The Planet Parade

There are some astronomical events that are common; one can often find a shooting star if they look hard enough, but there are some events that are extremely rare. There are many events that are considered to be once in a lifetime events. Whether it is the passing of a particularly rare comet or a solar eclipse, these events cause a great deal of excitement. Over 70 years ago, on February 28, 1940, star enthusiasts in Milwaukee, Wisconsin were lucky enough to experience such event first hand; the event was known as the Planet Parade.

In an event that may not be seen for another thousand years, planets were seen in a line with the naked eye. The line consisted of five planets, appearing in an ascending line to Earth’s star gazers. The planets involved in the upward diagonal line included: Mercury which was located closest to the Western horizon, Jupiter, Venus, Saturn, and Mars. The planetary “parade” even included Uranus, but it could not be viewed with the naked eye, making the assistance of a telescope necessary. This event is rare, but without acknowledgement of the varying speeds of orbit for these five planets, it is hard to understand why. For example, while Venus can often be seen with the naked eye, there are long periods of times when Saturn and other planets are left unseen in our night sky. This difficulty makes viewing multiple planets on one night a rare event itself, let alone witnessing these planets in a straight line. Another important prerequisite for this event was that Mercury needed to be at its greatest distance from the sun. Mercury is one of the most difficult planets for star gazers to spot, as it is usually blocked out by the sun and incapable of being seen in the night sky. However, it is only while at its farthest point from the sun that Mercury could escape the glare of the sun and maintain visibility. The chance to see all five planets in line only existed for a short period of time, because of Mercury’s elusive nature. For only a brief period, between 6:20 and 6:45pm was it possible to see Mercury, making the window of opportunity for the Planet Parade strikingly small.

Astronomers went through great lengths to capture this rare event on film; technological shortcomings of the 1940s made doing so much more difficult than it would be today. Members of the Milwaukee Astronomical society were forced to design a special camera to capture the five visible planets and Uranus in one frame. The special camera consisted of a unique wide angle lens, which held 8 inch by 10 inch plates. In order to prevent any issues with photographing the anomaly, the local observatory was very cautious. On the night of the planetary alignment, the public was not allowed into the observatory, out of fear that incoming car lights would hinder Mercury’s visibility. After the passing of February 28, the planets continued on their paths and proceeded to separate, but for those who witnessed the awe-inspiring cosmic event, the Planet Parade would not soon be forgotten.

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