Moon Jupiter Venus and Mercury fill the evening sky

What I saw on my evening walk – sadly without my camera:

Moon 50% full high and in line with three planets:


When the planets align

And why mathematicians will never be practical people:


In old Roman legends, Mercury was the swift-footed messenger of the gods.  The planet is well named for it is the closest planet to the Sun and the swiftest of the Sun’s family, averaging about 30 miles per second; making its yearly journey in only 88 Earth days.  Interestingly, the time it takes Mercury to rotate once on its axis is 59 days, so that all parts of its surface experiences periods of intense heat and extreme cold.  Although its mean distance from the Sun is only 36 million miles, Mercury experiences by far the greatest range of temperatures: nearly 900ºF./482ºC. on its day side; -300ºF./-184ºC. on its night side.

In the pre-Christian era, this planet actually had two names, as it was not realized it could alternately appear on one side of the Sun and then the other.  Mercury was called Mercury when in the evening sky, but was known as Apollo when it appeared in the morning.  It is said that Pythagoras, about the fifth century B.C., pointed out that they were one and the same.

Mercury (Apollo) in my camera at last!


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2 Responses to Moon Jupiter Venus and Mercury fill the evening sky

  1. Priya says:

    Very interesting.

    Forgive me if I am asking too much but I need to know. I couldn’t understand why the day and night temperatures would have such a big difference? The planet is small, its proximity to the sun the closest. Shouldn’t it be very hot all the time? Regardless of how long it takes to rotate?

    • EarthImage says:

      Earth and Venus have relatively uniform temperatures due to their atmospheres. The Earth averages 14 degrees C, but Venus 460 C, due to its carbon dioxide cloud cover.

      In the case of Mercury, there is nothing to hold the intense radiant heating of the lighted surface, once it turns away from the Sun.

      The point of the posting was the rarity of sighting Mercury, and seeing it in alignment to so many other planets at once. Mars is in opposition to the Sun now, but still visible in the same sky.

      This is only my second sighting of Mercury. It is said that Copernicus never saw it once.

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