Remember the recent excitement in astronomy circles over an extra-solar system visitor? The Institute for Astronomy at the University of Hawaii has a sort of introductory update:
“What we found was a rapidly rotating object, at least the size of a football field, that changed in brightness quite dramatically,” according to Meech. “This change in brightness hints that `Oumuamua could be more than 10 times longer than it is wide – something which has never been seen in our own Solar System,” according to Meech.
“An axis ratio like that is truly extraordinary – we have never seen anything in the solar system that is this elongated”, says Lance Benner, a specialist in radar imaging of near-Earth and main-belt asteroids at the Jet Propulsion Laboratory in California.
`Oumuamua does have some similarities to small objects in the outer Solar System, especially the distant worlds of the Kuiper Belt – a region of rocky, frigid worlds far beyond Neptune. “While study of `Oumuamua’s colors shows that this body shares characteristics with both Kuiper Belt objects and organic-rich comets and trojan asteroids,” said Meech, “its hyperbolic orbit says it comes from far beyond.”
“We are continuing to observe this unique object,” added Hainaut, “and we hope to more accurately pin down where it came from and where it is going next on its tour of the galaxy. And now that we have found the first interstellar rock, we are getting ready for the next ones!”
The report in Nature would be way beyond me, of course, and it costs money, but this is from the publicly available abstract:
Our observations reveal the object to be asteroidal, with no hint of cometary activity despite an approach within 0.25 au of the Sun. Spectroscopic measurements show that the object’s surface is consistent with comets or organic-rich asteroid surfaces found in our own Solar System. Light-curve observations indicate that the object has an extreme oblong shape, with a 10:1 axis ratio and a mean radius of 102±4 m, assuming an albedo of 0.04. Very few objects in our Solar System have such an extreme light curve. The presence of ‘Oumuamua suggests that previous estimates of the density of interstellar objects were pessimistically low. Imminent upgrades to contemporary asteroid survey instruments and improved data processing techniques are likely to produce more interstellar objects in the upcoming years.
I’m looking forward to the future reports! (Ah, I’m such a kid at heart.) From the Institute of Astronomy’s press release is this artist’s impression, which I have fallen in love with:
Credit: ESO/M. Kornmesser
Of course, a visible spectrum picture would have been even more entrancing, in sharp focus and high resolution. I’m so demanding.
