The "once-in-a-lifetime" eclipse of a bright star by an asteroid takes place tonight and will be viewable in parts of Canada, weather permitting.
Regulus, the brightest star in the constellation Leo, is expected to disappear for up to 14 seconds shortly after 2 a.m. ET Thursday morning when the asteroid Erigone passes in front of it. Erigone is about 72 kilometres wide and will remain in the asteroid belt between Mars and Jupiter – far from Earth.
The technical term for this type of celestial event an "occultation" and Regulus is the brightest star ever predicted to be occulted by a sizeable asteroid and visible from North America, says the International Occultation Timing Association, a group devoted to predicting such events.
"So it really is likely to be a once-in-a-lifetime experience for most who live within the path," the group said on its website.
The event is expected to be visible in the western sky around 2:06 a.m. along a diagonal path that passes slightly west of Kingston, Ont., from southeast to northwest. It should be visible in from North Bay and Quinte West to the eastern edge of Algonquin Park and Kingston.
For those who are not in the path, it will be broadcast live online by a number of groups, including the U.S.-based media company Slooh, which specializes in streaming celestial events on the internet.
The group has also released a free iPhone and iPad app called Occultation 1.0 to help amateur astronomers observe the event.
A moon for Erigone?
But even those who aren't on the path may end up seeing something extraordinary – IOTA suggests they may end up discovering a satellite or moon of the asteroid Erigone. Erigone has no known satellites, but many asteroids do. If Erigone does have a big one, Canadians from southern Manitoba to the Maritime provinces, may see Regulus blink out from half a second to as much as two or three seconds, IOTA predicts.
The group is asking people in southern Ontario, southern Quebec and the Maritimes to watch the skies from 2:03 to 2:12 a.m. ET and from southern Manitoba, northern Ontario and Quebec to watch from 2:05 to 2:14 a.m. ET (1:05 to 1:14 a.m. CT).