April 10

In April 837, Halley's Comet reaches its nearest point to Earth at a distance of 0.0342 astronomical units. This passage provides one of the earliest recorded observations of the comet’s orbit. Astronomers of the time document its bright tail and trajectory across the sky. The event contributes to the understanding of cometary motion long before telescopes. Halley’s periodic return patterns help shape future astronomical studies and celestial mechanics.

On April 10, 2019, an international team of astronomers from the Event Horizon Telescope project unveiled the first direct visual evidence of a black hole’s event horizon. Targeting the supermassive black hole at the center of galaxy M87, they combined data from a global network of radio telescopes. This breakthrough overcame immense technical challenges, including synchronizing observatories and processing vast volumes of data. The resulting image revealed a bright emission ring encircling a dark central shadow, precisely matching predictions from Einstein’s general relativity. Published in The Astrophysical Journal Letters, this milestone captivated both the scientific community and the public worldwide. It opened a new era for black hole astrophysics, paving the way for future studies of extreme gravity and cosmic phenomena.