On Monday night, Feb. 18th, the brightest star in the sky will disappear. It's a rare eclipse of Sirius by asteroid 4388 Jürgenstock.
As recently as two days ago, specialists thought the eclipse would be visible in a narrow corridor cutting across the central USA. New calculations, however, suggest a different path:
Sirius's shadow will cross southern parts of Chile and Argentina, Central America and the Caribbean. This will happen on Feb. 18th between 09:11 pm PST and 09:27 pm PST.
According to David Dunham of the International Occultation Timing Association, the eclipse could last for as much as 1.8 seconds, with Sirius fading to minimum brightness for 0.2 seconds of that time. The angular diameter of Sirius is 0.006 arcseconds. Asteroid Jürgenstock is just a little wider: 0.007 arcseconds, so theoretically Sirius should be completely blocked. "But the asteroid may be a little larger or smaller than predicted, and it's likely to be irregularly-shaped, so there is a good chance that even at the center, the star will not completely disappear," notes Dunham.
Named after Venezuelan astrometrist Jürgen Stock, asteroid 4388 Jürgenstock orbits the sun in the inner regions of the asteroid belt between Mars and Jupiter. It is approximately 5 kilometers (3.1 miles) in diameter. Video recordings of the eclipse could help trace the shape of the distant space rock.