January 9, 2013
Exoplanet Fomalhaut B’s Odd Orbit Could Be Caused By Star’s Vast Debris Disk
redOrbit Staff & Wire Reports — Your Universe Online
According to newly released images from the Hubble Space Telescope, a vast debris belt circling around a nearby star is wider than scientists believe, and the unusual orbit of a planet traveling around that star could be to blame.
In a statement released Tuesday, NASA officials stated that the images reveal that the debris disk traveling around the star Fomalhaut actually spans from 14 to 20 billion miles from the star — much larger than astronomers had previously believed.
Furthermore, the space telescope has returned pictures allowing experts to determine that the planet in question, dubbed Fomalhaut b, “follows an unusual elliptical orbit that carries it on a potentially destructive path through the vast dust ring” and “may provide forensic evidence of a titanic planetary disruption in the system.”
The so-called "zombie planet" Fomalhaut b comes as close as 4.6 billion miles to its star and travels as far as 27 billion miles away from it at its outermost point, the research team explained after recalculating the planet´s orbit based on observations made by Hubble last year.
The discovery, which was presented Tuesday during a meeting of the American Astronomical Society (AAS) in Long Beach, California, was shocking and unexpected says Paul Kalas of the University of California, Berkeley and the SETI Institute.
“The Fomalhaut team led by Kalas considers this circumstantial evidence there may be other planet-like bodies in the system that gravitationally disturbed Fomalhaut b to place it in such a highly eccentric orbit,” the U.S. space agency said.
“Among several scenarios to explain Fomalhaut b's 2,000-year-long orbit is the hypothesis that an as yet undiscovered planet gravitationally ejected Fomalhaut b from a position closer to the star, and sent it flying in an orbit that extends beyond the dust belt,” they added.
In addition, Hubble discovered that the ice and dust belt that orbits around Fomalhaut contains what appears to be a gap that slices across it. That gap could have been caused by another yet-undetected planet. The high-quality view of the debris shows a series of irregularities that scientists believe could mean that they need to start looking for additional worlds orbiting the star.
“If its orbit lies in the same plane with the dust belt, then Fomalhaut b will intersect the belt around 2032 on the outbound leg of its orbit,” NASA said. “During the crossing, icy and rocky debris in the belt could crash into the planet's atmosphere and create the type of cosmic fireworks seen when Comet Shoemaker-Levy 9 crashed into Jupiter. Most of the fireworks from collisions will be seen in infrared light.”
If the planet is not co-planar with the dust belt, however, the only thing that will be visible is a gradual dimming of Fomalhaut b as it moves farther away from the star, they explained.
“Kalas hypothesized that Fomalhaut b's extreme orbit is a major clue in explaining why the planet is unusually bright in visible light, but very dim in infrared light,” the researchers said. “It is possible the planet's optical brightness originates from a ring or shroud of dust around the planet, which reflects starlight. The dust would be rapidly produced by satellites orbiting the planet, which would suffer extreme erosion by impacts and gravitational stirring when Fomalhaut b enters into the planetary system after a millennium of deep freeze beyond the main belt.”
“The team has also considered a different scenario where a hypothetical second dwarf planet suffered a catastrophic collision with Fomalhaut b. The collision scenario would explain why the star Fomalhaut has a narrow outer belt linked to an extreme planet. But in this case the belt is young, less than 10,000 years old, and it is difficult to produce energetic collisions far from the star in such young systems,” they added.