Overview
"The Star" is an 1897 apocalyptic short story by H. G. Wells.
Plot summary
On New Year's Day (about 1900, presumably), astronomers announce that the orbit of the planet Neptune has become erratic. Soon it's discovered that a strange luminous object has entered the Solar System, its gravitational pull causing the disturbance. The object is visible in the sky through "any decent instrument" in the constellation of Leo near Regulus.
Although initially it is only of interest to astronomers, eventually the world media announces that the object is on a collision course with Neptune, and a "planetary collision" is predicted. People around the world gather to see the phenomenon. When the collision occurs, the impact causes a massive explosion, merging the two objects into a single massive conflagration. It is seen from Earth as a bright new star in the sky. The impact robs Neptune of its centrifugal force and out of its solar orbit, sending the fireball careening toward the sun.
As it rises each day, the star is noticeably brighter and larger than the day before, and people realize it is nearer. Many panic and take it as a sign of the end times, while others cite the year 1000, in which humanity also anticipated the world's end. Scientists assure the public there is no danger, as they have plotted the Star's trajectory to carry it harmlessly millions of miles from Earth. Most people go on about their lives without concern for the Star as anything more than a curiosity. Meanwhile a mathematician takes days to calculate a new trajectory, factoring the gravitational pull of Jupiter, previously overlooked by other scientists, which will alter the course of the Star and indeed put Earth in its path. The mathematician claims the fireball will either collide with or closely pass Earth. He is largely ridiculed by science deniers, but soon his theory is proven to be accurate.
From Wikipedia (CC BY-SA 4.0).