sonoran Desert in Arizona at the Kitt Peak National Observatory. The instrument captures the light from distant objects using 5,000 robotic optical fibers which feed into a bank of spectrographs. It’s first data release, published in March 2025, contained the spectra of roughly 4 million stars.
“Aishani characterized thousands of binary stars in the DESI survey,” said Medina, “which represents significant progress for the collaboration and results from her ability to work carefully and independently.”
Chaudhuri was able to able to shortlist about 170,000 of these SB1s and to place them on a colour-magnitude diagram – a tool used by astronomers to relate the temperature, described by their colour, to the luminosity, or brightness, of stars. The below figure is this colour-magnitude diagram, and it represents the months of work Chaudhuri spent on this project.
Credit: A. Chaudhuri
The horizontal axis of the diagram represents the colour of the stars in the DESI dataset, and the vertical axis represents their brightness. The clear diagonal line is called the “main sequence”, and describes the relationship between temperature and brightness for stars that are in the part of their life where Hydrogen Fusion is taking place in their core. One notable feature is a clear separation on the main sequence between the light-coloured region, where there are fewer binary stars, and the dark-coloured region, where there are more binary stars. This occurs because the light from two stars in a binary system is brighter than the light from a single star.
“My supervisors were very happy with it, and it was one of the moments that most made me feel like I’m cut out to pursue research in the future,” said Chaudhuri of this diagram.
“It was inspiring to see Aishani, coming from the UTSC campus and tackling her very first research project, grow so quickly as a scientist” said Li. “In only one summer, she mastered tools for mining Gaia and DESI data and modeling binary star orbits, all while communicating her results with remarkable clarity and enthusiasm.”
The Award includes a $2000 cash prize. Nominations can be made during the SURP program, which runs from May to August every year and is administered by the David A. Dunlap Department of Astronomy and Astrophysics and the Dunlap Institute for Astronomy & Astrophysics at the University of Toronto.
About the Award
The Professor Mercedes T. Richards Award for Excellence in Summer Undergraduate Research is awarded annually to a SURP student who has demonstrated outstanding achievement and growth in astronomy research.
This award honours the memory of Professor Mercedes T. Richards (1955-2016) and her tireless efforts to advance the fields of physics and astronomy. Originally from Jamaica, Prof. Richards earned her PhD in Astronomy and Astrophysics at the University of Toronto in 1986.
Prof. Richards performed groundbreaking research across computational astrophysics, stellar astrophysics, and exoplanets and brown dwarfs. In fact, she was the first astronomer to use the process of tomography to observe binary star systems, and model how gases flow around stars in binary systems.
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For more information, please contact:
Ilana MacDonald
Public Outreach, Communications and Events Strategist
Dunlap Institute for Astronomy & Astrophysics
University of Toronto