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Moon and Aldebaran
The Moon has been playing a game of celestial hide-and-seek all year long. Almost every month, it’s passed directly in front of Aldebaran, blocking the bright eye of Taurus the bull from view. And it will do so again tonight. The disappearing act, known as an occultation, will be visible across a wide swath of the United States.
The Moon’s orbital path is such that the Moon passes close to Aldebaran every month. But that path carries the Moon north and south of Aldebaran’s position in the sky. The path overlaps Aldebaran during cycles that last about four years. The current cycle began in January of last year, and continues through September of 2018. After that, we won’t see another occultation of Aldebaran for another 15 years.
Tonight’s occultation will be visible to the south and east of a line that runs from about Los Angeles to Minneapolis and on through the middle of Lake Superior.
The exact timing depends on your location. From Baltimore, for example, the occultation begins when Aldebaran disappears behind the Moon at about 1:38 a.m., and lasts for more than an hour. From Chicago, it starts at 12:38 a.m., and lasts for about 44 minutes. And from San Antonio, it starts a little after midnight and continues for an hour.
The view is especially beautiful before and after the occultation, as bright Aldebaran snuggles quite close to the Moon — an act that’ll be repeated many times over the next couple of years.