Lunar occultation of Mars

Mars Is Going To Disappear Behind The Moon This Week: How To Watch This Occultation?

Unlike the first half of April 2021, the second half is astronomically promising. There are three significant celestial events in store: the Lyrid meteor shower, the Super Pink Moon, and the lunar occultation of Mars. The Lyrids are known to end the meteor shower drought as they are the first ones to light up the night sky after the Quadrantids of January. Then we have the Super Pink Moon on April 27 – the second supermoon of 2021. And the third one, which we will discuss in this article, is the lunar occultation of Mars on April 17. You can read about the supermoon and the Lyrid meteor shower here.

What Is An Occultation?

An occultation is an astronomical event that occurs 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 is called an occultation.

Mars Occultation Moon
The Moon occulting Mars (Image: NASA/JPL)

But how is it different from the transit and an eclipse? Well, a transit occurs when the object in the foreground does not completely hide the object in the background. For example, when Mercury or Venus passes in front of the Sun as seen from the Earth, the event is known as 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 is called an eclipse.

Lunar Occultation

The term occultation is mostly 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 Mars In April 2021

On April 17, The Moon will pass in front of Mars, creating a lunar occultation visible from parts of Asia.

Mars Is Going To Disappear Behind The Moon This Week: How To Watch This Occultation? 2
Illustration of the lunar occultation created using Stellarium Web

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 that if the Moon is aligned to pass in front of a particular object for an observer on one side of the Earth, it will appear up to two degrees away from that object on the other side of the Earth. For the rest of the world, the Moon will appear to pass very close to the Red Planet in the constellation of Taurus.

The map below from in-the-sky shows the places where the occultation can be seen from Earth.

Mars Is Going To Disappear Behind The Moon This Week: How To Watch This Occultation? 3
Image: Dominic Ford, in-the-sky

Also Watch: The Super Pink Moon of 2021

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