An abnormal asteroid in the Kuiper belt

Artist's impression of 2004 <sub><figcaption class=EW95 (Image ESO/M. Kornmesser)" width="640" height="425" srcset=" 640w, 300w" sizes="(max-width: 640px) 100vw, 640px" /> Artist’s impression of 2004 EW95 (Image ESO/M. Kornmesser)

An article published in the journal “The Astrophysical Journal Letters” describes the study of an asteroid cataloged as 2004 EW95 which confirmed it has anomalous characteristics, being the first in the Kuiper belt to show a considerable carbon content. A team of astronomers used ESO’s VLT to study an asteroid that probably formed in the belt between Jupiter and Mars before being pushed to the outer solar system.

The asteroid 2004 EW95, whose complete classification is (120216) 2004 EW95, was discovered in 2004 and its orbit calculated thanks to observations made over the years indicate that its distance varies between about 4 and 7.86 billion kilometers from the Sun, between 27 (perihelion) and 52.6 (aphelion) times that of the Earth from the Sun. Currently, its distance is slightly greater than that at its perihelion.

Initially, 2004 EW95 seemed to be one of the many trans-Neptunian objects that are continuously sighted thanks to increasingly sophisticated instruments. It’s 291 kilometers across, a considerable size for an asteroid but in the Kuiper belt there are also dwarf planets so it seemed nothing special.

When 2004 EW95 was observed with the Hubble Space Telescope in recent years, astronomer Wesley Fraser of Queen’s University in Belfast noted that its reflection spectrum – the wavelength pattern of reflected light, in this case from the asteroid – was different from that of other celestial bodies in the Kuiper belt of similar size.

Wesley Fraser is part of the team led by Tom Seccull, also from Queen’s University, who conducted the new observations with the VLT (Very Large Telescope). To be precise, the X-Shooter and FORS2 (FOcal Reducer and low dispersion Spectrograph 2) instruments mounted on the VLT were used to try to obtain more information on the asteroid 2004 EW95.

Even a powerful telescope such as VLT struggles to observe an object as distant as 2004 EW95 so the researchers used an advanced data processing technique to get the information they needed. Eventually, they managed to detect the presence of ferric oxides and phyllosilicates. It’s the first time that those compounds have been detected with certainty in a Kuiper belt object and this suggests that it formed in the inner solar system.

In the past, other Kuiper belt objects showed abnormal characteristics but in the case of 2004 EW95 its carbonaceous asteroid nature was supported by evidence. Generally an asteroid doesn’t make the news unless it comes from another star system but in this case it’s likely to have formed between Mars and Jupiter and then got pushed into the Kuiper belt. This means that it will be useful to verify the models of formation of the solar system and the predictions about the chaotic period that characterized the evolution during the planets formation.

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