The first week of August was ‘astronomically dry’. There wasn’t much except for the conjunction of the Moon, Jupiter, and Saturn. But, the rest of the month has a lot for us its store. There are three meteor showers coming up in August: Perseids, Kappa Cygnids, and Aurigids. And then there are two asteroids that will make their closest approach to Earth on August 29. Now, let us learn about the first major event that will take place this week: the occultation of Mars by the Moon. The Red Planet will be ‘eclipsed’ by the Moon on August 9 and here is everything you need to know.
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.
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 view of the observer 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.
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.
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Lunar Occultation of Mars In August
On August 9, The Moon will pass in front of Mars, creating a lunar occultation visible from parts of South America.
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. The position of the Moon as seen from two points on opposite sides of the Earth 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 Pisces.
The map below from in-the-sky shows the places where the occultation can be seen from Earth.
Occultations of bright stars and planets typically occur a few times per year, often clustering with several occultations of the same object in successive months, since the Moon traces roughly the same path across the sky each month. These clusters come to an end after a few months, when gradual changes in the Moon’s orbit change the Moon’s path across the sky. Alternatively, in the case of planets, the planet’s own movement will eventually carry it away from the Moon’s path.
In 2020, there will be three more Lunar occultations. The Moon will again pass in front of Mars on September 6 and October 3. Later, on December 12, the Moon will pass in front of Venus.