A strange object was discovered by astronomer Lynne Allen from the University of the Canadian province of British Columbia (Vancouver) in images obtained by the Canada-France-Hawaii Telescope in December 2004. A new series of observations conducted since October 2005 made it possible to detect its strange and unusual orbit.
The object, designated 2004 XR190, has a diameter of 500–1000 km, meaning it is at least two times smaller than Pluto. Its orbit lies in the region of cold bodies known as the "Kuiper Belt." The oddity lies in the inconceivable inclination of its orbit to the ecliptic plane – it is 47 degrees. Astronomers have never encountered anything like this. In addition to this, its orbit is practically circular, reports New Scientist. Previously, a number of very unusual objects had already been found in the Kuiper Belt, fully capable of claiming planet status by their size, but nothing so strange had ever been found until now.
Currently, an assumption is being made that the deviations of the orbital planes of Kuiper Belt objects are caused by the perturbing gravitational influence of Neptune – the only massive planet whose orbit passes in close proximity to the Kuiper Belt. However, bodies that have experienced such influence should move along orbits with high eccentricity and approach Neptune's orbit at perihelion (approximately 30 astronomical units from the Sun).
But the orbit of object 2004 XR190 is practically circular and located too far away (52–62 astronomical units) to explain the entire wonder by the influence of Neptune's attraction.
Similarly, it is difficult to explain such an orbit by the hypothetical passage in the distant past of another star near the Sun. Astronomers call it "Buffy" – in honor of one of the characters from a popular US TV series about vampire slayers. "Perhaps Buffy will become the slayer of the existing theory," thinks Dr. Allen. However, a chance to explain all the strange phenomena, albeit ephemeral, remains – according to one of the widespread viewpoints, Neptune itself relatively recently arrived at its current orbit from the vicinity of Uranus.
In this case, its gravitational influence, spreading to the peripheral regions of the Solar System, formed resonance zones in which the orbital periods of celestial bodies become multiples of Neptune's own orbital period. In this case, one of the "resonances," passing near 2004 XR190, could theoretically have transferred it subsequently from a flat circular to an elliptical but significantly inclined orbit. Subsequently, as the inclination of its plane increased, the orbit could again become close to circular. True, it is unclear to what extent the resonance mechanism is capable of explaining such an astonishing inclination of 2004 XR190's orbit.
The discovery of a new object with such a strange orbit raises difficult questions for astronomers. Until now, the search for distant objects of the Solar System was conducted mainly near the ecliptic plane – it was believed that this is precisely where they concentrate. It was here that 2004 XR190 was also detected – however, this region accounts for at most 2% of the total length of its orbit. This means that a huge number of bodies similar to it have until now eluded astronomers simply as a result of an originally incorrectly made assumption.
Hal Levinson from the Southwest Research Institute (Boulder, Colorado) believes that the time has come to revive the hypothesis according to which the Sun has a companion – a massive star. True, astronomers have not yet managed to find such a star, which in itself does not add peace of mind.
The detection of 2004 XR190 makes the study of objects on the periphery of the Solar System very important, both by astronomical methods and with the help of spacecraft.
Currently, the research probe "New Horizons" is being prepared for launch; it is to study the Pluto-Charon system from a flyby trajectory and then continue studying Kuiper Belt objects. The question of sending a heavy nuclear-powered ship to Neptune and its satellite Triton is being considered. It is quite possible that their scientific program, under the influence of new discoveries, will be able to undergo significant changes long before the vehicles themselves reach the distances that beckon astronomers.