Mercury Rising

This morning, shortly after 6 am, I was outside watching the eastern sky as the stars above faded into the dawn. I was hoping for a rare glimpse of the planet Mercury. I did see it, and the tableau was interesting enough that I’ll be observing again tomorrow morning. Here is my simulation of what I expect to see so you can view the scene for yourself.

Mercury is the closest planet to the Sun, and in our sky it is usually too close to the glare of our star to be seen. We see its orbit almost edge on, so from the Earth, Mercury seems to dash from  one side of the Sun to the other. Sometimes it moves far enough away from the Sun so that it can be glimpsed in the sunset or sunrise.

Mercury at dawn 2016 September 29

Mercury rising on the morning of September 29, 2016
Click to see full size

The  Observer’s Handbook of the Royal Astronomical Society of Canada reports:

[Mercury] moves into the morning sky from the 20th to the 30th [of September 2016], reaching the greatest elongation on the 28th. This is the best morning apparition of the year for observers in the northern latitudes.

This image is a somewhat idealistic simulation. Today I found the sky was much brighter than the simulation, and the star-like objects that were visible in the brilliance of the pre-dawn sky were only Regulus in the constellation of Leo, and the planet Mercury. I recommend that you use binoculars to identify this part of the sky. Note: this is facing due east.

Even lower down than Mercury will be the 28-day-old crescent Moon.

Astronomical Simulation of Mercury Rising 2016sep29, showing the distance from the Sun, the horizon line, and the position of the Moon.

Astronomical Simulation of Mercury Rising on September 29, 2016
click to see full size

Seeing the almost-new Moon, plus Mercury rising just before the Sun is the unusual tableau that will make it worth going out to watch.

At this point, the old Moon is only 15º away from the Sun (which is still below the horizon.) This sighting should be valid for any mid-latitude in the Northern Hemisphere. The local time (British Columbia, Canada) of the simulation is 6:30 am.

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