2019, May 6-7: Aldebaran, Mars, and the Crescent Moon


(On the chart above, the moon’s size is exaggerated.  At this scale, the star Zeta would be covered in May 7.)

The chart shows the western sky at about 1 hour after sunset.  Start looking for the moon beginning about 30 minutes after sunset.  Check your sources — television, newspaper, or Internet — for the time of your local sunset.

On May 6, the crescent moon (2.1 days past the New phase, 5% illuminated), 11° up in the west-northwest, is 2.2° to the upper right of Aldebaran, the brightest star in Taurus.   The moon is nearly 14° below Mars.

An hour after sunset, locate Mars between Elnath and Zeta Tauri, 4.5° to the lower left of Elnath and 3.4° to the upper right of the Bull’s southern horn.

On the next evening, an hour after sunset, the moon (3.1 days old, 11% illuminated) is 0.3° to the lower left of Zeta Tauri. Mars is 3.3° to the upper right of the star.

Use a binocular to look that the moon these two evenings.  You’ll notice that the moon’s night portion is slightly illuminated.  This is known as Earthshine.  From the moon, Earth is nearly full, and would be very bright to an observer on the lunar surface; it is bright enough to cast shadows on the moon’s night portion.  Earthshine is from reflected sunlight from Earth’s clouds, land, and oceans.  This sunlight gently illuminates the night portion of the moon in the same manner our planet is illuminated when the moon is near its Full phase.  Click here for an example of the crescent moon with Earthshine.

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