Next Wednesday, January 31, will have a rare celestial phenomenon not occurring for the next 150 years: it will be a blue moon – the second full moon in a month, a supermoon (a full moon closely coinciding with perigee, the moon’s closest point to Earth in its monthly orbit) and a total lunar eclipse – all at the same time. Hence the name Super Blue Blood moon.
Blood Moon or total lunar eclipse occurs when the moon travels through the earth’s umbra, the dark central portion of its shadow. The earth blocks all direct sunlight from falling onto the Moon’s surface, but the Moon does not turn completely dark; it appears reddish, since part of the sunlight still reaches the lunar surface indirectly, via the earth’s atmosphere.
Being a supermoon, the January 31 full moon will be about 14 per cent brighter than usual. As it passes through the shadow of the earth, for 77 minutes, the usually silvery moon will be covered with a blood-red/ochre shadow.
This supermoon, which is the first blue moon of 2018, marks the last in a trilogy of supermoons. The first happened on December 3, 2017, NASA said in a report.
The eclipse will offer researchers a chance to see what happens when the surface of the moon cools quickly, helping them to understand some of the characteristics of the regolith – the mixture of soil and loose rocks on the surface – and how it changes over time, said a Hindustan Times (HT) report.
“During a lunar eclipse, the temperature swing is so dramatic that it’s as if the surface of the moon goes from being in an oven to being in a freezer in just a few hours,” said Noah Petro, deputy project scientist for NASA’s Lunar Reconnaissance Orbiter, or LRO, at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, reported the HT.
Using the astronomer’s equivalent of a heat-sensing, or thermal camera, the team will conduct their investigations at invisible wavelengths where heat is sensed, from the Haleakala Observatory in Hawaii. “The whole character of the moon changes when we observe with a thermal camera during an eclipse,” said Paul Hayne of the Laboratory for Atmospheric and Space Physics at the University of Colorado-Boulder, the HT report said.
“In the dark, many familiar craters and other features can’t be seen, and the normally non-descript areas around some craters start to ‘glow’, because the rocks there are still warm,” Hayne added.
“These studies will help us tell the story of how impacts large and small are changing the surface of the Moon over geological time,” Petro said.
In India, the partial shadow on the Moon would be seen at 4.21 pm, while the complete lunar eclipse would be visible at 6.21 pm. It will be brown or red in colour. The total eclipse will last till 7.37 pm, after which the earth’s shadow on moon will start retreating, turning it into a partial eclipse by 8.41 pm, after which the Moon will be fully visible once again. The duration of this rare sight will last for 76 minutes.