It was 50 years ago today that the son of a Russian farmer rocketed into space and became the first man to orbit the earth. Yuri Gagarin's 108 minute trip in his Vostok spacecraft ushered in the era of manned space flight, as the US followed up with the Mercury, Gemini, and later the Apollo missions to the moon. In 1975 the US and Russia stopped competing and began the Apollo-Soyuz missions. Joint missions continue today on the International Space Station.
To celebrate the event, Distant Suns 2 for the iPhone and iPod touch is free today only. The app is a pretty complete star map, with 130,000 stars, 88 constellations and the Messier catalog of galaxies, nebula and star clusters. I've reviewed the app in the past and found it a worthwhile purchase. It's even better for free. Author Mike Smithwick produced one of the first computerized star map programs way back in 1985 for the Amiga 1000. Mike also produced Distant Suns 3 for the iPhone and iPad, which is even more sophisticated. It's on sale for US$4.99 today only.
A couple other astronomy app notes of interest. Star Walk, the award winning astronomy guide has been updated to include augmented reality. It activates the camera and superimposes accurate star positions over the portion of sky you are pointing to. It's very cool to use during the day as well because it will show you where the planets and other objects are that are made invisible by the sun. The iPhone version of Star Walk is on sale for $0.99, and that sale ends today. The app also now supports TV out on the iPhone 4.