Wednesday December 18, 2024

Watch Algol Brighten

The star Algol in the constellation of Perseus represents the glowing eye of Medusa from Greek mythology. Also designated Beta Persei, it is among the most accessible variable stars for skywatchers. During a ten-hour period that repeats like clockwork every 2 days, 20 hours, and 49 minutes, Algol dims noticeably and re-brightens by about a third when a fainter companion star
with an orbit nearly edge-on to Earth crosses in front of its much brighter primary, reducing the total light output we perceive. Algol normally shines at magnitude 2.1, similar to the nearby star Almach (aka Gamma Andromedae). But while fully dimmed, Algol's brightness of magnitude 3.4 is almost identical to Rho Persei (or Gorgonea Tertia or ? Per), the star sitting just two finger widths to Algol's lower right (or 2.25 degrees to the celestial south). On Wednesday evening, December 18 at 6:47 p.m. EST or 23:47 UT, Algol will be at its minimum brightness while it shines about two thirds of the way up the eastern sky, above and between the bright star Capella and Jupiter. Five hours later Algol will return to full intensity while it shines high in the western sky below Capella and Jupiter.

(Data courtesy of Starry Night)
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