National Aeronautics and Space Administration

A Brief History of High-Energy Astronomy: 1700 - 1799 Era

In Reverse Chronological Order

1790-1825	Studies of the frequency of sunspots indicate a 35-year period of lower than average solar activity, now called the Dalton Minimum. This period was, likely not coincidentally, one with cooler than average global temperatures, implying that the solar luminosity was also reduced during this interval.
1784 & 1795	The English philosopher John Michell (in 1784) and the French mathematician Pierre Laplace (in 1795) consider the problem of classical bodies for which the force of gravity might be so strong that light cannot escape from them, i.e., the escape velocity from their surfaces would be in excess of the speed of light. These are the first `scientific' discussions of what are today called black holes (and which really require the framework of general relativity to describe their properties).
13 Mar 1781	Musician and (then) amateur astronomer William Herschel and his sister Caroline Herschel `discover' the planet Uranus, the first `new' planet to be discovered since antiquity. In fact, it was later realized that Uranus had been observed much earlier (in 1690 by John Flamsteed) but misidentified as a star and dubbed 34 Tauri.
25 Dec 1758	German amateur astronomer (and farmer) Johann Georg Palitzsch is the first to observe the return of the comet of 1682.. The comet is dubbed Halley's Comet (P/Halley) in honor of Edmond Halley, who had predicted its return (the comet actually was about a year late!).
1750	Thomas Wright, an English scientist (also an architect and landscape gardener), publishes "An Original Theory or New Hypothesis of the Universe" in which he argues (correctly) that the band of the Milky Way which is visible in the sky is due to a multitude of stars confined to a disk-like geometry. This realization of the structure of our Galaxy was later taken up by others, including Immanuel Kant and William Herschel.
1718	Edmond Halley publishes the first measurements of the proper motions of the `fixed' stars, e.g., the nearby stars Arcturus and Sirius, by comparing their contemporary positions with those determined by Ptolemy and Hipparchus during their lifetimes (87-150 CE and 190-120 BCE, respectively) and realizing that they were different (Halley 1718, Phil. Trans., 30, 736).
1705	Edmond Halley notes that the comets observed in 1531, 1607, & 1682 all appear to have similar orbital elements based on Newtonian mechanics. He suggests that they are all the same object and predicts that the comet will return in 1757.

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Acknowledgements

Web page author: Stephen A. Drake (based on an original by Jesse S. Allen)

Web page maintainer: Stephen A. Drake