For the first time in the history of astronomy, researchers believe they may have tracked a comet that doesn't appear to have originated from within our solar system.
On Sept. 25, the Pan-STARRS 1 telescope in Hawaii discovered an object on its way back from a close approach of the sun (within 24 million miles). Unlike other comets that generally either burn up in such close proximity to a star or brighten dramatically as their icy cores change to gas, this one was relatively dim. Designated C/2017 U1, the object was also traveling exceptionally fast –– a characteristic that may have saved it from the fate of other sun grazers.
"It went past the Sun really fast," dynamicist Bill Gray, who estimates the comet's diameter in the range of 585 feet, told Sky and Telescope, "and may not have had time to heat up enough to break apart."
What makes this comet so special
What's really unusual about C/2017 U1 and has scientists around the world scrambling to learn more, is the comet's hyperbolic orbit.
And here's an animation:
A majority of known comets, originating from our solar system's asteroid belt, the Kuiper belt, or the Oort cloud, generally follow a locked elliptical orbit with eccentricities on average less than 1. C/2017 U1 is not only hyperbolic and moving at escape velocity with respect to the sun, but also has an eccentricity of 1.18, the highest ever recorded.
While the comet appears to have come from the direction of the star Vega, as Bill Gray explained in a Yahoo forum, there's no telling where this wandering object may have truly originated.
"Once one of these objects gets kicked loose, it'll roam the Milky Way for billions of years," he shared. "Massive amounts of material were ejected from the solar system when it was formed; much of it is probably still wandering around, having gone around the galaxy over a hundred times. (Long enough to get separated from its star of origin by roughly half the diameter of the galaxy.) Other stars, we may assume, have similarly scattered bits all over the place."
One thing we do know is that interstellar comets are extremely rare, with astronomers estimating an opportunity to catch one only once every couple centuries. With this in mind, astronomers are eagerly pouring over all available data and observations.
"Further observations of this object are very much desired," Gareth V. Williams, associate director of the Minor Planet Center, wrote. "Unless there are serious problems with much of the astrometry listed below, strongly hyperbolic orbits are the only viable solutions. Although it is probably not too sensible to compute meaningful original and future barycentric orbits, given the very short arc of observations, the orbit below has e ~ 1.2 for both values. If further observations confirm the unusual nature of this orbit, this object may be the first clear case of an interstellar comet."