On Sunday morning, October 15th, stargazers will have an opportunity to view a very interesting sight: the bright bluish star, Regulus, known as the heart of the Lion in the constellation Leo (Regulus is Latin for “little king”), will be eclipsed by the Moon.
Regulus is also the only 1st-magnitude star to sit almost exactly on the ecliptic, or Sun’s yearly path, in front of the constellations of the zodiac — it lies only 0.46° from the ecliptic line. As a consequence, it can, on occasion be hidden by the Moon (called an “occultation”) and very early Sunday morning, that’s exactly many of us will be able to witness.
This occultation will be visible to those living in the contiguous U.S., except the Pacific Northwest and parts of the Northern Plains, as well as over a slice of Southeast Canada, and parts of the Maritime Provinces.
How Often Does This Happen?
Occultations of Regulus happen in cycles of roughly 9 years and each cycle lasts about 18 months. The current cycle began last year on December 18th 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, and this month it will be our turn. Call this a “stellar eclipse” — as the Moon moves east against the background stars, the bright side of the slender waning crescent will first pass in front Regulus (called “immersion”), and then the star will dramatically “pop” back into view (“emersion”) up to 70 minutes later, depending on your location, from behind the “dark” part of the Moon, which likely will be dimly illuminated by earthshine.
Near and along the West Coast, Regulus will already be hidden behind the Moon when it rises shortly after 2:30 a.m. local time.
The disappearance will be best viewed with binoculars or a small telescope, but the reappearance can be seen even with your unaided eyes – providing the twilight sky is not too bright.
For your convenience, we’ve included occultation times of 3 cites:
New York City, NY
Disappearance: 5:44:03 a.m. EDT
Reappearance: 6:43:25 a.m. EDT
Disappearance: 4:20:46 a.m. CDT
Reappearance: 5:18:19 a.m. CDT
Disappearance: 3:31:04 a.m. MDT
Reappearance: 4:15:44 a.m. MDT
Click here to find out the occultation times for many hundreds of localities (in Universal Time). Remember to convert Universal Time to your local time using the formula below:
Eastern Daylight Time = UT – 4 hours
Central Daylight Time = UT – 5 hours
Mountain Daylight Time = UT – 6 hours
Pacific Daylight Time = UT – 7 hours.
Interestingly, many Americans probably got their first view of Regulus not at night, but during the day! Remember the Solar Eclipse of August 21st? When the Sun was totally eclipsed, Regulus was positioned to its left. So when the Sun disappeared and an eerie darkness descended, many were able to catch sight of Regulus. The Moon eclipsed the Sun that day, and on October 15th, it will eclipse Regulus.