Watch an asteroid approach a star and block its light, all in a fraction of a second.

Have you ever seen a stellar occultation? If not, Jennifer West, Ian Cameron (University of Manitoba, Canada), and Jay Anderson (Royal Astronomical Society of Canada) shares their excellent video of asteroid Juno as it occults the 7th-magnitude star SAO 117176 in Hydra on November 19th, at 6:50 UT.

West writes: “Early this morning, our team observed the 9th-magnitude asteroid Juno as it occulted SAO 117176 (HIP 43357) from the Glenlea Astronomical Observatory in Manitoba, Canada. Manitoba was the only location in North America where the event was visible under clear skies. We recorded the entire event using the observatory’s 16-inch telescope and an Apogee AP47 CCD camera. The entire occultation lasted approximately 20 seconds, though our time-lapse sequence has been sped up about 20 times real speed. Watch it here (actual occultation occurs around 0:35):

Their excellent work really gives viewers a feel for how quickly an occultation “blinks out” a star; nearly all stars appear as a tiny pin-prick of light as seen from Earth, so they take a fraction of a second to disappear behind an occulting object in our solar system. Reappearance is just as abrupt.

Occultations are fun to observe, and good science can be had by recording the event. Precise timing of the disappearance and reappearance of the star from multiple locations help astronomers build an accurate shape profile of the asteroid. And in rare cases, tiny moons of these larger asteroids have been discovered during occultations when the star unexpectedly winked out twice.

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Image of TVR


November 28, 2014 at 5:34 pm

Very cool to have it on video. I still consider witnessing the 372 Palma & 32 Lyncis occultation in January 2007 my "greatest observation achievement" considering how rare it is and how few people observed the event.

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Image of Randall Osczevski

Randall Osczevski

November 29, 2014 at 4:25 pm

Interesting how, as Juno occults the star, a diminished intensity image of the star whips around Juno in a clockwise direction. It then appears below where its image used to be. Did someone bump the telescope at that exact moment, or is there some other explanation?

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