In the relatively starless gap bordered by the constellations Pegasus, Delphinus, and Aquarius is the obscure constellation Equuleus, the Little Horse or Foal.
To find it, look straight away from Pegasus’ nose. You’ll see a small, flat, right triangle of three dim, naked-eye stars. You’ll need a dark, rural sky to see it. It is invisible from my suburban backyard.
Virtually all of these obscure constellations were invented by stellar cartographers after the invention of the astronomical telescope in the early 17th century. The Little Horse is the notable exception.
It appears in Greek astronomer Ptolemy’s seminal “Almagest,” a second-century CE list of 48 constellations, all of which we still recognize today. Ptolemy calls it Hippou Protome, the “forequarters of a horse.” Subsequent star maps generally depict only the Little Horse’s head. Subsequent astronomers Latinized the name to Equuleus.
As a result, many scholars assumed that Ptolemy invented the constellation, and with good reason. Equuleus does not appear in earlier descriptions of constellation stories. It is nowhere to be found in the writings of Aratus, Hyginus, or Pseudo-Eratosthenes.
However, the Greek astronomer Geminus, who wrote during the first century BCE, mentions the constellation in his “Introduction to the Phenomena.”
Geminus claims that a constellation called “Protome hippou” was invented by the renowned Greek astronomer Hipparchus. Hipparchus, who lived during the second century BCE, predates Ptolemy by perhaps 300 years.
No other ancient writing about Equuleus survives, but that didn’t stop modern scholars from often dubious speculation about its origins.
During the early 20th century, a flowering of interest in the mythological antecedents of the constellations occurred. But try as they might, those constellational scholars couldn’t find reliable mythological antecedents to Equuleus.
In “Star Names: Their Lore and Meaning,” RH Allen connects Equuleus to the Greek story of Philyra and the titan Cronos, Saturn to the Romans.
Philyra was one of 3,000 Oceanids, daughters of the prolific Titans Oceanus and Tethys. In the myth, Philyra was the mother of the half-human, half-horse centaur Chiron by the Titan Cronos, the Roman Saturn.
As Philyra and Cronos coupled, they were caught in flagrante delicto by Cronos’s wife, Rhea. Fearing his wife, cowardly Cronos transformed himself into a stallion and galloped away.
Allen implies that Equuleus represents Cronos/Saturn in his equine guise. One wonders if Allen was familiar with the painting “Philyra e Saturno” by 16th-century Mannerist painter Parmigianino. It depicts the nude Philyra, a winged horse resembling Pegasus, and Cupid, the patron of erotic love.
Allen also suggests that Equuleus could be the brother of Pegasus, which explains the wings, or the centaur Cyllarus, a gift to the horseman Pollux from the goddess Juno. To put it bluntly, Allen is grasping at mythological straws.
So, too, is William Tyler Olcott, a mythologist from the same period as Allen, except that, in that case, Olcott is looking for Christian connections. He cites the 17th-century poet Caesius, who connects the constellation to the “King’s Horse that Hamon hoped for,” quoting Olcott, in the Biblical book of Esther (6:11).
Generally, there is little reason to observe the constellation, except for an astronerdish obsession with constellational completeness. It contains little of interest to a stargazer or telescopist.
However, it does contain a few very faint galaxies that are monuments to the 19th-century obsession of some astronomers to use their telescopes to find anything and everything discoverable.
The earliest galaxy discovered in Equuleus was designated NGC 7046 by the great English astronomer William Herschel in his New General Catalog of non-stellar objects. In 1790, he was sweeping the sky with his telescope when he found a faint fuzzy. He saw only the central core of what astronomers now characterize as a barred spiral galaxy.
Herschel had reduced success with another discovery called NGC 7045. He designated it as a nebula, a cloud of gas in space. As it turns out, the object is a simple triple-star system that even Herschel’s superb vision could not resolve.
As telescopes grew larger, astronomers discovered more galaxies, but they are of little interest to stargazers today, even those with enormous telescopes. They include spiral galaxy NGC 7015, first seen by French astronomer Edouard Stephan in 1878, and NGC 7040, discovered by Mark Harrington in 1882.
Tom Burns is the former director of the Perkins Observatory in Delaware.
