A Rare Meeting of Planets and Spaceships

May 13, 2010: This weekend, Venus and the crescent Moon are gathering in the western sky for a spectacular conjunction, and they're not alone. The International Space Station and, very likely, space shuttle Atlantis will join them for a rare four-way meeting of spaceships and planets over many locations.

Ladanyi. [more] The show begins at sunset when Venus and the Moon emerge from the twilight in close proximity to one another. The Moon will be exquisitely slender, a 5% crescent on Saturday, May 15th (sky map), and a slightly fatter 10% crescent on Sunday, May 16th (sky map). Between the horns of the crescent, a ghostly image of the full Moon can be seen. That's "Earthshine"—the light of our own planet reflected back toward us by the Moon's dark terrain. In conjunction with Venus, a crescent Moon with Earthshine is regarded as one of the most beautiful sights in the heavens.

Into this tableau of surpassing beauty comes a spaceship--and maybe two!

The International Space Station is due to fly over many US towns and cities this weekend. The ISS appears just after sunset, about the same time as the Venus-Moon encounter, and it glides slowly across the sky shining as brightly as Venus herself. Check NASA's SkyWatch web site to see if you are favored with a flyby and to find out exactly when to look.

If the ISS appears over your hometown, Atlantis is likely to be there as well. The shuttle is scheduled to launch from the Kennedy Space Center on Friday, May 14th, at 2:20 pm EDT (updates). It would then spend the weekend catching up and docking with the ISS, appearing as a distinct point of light in company with the brighter space station. People who have seen double flybys of station and shuttle say it is even better than a Venus-Moon conjunction. Something about two spacecraft gliding silently together among the stars multiplies the beauty and wonder far beyond a factor of two.

This kind of station-shuttle double flyby is rare and soon to be a thing of the past. With only three flights remaining, the shuttle program is coming to an end. Indeed, this is the last scheduled flight of Atlantis and the last time it can appear side-by-side with the ISS in the night sky.

Atlantis's 12-day mission to the ISS helps lay the groundwork for the post-shuttle era. The orbiter will deliver thousands of pounds of supplies and spare parts, plus a new Russian research module and a European robotic arm. Astronauts plan to conduct three spacewalks totaling almost 20 hours to install batteries, an antenna and other hardware around the exterior of the station.

Flying through the sunset in the company of ISS, Venus and the crescent Moon is a nice way for Atlantis to wave goodbye.

Just don't forget to wave back.