A cat with no tail is a Manx. A dog with no tail could be a Corgi. A lobster with no tail is the remains of a good meal. A comet with no tail is a mystery that may give us a clue as to how the solar system was formed.
The comet, named C/2014 S3 and referred to as a Manx object for obvious reasons, was first spotted in 2014 by astronomers using the Pan-STARRS telescope in Hawaii. It appears to be part of the Oort cloud of space objects, as its 860-year orbit takes it to the far reaches of the solar system.
After its discovery, S3 was tracked by astronomers using the European Southern Observatory’s Very Large Telescope in Chile and the Canada-France-Hawaii Telescope and they’re the ones who noticed something unusual about it.
We’ve found the first rocky comet.
Astronomer Olivier Hainaut, co-author of the new study about C/2014 S3 in the current edition of Scientific Advances, points out that all comets have tails as their ice melts on their approach to the sun and mixes with dust to leave a dirty trail behind them. Why doesn’t S3 have a tail? Hainaut believes that S3 may have formed at the same time as Earth and in the same general area.
It is very exciting — S3 would have been kicked out while the Earth was being formed, possibly even by the early-days Earth. S3 would then be a planetesimal like those which formed the Earth, but preserved since that time in the cold of outer space.
This makes S3 more of an asteroid than a comet but it’s an unusual asteroid as well. Because C/2014 S3 spends most of its orbit so far from the sun, it hasn’t been baked by solar heat for millions of years and is probably closer to its early state. Astronomer and lead author Karen Meech describes it as only an astronomer can:
This one is the first uncooked asteroid we could observe — it has been preserved in the best freezer there is.
If there’s one tailless comet, there’s probably more. Hainaut is now scheduling telescope time to determine which part of the Oort cloud C/2014 S3 and its tailless cohorts came from. Finding them and developing models to predict from where in the inner solar system a planetary collision or gravitational action chucked them out of will help better understand how the solar system was formed.
If I ever get an offer to be a porn star, my name will be Rocky Comet.