There is something unexpectedly thrilling about watching one celestial object pass in front of another, an eclipse being the obvious example. On the evening of 29 March, the moon will briefly blot out one of the brightest stars in the spring sky. Such an event is known as an occultation, and this week the occulted star is Regulus, the brightest star in the constellation Leo, the lion.
Regulus is found at the base of Leo’s distinctive “sickle” asterism, the backward question mark of stars that outlines the lion’s head. It shines at magnitude 1.4 and is readily visible, even from towns and cities.
On 29 March, begin looking towards the western sky after sunset. The moon and Regulus will be visible together as twilight fades, with the star appearing close to the moon’s bright limb. The chart shows the view looking east from London at 7pm BST (British summer time will have begun at 1am that very morning).
While precise timings vary depending on your location in the UK, from London Regulus will disappear behind the moon at 7.14pm. Because the moon has no atmosphere to blur the view, the star will vanish almost instantaneously as it slips behind the lunar edge. It will re-emerge from the opposite limb of the moon at 9.21pm.
