RW Aurigae

Lore & Background

The RW Aurigae system consists of two pre-main-sequence stars, RW Aurigae A and B, the latter discovered in 1944. They are loosely bound on a nearly parabolic, retrograde orbit with a period of 1000–1500 years, evidenced by the structure of ejected dust jets. The primary is suspected to be a close binary since 1999. Both stars are accreting mass and contracting toward the main sequence, with ages of 3 million years. The system is surrounded by a complex accretion structure including a circumbinary shell, spiral arms, bow shocks, and protoplanetary disks. RW Aur A produces bipolar jets extending up to 46,000 AU, and its protoplanetary disk is inclined 45–60 degrees to the line of sight.

Reader's Guide

RW Aurigae serves as a key laboratory for studying star formation, binary interactions, and planet formation in young systems. Its variability, driven by the companion's periastron passages, provides insight into how stellar encounters shape protoplanetary disks. The detection of a Vesta-sized differentiated planetesimal's iron core funneled into the star's atmosphere and jets, reported in work from 2018–2022, demonstrates that large asteroid-like bodies can form in outer disk regions, migrate inward, and undergo catastrophic collisions. This challenges and informs models of planetary system evolution. The system's long-lasting dimming events (2010–2011, 2014–2016) and the new dimming starting February 2025 continue to offer real-time data on disk dynamics and accretion processes.

Did You Know?

• A previous periastron passage of RW Aurigae B occurred about 400 years ago.
• The system's orbit is retrograde compared to the rotation direction of the disk orbiting the primary star.
• In February 2025 a new major dimming event started.

Mythological Identity and Cultural Layers

The constellation Auriga carries one of the richest mythological portfolios in the night sky, with no single narrative ever settling as definitive. In Greek tradition it is most commonly identified as Erichthonius, the chthonic son of Hephaestus raised by Athena, who invented the four-horse chariot and won the kingship of Athens before Zeus elevated him to the heavens. Yet other Greek sources cast the figure as Myrtilus, Hermes's son and charioteer for Oenomaus, whose life ended at the hands of Pelops before his father placed him among the stars. A third Greek reading sees Hippolytus, Theseus's son, whose chariot was wrecked after his exile from Athens. In late antiquity the Latin poets Claudian and Nonnus offered yet another identity: Phaethon, Helios's son, who lost control of the sun chariot and was struck down by Zeus before being memorialized in the sky. Even Medea's dismembered brother, flung into the sea during the Argonauts' homeward voyage, is said to be represented by Auriga's stars scattered along the Milky Way. This multiplicity suggests the Greeks may have shaped the constellation to honor the chariot's central role in their own society rather than to memorialize one specific hero.

Astronomical Significance and Notable Objects

Auriga occupies 657 square degrees of the northern sky, making it roughly half the area of Hydra, the largest of all 88 modern constellations. Its stellar and deep-sky content rewards both professional and amateur observers. Capella, the constellation's brightest star, is an unusual multiple system that ranks among the most luminous objects visible to the naked eye. Beta Aurigae draws interest as a variable star, while Epsilon Aurigae has been the subject of intensive study owing to its status as a nearby eclipsing binary with an unusually long orbital period. Because Auriga sits close to the winter band of the Milky Way, it hosts several bright open clusters—M36, M37, and M38—that are popular targets for backyard telescopes. The Flaming Star Nebula, linked to the variable star AE Aurigae, adds a prominent emission nebula to the constellation's inventory. Auriga also serves as the radiant point for several meteor showers, including the Aurigids, Zeta Aurigids, Delta Aurigids, and the hypothesized Iota Aurigids. Visibility, however, is latitude-dependent: because of its northern declination, the full constellation can be seen only as far south as minus 34 degrees, beyond which it sinks partially or entirely below the horizon.

Historical Record and Cultural Transmission

The earliest known record of Auriga's stars traces back to Mesopotamian astronomy, where they appeared under the name GAM, representing a scimitar or crook, alternatively called Gamlum or MUL.GAM in the MUL.APIN catalogue. In that context the crook symbolized a goat-herd or shepherd, and the figure incorporated most of the modern constellation's bright stars, with the notable exception of Elnath, which was traditionally shared with Taurus. Bedouin astronomers later reinterpreted the same stellar pattern as a herd of goats, each star representing one animal—an association that also surfaced in Greek mythology. The Greek tradition preserved the goat link while gradually overlaying the charioteer narrative. Ptolemy's 2nd-century Almagest formally merged the Charioteer with the Goats, a separate constellation that earlier writers such as Pliny the Elder and Manilius had treated independently under names like Capra, Caper, or Hircus. The constellation's stars were also woven into Chinese celestial mythology, where they formed part of the celestial emperors' chariots. Auriga endures today as one of the 48 Ptolemaic constellations carried into the modern 88-constellation system, most prominently visible during winter evenings in the northern hemisphere as part of the Winter Hexagon asterism.

Visual Representation and Iconography

Traditional star atlases depict Auriga as a charioteer gripping the reins in his right hand while balancing a goat—Capella—over his left shoulder and tucking two kids, Zeta and Eta Aurigae, under his left arm. The two kids were first given their name by the ancient Greek astronomer Cleostratus, and the goat-and-kids group had once stood as its own constellation before Ptolemy's merger. Yet illustrations of the figure have never been uniform. In some renderings the reins in the charioteer's right hand are drawn as a whip instead, and the overall pose shifts from atlas to atlas. The 1488 edition of Hyginus's work is one example of the long tradition of inconsistent depictions. Capella's mythological link to Amalthea, the she-goat who nursed the infant Zeus, reinforces the goat imagery, though some sources instead associate the star with the nymph who owned the goat. In that variant, the goat's hideous, Gorgon-like appearance played a role in the Titans' defeat when Zeus skinned it and wore the hide as his aegis. The asterism of Capella with Epsilon, Zeta, and Eta Aurigae thus carries layered mythological meaning that has persisted from antiquity into modern star charts.