Mercury
An astronomer told me one day that most of his mates have never seen Mercury. Why? Simple. Mercury being the closest planet to the Sun (at most 28 degrees from it), you can only see it during twilight. Most astronomers need full darkness to do their jobs, so by the time they start observing stuff, Mercury is well and truly set.
Tonight at around 6:30 - 7 pm you can beat that lot. If you look at the Western sky, you can’t miss Venus, the brightest object after the Moon. Mercury is about half-way between Venus and the horizon just a tad under Alpha Virgo. Done!
Mercury is quite interesting. It is hardly bigger than our Moon and looks a lot like it. That makes it the smallest planet. It is also the most eccentric. Most planets have a semi-circular orbit but Mercury’s is very egg-shaped. Its perihelion point (the closest to the Sun) is only 2/3 of its aphelion (the farthest point).
Being so close to the sun it is the fastest, with a period of only 88 days. So it goes at a mere 47 km per second. In fact it is so fast that the astronomers from Kepler’s time to Einstein’s had trouble calculating its orbit. Urbain le Verrier, the French guy who helped discovering Neptune, thought a planet inside Mercury’s orbit was messing things up. He even called it Vulcan! Bad luck, Urbain, Vulcan does not exist. Mercury’s orbit “anomalies” are fully explained by the Theory of Relativity.
References:
NASA: https://solarsystem.nasa.gov/planets/mercury/in-depth/
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