Venus crosses the Sun in 1874

Triton became the first known object orbiting Neptune.

Carrington observed bright white patches near a sunspot during his regular solar observations.

Richard Hodgson independently observed the unusual white-light flare.

The 1 September observations are among the first recorded sightings of a solar flare.

A powerful geomagnetic storm followed; the sequence later helped develop the study of space weather.

Observing campaigns used cameras as well as telescopes to document Venus crossing the Sun.

Teams sought to estimate the Earth–Sun distance from observations at widely separated locations.

The 1874 event drew coordinated work across multiple countries and hemispheres.

Hall spotted the first of Mars's two known moons; the recorded date is 11 August in US local time.

Finding Deimos overturned the assumption that Mars had no detectable satellites.