Looking Up: Find the Dolphin in the evening sky
If a constellation can be cute, this has to be it. Delphinus the Dolphin is a small but obvious pattern of stars that catches the eye on any clear, late summer evening.
Few star patterns are so easily recognized and appropriately named by people long before us. Other obvious patterns are the Big Dipper and the Northern Cross (both of which are “asterisms” rather then officially designated constellations).
It’s easy to find the Dolphin if the sky is reasonably dark. Moonlight won’t be overwhelming this week. The moon is a crescent, low in the west to southwest, leading up to first quarter moon on Sept. 5.
At around 9 or 10 p.m., look about half way up in the south-southeast, for the bright blue-white star Altair, flanked on both sides by conspicuous but less bright stars. This is part of the constellation Aquilia the Eagle.
Directly above (north of) the Dolphin is Cygnus the Swan (including the Northern Cross) and Lyra the Lyre with its brilliant star Vega.
The Eagle seems to be facing the Dolphin, about 12 degrees to the left (east). Tip: A clenched fist extended toward the stars spans approximately 10 degrees.
Delphinus the Dolphin consists of five faint stars. Four of them make a parallelogram, a sort of squat diamond shape, which is visualized as the Dolphin’s “body.” A fifth star to the lower right (southwest) marks the end of its “tail.”
The two stars marking the right side of the parallelogram, which leads to the “tail” star, have peculiar names. The star on top is Sualocin (cataloged as Alpha Delphini). The star at lower right is Rotanev (or Beta Delphini).
Here’s the story behind these names.
The Italian astronomer Giuseppe Piazzi (1746-1826) did important work supervising an incredible precise star catalog, and in 1801 he made the first discovery of an asteroid, which was named 1 Ceres. Piazzi’s assistant was named Niccolo’ Cacciatore (1770-1841). Cacciatore did the bulk of the work on the star catalog, and headed the project at Palermo Observatory in 1807. The star catalog was published in 1814.
The English translation of Cacciatore’s name was Nicholas Hunter. When Latinized, it became Nicolaus Venator. Reversing the spelling, he came up with names for this two stars in the Dolphin, Sualocin and Rotanev. He thus named them for himself.
This explanation was unraveled 45 years after the catalog was published, by English astronomer Rev. Thomas William Webb. This information was reported in “Secrets of the 1814 Pal memo Star Catalogue” (2003) by Mark Hurn, Institute of Astronomy Library, University for Cambridge.
Despite the lore behind the naming of these two stars, the Dolphin star probably of most interest to amateur astronomers is Gamma Delphini, the “nose” star on the far left (east). A small telescope easily splits this star into two components, a true binary star system. The brighter star (magnitude +4.3) appears orange-gold; the other star is magnitude +5.1 and of a light yellow hue. These stars spin about a common center of gravity about every 3,000 years. The pair is 125 lights years from the Sun.
The bottom (southern) star of the parallelogram is listed as Delta Delphini. The star marking the “tail” is Epsilon Delphini.
Alpha, Beta, Gamma, etc., are letters of the Greek alphabet; stars in each constellation have these designations, roughly in order of brightness with Alpha usually being the brightest star. By rights I should type them with the Greek letters, but I haven’t a clue of how to do that with this keyboard.
This area of the sky is rich in stars, where the Milky Way Band passes. This whole region is marvelous with eyes alone, and a deep experience with binoculars, exploring the star clouds and nebulous dust of our galaxy’s spiral arms.
Ancient Greeks named this constellation, as part of their mythological fables.
Delphinus the Dolphin has also been known as Job’s Coffin.
A short way to the upper right (northwest) is another interesting and small constellation, Sagitta the Arrow. I’ll make that point in another column.
Keep looking up!
Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at email@example.com. Please mention in what newspaper or web site you read this column.