Happy birthday Andreas Mogensen! International Space Station astronaut celebrates in space

Denmark's astronaut Andreas Mogensen said he was happy to see the sun on his birthday in space.

The Expedition 70 commander on the International Space Station, who was also the first Dane in space in 2015, posted about his orbital birthday on X (formerly Twitter) about why solar views are especially celebrated on birthdays.

"We also have a saying that if the sun shines on your birthday, it means you have been good this year — and the sun is always shining in space," Mogensen wrote on Thursday (Nov. 2), alongside a photo of him behind the camera at the ISS wraparound Cupola window.

Mogensen added he is missing his family, but he was glad to spend time with a "great crew who celebrated it (my birthday) with me."

Related: Spectacular purple and gold auroras glow over Denmark (photos)

People who live in Denmark also celebrate birthdays by flying the national flag, the Dannebrog, Mogensen explained. "It becomes a birthday flag, which symbolizes happiness, celebration, and smiles," he said.

Mogensen also included a view of the Dannebrog in the ISS, nestled in between the flags of Greenland (left) and the flag of the Faroe Islands (at right). These are two special autonomous regions of Denmark that are not part of the European Union.

The Dannebrog has been referenced in historical documentation at least as far back as the 14th century. Legend, however, says it fell from heaven during the Crusades-era Battle of Lyndanisse (near modern Tallinn, Estonia) in 1219, according to Encyclopedia Britannica.

Mogensen's birthday came amid a busy week for the ISS. On Tuesday (Nov. 1), Expedition 70 crewmates and NASA astronauts Jasmin Moghbeli and Loral O'Hara completed the fourth all-woman spacewalk in history, spending 6 hours and 42 minutes doing maintenance. Mogensen is set for his own extravehicular activity later in 2023.