A 5 km asteroid can briefly obscure the brightest star of the night sky

Sirius, a binary system, is the brightest star of the night sky. The larger of the two stars, Sirius A, is about 25 times brighter than the Sun and Sirius is relatively close, within 9 light years of our solar system.

On Monday evening, Sirius may disappear briefly in a few areas of South America and Central America, as well as in the Caribbean. This will happen when a small asteroid passes in front of the star, blanking 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 Jürgenstock will have an apparent diameter equal to one iota higher than that of Sirius. The angular diameter of the asteroid is about 0.007 second arc (a second is 1/3 600th degree of the night sky), while the angular diameter of Sirius is 0.006 seconds. So, when the asteroid passes Sirius, the star darkens briefly, perhaps completely, before quickly re-igniting. Sirius may seem to blink once, slowly.

Unfortunately, the path for this event will be held primarily on the water. On the basis of IOTA maps, the occultation will appear on extracts from Argentina and Chile, Panama, the tip of Haiti and perhaps the Turks and Caicos Islands. There is still some uncertainty as to the timing, which should take place along its journey, starting at 05:11 UTC and ending at 05:26 UTC on Tuesday, 19 February.

With a diameter of 4.7 km, this inner asteroid belt object was discovered in 1964 by a named astronomer – you guessed it – Jürgen Stock. This occultation should give astronomers a rare opportunity to better characterize the dimensions of the asteroid. It will probably have an irregular shape, further contributing to uncertainty as to how much it will block Sirius' light.

Sirius has long held an important place in many cultures because of its exceptional brightness in the sky, with more than four dozen well-known names attributed to it. The name commonly used, Sirius, has Greek origins, which means "glowing".

The star could also play an important role in future explorations, as the brightness of Sirius makes it a good candidate for early interstellar solar navigation missions. The brightness of the star would help the solar sailing vessel to slow down as the star system approaches. For the moment, however, there is no confirmed planet around one or the other of the two stars.