The planet with three suns
If HD 188753 Ab were inhabitable, there would probably be some fantastically expensive beachfront real estate available for sale, of for no other reason than the planet experiences triple sunsets on occasion. Located in the Cygnus constellation, the planet was discovered by Dr. Konacki of Caltech using the Keck I telescope. Alas, the planet is a hot gas giant, and thus will not be explored by Spaceman Spiff.
What is interesting about the find is the light that it sheds on planet-formation. This planet exists in the most gravitationally-complex solar system yet found. The triple sunset would be a rare occurence.
“Multiple-star systems have not been popular planet-hunting grounds,” said Konacki. “They are difficult to observe and were believed to be inhospitable to planets.”
The new planet belongs to a common class of extrasolar planets called “hot Jupiters,” which are gas giants that zip closely around their parent stars. In this case, the planet whips every 3.3 days around a star that is circled every 25.7 years by a pirouetting pair of stars locked in a 156-day orbit.
The existence of this particular arrangement of stars and planet calls into questions astronomers’ understanding of how hot gas giants actually form.
The circus-like trio of stars is a cramped bunch, fitting into the same amount of space as the distance between Saturn and our Sun. Such tight living quarters throw theories of hot Jupiter formation into question. Astronomers had thought that hot Jupiters formed far away from their parent stars, before migrating inward.
“In this close-knit system, there would be no room at the outskirts of the parent star system for a planet to grow,” said Konacki.
Hot Jupiters are believed to form out of thick disks, or “doughnuts,” of material that swirl around the outer fringes of young stars. The disk material clumps together to form a solid core, then pulls gas onto it. Eventually, the gas giant drifts inward. The discovery of a world under three suns contradicts this scenario. HD 188753 would have sported a truncated disk in its youth, due to the disruptive presence of its stellar companions. That leaves no room for HD 188753’s planet to form, and raises a host of new questions.
The masses of the three stars in HD 188753 system range from two-thirds to about the same mass as our Sun. The planet is slightly more massive than Jupiter.
Oh well. Maybe it has a moon with some nice beachfront property…
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