by William J. Bechaver
The Moon continues on through it’s last leg of the journey amongst the planets. Now past full, it is waning in it’s monthly cycle, and calmly passing into the early morning sky.
For the past three weeks, the Moon has encountered our brightest planets, precisely seven days apart, three Saturdays in a row.
First it was Venus, then last week, Jupiter, now this Saturday, it will encounter Mars.
This indicates that the three planets are spread across the sky, virtually evenly spaced. Since the Moon moves about twelve degrees in a twenty four hour period, this determines that the three brightest planets are about 84 degrees apart, not taking into account the amount they have moved during the intervening weeks. The three are spread across about 170 degrees of sky.
So, when Venus is low in the west, Jupiter will be high in the sky, and Mars low in the East. About six hours later, Jupiter should be at the position in the sky where we first observed Venus, and Mars should be where Jupiter was earlier. Of course, Venus will have set by then, and will be below the horizon.
There is a very short period right now, when both Venus and Mars can be seen in the sky at the same time, and you would need very low, flat, and clear horizons both in the east and in the west to see them.
But, we are still quickly gaining on Mars, so the red planet rises a little earlier each night. If you will remember, the Moon encountered Mars on June 3rd. And they will again be close on the evening of Saturday 30 June. So, we are gaining about four days on Mars every month.
This month’s second encounter won’t be quite as close as the one earlier. The Moon will rise with Mars at about ten o’clock Saturday night. Notice how much brighter Mars has become in the past month, and note the noticably ruddy hue of the decidedly red planet.
We continue to gain on Mars in our orbit. We travel around the Sun at a greater speed, and we are closer to the Sun, so have a shorter distance to travel.
We will be at our closest to Mars in late July. When we began keeping track of our progress seven weeks ago, we were 72 million miles from Mars. This weekend, when we observe the red planet rising with the Moon, we will be less than 42 million miles away. We are an astounding 30 million miles closer to Mars than we were a mere seven weeks ago! And we are less than half the distance from Mars than we are from the Sun.
In fact, since we observed Mars with the Moon earlier in the month, it has increased in brightness by almost one magnitude, as we are 15 million miles closer than we were when the month began.
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• · William J. Bechaver is the director of SPACE • Spanish Peaks Amateur Cosmos Enthusiasts, the premier Astronomical Society for Southern Colorado and Northern New Mexico.