BENGALURU: On January 31, a relatively rare phenomena will occur in the skies — Blood Moon — when the Earth's satellite will be deep red in colour during an eclipse, which the world and India, including cities like Bengaluru, will be able to witness if the skies are clear.
But astronomers say that the Moon is red in colour during all eclipses and that only the shade differs. If there is anything spectacular about the Blood Moon, they say, it is how much we've polluted the Earth's atmosphere, to make it look deep red.
HR Madhusudan, senior scientific officer, Jawaharlal Nehru Planetarium, says: ""It is a bit of a hype actually. There is nothing really special. All lunar eclipses, depending on the dust the atmosphere has can make the Moon look in faint red to deep red. Deep red is only a grim reminder that there is more dust particles in the atmosphere."
Technically, the Moon should not be visible during an eclipse because it would have come in the Earth's shadow region, and anything in the shadow region should not be visible if it is shining with reflected light (like the moon). "It should be black. But you see a reddish colour because of scattering of light by earth atmosphere, while shades of red change, the object itself is always red during eclipses," he said, adding that it is because of the same reason (scattering) that the rising and setting Sun appears red.
Astronomer TS Ganesh, while agreeing with Madhusudhan said that it is only in the US that people are seeing this after 150 years, and that India and some other parts of the world had recorded it in 1982 and 1963 too.
Madhusudhan pointed out that descriptions of the Blood Moon have been recorded even in the works of mathematician-astronomer Aryabhatta as early as 576 AD, and attributed the dust in the atmosphere then to more active volcanoes.
"...The brightness of the Moon is considerably reduced when it is in the shadow of Earth, and the atmosphere acts like a filter, the particles in the atmosphere scatter the sunlight, letting through only the orange or red portion of the spectrum. It may appear blood red when seen through highly polluted atmosphere," he said.