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Jonathan Gagné

6 min read

Jonathan Gagné

Quick Facts

  • Full name: Jonathan GagnĂ©
  • Also known as: Author of Coffee ad Astra, The Physics of Filter Coffee and The Physics of Espresso
  • Nationality: Canadian (coffeenutz.net)
  • Primary fields: astrophysics, exoplanets, brown dwarfs, coffee science (jgagneastro.com)
  • Best known for: Mapping nearby young stellar associations and free-floating planetary-mass objects in the Milky Way, and for bringing the same quantitative mindset to specialty coffee brewing. (arXiv)

One-Sentence Summary

“Jonathan GagnĂ© is a Canadian astrophysicist who studies brown dwarfs, young stars and exoplanets—and dissects coffee brewing with the same data-driven precision.”

Biography

Early Life & Education

Jonathan GagnĂ© grew up in QuĂ©bec and followed a classic physics route at UniversitĂ© de MontrĂ©al, completing a Bachelor’s in physics and then proceeding directly into a PhD in astrophysics. His graduate work focused on low-mass stars and brown dwarfs in young moving groups, using Bayesian tools to identify and characterize nearby young objects. (Loop)

During his PhD he became deeply involved with observational campaigns and catalog work that would later become central to his career: surveying the solar neighbourhood for young, ultracool dwarfs and potential planetary-mass objects.

Astrophysics Career

After his doctorate, Gagné held several competitive research positions, including:

  • Trottier / iREx postdoctoral researcher at UniversitĂ© de MontrĂ©al

  • NASA Sagan Postdoctoral Fellow at the Carnegie Institution for Science

  • Banting Postdoctoral Fellow at the Institute for Research on Exoplanets (iREx) (A Waste of Coffee)

His scientific work centres on:

  • Brown dwarfs and free-floating planetary-mass objects – identifying and characterising very low-mass objects in nearby young associations, often at or below the deuterium-burning limit. (arXiv)

  • Young moving groups and stellar kinematics – building and refining tools to assign stars and brown dwarfs to nearby associations using positions, proper motions, radial velocities and parallaxes. This led to the BANYAN series of Bayesian classification tools and the BANYAN All-Sky Survey (BASS). (arXiv)

  • Directly imaged exoplanet analogues – studying the atmospheres and variability of young giant planet analogs, often using space telescopes such as Spitzer. (arXiv)

GagnĂ© has been a key contributor to the discovery or detailed study of multiple free-floating planetary-mass candidates and wide-orbit companions (for example CFBDSIR 2149-0403 and GU Piscium b), objects that blur the line between “planet” and “brown dwarf.” (Wikipedia)

He is now a Scientific Advisor at the Rio Tinto Alcan Planetarium (Espace pour la vie) in Montréal and an associate / adjunct professor at Université de Montréal, affiliated with the Trottier Institute for Research on Exoplanets. (exoplanetes.umontreal.ca)

Public Outreach & Museum Work

At the MontrĂ©al Planetarium, Gagné’s role sits at the intersection of research, education and exhibit design. He helps shape scientific content for shows and installations, ensuring that topics like exoplanets, meteorites and data visualization are grounded in current research while remaining accessible to the public. (Espace pour la vie)

Beyond formal research, he frequently participates in talks, workshops and media pieces explaining how studies of brown dwarfs and exoplanets help us understand planet formation and the broader Galaxy.

From Astrophysics to Coffee

Coffee started as a hobby and gradually became a second, very public “career.” Drawing on his background in physics and statistics, GagnĂ© launched the blog Coffee ad Astra to share data-driven approaches to brewing—particle-size measurements, temperature experiments, extraction modelling and controlled blind tastings. (Coffee ad Astra)

On the blog he applies tools familiar from astrophysics—Bayesian inference, Monte-Carlo simulations, error analysis—to questions like:

  • How grind distribution affects extraction curves

  • What water chemistry profiles work best for different brews

  • How brew temperature and agitation influence flavour

His work has influenced baristas and home brewers worldwide; Coffee ad Astra is routinely cited as one of the most technical and rigorous resources in specialty coffee. (Blogs Database)

Books: The Physics of Filter Coffee and The Physics of Espresso

Gagné distilled his blog and further research into two substantial books:

  • The Physics of Filter Coffee – a deep dive into percolation brewing, covering everything from grinder physics and bed depth to water chemistry and sensory experiments. (coffeenutz.net)

  • The Physics of Espresso – an equally technical treatment of espresso extraction, flow dynamics, puck resistance and the impact of baskets, grinders and pressure profiling. (Coffee ad Astra)

Both books have been praised for turning complex physics into practical guidance for baristas while keeping academic-level rigour.

Career & Major Milestones

  • 2006–2010 – Undergraduate physics at UniversitĂ© de MontrĂ©al
    Focus on astronomy and observational techniques. (A Waste of Coffee)

  • 2010–2015 – PhD in astrophysics
    Develops Bayesian tools (BANYAN) to identify young moving-group members; begins large-scale surveys for ultracool dwarfs. (arXiv)

  • 2012–2014 – Discoveries of free-floating planetary-mass objects
    Co-discovers objects such as CFBDSIR 2149-0403, helping define the population of isolated planetary-mass bodies. (Wikipedia)

  • Mid-2010s – NASA Sagan Fellow & Carnegie postdoc
    Works on brown dwarfs and exoplanet analogues, combining survey data with high-contrast imaging and spectroscopy. (Loop)

  • 2014–2018 – BANYAN & BASS surveys
    Leads or co-leads the BANYAN All-Sky Survey, assembling large samples of young brown dwarfs and planetary-mass candidates in nearby associations. (arXiv)

  • 2020 – Joins UniversitĂ© de MontrĂ©al as associate professor and iREx member
    Formalizes his dual role as Planetarium scientific advisor and university researcher. (Espace pour la vie)

  • 2018–present – Coffee ad Astra & coffee books
    Coffee ad Astra becomes a widely referenced blog; The Physics of Filter Coffee and later The Physics of Espresso are published, cementing his influence in specialty coffee circles. (Coffee ad Astra)

Key Contributions

In Astrophysics

  • Systematic mapping of young moving groups via BANYAN/BASS, providing catalogues of young low-mass stars and substellar objects used by many subsequent surveys. (arXiv)

  • Discovery and characterization of planetary-mass objects that serve as analogues to directly imaged exoplanets and help calibrate evolutionary models. (arXiv)

  • Kinematic and variability studies of young brown dwarfs, clarifying their rotation, atmospheres and relation to exoplanets. (arXiv)

In Coffee

  • Bringing quantitative methods to home brewing, popularising the use of refractometers, particle-size analysis and statistical experiments in everyday coffee practice. (Coffee ad Astra)

  • Widely adopted brewing frameworks, such as his high-extraction filter recipes, freeze-grinding studies and long-steep AeroPress approaches, which many modern recipes cite or build upon. (Coffee ad Astra)

Notable Quotes

“I love to think about coffee brewing and use the tools of science to learn how to brew better coffee.” (Coffee ad Astra)

“I study brown dwarfs, exoplanets and young stars in our neighborhood of the Galaxy.” (jgagneastro.com)

Trivia / Fun Facts

  • Maintains two blogs: one for astrophysics and one for coffee, reflecting his split life between galaxies and grinders. (jgagneastro.com)

  • Holds a Professional Physicist Certification from the Canadian Association of Physicists.

  • Frequently collaborates with well-known figures in both worlds—astronomers in large survey teams and coffee professionals such as Scott Rao. (jgagneastro.com)

Sources & Further Reading

  • Astrophysics:

  • Coffee:

    • Coffee ad Astra blog – coffeeadastra.com (Coffee ad Astra)

    • The Physics of Filter Coffee and The Physics of Espresso descriptions and reviews (coffeenutz.net)

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