Srilakshmi N

As today, 19 September, is observed as “International Observe the Moon Night”, let me take you through my experience of a recent celestial event.

An occultation is a celestial event where one object temporarily hides another object from our viewpoint on Earth. The word occult means to hide or block from view. On 14 September, Venus decided to play a little game of hide-and-seek with the Moon!

Given the recent unpredictable weather, I wasn’t sure if the skies would cooperate. Nevertheless, I decided to set up my telescope and imaging equipment. To my delight, the skies turned out to be exceptionally clear.

The occultation began at 5:20 PM, with Venus slipping behind the Moon. At around 6:45 PM, Venus started to emerge from the other side of the lunar disk. What a sight it was! It felt very surreal to watch the celestial mechanics in action, right in front of my eyes.

A Celestial Game of Hide-and-Seek – Why did Venus appear as a crescent?

Venus is one of the two inner planets in our solar system; it orbits between Earth and our Sun. As Venus travels around the Sun, the angle between the Sun, Venus and Earth continually changes. As a result, we see different portions of Venus’s sunlit hemisphere at different times of the year, producing its familiar phases, much like the phases of our Moon.

How rare is a Venus occultation?

Due to the geometry of their orbits, a lunar occultation of Venus occurs roughly twice every year somewhere on Earth. However, the event is visible only from a relatively narrow region of Earth’s surface. So, while the event itself isn’t extraordinarily rare on a global scale, witnessing it from a particular location is a much rarer opportunity.

How can the smaller Moon hide the much larger Venus?

This is where angular size comes into play. Although Venus is much larger than our Moon, the Moon is much closer to us. Because of this, the Moon is able to hide Venus when seen from Earth.

Celestial events like these are a beautiful reminder that the night sky is not a flat ceiling, but rather a three-dimensional Universe projected onto our two-dimensional field of view. An occultation gives us the opportunity to experience this depth and perspective in action. These events also make us profoundly realise how significantly insignificant we are in the vast realms of our Universe.

As Carl Sagan famously said – “Astronomy is a humbling and character-building experience.” And I cannot vouch for it enough!