Imagine the two brightest objects in the night sky playing hide and seek with each other. The lunar occultation of Venus is one of the most spectacular astronomical events of November and here is everything you must know.
What is an occultation?
An occultation is an astronomical event when one object is hidden by another object that passes between it and the observer. In other words, when the object in the foreground blocks the view of the object in the background, it’s an occultation.
But how is it different from the transit and an eclipse? A transit occurs when the object in the foreground does not entirely hide the object in the background. So, for example, when Mercury or Venus passes in front of the Sun as seen from Earth, it’s a transit.
An eclipse is an astronomical event when a celestial body totally or partially disappears from the observer’s view either by an occultation or a transit. In simple words, if a shadow is cast onto an observer during an occultation or transit, it’s an eclipse.
The term occultation is mainly used when the Moon passes in front of an astronomical object. The Moon’s orbit is inclined slightly with respect to the ecliptic, meaning any stars with an ecliptic latitude of less than about ± 6.5 degrees may be occulted by it. Since the planets also lie in the ecliptic, they are often occulted by the Moon.
Lunar occultation of Venus on November 8, 2021
On November 8, the Moon will pass in front of Venus, creating a lunar occultation visible from parts of Eastern Asia. The map below from in-the-sky shows the places where the occultation can be seen from Earth.
Lunar occultations are only ever visible from a small fraction of the Earth’s surface. Since the Moon is much closer to the Earth than other celestial objects, its exact position in the sky differs depending on your exact location on Earth due to its large parallax. As seen from two points on opposite sides of the Earth, the Moon’s position varies by up to two degrees or four times the diameter of the full Moon.
This means if the Moon is aligned to pass in front of a particular object for an observer on one side of Earth, it will appear up to two degrees away from that object on the other side of Earth. For the rest of the world, the Moon will pass very close to Venus in Sagittarius. Look for the two celestial objects in the southwest at dusk. The waxing crescent Moon will be four days old. You may also use these space apps to locate Venus and other planets according to the place you live.