http://aasnova.org/2018/01/19/update-on-an-interstellar-asteroid/

In late October 2017, the discovery of minor planet 1I/’Oumuamua was announced. This body — which researchers first labeled as a comet and later revised to an asteroid — had just zipped around the Sun and was already in the process of speeding away when we trained our telescopes on it. Its trajectory, however, marked it as being a visitor from outside our solar system: the first known visitor of its kind.

Since ‘Oumuamua’s discovery, scientists have been gathering as many observations of this body as possible before it vanishes into the distance. Simultaneously, theorists have leapt at the opportunity to explain its presence and the implications its passage has on our understanding of our surroundings. Here we present just a few of the latest studies that have been published on this first detected interstellar asteroid — including several timely studies published in our new journal…

A team of University of Maryland scientists led by Matthew Knight captured a light curve of ‘Oumuamua using Lowell Observatory’s 4.3-m Discovery Channel Telescope. The data indicate that the asteroid’s period is at least 3 hours in length, and most likely more than 5 hours. Assuming the light curve’s variation is caused by the tumbling asteroid’s changing cross-section, ‘Oumuamua must be a minimum of 3 times as long as it is wide. Knight and collaborators see no signs in their images of a coma or tail emitted from ‘Oumuamua, suggesting there is no volatile material sublimating from its surface under the heat of the Sun.
A study of the asteroid’s photometry, led by Michele Bannister (Queen’s University Belfast, UK), used the Gemini-North telescope in Hawaii and the William Herschel Telescope in Spain to explore the asteroid’s shape and color. Bannister and collaborators refined the estimate of the asteroid’s shape to be at least 5.3 times as long as it is wide, which requires this body to have significant internal cohesion to hold together as it tumbles. Their measured color for ‘Oumuamua is largely neutral.