Today the innermost planet Mercury reaches a point along its orbit around the Sun where it is more or less at a right angle from the Earth and the Sun, as the banner graphic at the top of the page shows. As viewed from above Mercury is to the right from the Sun, while from the backyard view on the Earth’s surface Mercury is also to the right from the Sun, or on its west side. This puts Mercury in the morning skies rising before the Sun rises and leading the Sun across the sky from east to west as the Earth rotates from west to east.
Earth, Inner Planets, and the Ecliptic
From our backyard perspective we view the planets at more or less the same level because the 8 planets orbit the Sun on or close to the plane of the ecliptic, the Earth’s orbit extended outward from the Sun. So from this perspective the two inner planets appear to move back and forth, left to right to left, as they orbit the Sun. Today Mercury is at the ‘turning point’ on the right side of the Sun, which places Mercury at its greatest western elongation, or at its maximum angular separation from the Sun as seen from Earth. Today Mercury is approximately 20 degrees from the Sun. Due to its closeness to the Sun Mercury never gets more than around 30 or so degrees from the Sun which means that Mercury never rises or sets more than about 2 hours from the Sun. (The Earth rotates approximately 15 degrees every hour)
Click here to learn a little (or a lot) about the innermost planet Mercury from two MESSENGER web sites.
30 July – 5:30 am CDT
While out observing Mercury look a little higher to the right for the planets Mars and Jupiter, plus some of the stars of the northern hemisphere winter season. While these two outer planets are also to the west from the Sun they do not have an elongation position as outer planets orbit the Sun beyond the Earth’s orbit rather than between the Earth and the Sun. Outer planets do reach a 90 degree angle relative to the Earth and the Sun but it is known as either east or west quadrature
30 seconds worth of Mercury from the Orbit performance.
Click here to go to the Qué tal in the Current Skies web site for more observing information.