The Sun appears to be about 0.5° in diameter. On the equator, approximately how long does it take for the Sun to set, from first contact with the horizon to complete disappearance below the horizon?

It takes about 2 minutes for the sun to completely disappear below the horizon.

Explanation:

Earth's rotation in a day= 360 degrees

Sun's Diameter= 0.5 degrees

360/24hr= Earth's rotation is 15 degrees/hour

If the sun's diameter is 0.5 degrees it takes:

15/0.5=30

60/30= 2 minutes (since there are 60 minutes in an hour)

not completely sure but i think it’s many moons, smaller in size and a ring system.