[4] In 2000, together with Fulvio Melia and Heino Falcke, he proposed the possibility of observing the event horizon of the supermassive black hole in the center of the Milky Way (Sagittarius A *) with interconnected radio telescopes (VLBI at submillimeter wavelengths).
[5] This was implemented as the Event Horizon Telescope which detected the shadow of the black hole in the galaxy M87 in 2019, confirming a prediction of General Relativity.
[10] In 2011 he proposed that white dwarfs might support a habitable zone for planets which migrate inwards after the red giant phase, and that these could be found with transit surveys.
[18][19] He developed a fast Gaussian process technique based on the Rybicki Press algorithm which has been used to model stellar variability in data from the NASA TESS spacecraft.
[20] Most recently he led a team which used transit-timing with the Spitzer Space Telescope to precisely characterize the Terrestrial Planets in the Trappist-1 system,[21] showing that they share a common composition that differs from the terrestrial planets of the Solar System[22][23] Agol is the identical twin brother of mathematician Ian Agol.