In 1999, Matese and colleague Daniel Whitmire suggested the sun has a hidden companion that boots icy bodies from the Oort Cloud, a spherical haze of comets at the solar system’s fringes, into the inner solar system where we can see them.
In a new analysis of observations dating back to 1898, Matese and Whitmire confirm their original idea: About 20 percent of the comets visible from Earth were sent by a dark, distant planet.
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The cosmic snowballs that form the hearts of comets generally hang out in the Oort Cloud until their orbits are nudged by some outside force. This push could come from one of three things, Matese said. The constant gravitational pull of the Milky Way’s disk can drag comets out of their icy homes and into the inner solar system. A passing star can shake comets loose from the Oort Cloud as it zips by. Or a large companion like Nemesis or Tyche can pull comets out of their comfort zones.
Computational models show that comets in each of these scenarios, when their apparent origins are mapped in space, make a characteristic pattern in the sky.
“We looked at the patterns and asked, ‘Is there additional evidence of a pattern that might be associated with a passing star or with a bound object?’” Matese said.
After examining the orbits of more than 100 comets in the Minor Planet Center database, the researchers concluded that 80 percent of comets born in the Oort Cloud were pushed out by the galaxy’s gravity. The remaining 20 percent, however, needed a nudge from a distant object about 1.4 times the mass of Jupiter.
“Something smaller than Jovian mass wouldn’t be strong enough to do the deed,” Matese said. “Something more massive, like a brown dwarf, would give a much stronger signal than the 20 percent we assert.”
Matese and Whitmire propose the name Tyche, "the presiding tutelary deity that governed the fortune and prosperity of a city, its destiny," as name for this planet.
Whitmire's website links to the arXiv-hosted paper where they set forth their theory in detail, "Persistent Evidence of a Jovian Mass Solar Companion in the Oort Cloud." Their abstract?
We present an updated dynamical and statistical analysis of outer Oort cloud cometary evidence suggesting the sun has a wide-binary Jovian mass companion. The results support a conjecture that there exists a companion of mass ~ 1-4 M_Jup orbiting in the innermost region of the outer Oort cloud. Our most restrictive prediction is that the orientation angles of the orbit normal in galactic coordinates are centered on the galactic longitude of the ascending node Omega = 319 degree and the galactic inclination i = 103 degree (or the opposite direction) with an uncertainty in the normal direction subtending ~ 2% of the sky. A Bayesian statistical analysis suggests that the probability of the companion hypothesis is comparable to or greater than the probability of the null hypothesis of a statistical fluke. Such a companion could also have produced the detached Kuiper Belt object Sedna. The putative companion could be easily detected by the recently launched Wide-field Infrared Survey Explorer (WISE).
I lack the mathematical skills necessary to evaluate this paper. Going into the paper, they suggest that Tyche's orbit may be quite distant indeed from the heart of the solar system. According to the inverse-square law, in order to exert the same gravitational force on the eight planets and various dwarf planets and comets that Matese and Whitmire's theory predicts, the closer the planet orbits the sun, the less massive it would have to be. Existing surveys of the solar system in infrared and other frequencies also limit Tyche's parameters (if it exists). The maximum distance predicted--30 000 AU--isn't different from the ~0.237 AUY that separates Proxima Centauri from the Alpha Centauri A/B binary to which it seems gravitationally bound.