Sky Map: August 2019

See Elusive Planet Mercury at Dawn

By Jeff DeTray from AstronomyBoy.com
August 8, 2019
Sky Map August 2019
Jeff DeTray

Spot the elusive planet Mercury in the east before sunrise! It’s a rare opportunity to get a glimpse of the Sun’s innermost planet. Here’s more viewing information and our complimentary, printable August Sky Map to help you navigate easily. 

Just click here or on the image below to open the printable map—then bring outside!

August printable sky map

This month’s highlight: Mercury, the Fleet-Footed Messenger

Pass the sun-block!
Can’t you see,
It’s really bright,
Cried Mercury . . 

–Mr. R.’s World of Science (online)
 
Mercury ís brave
close to the sun
lost in its glare
how quickly it runs

–Kamtime (online)

Poems devoted to the planet Mercury are few and far between, but they share common themes. They typically refer either to Mercury’s extreme relationship with the Sun or its speedy movement through the sky—or both. Mercury is closer to the Sun than any other planet and thus endures a surface temperature of up to 800°F. Sunblock, indeed! And Mercury is fast! It whips around the Sun once every 88 days, compared to our Earth’s 365 days. The ancient Romans noted how swiftly Mercury moves across the sky and named it for the fleet-footed Messenger of the Gods.

It’s a testament to the exquisite observing skills of ancient astronomers that they ever noticed Mercury at all. From our Earthly perspective, the innermost planet never ventures very far from the Sun; you have to know exactly when and where to look.

Spot Mercury Before Dawn

Fortunately, August brings the best opportunity to see the elusive planet.  Mercury rises before the Sun all of this month, and is surprisingly easy to see from now through August 27.

The planet attains a greatest elongation 19 degrees west of the Sun on August 9.

So, the several mornings before and after August 9 are the best times to see Mercury with the eye alone.

Here’s how:

  • Go outside 30 to 45 minutes before sunrise. Consult the Almanac’s Sunrise and Sunset Calculator to find the exact time of sunrise for your location. With sunrise not far away, the sky will be brightening quickly, so don’t be late!
  • Look to the east-southeast, low in the sky for a bright yellowish-orange “star.” If the skies are clear, you should even be able to see Mercury without a telescope for the planet is a bright as a 1st-magnitude star.

See the Sky Map on this page to get oriented. Castor and Pollux, the famous “Twin Stars” in the constellation Gemini, are the bright stars nearest to Mercury, but they are both slightly dimmer than Mercury. There are several bright stars in the area, in addition to the planet Mercury. Betelgeuse, Rigel, Procyon, and Capella are all approximately the same brightness as Mercury.

More about Mercury

Exploratory spacecraft have visited Mercury only twice! 

  1. In 1974–75, NASA’s Mariner 10 probe made three flybys of Mercury, sending back the first close-up photos and discovering that the tiny planet has its own magnetic field, a finding that surprised researchers.
  2. Then, in 2011, NASA’s MESSENGER  (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft reached Mercury and went into orbit around it. MESSENGER spent the next four years collecting science data and making thousands of high-resolution photographs of Mercury. The MESSENGER photo reproduced on this month’s sky map shows how closely Mercury resembles the Moon, at least on its surface.

A third spacecraft is currently on its way to Mercury! BepiColombo is a collaboration between the European Space Agency and the Japanese Space Agency. The mission carries two separate probes, which will separate from one another once BepiColombo reaches Mercury in 2025.

Fortunately, you won’t have to wait that long to undertake your own exploration of Mercury. You merely have to wake up before dawn on August 9 or 10 (or thereabouts) to see the hot and speedy planet for yourself.

August 2019 Sky Map

Click here or on map below to enlarge (PDF).

August 2019 Sky Map
Sky map produced using Chris Marriott’s Skymap Pro

Note: How to Read the Sky Map

Our sky map does not show the entire sky which would be almost impossible. Instead, the monthly map focuses on a particular region of the sky where something interesting is happening that month. The legend on the map always tells you which direction you should facing, based on midnight viewing. For example, if the map legend says “Looking Southeast,” you should face southeast when using the map.

The map is accurate for any location at a so-called “mid northern” latitude. That includes anywhere in the 48 U.S. states, southern Canada, central and southern Europe, central Asia, and Japan. If you are located substantially north of these areas, objects on our map will appear lower in your sky, and some objects near the horizon will not be visible at all. If you are substantially south of these areas, everything on our map will appear higher in your sky.

The items labeled in green on the sky map are known as asterisms. These are distinctive star patterns that lie within constellations. When getting your bearings under the stars, it’s often easiest to spot an asterism and use it as a guide to finding the parent constellation.

The numbers along the white “Your Horizon” curve at the bottom of the map are compass points, shown on degrees. As you turn your head from side to side, you will be looking in the compass direction indicated by those numbers. The horizon line is curved in order to preserve the geometry of objects in the sky. If we made the horizon line straight, the geometry of objects in the sky would be distorted.

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Mercury

The blurb in the newsletter has Mercury visible 30 minutes before sunset, instead of sunrise.