On October 15, Sunday, during the predawn hours, a waning crescent moon will temporarily hide the star Regulus in what’s known as an occultation. As scientists suggest, this will be the last good view of the event till 2026.
The event early on Sunday morning can be seen by people living in most of the contiguous U.S., a slice of southeast Canada and parts of the Maritime Provinces.
The northern limit of the visibility zone of the occultation begins over central Oregon and then tracks to the northeast through the middle of Idaho. Then it skims over portions of southern Montana and North Dakota and continues east-northeast through northern Minnesota, cutting straight through the Arrowhead region before heading out over Lake Superior.
Those who are located above or to the north of the visibility line will lose out, having to settle for a close approach of the moon to the star. Nonetheless, if your area is slated for a miss, go out and watch anyway. It’s breathtaking to watch a bright star “flying” so near to the moon!
You can also see the grazing occultation path on Google Map here.
Regulus is the only first-magnitude star to sit almost exactly on the ecliptic. Thus, its graze observations will offer a detailed analysis of that part of the lunar profile needed for analysis of solar-eclipse observations.
Generally, Occultations of Regulus happens after every 9 years and lasts for almost 18 months. The current cycle began last year on Dec. 18 and will come to an end on April 24, 2018. So each month, the moon will cross paths with Regulus, hiding it from view for various parts of the world.
On Sunday, as the occultation approaches, it will be interesting to compare the surface brightness of the star to that of the moon.
For those who are situated in the eastern U.S. and southeast Canada, the reappearance of Regulus will take place during morning twilight. The closer you are to the Atlantic seaboard, the closer the reappearance will come to sunrise.
You can check the occultation timetable here.