At nearly eighth magnitude, HD 188753 (in the constellation Cygnus is just barely visible at the center
of the labelled circle and requires a telescope or large binoculars
to see. HD 188753 is unique in that the planet orbits within a
triple star system. The planet, a "hot Jupiter," goes around the
primary of the system as does a remarkably-nearby close double
star. How such a system could have developed is a mystery since
the secondary double star should have destroyed the raw material
from which the planet should have formed.
The planet, with a mass at least 1.14 times that of Jupiter, orbits
very close to the primary (brighter) star of the triple system HD
188753 with a period of only 3.3481 days at a distance of but
0.0446 Astronomical Units (6.7 million miles, 10.8 million
kilometers), 11.5 percent the distance of Mercury from the Sun.