What event has just occurred? Asteroid (188847) 2006 FT9, discovered 23 March 2006 by Calvin student Josh Vanderhill and Prof. Larry Molnar, was officially given the name "Rhipeus" (Minor Planet Circular 63643, 2008 August 19).
What is the history of the asteroid? Asteroid Rhipeus was discovered during the 2006 Spring break by Calvin student Josh Vanderhill and Prof. Larry Molnar. It quickly became evident that this asteroid was unique among the asteroids discovered by Calvin College: it is much larger and more distant than all the others. Indeed, alone among the 180 asteroids discovered as of this writing, it does not orbit in the asteroid belt (a wide region of space between the orbits of Mars and Jupiter). Instead, its orbit directly overlaps that of Jupiter. It is in one of two clusters of asteroids (known as Trojan asteroids) that have orbits synchronized by Jupiter to exactly match the average motion of Jupiter. As a consequence these asteroids maintain a nearly constant distance from Jupiter, either leading or lagging Jupiter by about 60 degrees in their orbit. See the separate web page on the discovery of asteroid Rhipeus and the nature of Trojan asteroids.
Why was the specific name chosen? Once an asteroid has received its permanent numerical designation (recognizing that its orbit is well established), it is the privilege of the discoverer to suggest a permanent name to the committee on nomenclature of the International Astronomical Union (IAU). However, in the case of Trojan asteroids a special tradition applies. Following the precedent set in 1906 by Max Wolf upon the first discovery of a Trojan asteroid (588 Achilles), Trojan asteroids are named after participants in the ancient war between the Greeks and the Trojans as described in Homer's Iliad, and Vergil's Aeneid. Specifically, asteroids in the leading group are named for Greek heroes and those in the lagging group for Trojan heroes.
The formal citation as published by the IAU is as follows:
"According to Vergil, Rhipeus died fighting alongside Aeneas in the fall of Troy. The poet says that Rhipeus was 'the single most just man among the Trojans and the best preserver of fairness, but the gods thought otherwise'. In the Paradiso, Dante places him in the sphere of Jupiter in the eye of the eagle."
Vergil's brief mention (Aeneid 2.426-7) of Rhipeus describes a brave and upright character, good qualities for being memorialized by an asteroid name. The curious postscript "but the gods thought otherwise" points to the irony that his good character did not prevent him from being killed.
Dante took note of Vergil's description and placed him among the characters he meets in the Paradiso, his fictional tour of the levels of heaven. The theme of justice was important to Dante, and he places Rhipeus in the orbit of Jupiter, the level reserved for souls known for just actions in life. Moreover, he places him in the eye of the eagle, in a list of the all-time top six: "Who in the erring world below would think / that Trojan Ripheus should be the fifth / among the holy lights along this arc?" (Paradiso XX.67-69; note "Ripheus" is an alternative English spelling of "Rhipeus".)
Dante's phrasing shows he is well aware the reader will be surprised to find Rhipeus included at all, as Christian theology makes clear that only faith in Christ is sufficient to gain entry into Paradise (and Troy fell centuries before the coming of Christ). The next line of the poem continues about Rhipeus: "Now he knows much the world cannot discern / of heavenly grace, although his sight / cannot make out the bottom of this sea." (Paradiso XX.70-72) God has shown grace by miraculously granting Rhipeus a conversion opportunity. This becomes a partial answer to Dante's questioning the justice of God. We can perceive God's grace and justice in this action, although we can no more perceive his full mind or methods than we can see the bottom of the sea (an answer reminiscent of that given Job).
In summary, the selection of the name Rhipeus honors both the just nature of Rhipeus and the just (if sometimes mysterious) nature of God. And, of course, it is satisfying poetically to note that while it seems a coincidence that Max Wolf began the practice of giving Trojan names to asteroids in the orbit of Jupiter, Dante had already placed one Trojan in Jupiter's orbit nearly six centuries before.
A postscript on Dante's personal interest in the cause of justice: Before writing the Divine Comedy (of which the Paradiso is the third part), Dante was exiled from his home city of Florence on pain of death should he ever return. The ban was finally lifted in 2008 (over 700 years later!) [link to Telegraph news item].
Special thanks to H. D. Cameron, Professor of Greek and Latin and Director of the Great Books Program at the University of Michigan, for his generous and expert advice in the naming of asteroid Rhipeus.
English translations from Paradiso were quoted from the verse translation by Robert and Jean Hollander (Doubleday, New York, 2007).
[Text by L. Molnar, posted 9/1/08.]