Venus and Mars in Western Sky after Sunset
Image above shows Venus and Mars above the western horizon Feb 18, 2017
Canon 6D 10 s ISO 3200 f/8 24 mm lens
Venus, on Feb 17, was its brightest for this apparition since it had the largest sunlit surface facing us and was on the inside track of its orbit so it was also larger in area due to proximity. The two effects work against each other, -as the planet gets closer and larger, less and less of its surface is light from our perspective. There is a happy medium, however, on Feb 17 when the two produce a maximum lit surface. See SKY SIGHTS entry for Feb 17 for more.
Image above shows Venus on Feb 18, 2017 at its maximum brightness. (-4.6)
Canon 6D eyepiece projection through 20 mm eyepiece on C-9.25 Edge HD 1/40 s ISO100 f/40 eff. foc.len.
The difference in visual appearance of the two planets is based mostly on distance. Venus in its orbit is approaching the Earth right now and on March 24, it passes between us and the Sun at a mere 41 million kilometres. On rare occasions, it can even shave another 3 million km off that figure. Mars is about 6 times farther than Venus right now and on the opposite side of the solar system from Earth. In a year or so, however, Mars and Earth will be much closer, only 56 million km apart and so Mars will shine as a bright planet in our sky once again. But because Mars is smaller than Earth, (half of Earth’s diameter) and reflects less light our way (16%) it can never get as bright as Venus in our sky. Venus is an Earth-sized planet and its thick atmosphere of clouds reflects 75% of the sunlight in our direction. Mars and our Moon are very poor reflectors with similar albedos (the technical term for reflectivity) of 16% and 12% respectively, about the same as a slate blackboard.
Both planets, Venus and Mars are named after mythological gods. The Roman goddess of love was Venus and in Greek mythology, she was Aphrodite. She is always depicted as demur, lovely and beautifully curvy. The Roman god of war, Mars, and the equivalent Greek war god, Ares are shown in statues and paintings as bold, handsome and certainly manly (and deadly in battle). As the story goes, Mars and Venus at one point were a couple and produced twin offspring which judging by their names were probably poorly behaved: Deimos (meaning terror or dread) and Phobos (panic/fear). These names are used for the two real moons of the planet Mars.
So in the summer of 2018, a much brighter Mars will be the planet to observe with surface features like ice caps and dust storms visible in a telescope. (Even Deimos and Phobos may be glimpsed). But Venus, though closest and brightest in our sky right now, will forever remain mysterious, never dropping her thick veil of clouds and revealing her surface features (unless you have radar eyes, of course). Do enjoy the naked eye or binocular views of Venus right now because by April, Aphrodite’s month, she passes behind the Sun and disappears from our western sky. Later in spring, Venus returns to the east as an equally bright Morning Star, but by then she has left Mars far behind. This is only a temporary separation as the two are back together in a spectacular “embrace” in October -stay tuned.