Something weird is sailing toward us, and it is small and cold and swift. No one knows where it came from, and where it is going to. But it is not from the Earth. It is an interstellar comet, that is the first ball of ice, gas, and dust, made on the frozen ambit of a distant star, which some lucky dodge of gravity has tossed into the path of the Earth. For astronomers, the comet is a care package from the sky, a piece of a place they will never be capable of visiting, and the key to all the worlds they can’t observe directly. It is only the stellar interloper that scientists have seen in the solar system. It is the first one they have been capable of getting a good view of. By tracking the movement of the comet, measuring its formation, and monitoring its behavior, researchers are finding clues about the place it came from and the space it crossed to get here.
As the sun sets behind the Tennessee mountains and stars wink into view, astronomer Doug Durig comes off onto the rooftop of his observatory, powers up his three telescopes, and angles them skyward. Every night the comet gets bigger and brighter in the sky, warding off streams of gas and dust that may provide up clues to its history. On 8th December, it will make its nearest access to Earth, providing researchers with an up-close semblance before it zooms back into the cold, featureless void. Each star in the night sky illustrates a possible solar system. Every light in the universe is, more likely than not, some alien planet’s sun.
Scientists have identified thousands of worlds far from our solar system, gas giants and tiny rocky orbits, worlds lit by dim red suns and ones that sphere the spinning remains of collapsed stars. There are even planets spinning medium-size yellow suns like ours, though nothing got so far can match the breathable ambiance and dense, blue oceans of Earth. Scientists’ best expectation for closely observing another solar system was to wait for a piece of one to come to us.