Dominic Ford, Editor
From the Inner Planets feed
Unlike most of the planets, which follow almost exactly circular orbits around the Sun only varying in their distance from the Sun by a few percent, Mercury has a significantly elliptical orbit.
Its distance from the Sun varies between 0.307 AU at perihelion (closest approach to the Sun), and 0.467 AU at aphelion (furthest recess from the Sun). This variation, of over 50%, means that its surface receives over twice as much energy from the Sun at perihelion as compared to aphelion.
However, this makes little difference to Mercury's telescopic appearance, since little if any detail on its surface can be resolved by ground-based telescopes. Although its changing seasons have an incredible effect upon its surface temperatures, there is little change that is visible to amateur observers.
The exact position of Mercury at the moment it passes aphelion will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
From Ashburn (click to change), Mercury will not be observable – it will reach its highest point in the sky during daytime and will be 1° below the horizon at dawn.
|The sky on 06 May 2017|
10 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|01 Apr 2017, 01:52 EDT||– Mercury at greatest elongation east|
|17 May 2017, 18:58 EDT||– Mercury at greatest elongation west|
|29 Jul 2017, 20:24 EDT||– Mercury at greatest elongation east|
|12 Sep 2017, 05:11 EDT||– Mercury at greatest elongation west|