Mercury at Eastern Elongation

orbital-positions    On Tuesday February 26th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (inferior conjunction) between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun (superior conjunction) and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   I’ve added Mercury’s orbit to the ‘horizon view’ graphic below. Mercury is never very far ‘out’ from the Sun at elongation because of how close to the Sun is Mercury.
   Currently Mercury is visible over the western horizon at sunset local time. Joining Mercury to the east (up to the left) is the planet Mars. A few degrees west from Mars, (to the right), is the star Hamal. This is the brightest star in the small constellation of Aries the Ram.
   Additionally, if your skies are dark enough it should be possible to see the “Square of Pegasus”, a part of the constellation Pegasus the Winged Horse. And look for the star Mirach, part of the constellation Andromeda the Princess. Just a few degrees to its right is a fuzzy looking smear of light – M-31, the Andromeda Galaxy.
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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