As outgassing is behaviour typical for comets, the team thinks that `Oumuamua’s previous classification as an interstellar asteroid has to be corrected. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser
`Oumuamua, the first interstellar object discovered in the Solar System, is moving away from the Sun faster than expected. This anomalous behaviour was detected by a worldwide astronomical collaboration including European Southern Observatory’s (ESO) Very Large Telescope in Chile. The new results suggest that `Oumuamua is most likely an interstellar comet and not an asteroid. The discovery appears in the journal Nature.
`Oumuamua — the first interstellar object discovered within our Solar System — has been the subject of intense scrutiny since its discovery in October 2017. Now, by combining data from the ESO’s Very Large Telescope and other observatories, an international team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumuamua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial mechanics.
The team, led by Marco Micheli of the European Space Agency, explored several scenarios to explain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely ...