Free Astronomy Magazine September-October 2018

12 SEPTEMBER-OCTOBER 2018 SPACE CHRONICLES other observatories, an interna- tional team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumua- mua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial me- chanics. The team, led by Marco Micheli (European Space Agency) explored several scenarios to ex- plain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely explanation is that `Oumuamua is venting mate- rial from its surface due to solar heating — a behaviour known as outgassing. The thrust from this ejected material is thought to pro- T his artist’s impression shows the first interstellar object discovered in the Solar System, `Oumuamua. Ob- servations made with ESO’s Very Large Telescope, the NASA/ESA Hub- ble Space Telescope, and others show that the object is moving faster than predicted while leaving the Solar Sys- tem. Researchers assume that venting material from its surface due to solar heating is responsible for this behav- iour. This outgassing can be seen in this artist’s impression as a subtle cloud being ejected from the side of the object facing the Sun. As outgas- sing is a behaviour typical for comets, the team thinks that `Oumuamua’s previous classification as an interstel- lar asteroid has to be corrected. [ESA/ Hubble, NASA, ESO, M. Kornmesser] by ESO `O umuamua — the first in- terstellar object discov- ered within our Solar System— has been the subject of in- tense scrutiny since its discovery in October 2017. `Oumuamua, pro- nounced “oh-MOO-ah-MOO-ah”, was first discovered using the Pan- STARRS telescope at the Haleakala Observatory, Hawaii. Its name means “scout” in Hawaiian, and re- flects its nature as the first known object of interstellar origin to have entered the Solar System. The orig- inal observations indicated it was an elongated, tiny object whose colour were similar to that of a comet. Now, by combining data from the ESO’s Very Large Telescope and ESO’s VLT sees `Oumuamua getting a boost