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Sun May Still Have Low-Mass Solar Companion, Say Astrophysicists Searching NASA WISE Mission Data
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Our sun may indeed have a far-flung gravitationally-bound companion — just not with the size or orbit that could have triggered periodicity in earth’s paleontological record, say astrophysicists now actively searching data from NASA’s WISE (Wide-field Infrared Survey Explorer) spacecraft.
For decades astronomers and paleontologists have debated whether our sun has a stellar mass M-dwarf companion dubbed “Nemesis” that could have caused a 26 million-year periodicity in earth’s asteroidal and cometary impact record.
Such a small M-dwarf star has long been ruled out by WISE data, however, since observers would surely have spotted an object larger than roughly five Jupiter masses.
However, John Matese and Dan Whitmire, two astrophysicists at the University of Louisiana in Lafayette, continue to scour the spacecraft’s data for the signatures of “Tyche,” a totally different type of solar companion. Unlike Nemesis, Tyche (or Nemesis’ good sister), is a hypothetical 1 to 4 Jupiter-mass object that would lie about a third of a light year away, on a very long four million-year circular solar orbit inclined at least 45 degrees to the plane of our solar system.
“Physically, it would be a captured planet from another star in the complex of stars and clouds from which the sun formed,” said Whitmire, who has spent a large part of his career pursuing both Nemesis and Tyche. “We don’t think it formed like a star. But the door is definitely still open for a companion of mass less than about two Jupiters, [at least] in the one sixth of the sky we have investigated.”
Whitmire and colleague John Matese’s primary evidence for Tyche stems from cometary perturbations within the Oort cloud, a massive reservoir of comets thought to circle our solar system at a distance of roughly a light year.
Whitmire says there is an anomalous and “statistically-unlikely” number of comets along this band of sky, which suggests some form of gravitational perturbation. In Matese and Whitmore’s model, Tyche slightly perturbs the comets in conjunction with the galactic tide, a gravitational force produced by the disk of the Milky Way.
“We argue that Tyche has enough mass to work in conjunction with the galactic tide and cause comets to preferentially migrate in along its circular orbit,” said Whitmire. “We’re basing our evidence on comets that are being observed today.”
Because Tyche would have a circular orbit, says Whitmire, it would be perturb a portion of the Oort cloud’s estimated trillion comet reservoir, a very small fraction of which would then fall into the inner solar system.
Whitmire notes that the Kuiper Belt Object Sedna may have also been perturbed by Tyche, since Sedna has an orbit well beyond that of Neptune.
“Our own Tyche search has thus far focused only on the predicted great circle, or a sixth of the sky,” said Whitmire. “We would have already identified any object more massive than roughly three Jupiter masses within a third of a light year in that band of sky. The search is not as easy as originally claimed primarily because of the lack of a robust theoretical model for an [identifying] spectrum from such an isolated one Jupiter-mass object.”
By year’s end, Matese says the WISE team will likely announce whether a one- to two-mass Jupiter object like Tyche can be definitively rejected as a possible solar companion.
[link to www.forbes.com]
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