Here’s what to expect for the penumbral lunar eclipse on June 5

The second lunar eclipse of the year will take place tomorrow night but is unlikely to be visible to the lay observer

June 04, 2020 04:35 pm | Updated June 06, 2020 12:40 pm IST

The shadow will cover only 58 % of the moon

The shadow will cover only 58 % of the moon

Between 11.15 pm tomorrow night and 2.34 am on June 6, the Earth will imperfectly align itself between the Sun and the moon, casting a shadow on the latter, marking the second lunar eclipse of the year. This time, it will be a penumbral eclipse, the maximum extent of which will be visible at 12.54 am on June 6.

This eclipse is also called a strawberry moon eclipse — the term, interestingly, originates from an American concept and has little to do with the Euro-Asia region. June’s full moon usually coincides with the harvesting season of wild strawberries in America and the phenomenon was often addressed in reference to that.

India had already witnessed an eclipse earlier this year, in January. The strawberry moon eclipse is going to be its second and probably the last visible lunar one in 2020.

“It is not going to be very visible, since it is a penumbral eclipse; which means only a diffused shadow will fall on the moon. Moreover, it is going to cover only 58 % of the moon,” says TV Venkateswaran, senior scientist at Vigyan Prasar, New Delhi. “So, only during the maximum time of eclipse, if you are a very careful observer and the sky conditions are clear, you will see a difference in brightness in the northern and southern parts of the moon,” he continues.

Before understanding what a penumbral lunar eclipse is, TV Venkateshwar says it is important to know about two types of shadows. He says, “Any object that obstructs light will produce two shadows: one which will be dark and dense, is called the umbra; and the other which is light and diffused is called the penumbra. The difference between these two are: if you are standing in the umbra region, the whole light source will be covered by whatever that obstructs it. But if you are standing in the penumbra region, the whole light source will not be covered.”

Every year has two eclipse seasons, within a gap of 173 to 174 days. This season is 35 days long. “If the eclipses are going to take up in the beginning or end of the season, the chances that they are going to be total eclipses are very slim,” he explains. Because, the moon would be within the shadow region of the Earth, but not in the umbral (inner) shadow region. “This time, for example, there is going to be one full moon this week, which is a penumbral eclipse. There is going to be another full moon next month, also a penumbral eclipse. Essentially, the moon will not be aligned with the centre of the Sun and the Earth in a straight line,” says Dr Venkateshwar adding that this time, the southern part of the moon will pass through the penumbra while next month, it will be the northern part.

This eclipse will be visible to the Eastern hemisphere, this time. However, if the sky is cloudy and the atmosphere polluted, the visibility will be in question.

More to come

Discussing astronomical events to look forward to this year, the scientist says,“There are going to be four lunar eclipses and two solar eclipses — the first annular solar eclipse will take place on June 21, and is going to be visible in certain locations in Northern India: Rajasthan, Haryana, Dehradun etc. The rest of India will see a partial eclipse.”

Dr Venkateshwaran adds that this is definitely something to look forward to, since there is not going to be another solar eclipse visible from India for the next 11 years. The next one will be in May 2031.

“Mercury will be also visible somewhere between July 22 and 25, in the morning just before sunrise. It’s a rare sight: Mercury is quite close to the sun, and hence is visible only on a few days in the year.”

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