Astronomers have now discovered about 10 planets orbiting other stars. When and how will these planets receive names? Who gets to name them?

After years of fruitless searching astronomers have been delighted and a little astounded by the rapid pace of discovery of planets around nearby stars. Thee first of these, around the star 51 Pegasi, was found just in October 1995. There is now strong evidence for planets circling at least eight sunlike stars. ( The exact number depends on how much faith one puts in some tentative observations and on whether one classifies certain extremely massive bodies as true planets; the Extrasolar Planets Catalogue maintains a frequently updated list of the various candidates.) Such swift progress has caught the scientific community off guard, so there is as yet no standard set of rules for naming the new planets.

Geoffrey Marcy of San Francisco State University leads the team that has produced most of the new discoveries. He provides this insider's view of the current ferment:

"Formal names of astronomical objects and features are set by the International Astronomical Union (IAU). At the meeting of the IAU General Assembly in Kyoto, Japan, in August 1997, there will be a convening of the IAU's Naming Commission. The commission is the body that normally is responsible for assigning names to new asteroids, craters and so on. At the Kyoto meeting, the IAU will bring up the issue of naming new planets around other stars.

"The issue of extrasolar planet names has become quite pressing. For example, William D. Cochran of the University of Texas and our group at San Francisco State recently announced the discovery of a planet orbiting the star 16 Cygni B (a sunlike star roughly 70 light-years distant in the constellation Cygnus). What should we call this planet? We cannot call it ' 16 Cyg B b.' And we certainly cannot call it '16 Cyg A,' because 16 Cyg B already has a stellar companion by that name. We cannot call it 16 Cyg C ( which would seem to denote a third star in the system); even '16 Cyg 3' or '16 Cyg B 2' seems too cumbersome and nondescript. So some uniform naming system is needed.

"Assigning Greek names, akin to the ones we use for the planets of our own solar system, would be fine, but it would not constitute a coherent naming system per se. Likewise we could designate the planets using lowercase Roman numerals after the name of the star, but that system is also very bland and does not work well verbally. In retrospect, simply using numbers to denote planets might be adequate--'16 Cyg B 2,' as suggested above, might be okay. But, of course, the first planet discovered around a star might not be the closest one nor the biggest one. Perhaps we could number the planets as they are found; then centuries from now, when the planetary inventories are more complete, someone could rename them all, just as Scarlatti's sonatas were renumbered years later, putting them in correct order.

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