Will you catch Mercury at dawn?

Posted by Bruce McClure in Tonight | August 6, 2019

  • Aug 06 – Aug 12

The photo above – by Radu Anghel in Bacau, Romania – shows our sun’s innermost planet Mercury after sunset in February 2019. Although it’s intrinsically a bright object, Mercury often appears as this photo shows it, in a sky washed with twilight colors. Seeing it often requires a search. On the other hand, for much of every year, Mercury is lost in the glare of the sun, not visible at all. It’s only at opportune times, when Mercury nears or reaches its greatest elongation (maximum angular separation) from the sun on the sky’s dome, that it’s possible to catch Mercury at its highest above the sunset or sunrise. Now is such a time.

In early August – as viewed from around Earth’s globe – Mercury appears in the east before sunrise. On August 9, 2019, Mercury will reach its greatest elongation of 19 degrees west of the sun. Given clear skies, there’s a good chance that you’ll see Mercury with the eye alone, for this world is a bright as a 1st-magnitude star.

Mercury will be over 18 degrees west of the sun all this upcoming week, from August 7 to 14. The amount of time that Mercury rises before the sun, however, depends on your latitude, with the Northern Hemisphere enjoying the advantage. We give the rising times for various latitudes below, but please keep in mind that these times presume a level horizon.

40 degrees north latitude
August 7: Mercury rises 1 hour and 26 minutes before the sun
August 14: Mercury rises 1 hour and 28 minutes before the sun

Equator (0 degrees latitude)
August 7: Mercury rises 1 hour and 16 minutes before the sun
August 14: Mercury rises 1 hour and 12 minutes before the sun

35 degrees south latitude
August 7: Mercury rises 1 hour and 9 minutes before the sun
August 14: Mercury rises 56 minutes before the sun

Source: US Naval Observatory

Want more specific rising times? Click here for a recommended sky almanac.

Transit of Mercury

Tomorrow … Last transit of Mercury until 2032
Our solar system’s innermost planet, Mercury, will pass directly in front of the sun tomorrow. It’ll come into view as a small black dot on the sun’s face around 7:36 a.m. Eastern Standard Time (12:36 UTC; translate UTC to your time) Monday morning. It’ll make a 5.5-hour journey across the sun’s face, reaching greatest transit (closest to the sun’s center) at approximately 10:20 a.m. EST (15:20 UTC) and finally exiting around 1:04 p.m. EST (18:04 UTC). Much of the world can see some part of the transit. The entire transit will be visible across the U.S. East – with magnification and proper solar filters – while those in the U.S. West can observe the transit already in progress after sunrise. Learn how to watch in the sky or online