Unsolved mysteries of an interstellar event called Oumuamua. David Grinspoon. David Livingston.

Nov 29, 2017, 01:21 AM

11-28-2017 (Photo: This artist’s impression shows the first interstellar asteroid: Oumuamua. This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Subsequent observations from ESO’s Very Large Telescope in Chile and other observatories around the world show that it was travelling through space for millions of years before its chance encounter with our star system. `Oumuamua seems to be a dark red highly-elongated metallic or rocky object, about 400 metres long, and is unlike anything normally found in the Solar System.) http://JohnBatchelorShow.com/contact http://JohnBatchelorShow.com/schedules Twitter: @BatchelorShow

Unsolved mysteries of an interstellar event called Oumuamua. David Grinspoon. David Livingston.

ʻOumuamua was not seen in STEREO HI-1A observations near its perihelion on 9 September 2017, limiting its brightness to ~13.5 mag.[10]

Spectra recorded by the 4.2 m (14 ft) William Herschel Telescope on 25 October showed that the object was featureless, and colored red like Kuiper belt objects.[12] Spectra from the Hale Telescope showed a less-red color resembling comet nuclei or Trojans.[35] Its spectrum is similar to that of D-type[8] or P-type asteroids.[10]

ʻOumuamua has a rotation period of 8.10 hours,[10][11] with a lightcurve amplitude of 1.5–2.1 mag.[11] Meech et al. reported a rotation period of 7.3 hours and a lightcurve amplitude of 2.5 mag.[40] This indicates that it is a highly elongated object with an axial ratio of 4.1 to 6.9,[10][11] comparable to or greater than the most elongated Solar System objects.[10][11] According to astronomer David Jewitt, the object is physically unremarkable except for its highly elongated shape.[9]

Assuming an albedo of 10% (typical for D-type asteroids), ʻOumuamua has dimensions of approximately 180 m × 30 m × 30 m (600 ft × 100 ft × 100 ft).[8][9] Bannister et al. have suggested that it could also be a contact binary,[10] although this may not be compatible with its rapid rotation.[27] One speculation regarding its shape is that it is a result of a violent event (such as a collision or stellar explosion) that caused its ejection from its system of origin.[27]