Observations of a tailless comet called C/2014 S3 (PanSTARRS), made with ESO’s Very Large Telescope and the Canada France Hawaii Telescope, show that it is the first object to be discovered on a long-period cometary orbit that has the characteristics of a pristine inner Solar System asteroid.
Artist’s impression of C/2014 S3 (PanSTARRS). The comet’s current long orbital period (approximately 860 years) suggests that its source is in the Oort Cloud — a large region surrounding the Sun like a giant, thick soap bubble — and it was nudged comparatively recently into an orbit that brings it closer to the Sun. Image credit: M. Kornmesser / ESO.
C/2014 S3 (PanSTARRS) was discovered in 2014 by University of Hawai’i astronomer Karen Meech and her colleagues using the Pan STARRS1 survey telescope.
The astronomers immediately noticed that C/2014 S3 (PanSTARRS) was unusual, as it does not have the characteristic tail that most long-period comets have when they approach so close to the Sun. As a result, it has been dubbed a Manx comet, after the tailless cat.
In their new paper, published online today in the journal Science Advances, Dr. Meech and co-authors conclude that C/2014 S3 (PanSTARRS) formed in the inner Solar System at the same time as the Earth itself, but was ejected at a very early stage.
Their observations indicate that it is an ancient rocky body, rather than a contemporary asteroid that strayed out.
As such, it is one of the potential building blocks of the rocky planets, such as the Earth, that was expelled from the inner Solar System and preserved in the deep freeze of the Oort Cloud for billions of years.
This image of C/2014 S3 (PanSTARRS) was acquired using the Canada France Hawai’i Telescope. Image credit: K. Meech / IfA / UH / CFHT / ESO.
“We already knew of many asteroids, but they have all been baked by billions of years near the Sun,” Dr. Meech said.
“This one is the first uncooked asteroid we could observe: it has been preserved in the best freezer there is.”
Analysis of the light reflected by C/2014 S3 (PanSTARRS) indicates that it is typical of asteroids known as S-type, which are usually found in the main asteroid belt.
It does not look like a typical comet, which are believed to form in the outer Solar System and are icy, rather than rocky.
It appears that the material has undergone very little processing, indicating that it has been deep frozen for a very long time.
The very weak comet-like activity associated with this comet, which is consistent with the sublimation of water ice, is about a million times lower than active long-period comets at a similar distance from the Sun.
According to the team, C/2014 S3 (PanSTARRS) is probably made of fresh inner Solar System material that has been stored in the Oort Cloud and is now making its way back into the inner Solar System.
_____
Karen Meech et al. Inner Solar System Material Discovered in the Oort Cloud. Science Advances, published online April 29, 2016
