[BBC] Bizarre shape of interstellar asteroid

[Mr. Man-wai Chang]

[BBC] Bizarre shape of interstellar asteroid
Full story: http://www.bbc.com/news/science-environment-42053634

An asteroid that visited us from interstellar space is one of the most
elongated cosmic objects known to science, a study has shown.

Discovered on 19 October, the object's speed and trajectory strongly
suggested it originated in a planetary system around another star.

Astronomers have been scrambling to observe the unique space rock, known
as 'Oumuamua, before it fades from view.

Their results so far suggest it is at least 10 times longer than it is wide.

That ratio is more extreme than that of any asteroid or comet ever
observed in our Solar System.

Interstellar visitor given a name

Using observations from the Very Large Telescope in Chile, Karen Meech,
from the Institute for Astronomy in Honolulu, Hawaii, and colleagues
determined that the object was about 400m long, rapidly rotating and
subject to dramatic changes in brightness.

These changes in brightness were the clue to 'Oumuamua's bizarre shape.

"Looking at the asteroid light curve database, there are five objects
(out of 20,000) that have light curves that would suggest a shape up to
an axis ratio of about 7-8 to 1," Dr Meech told BBC News.

"Our errors are very small, so we are confident this is really
elongated. Also, one has to realise we don't know where the rotation
pole is pointed. We assumed that it was perpendicular to the line of
sight. If it were tipped over at all, then there are projection effects
and the 10:1 is a minimum. It could be more elongated!"

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