Kuiper Belt asteroid likely originated in region between Mars and Jupiter

Object's carbon-rich composition, unlike that of most KBOs, reflects its origin.
By Laurel Kornfeld | Oct 05, 2018
A carbon-rich asteroid discovered in the Kuiper Belt likely originated in the asteroid belt between Mars and Jupiter and was at some point ejected from its original orbit, according to an international team of astronomers.

Kuiper Belt Object (KBO) 2004 EW95, initially found more than a decade ago, was recently found to be carbonaceous when viewed with the Hubble Space Telescope (HST) during routine observations.

Followup studies of the asteroid with the European Southern Observatory's (ESO) Very Large Telescope (VLT) confirmed its carbonaceous composition.

Although 2004 EW95 is both small and distant, scientists were able to determine its composition by measuring its reflectance spectrum, the pattern of light wavelengths it reflects, which is very different from that of most KBOs.

Typical KBO spectra are featureless and reveal little about the objects.

"The reflectance spectrum of 2004 EW95 was clearly distinct from the other observed outer solar system objects," emphasized Tom Seccull of Queens University in Belfast, who led the study. "It looked enough of a weirdo for us to take a closer look."

That closer look was done using two of the VLT's sensitive spectrographs, which reveals more details about light patterns reflected by objects, enough for scientists to learn their compositions.

Just 186.4 miles (300 km) wide and located four billion km from Earth, the asteroid was difficult to detect and measure even with the most sophisticated and sensitive instruments.

Two specific features in 2004 EW95's spectra indicated the presence of ferric oxides and phyllosilicates, substances never previously seen in any KBO, suggesting this asteroid formed in the inner solar system.

During its early years, the solar system was a much more active and violent place, with regular impacts of small objects that flung some into distant orbits beyond Neptune and Pluto.

Computer models of the Kuiper Belt confirm it harbors a small number of asteroids that originated in the belt between Mars and Jupiter.

"Given 2004 EW95's present day abode in the icy outer reaches of the solar system, this implies that it has been flung out into its present orbit by a migratory planet in the early days of the solar system," Seccull stated.

"While there have been previous reports of other 'atypical' Kuiper Belt Object spectra, none were confirmed to this level of quality," said ESO astronomer Olivier Hainaut, who did not take part in the study. "The discovery of a carbonaceous asteroid in the Kuiper Belt is a key verification of one of the fundamental predictions of dynamical models of the early solar system."

Findings of the study have been published in the journal Astrophysical Journal Letters.

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