1. Mercury

2. (a little bigger than the Moon)
Mercury Stats
Size: 2,439 km radius, of Earth’s Radius
(a little bigger than the Moon)
Mass: .055 Earth Masses (3.3 x 10^23 kg)
Density: 5.43 g/cm³ (about the same as Earth)
Average Distance to the Sun: .387 A.U.
Orbital period (Year): 88 Earth Days (87.97)
Sidereal Day: 59 Earth Days (58.65)
Solar Day: 176 Earth Days
Name Origin
It is named after the Roman Messenger of the Gods (among other things)

3. The Long Day of Mercury Mercury’s sidereal day is 2/3 its year.
As you know from Earth a solar day is longer than a sidereal day because the planet moves relative to the Sun as it orbits (revolves)
Mercury rotates so slowly relative to its revolution that the solar day is extended to the point it is twice as long as its year!
This also makes the Sun’s apparent motion from the surface of Mercury most interesting.

5. Resonance
As Mercury nears perihelion the Sun’s gravity gives it a pull
This regular force makes Mercury go a little faster like a parent pushing a child on a swing.
It creates a Resonance
This Resonance sends Mercury into a very elliptical orbit, more than the other planets

6. A Sun that changes Direction
Mercury’s orbit is very elliptical.
This combined with its slow rotation means that as Mercury passes its perihelion…
the Sun moves faster backward due to its revolution than does forward due to its rotation
The Sun will briefly move backward in the sky!

7. A Double Sunset/ Sunrise
If you are on the right spot so that this happens at sunset the Sun will set, rise briefly, and set again
A Double Sunset
At a different spot the Sun will rise, set briefly, and rise again
A Double Sunrise