Mercury is the closest planet to the Sun and the smallest planet in the solar system. All the planets out in space seem cold to us, but the average surface temperature on Mercury is 333 degrees Fahrenheit (about 165 Celsius). It’s hot.
Mercury has a large iron core that is much larger than Earth’s core. Mercury has almost no atmosphere. Its gray surface is covered with impact craters caused by asteroids and comets, so that it appears similar to our Moon.
It has a strong magnetic field, generated by a dynamo effect, in a manner similar to the magnetic field of Earth, resulting from the circulation of the planet’s iron-rich liquid core. Particularly strong tidal heating effects caused by the planet’s high orbital eccentricity would serve to keep part of the core in the liquid state necessary for this dynamo effect.
Because Mercury is small and is close to the Sun, it can be difficult to observe. The best times to see it with the naked eye are shortly before sunrise or right after sunset. The best time to catch Mercury is within a week or so of its greatest elongation. That is the time when Mercury appears to be at its farthest distance from Sun as seen from Earth. That happens about every four months.
The greatest elongation west is when Mercury is farthest from the Sun in the morning sky and its greatest elongation east is when the two bodies are farthest apart in the evening sky. The greatest elongation east (night sky) occurs on December 21, 2022. So the next few nights are a good time to look for Mercury after sunset.
You can check out tonight’s sky here.
In Roman mythology, most people today think of Mercury as the winged-foot god associated with speed. That is probably closer to the Greek god Hermes who is the equivalent of the Roman Mercury.
To the Romans, he was the god of financial gain, commerce, eloquence, messages, communication (including divination), travelers, boundaries, luck, trickery, and thieves. He was also the guide of souls to the underworld.