During these next three weeks we will be presented with an excellent opportunity to view Mercury in the early morning dawn sky. Mercury is called an “inferior planet” because its orbit is nearer to the sun than the Earth’s. Therefore, it always appears from our vantage point to be in the same general direction as the sun…
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 rises before the sun all of this month and is surprisingly easy to see from now through Nov. 5. All you have to do is just look low above the eastern horizon during morning twilight, from about 30 to 45 minutes before sunrise for a bright yellowish-orange “star.”
Mercury will be at its greatest western elongation, 18 degrees to the west of the sun, on Oct. 22, rising as dawn breaks, and making this Mercury’s best morning apparition of 2004. Mercury, like Venus, appears to go through phases like the moon. Shortly after passing inferior conjunction on Oct. 6, Mercury was just a slender crescent. Currently, it appears about one-third illuminated, but the amount of its surface illuminated by the sun will continue to increase in the days to come. So although it will begin to turn back toward the sun’s vicinity after Oct. 22, it will continue to brighten steadily, which should help keep it in easy view over the following couple of weeks.
Helping to aid in identifying Mercury will be a lovely crescent moon. Early on the morning of Oct. 26, at about an hour before sunrise, you’ll find the moon low in the east-southeast sky and Mercury will appear as a bright star-like object well below and to the moon’s left.
The article has plenty of detail, history, science and common sense suggestions for watching. Enjoy this special opportunity to see one of our downhill neighbors.