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Can ALMA or the VLA Measure Oumuamua?

-- | January 14, 2018

Question: On the topic of Oumuamua’s interstellar visit to our system’s inner planets’ orbits. Can ALMA resolve this asteroid, even now?

I see from NRAO’s website that ALMA has been used to analyze Io’s gas and is being used to analyze our Sun’s activity. There was no mention made of ALMA’s activity being dependent on Arecibo’s output so I was wondering why Oumuamua has not been imaged? This would seem to be a rather urgent, prime target with its hyperbolic trajectory, and the 1st interstellar visitor ever.

There was a short 4-frame gif/video from an observatory in Arizona that showed the object clearly tumbling and it did not appear “cigar-shaped”. Convoluted, yes, but not cylindrical and not “spinning”.

Nor does a jpg from Gemini suggest an elongation. Can ALMA be of use here? Surely near-earth asteroid radar imaging is not so dependent on Arecibo? the DSN could give ALMA working material ‘in return’?? — Doug

Answer: Since ALMA or the VLA would need to have detected Oumuamua through its thermal emission, it would have been very difficult given the relatively small size of this asteroid. Also, since Oumuamua was discovered when it was already relatively far away from the Sun, and on its way out of the solar system, its thermal emission would have been very weak. ALMA does not have radar capabilities, but the VLA does (done in the past in conjunction with the Goldstone Deep Space Network antenna in California). I am not aware of any radar observations using the VLA, though.

Jeff Mangum

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