Free Astronomy Magazine July-August 2018

50 JULY-AUGUST 2018 SPACE CHRONICLES an astronomer from Queen’s University Belfast who was also a member of the team behind this discovery. The asteroid’s re- flectance spectrum — the specific pattern of wavelengths of light reflected from an ob- ject — was different to that of similar small Kuiper Belt Objects (KBOs), which typically have uninteresting, featureless spectra that reveal little infor- mation about their composition. “The reflectance spec- trum of 2004 EW 95 was clearly dis- tinct from the other observed outer Solar System objects,” explains lead author Seccull. “It looked enough of a weirdo for us to take a closer look.” The team observed 2004 EW 95 with the X-Shooter and FORS2 in- struments on the VLT. The sensitivity of these spectrographs allowed the team to obtain more detailed meas- urements of the pattern of light re- flected from the asteroid and thus T his short video shows an artist's impression of 2004 EW 95 , the first car- bon-rich asteroid confirmed to exist in the Kuiper Belt and a relic of the primordial Solar System. The video shows a fly-by of the enigmatic as- teroid as it tumbles through the icy outer reaches of the Solar System due to past interactions with migrating planets. [ESO/M. Kornmesser] T he red line in this animation shows the orbit of 2004 EW 95 , with the orbits of other Solar System bodies shown in green for comparison. [ESO/L. Calçada] Thomas Puzia from the Pontificia Universidad Católica de Chile. “Not only is 2004 EW 95 moving, it’s also very faint,” adds Seccull. “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 fer- ric oxides and phyllosilicates. The presence of these materials had never before been confirmed in a KBO, and they strongly suggest that 2004 EW 95 formed in the inner Solar System. Seccull concludes: “Given 2004 EW 95 ’s present-day abode in the icy outer reaches of the Solar System, this im- plies 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 re- ports of other ‘atypical’ Kuiper Belt Object spectra, none were con- firmed to this level of quality,” com- ments Olivier Hainaut, an ESO astron- omer who was not part of the team. “The discovery of a carbonaceous as- teroid in the Kuiper Belt is a key ver- ification of one of the fundamental predictions of dynamical models of the early Solar System.” infer its composition. However, even with the impressive light-collecting power of the VLT, 2004 EW 95 was still difficult to observe. Though the object is 300 kilometres across, it is currently a colossal four billion kilometres from Earth, mak- ing gathering data from its dark, carbon-rich surface a demanding scientific challenge. “It’s like observing a giant mountain of coal against the pitch-black can- vas of the night sky,” says co-author !