International Moon Day

International Moon Day (IMD) is a United Nations-proclamed annual celebration held on July 20 to mark the anniversary of the first human landing on the Moon by Apollo 11 in 1969. IMD serves as a platform to educate, inspire, and promote awareness about the past, present, and future of sustainable lunar exploration and utilization.

Bryon sent a postcard to celebrate it!

Another related stamp I got form Phillip (the USA):

Moon Landing

This is Phobos, one of Mars' moons.
Last year the world celebrated the 50th anniversary of the First Moon Landing with the issue of several stamps.

Early this year, I received some of them, on a letter sent by Phillip (the USA), on a thematic recycled envelope. (See on his blog.) 

The stamp on the middle shows the Sea of Tranquility, the site where the lunar module, Eagle, landed. 

And a French stamp features also one of the most ionic pictures of the event: the first steps on the Moon.

How many famous astronomers do you know?

Wang Zhenyi (1768-1797)

Cecilia Payne-Gaposchkin (1900-1979)

Vera Rubin (1928-2016)

The stamps on thes envelopes are very appropriate, as they belongs to the Spacious Skies part of the O Beautiful stamps: