Printable Star Map
Look up with the September 2017 sky map to navigate the stars and constellations in the night sky. On this page is both a color sky map and a black and white printable map to bring outside!
Just click here or on the image below to open the printable map—then bring outside!
Mercury in the Morning
We usually think of stargazing as an evening activity. The Sun sets, the sky slowly darkens, and, one by one, the stars and planets are revealed. Of course, celestial objects don’t know or care what time of day it is. For example, there are always stars in the sky—even in the daytime—but the bright Sun prevents us from seeing them.
Sometimes, the best sights in the sky make their appearance in the early morning, before the Sun has risen. That’s the case in September with the planet Mercury, an orb most people have never seen.
Ancient astronomers noted that Mercury appears to move across the sky faster than any other planet. That’s why the Romans named it after their eet-footed messenger of the gods. Indeed, Mercury zips around the Sun once every 88 days, compared to the leisurely 365-day pace of Earth.
Mercury is the closest planet to the Sun, and it is hidden in the Sun’s glare much of the time. Only a few times a year does Mercury venture far enough from the Sun to become easy for us to see; the predawn sky of mid-September is one of those infrequent occasions.
In mid-September, Mercury will be visible low in the east before sunrise, starting shortly after 6:00 a.m. It is best viewed from a location where the eastern horizon is not obscured by trees and buildings. The sky will be brightening quickly at this time of day, so your window of opportunity for observing Mercury is fairly brief—about 90 minutes.
Mercury is not impressively bright, but fortunately we have the blazing planet Venus to guide us. Venus is by far the brightest object in the area and impossible to miss. Below it is the much dimmer star, Regulus, and just a little lower is Mercury, brighter than Regulus but nowhere near as bright as Venus. (Look just below Mercury for a bonus glimpse of the planet Mars.)
The map shows the arrangement of these four objects on the morning on September 12. Over the following days, Mercury will move closer to Mars until September 16, when the two planets will appear to be nearly touching. Mercury will continue to move downward. By the third week of September, it will become dif cult to see as it nears the horizon.
When you have spotted elusive Mercury, you will join a select group of individuals who have knowingly done so. Quite a few people have viewed Mercury by accident, without know what they were seeing. However, the real joy of sky gazing is not just in appreciating a beautiful view, but in knowing something about the things you are observing.
Mercury is not the only object in the early morning sky in September. There’s an array of of extremely bright stars. In this one view, you can see 5 of the top 10 brightest stars and 9 of the top 25, including Sirius, the brightest star of all. So, take a look at Mercury, enjoy some of the sky’s brightest stars, and watch the Sun come up!
September Sky Map
Click here or on image below to enlarge this map (PDF).
Sky map produced using Chris Marriott’s Skymap Pro
Enjoy astronomy? Check out Bob Berman’s column, “This Week’s Amazing Sky.”