A peculiar comet by the name of Machholz 1 was found more than two decades ago, in 1986, by Donald Machholz from Loma Prieta, California. So far, experts determined that, judging by its abnormal chemical composition, which requires assigning it to an entirely new category, it must have arrived here from somewhere well outside our solar system. The last of the several appearances of the comet took place last year.

"A large fraction of comets in our own solar system have escaped into interstellar space, so we expect that many comets formed around other stars would also have escaped," explained David Schleicher, a planetary astronomer from the Lowell Observatory in Arizona, cited by Space. "Some of these will have crossed paths with the sun, and Machholz 1 could be an interstellar interloper." This type of object is thought to be made of the oldest material in our system, holding clues related to the nebula that spawned it.

During the light sight, Schleicher determined the quantity of some carbon and other compounds existing in the tail of Machholz 1 and compared them to similar data from 150 different comets, which led him to conclude that this is indeed a strange build. The comet has 72 times less cyanogen molecules than average comets, and also far less C2 and C3 molecules, which requires integrating it into a new class, perhaps together with another odd one, named Yanaka.

 

"I'm not real thrilled with any of the three [scenarios]" that were proposed for the comet's place of origin, shared Schleicher. The first of these implies that Machholz 1 came from another star system whose proto-planetary disk contained much less carbon than ours. Another suggests that it formed in our system but in an extreme environment far from the Sun, comparing to other comets. The third possibility envisions the young Machholz 1 as a carbon-chain depleted comet with a chemistry modified by intense Sun heat. Perhaps the next sighting of the comet - in 2012 - will shed more light on the topic.