About Me

about me

Hi, I am Henry, an astronomy graduate student at University of Toronto with interests in astrophotography, you can see my photography below. For research aspect, both galactic astrophysics, deep learning and open source science are currently my research interest. The main reserach project I am working on is deep learning application in stellar and galactic astronomy with a python package in development called astroNN to facilitate my reserach. You can learn more about astroNN in Code.

I am a Hong Kong Canadian grew up in Hong Kong which is named the worst light polluted country in the world because of the dense population. But it makes the universe more mysterious to the young me.

Me on snowy mountain

During a trip with UTOC in northern Ontario

Me with a giant Sun art near the city hall

During Toronto Nuit Blanche

UofT squash

UofT squash

My Astrophotography

I like astrophotography, here are some of my works done at different places around the globe. Most of them are captured with Skywatcher 80ED on Star Adventurer equaatorial mount with a modified Canon 600D.

Some of the best stargazing place I have been include Mount Everest Base Camp at 5400m above sea level and Uluru, Australia

M42 Orion Nebula

8 Nov 2015, Home at Downtown Toronto

Startrails over University College at UofT

18-19 March 2016, Front Campus at U of Toronto

Milkyway over Idaho Fall

Summer 2017 during the Great American Total Eclipse Trip

Milkyway over Mount Everest

Mount Everest Base Camp @ 5400m sea level during my trip to Tibet in 2015

M57 Dumbbell Nebula

17 Sept 2015, Home at Downtown Toronto

Lagoon Nebula (Left)& Triffid Nebula(Right)

4 July 2016, Near U of Toronto downtown campus

Area around Scorpius Antares

Summer 2014, Ayers Rock Desert Gardens Hotel, Australia

Eta Carinae Nebula

Summer 2014, Ayers Rock Desert Gardens Hotel, Australia

Large Magellanic Cloud

Summer 2014, Ayers Rock Desert Gardens Hotel, Australia

Beside deepsky imaging, I also occassionaly do planetary imaging with my small telescope.

Mars in 2016

You can see Syrtis Major on Mars and was taken with my 80mm refractor on 23 May 2016

Saturn in 2016

You can clearly see multiple rings and it is taken with my 80mm refractor

Jupiter in 2016

You can clearly see multiple atmospheric bands and it is taken with my 80mm refractor

And of course the Sun and the Moon

The moon

It is a moasic taken with my 80mm refractor

Total Solar Eclipse 2017

HDR composite images during the moment of totality

Total Lunar Eclipse 2019

Single shot image during totality

Featured codes

I release most of my code including code for my papers on my Github profile at https://github.com/henrysky




My Research

My current research focuses on using new robust machine learning methodology to analyze big astronomical survey data-sets, such as spectroscopic data from the Sloan Apache Point Observatory Galaxy Evolution Experiment (APOGEE) and Gaia astrometric data to better understand the Milky Way Galaxy. I use new robust machine learning methodologies such as multi-layer ("deep") Bayesian artificial neural networks, which can learn complex mapping functions between inputs andoutputs while considering uncertainty in training data and also providing uncertainty estimates for predicted values. These new machine learning technologies provide data products withhigher precision than available from traditional analyses which helps further our understanding the formation and evolution of the Milky Way galaxy. I am currently applying these techniques tothe problems of determining stellar parameters and chemical abundances, spectro-photometric distances, and stellar ages without relying much on stellar evolutionary models, allowing almost completely data-driven studies of the structure and dynamics of the Milky Way. The elemental abundances I have determined for APOGEE stars are the best available of any method applied to APOGEE stars and the spectro-photometric distance method that I am currently writing up provides distances more precise than 10% for stars out to 10 kpc, much higher precision than Gaia itself provides. These distances are already being used by groups around the world.

To facilitate my projects in this new area of big data astronomy with deep learning, I am developing astroNN, an open source python package designed for fast deep learning in astronomy that is based on Tensorflow, a general deep learning framework. The goals of astroNN are:(a) to provide a code that focuses on deep learning in astronomy, (b) to develop tools and datasets that are relevant to astronomers, (c) to provide an easily accessible tool that is well tested against errors, and (d) to act as a platform to share astronomy-oriented neural networks.astroNN makes it easy for non-machine learning experts like typical astronomers to use advanced tools like Bayesian neural networks to analyze data

My research focused on application of neural network in astronomy. Current projects include
  • Stellar Spectra Analysis using Bayesian Neural Network with Dropout Variational Inference
  • Data-Driven stellar distance trained with Gaia with Neural Network
  • Asteroseismic ages with deep learning
  • Novel deep learning methods for astronomical time-series data
Neural Network distance vs Gaia DR2

Neural Network did much better than Gaia DR2

Gaia DR1 with 20% parallax error cut

Neural Network trained on Gaia DR1 to map the milkyway further away

MilkyWay kinematics map

This map is made with distances from neural network and Gaia DR2

Education and Co-curricular

  • PhD, University of Toronto (2020-2024)
  • MSc, University of Toronto (2019-2020)
  • BSc, University of Toronto (2014-2019)
  • Hong Kong Diploma of Secondary Education (2008-2014)

  • 2020 Summer (Supervisor: Prof. Abigail Crites): Tomographic Ionized Carbon Intensity Mapping Experiment (TIME)
  • 2019 Fall: Teaching Assistant for AST101H1: The Sun and Its Neighbours
  • 2019 Winter & 2020 Winter: Teaching Assistant for AST201H1: Stars and Galaxies
  • 2017 - Present (Supervisor: Prof. Jo Bovy): Application of Deep Learning in Stellar and Galartic Astronomy
  • 2016 (Supervisor: Prof. John Percy): Studies of the Long Secondary Periods in Pulsating Red Giants - arXiv:1611.03334

Featured Co-curricular:
  • 2019-2020: Tea Master & Webmaster, UofT Graduate Astronomy Students Association
  • 2017-2018: Vice President, UofT Astronomy & Space Exploration Society
  • 2016-2018: Vice President, UofT St. George Squash Club
  • 2015-2018: Multiple Roles, UofT Footprint Publication
  • 2016-2017: Observing Director, UofT Astronomy & Space Exploration Society
  • 2015-2017: Director of Observation, UofT Amateur Astronomers' Society
UofT Amateur Astronomers' Winter Trip 2017

I was one of the organizer of this trip

UofT Amateur Astronomers Autume Festival Observation 2016

I was one of the organizer of this astronomy-related cultural activity

Total Eclipse 2017

We organized a trip to Saltlake city/Idaho Falls to watch the Eclipse


You can view my ORCID associated ADS here

  • None

  • Published:
    • Searching for Solar Siblings in APOGEE and Gaia DR2 with N-body Simulations [arXiv:1910.01646][ADS]
    • Jeremy J. Webb, Natalie Price-Jones, Jo Bovy, Simon Portegies Zwart, Jason A. S. Hunt, J. Ted Mackereth & Henry W. Leung (2019)
    • Life in the fast lane: a direct view of the dynamics, formation, and evolution of the Milky Way's bar [arXiv:1905.11404][ADS]
    • Jo Bovy, Henry W. Leung, Jason A. S. Hunt, J. Ted Mackereth, D. Anibal García-Hernández, & Alexandre Roman-Lopes (2019)
    • Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning [arXiv:1902.08634][ADS][Code]
    • Henry W. Leung & Jo Bovy (2019)
    • J. Ted Mackereth, Jo Bovy, Henry W. Leung, Ricardo Schiavon, Wilma Trick et al. (2019)
    • Henry W. Leung & Jo Bovy (2019)
    • Studies of the Long Secondary Periods in Pulsating Red Giants. II. Lower-Luminosity Stars [arXiv:1611.03334][ADS]
    • John Percy & Henry W. Leung (2017)

    A list of collaboration paper:
    • The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra [arXiv:1912.00290][ADS]

    Henry On the News

    • I was mentioned in the news for providing expert opinion
    • I was mentioned in the news for providing expert opinion
    • I was appeared in the news for being in an excahnge program with US Chabot Space & Science Center
    • I was appeared in the news for being in an excahnge program with US Chabot Space & Science Center