Here is an article I wrote over the past week

The Elder Things first appeared by name in the story "At the Mountains of Madness" by H.P. Lovecraft, the two sources for their origins as well as which class of mythos creature they belong to are found within the story, the first of these according to Lovecraft is the Necronomicon, it is here that they are referred to as Elder Things, while the characters within the narrative refer to them as "Elder Ones"

The Elder Things were the first of Lovecraft's extraterrestrial mythos beings to migrate to Earth, which occurred roughly one billion years ago, unlike Lovecraft's other beings these aliens were particularly aggressive toward other mythos creatures, including The Great Race of Yith and the spawn of Cthulhu. Despite this it was the last ice age that ultimately lead to their demise, though its suggested that they simply retreated to their underwater cities within the Antarctic. This city would be rediscovered in 1931 by two members of an Antarctic expedition from Miskatonic University, as told within the story At the Mountains of Madness.

It is within H.P. Lovecraft's much maligned story "The Dreams in the Witch-House," where we learn that the Elder Things originated from a planet in a triple star system located between the constellations of Hydra and Argo Navis. Hydra is the largest of the 88 modern constellations, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy, originally much larger in the sky the smaller constellations of Corvus and Crater, together with Sextans, were added to reduce its size. Hydra is named after the serpent defeated by Hercules and is therefore represented as a water snake. Argo Navis (listed by the 2nd century astronomer Ptolemy) was once the largest of all constellations until the year 1752 when the French astronomer Nicolas Louis de Lacaille subdivided it. The large constellation was divided into Puppis (Poop deck), Vela (Sails), Pyxis (Compass), and Carina (the Keel). The constellation Puppis is the largest of the four individual constellations beneath Hydra, Puppis represents the deck of the ship and its deckhouse, to its left in the sky is Vela which sits beneath Pyxis, which is the smallest of the four constellations and yet the closest to Hydra.

Lovecraft had taught himself Astronomy at a young age and so when he spoke of a three star system existing between the constellations of Hydra and Argo Navis he was speaking with some degree of scientific certainty. The constellations of Antlia and Pyxis have only been known since about 1603 AD and so they were not on Ptolemy's list of the 48 known constellations. The fact that Lovecraft was aware of this makes one wonder why he did not mention it, in fact he doesn't even acknowledge their existence. Its also a bit curious that he refers to the constellation as Argo Navis, when it had been known since the 17th century to have been broken down into four separate designations, de Lacaille created both Pyxis and Antlia. One possible answer could be that Lovecraft intentionally left out these facts to make the statement of star system existing between Hydra and Argo Navis more definitive, the two constellations exist side by side and so it might prove overly confusing as to which of them Lovecraft intended as the location for the home planet of the Elder Things.

Several facts suggest that Lovecraft did indeed mean to suggest Antlia as the basis for a home planet for his mythological race of beings, the first of which is his mentioning of a three star system. Ironically the constellation does indeed have three major stars, the others are very faint, Antlia has only one bright star, Alpha Antliae which is approximately 370 light-years from the Solar System, Zeta Antliae is a binary star approximately 372 light years from Earth. The ultimate irony of Lovecraft associating the Antlia constellation with the birthplace of his mythos creatures lay in the naming of the constellation, anyone familiar with the works of H.P. Lovecraft are no doubt acutely aware of his total discontent for religion and myth and how for Lovecraft science was a kind of religion. This makes the following facts all the more interesting, Antlia was created by the French astronomer Nicolas Louis de Lacaille and for the fist time in history a constellation wasn't named after a mythological character, but instead was named after a scientific instruments, as a lifetime student of Astronomy it is likely that Lovecraft was aware of this fact. Now let's turn our attention to one of the strangest examples of synchronicity between Lovecraft's mythos creations and science, that being the supposed planet Lovecraft claimed to exist between the constellations of Hydra and Argo (Pyxis,Vela etc).

HD 93083 is the brightest of all the stars within the constellation of Antlia, the star is located a mere 94 light years away, and once again it has yet to be named. Lovecraft had used his knowledge of Astronomy to great effect within the story "Dreams in the Witch House" but there is one fact that he could not have possibly known about, for it was discovered six decades after his death, in 2005 to be precise. This great discovery and ultimate proof of the reality of Lovecraft's mythos is a newly discovered planet orbiting the third star on the edge of the Antlia constellation; exactly where H.P. Lovecraft said it would be.

The Antlia system has actually had a long history of near misses starting roughly 12,300 years ago as witnessed by the discovery of the Vela supernova remnant, a second remnant (RX J0852.0-4622) was discovered in the southeastern part of the Vela remnant, it exploded within the last thousand years or so. These two galactic phenomena were not the systems first, nor its closest encounter with mass destruction. The closest that the constellation Antlia has come to being destroyed occurred roughly one billion years ago in connection with two small galaxies, the first of which is "The Antlia Dwarf" a dwarf spheroidal galaxy which lies in the constellation Antlia, the other is the small barred spiral galaxy designated as NGC 3109 which also lies within Antlia, but in the direction of the constellation of Hydra. The warped disk of NGC 3109 has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago, which also corresponds to the first migration of Lovecraft's Elder Things to the Earth.

Bruce Fox (2011)