Using ESO telescope, astronomers discovered an unusual Kuiper Belt Object 2004 EW95 is a carbon-rich asteroid while investigating a relic of the primordial Solar System. The asteroid is the first of its kind to be confirmed in the cold outer reaches of the Solar System.
The discovery suggests that the Kuiper Belt — a cold region beyond the orbit of Neptune — should contain a small fraction of rocky bodies from the inner Solar System, such as carbon-rich asteroids, referred to as carbonaceous asteroids. It also provides strong support for these theoretical models of our Solar System’s troubled youth.
After painstaking measurements from multiple instruments at ESO’s Very Large Telescope (VLT), a small team of astronomers led by Tom Seccull of Queen’s University Belfast in the UK was able to measure the composition of the anomalous Kuiper Belt Object 2004 EW95, and thus determine that it is a carbonaceous asteroid. This suggests that it originally formed in the inner Solar System and must have since migrated outwards.
The team observed 2004 EW95 with the X-Shooter and FORS2 instruments on the VLT. The sensitivity of these spectrographs allowed the team to obtain more detailed measurements of the pattern of light reflected from the asteroid and thus infer its composition.
However, even with the impressive light-collecting power of the VLT, 2004 EW95 was still difficult to observe. Though the object is 300 kilometers across, it is currently a colossal four billion kilometers from Earth, making gathering data from its dark, carbon-rich surface a demanding scientific challenge.
Co-author Thomas Puzia from the Pontificia Universidad Católica de Chile said, “It’s like observing a giant mountain of coal against the pitch-black canvas of the night sky. Not only is 2004 EW95 moving, it’s also very faint. We had to use a pretty advanced data processing technique to get as much out of the data as possible.”
Two features of the object’s spectra were particularly eye-catching and corresponded to the presence of ferric oxides and phyllosilicates. The presence of these materials had never before been confirmed in a KBO, and they strongly suggest that 2004 EW95 formed in the inner Solar System.
Seccull concludes: “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.”
“While there have been previous reports of other ‘atypical’ Kuiper Belt Object spectra, none were confirmed to this level of quality,” comments Olivier Hainaut, an ESO astronomer who was not part of the team. “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.”