HD 188753

Did You Know?

• The secondary pair of stars orbit each other with a semi-major axis of 0.67 AU.
• The secondary pair have estimated masses of 0.96 and 0.67 solar masses.

Possible planet

In 2005, Dr. Maciej Konacki, a Polish astronomer working in the United States, announced the discovery of a candidate planet orbiting the primary star of the triple star system. The planet, designated HD 188753 Ab, would not have been the first known planet in a triple star system, as 16 Cygni Bb had been discovered earlier in a wide triple system also in Cygnus. Konacki referred to such planets as "Tatooine planets," after Luke Skywalker's home world. The candidate was a hot Jupiter gas giant slightly more massive than Jupiter, thought to orbit HD 188753 A once every 80 hours (3.3 days) at a distance of about 8 million kilometers, one-twentieth of the Earth-Sun distance. Its existence in a relatively close triple star system challenged models of planet formation, since any protoplanetary disk would have ended around 1 astronomical unit from the primary due to the secondary stars, making it difficult for a Jovian planet to form or migrate inward. One suggested possibility was that the planet formed before the secondary stars reached their current configuration, implying they were once more distant. The detection was challenged by Eggenberger et al., and in 2007 a team at the Geneva Observatory stated they had sufficient precision and sampling rate to detect the planet but did not. Konacki responded that the follow-up measurements lacked sufficient precision to confirm or deny the planet's existence, and he planned to release an update in 2007, though no update appears to have been published.