A 5km asteroid may briefly occult the brightest star in the night sky

Enlarge / An artist's impression showing the binary star system of Sirius A and its diminutive blue companion, Sirius B. (credit: NASA, ESA and G. Bacon)

Sirius, a binary system, is the brightest star in the night sky. The larger of the two stars, Sirius A, is about 25 times more luminous than the Sun, and Sirius is relatively nearby, at less than 9 light years from our Solar System.

On Monday night, for a few areas of South and Central America, as well as the Caribbean, Sirius will probably briefly disappear. This will occur as a small asteroid passes in front of the star, occulting it for up to 1.6 seconds, according to the International Occultation Timing Association. (Yes, the acronym is IOTA).

In this case, the asteroid 4388 Ji1/4rgenstock will have an apparent diameter just an iota bigger than Sirius. The angular diameter of the asteroid is about 0.007 arcseconds (an arcsecond is 1/3,600th of a degree of the night sky), whereas the angular diameter of Sirius is 0.006 arcseconds. Thus, as the asteroid passes in front of Sirius, the star will briefly dim, perhaps completely, before quickly brightening again. Sirius may appear to blink once, slowly.

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