On Wednesday, much of the world, including India, will get to see not only a blue moon and a super moon, but also a total lunar eclipse, all rolled into one. There hasn’t been a lunar trifecta like this in many years, and the next won’t occur in a hurry either. The eclipse will be visible best in the western half of the US and Canada before the moon sets early Wednesday, and across the Pacific into Asia as the moon rises Wednesday night.
The coincidence of Wednesday’s blood moon with other astronomical events is what makes this event special. A blue moon means it is the second full moon to occur in a month; and a supermoon means it will be closer to the Earth than usual.
Blue and Blood
As is well known, “blue moon” is just a name — the moon won’t turn blue tomorrow (or at any other time). Rather, during the peak total phase of the lunar eclipse, it will have a reddish or coppery tinge. This is because even though the moon is in the shadow of the Earth, some light does reach it. Fine particles in the atmosphere scatter the blue component of the solar spectrum, and what reaches us is the longer wavelength red light.
‘Supermoon’ was coined by an astrologer in the 1970s, not by a scientist. The term has come to mean a full moon that is at perigee, or when the moon is at its closest position to Earth along its orbit. As a result, the moon appears somewhat bigger — even though the enlargement is clear only in comparison with the full moon at apogee, or its farthest position from Earth. The supermoon is 14% larger than the apogee full moon and 30% brighter.
Of the five eclipses this year, three will be partial solar eclipses — February 15, July 13 and August 11 — that will not be visible from India. Of the two total lunar eclipses, the one on Wednesday will be partially visible from India; the next one, on July 28, will be entirely visible. On Wednesday, the total eclipse will start at 6.21 pm, and totality will end at 7.38 pm.