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Saturday, May 23, 2015

Earthsky Tonight – January 26, 2010 Mercury’s greatest morning elongation tomorrow

Courtesy of EarthSky
A Clear Voice for Science

Mercury in the predawn of January 27
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As seen from Earth, the planet Mercury – the solar system’s innermost planet – appears to be closely tethered to the sun. But tomorrow morning, Mercury will swing to the end of its tether – the outermost point of its orbit. Astronomers call this event Mercury’s greatest western elongation.

Therefore, Mercury will appear in the early dawn sky before sunrise for the next week or so. However, it’ll still take a deliberate effort to catch Mercury. If you’re up for the challenge, get up a good hour before sunrise. To find out your sunrise time, check out our almanac page.

At mid-northern latitudes, Mercury will rise about 1.5 hours before the sun (given a level horizon). But Mercury probably won’t be visible for 15 or so minutes after it rises. If your sky is good and clear, you should be able to spot Mercury in the east-southeast (the direction of sunrise) about one hour before sunrise.

Mercury is as brilliant as a bright star, so it’s possible to see this world with the unaided eye. Yet, binoculars are almost indispensable for seeking Mercury. Many times binoculars have enabled me to spot this phantom world that otherwise would have been hidden in the murk of twilight.

Written by Bruce McClure

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