Corona Australis

Corona Australis's faint arc sits beneath the feet of Sagittarius, and just behind that arc, invisible to the naked eye, is one of the nearest places in the sky where new stars are still actively forming.

The Corona Australis molecular cloud lies roughly 430 light years away, making it one of the closest active star-forming regions to Earth, a dense pocket of gas and dust where young stars are still gathering material from their birth cloud rather than having finished forming long ago. Astronomers studying star formation favour regions this close because fainter, earlier stages of a young star's life, still wrapped in the disc of material that may eventually build planets, are only bright enough to study in detail when the whole system is relatively nearby.

None of this shows in the constellation's shape or its old identity as a wreath or garland beneath the archer; the molecular cloud does not trace an outline the way the visible stars of the crown do, and it was entirely unknown to any tradition that named the constellation, ancient or otherwise, since it requires instruments sensitive to infrared or radio light rather than the naked eye.

A crown of ancient starlight and a nursery of genuinely new stars occupy the same small patch of sky, one visible for millennia and the other found only once the right instruments existed.

Corona Australis, the Southern Crown, is a small southern constellation, one of Ptolemy's forty-eight, the southern counterpart to the Northern Crown, its faint stars forming a delicate arc beneath the feet of Sagittarius the archer. The classical tradition sometimes saw it as a wreath or garland rather than a crown. Though none of its stars is bright, the semicircle is neat and distinct, set against a rich region of the Milky Way that holds nebulae and clusters. In astronomical tradition the constellation is a pattern of stars rather than a zodiac sign. These are the features of Corona Australis as the classical and modern traditions describe it, distinct from any astrological reading; it pairs with its northern namesake as one of the two small crowns set among the larger figures of the sky.

Corona Australis, like Ara its neighbour, borders Lacaille's eighteenth-century Telescopium, so that this corner of the southern sky mixes a small, ancient, mythologically named crown with an eighteenth-century constellation commemorating the very instrument used to chart it precisely for the first time. Corona Australis appears already in some of the oldest surviving Greek constellation lists, considerably more securely ancient than its far larger neighbour Sagittarius acquired any settled fixed form, though its faint stars have always kept it a minor figure next to the archer it sits beneath.