Given clear skies, almost everyone worldwide will be able to see the moon and the planet Venus over the eastern horizon in the predawn and/or dawn sky on March 28. From the Southern Hemisphere, or at tropical latitudes in the Northern Hemisphere, you have the best chance of seeing the planet Mercury below the waning crescent moon.
The moon and Venus rank as the brightest and second-brightest celestial bodies of nighttime, respectively, so these two luminaries should stand out mightily in tomorrow’s early morning sky. Mercury, though nowhere as brilliant as Venus, still shines as brilliantly as the sky’s brightest stars. Yet, from temperate and far northern latitudes in the Northern Hemisphere, Mercury sits too low in the glare of sunrise to be seen easily, if at all.
Mercury and Venus are called inferior planets because they orbit the sun inside of Earth’s orbit. In their outward order from the sun, the eight planets of the solar system are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
If you could look upon the planets from the north side of the solar system, you’d see that all the planets revolve counter-clockwise around the sun. You’d also see that most of the solar system planets rotate in the same direction that they revolve: counter-clockwise (as seen from the north side of the solar system plane).
Oftentimes, the hemisphere that rotates counter-clockwise is said to be the northern hemisphere of that planet. This is known as the right hand rule for determining planet’s northern hemisphere and northern axis. The graphic at the right helps to illustrate the concept.
However, the planet Venus throws a monkey-wrench at this way of looking at things, because Venus’ direction of rotation is contrary to its orbital motion. If you could look at Venus from the north side of the solar system plane, you’d see Venus orbiting the sun counter-clockwise yet rotating around its axis clockwise. For this reason, Venus is sometimes called the “upside-down” planet.
Whether the solar system geometry makes sense to you or not, you can’t help but appreciate the celestial attraction in the early morning sky: the waning crescent moon, the planet Venus and at southerly latitudes: the planet Mercury.