In the northern constellation Cygnus (The Swan) a planet the size of Jupiter orbits around three stars 149 light-years (1200 trillion kilometres) from Earth.
From the Caltech news release comes a challenge to the theories about planetary formations in complex solar systems.
Maciej Konacki reported this discovery in the May 2005 issue of Nature.
"If the parent star is orbited by a close stellar companion, then its gravitational pull can significantly truncate a protoplanetary disk around the main star. In the case of HD 188753, the two stellar companions would truncate the disk around the main star to a radius of only 1.3 astronomical units, leaving no space for a planet to form." - http://pr.caltech.edu/media/Press_Releases/PR12716.html
In the case of this triple star system, a red giant and an orange star orbit around a yellow star, according to SpaceFlight News http://www.spaceflightnews.com/forum/lofiversion/index.php/t1161.html.
"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." - NASA Jet Propulsion Laboratory website http://planetquest.jpl.nasa.gov/
Regarding star system HD 188753, perhaps only large planetary masses can survive the combined tidal and solar forces of three stars in close orbit around each other.
My guess is that the planet, which is slightly larger than Jupiter, was too small to become a star.
Thus, in the formation of star systems, the larger masses become stars.
Any masses smaller than a certain size become planets. Judging from this example, the size limit may be slightly more than the size of Jupiter.
The size (diameter, surface area, volume and mass) of Jupiter is as follows:
Diameter: 108 × 1.43 m
Surface area: 1017 × 0.641 m2
Volume: 1025 × 1.52 m3
Density: 103 × 1.3 kg/m3 (1.3 g/cm3)
Mass: 1027 × 1.9 kg
Note: 10E8 = 100,000,000
cm = centimetre
m = metres
kg = kilograms
http://www.vendian.org/envelope/dir1/earth_jupiter_sun.html
4 comments:
Within the context of a triple-star system, the planet was too small to become a star.
Not being massive enough, it didn't accumulate the helium and hydrogen needed to fuel the stellar thermonuclear reaction.
Thus, it became a planet that was only detectable because it is slightly larger than Jupiter.
Theory of Hot Jupiters: "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."
So, what if the planet in star system HD188753 is a failed star in a double-binary system?
This system consists of a larger yellow star around which the planet, and the smaller red and orange binary pair, revolves.
Perhaps in the early years of formation, the binary pair orbited the yellow star further away than today.
This would leave room for the planet to form.
Google results on Cygnus and Maciej Konacki
The topic of hot Jupiters is further explained at Astronomy Cast Episode 3: http://www.astronomycast.com/extrasolar-planets/hot-jupiters-and-pulsar-planets/
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