A flare enters the solar record

The discovery showed that the newly identified planet has a moon.

Lassell's telescope revealed a faint moving companion near the planet.

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.

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

The UTC catalog fixes the transit on 9 December, giving astronomers another rare timing opportunity.

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.