THE SOUTHWORTH PLANETARIUM

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Founded January 1970

Julian date: 2458780.16

2019-2020: XXXVIII

"Nearer the gods no mortal may approach."

-Edmond Halley

THE DAILY ASTRONOMER

Thursday, October 24, 2019

Rober Carolinum

Edmond Halley

(1656-1741)

In December 2023, Halley's Comet, the most famous of all the ice-encrusted interlopers that periodically infiltrate our inner solar system, will reach aphelion, its farthest point from the Sun, at a distance 35 times greater than Earth's average heliocentric distance. After reaching this far point, the comet will slowly swing around and begin a long, initially lethargic trek back toward the Sun. It's due to adorn our night sky again in 2061.

It is from this comet's renown that the British mathematician/astronomer Edmond Halley (1656-1741) derives most of his posthumous fame. He was the one who first proposed that the comet, which was first recorded by Chinese astronomers in 240 BC and which appeared in various texts in subsequent centuries, most notably in 1066 AD during the time of the Battle of Hastings, was actually the same comet that revisited the inner solar system every 76 years or so. In late 1759, the comet reappeared, just as Halley had predicted. (Halley died eighteen years prior to its predicted return.) From that time on, the comet has borne his name.

What is less known is that Edmond Halley made another attempt to place his personal stamp indelibly onto the firmament. He created the constellation known as Rober Carolinum, "Charles' Oak." Have you heard of it? No worries. It doesn't exist, anymore. In fact, it only lasted about 50 years. This constellation, composed of stars now comprising the ship constellation "Argo Navis," didn't last principally because Halley was motivated more by political flattery than artistic impulse.

Rober Carolinum "Charles' Oak." A now extinct constellation here

seen in Johannes Bode's 1801 Uranographia. Bode labeled it

Rober Caroli II. Bode's Uranographia was the last publication to

contain Halley's constellation.

Halley developed this constellation in 1676 to honor English king Charles II. This king had lived in exile for years following the House of Stuart's defeat in the English civil war, a war that during which his father, Charles I, was executed in 1649. During Charles II exile, England was governed first by Oliver Cromwell and then, briefly, by his less formidable son, Richard. Richard ruled for less than a year, which allowed for the prompt restoration of the monarchy in 1660.

Charles II. Started his reign in 1660 after he spent

years in exile during the Cromwellian period.

The constellation Rober Carolinum was supposed to depict the tall oak in which Charles Stuart, as he was then known, hid following his disastrous loss at the Battle of Worcester in 1651. After this battle the Civil War ended with the Roundheads prevailing over the Cavaliers.

Halley mapped out the constellation's component stars following a visit to St Helena he made in order to observe the southern sky. In 1678, he published his catalog, "Catalogus Stellarum Australium," (Catalog of Southern Stars) which included this newly crafted constellation. Halley intended is as a permanent stellar monument to glorious king. However, it was not last. Within less than a century, French astronomer Nicolas Louis de Lacaille developed a more comprehensive map of the southern sky. He erased all traces of Rober Carolinum from his maps and restored the stars back to the Argo Navis.

Although Johannes Bode made a valiant attempt to establish Halley's constellation as a fixed structure by including it in his 1801 Uranographia, Rober Carolinum soon vanished from all maps and joined the sad list of "extinct constellations.

One interesting astronomica note pertaining to this constellation: it was the first to include the eruptive variable star Eta Carinae, a star whose explosive nebula structure was so beautifully captured by the Hubble Space Telescope.

Eta Carinae

Edmond Halley is truly one of astronomy's immortals, for his cometary namesake is due to return to Earth's sky many more times before it becomes a dead comet. It might have pleased Halley to know that his name persists, even if his tribute to King Charles II has been long forgotten.

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