2016: The Morning Sky


chicago_morning_2016a

This chart shows the visibility of planets and bright stars near the planets’ orbital paths in the eastern morning sky in 2016.  The chart shows the objects’ rising times compared to sunrise.  The earliest activity begins at 5 hours before sunrise.  The moon’s rising time is shown by the vertical sets of circles.  The beginning dates of each morning appearance start at the top of the chart.  As the moon moves toward its new phase, it appears lower on the chart, rising closer to sunrise.  The last date of the lunar cycle appears near the bottom of the chart.  The vertical lines represent 7-day intervals.

In addition, the settings of Jupiter, Mars, and Saturn are added to indicate that they are in the western sky.  The times for these three planets are “setting after sunrise.”  Notice that during mid-March, Jupiter sets in the west (0 time difference) as the sun rises.  This indicates that Jupiter is at opposition where it rises in the east at sunset, appears in the southern sky near midnight, and  sets in the western sky at sunrise.  Like a full moon, it is in the sky all night.  Notice the opposition dates Mars and Saturn, the dates when the time difference between sunrise and the planets setting times is zero.

During late January, Mercury, Saturn and  Venus appear in the eastern morning sky, Jupiter is in the western, and Mars is in the southern sky.  That makes all five visible  planets in the sky at the same time.

As an observer scans along the horizon, two stars can rise at the same time, but be very far apart in the sky.  The stars were chosen because they lie near the solar system’s plane.  They are sign posts of the orbital plane and the planets appear to pass them. Notice that the Jupiter rising line is converging with the Spica line.  Jupiter slowly approaches Spica throughout the year.  The planet passes the star in 2017, because Jupiter moves slowly.

The three twilight lines represent the beginning of astronomical twilight, nautical twilight, and civil twilight.  The three terms are defined at this end of this article.

Summary:

The activity that occurred in the morning sky during late 2015 is missing in 2016.  Mars and Jupiter are well up in the southern sky at sunrise and widely separated.  Venus and Saturn are in the southeast as rising 3 hours and 2 hours respectively before the sun.  During the early part of the year, Saturn inches past the star Antares.   As noted above with Jupiter, Saturn’s rising line diverges from Antares. Moving more slowly than Jupiter, Saturn slowly moves past and away from Antares during the year. Venus continues is slow disappearing act as it heads for superior conjunction.

In February, Venus and Mercury appear near each  other during morning twilight. The best morning appearance of Mercury is in September.  On September 29, the moon stands 1 degree below the speedy planet.

Jupiter reappears in the morning sky in October and passes with 0.5 degree of Mercury on October 11.  The moon and Jupiter appear together on the mornings of October 28 and December 22.

Twilight Definitions

Civil twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is 6 degrees below the horizon. This is the limit at which twilight illumination is sufficient, under good weather conditions, for terrestrial objects to be clearly distinguished. In the morning before the beginning of civil twilight and in the evening after the end of civil twilight, artificial illumination is normally required to carry on ordinary outdoor activities.

Nautical twilight is defined to begin in the morning, and to end in the evening, when the center of the sun is  12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other lighting, general outlines of ground objects may be distinguishable. During nautical twilight the illumination level is such that the horizon is still visible even on a Moonless night.

Astronomical twilight is defined to begin in the morning, and to end in the evening when the center of the Sun is 18 degrees below the horizon. Before the beginning of astronomical twilight in the morning and after the end of astronomical twilight in the evening, light from the Sun is less than that from starlight and other natural sources. For a considerable interval after the beginning of morning twilight and before the end of evening twilight, sky illumination is so faint that it is practically imperceptible. (Source)

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