August 20
The Voyager Departs
Sun Position
The Sun is in late Leo at approximately +10° declination. The Northern Hemisphere is six weeks from the autumnal equinox; the Southern Hemisphere is six weeks from the vernal equinox.
Sky Highlight
The late-August sky in both hemispheres offers good conditions for observing the Cygnus Milky Way, now high overhead from northern mid-latitudes and accessible from the Southern Hemisphere's winter sky. The galactic plane runs nearly overhead for observers around 45° N, bisected by dark dust lanes visible to the naked eye.
Deep Sky Object
M29, an open cluster in Cygnus, lies roughly 4,000 light-years away in the dense Milky Way star fields near Sadr, the central star of the Northern Cross. It is a young, loose cluster easily found with binoculars in the rich Cygnus background, though its modest brightness means it competes with the surrounding star fields rather than standing apart from them.
Featured Star
Albireo, the beta Cygni pair about 430 light-years away, shows its orange K3II primary and blue-white B8Ve companion in any small telescope, the most frequently cited color-contrast double in the sky. Whether the two stars are physically bound or a chance optical pair is still debated; their projected separation corresponds to at least 4,400 AU.
Around This Date
- August 20, 1977Voyager 2 launched from Cape Canaveral on the Grand Tour trajectory, and as of the 2020s it is one of only two human-made objects to have crossed the heliopause into interstellar space.
- August 22, 2003The Spitzer Space Telescope launched on a Delta II rocket, opening a new era of infrared observation and eventually contributing to the first atmosphere detections of exoplanets.
Voyager 2 launched 47 years ago and is still transmitting, a small fact that tends to stop people who hear it for the first time.