July 27
The Swan's Distant Tail
Sun Position
The Sun is in Leo at about +18.8° declination. Northern Hemisphere summer; Southern Hemisphere winter. Cygnus reaches the meridian just after midnight, high overhead for mid-northern observers.
Sky Highlight
No named meteor shower peaks on July 27. The Southern Delta Aquariids are near their peak; from dark southern sites, 20 or more meteors per hour may be visible. The Perseids are beginning their build-up, with low but increasing activity detectable from the Northern Hemisphere in the predawn hours.
Deep Sky Object
M29 (NGC 6913), a small open cluster in Cygnus roughly 4,000 light-years away. It contains about 50 stars in a compact group that sits in one of the densest parts of the Milky Way; the heavy dust extinction in this direction makes the stars appear fainter than they are. A compact, interesting object in a binocular or telescope field. Best from Northern Hemisphere latitudes.
Featured Star
Deneb (α Cyg) is approximately 2,600 light-years away in Cygnus, one of the most distant stars visible to the naked eye. Its A2Ia classification identifies it as a blue-white supergiant with a luminosity estimated at roughly 200,000 times the Sun's; it sits at the tail of the swan and the top of the Northern Cross, a fixed beacon in the summer sky.
Around This Date
- July 27, 1949The de Havilland Comet made its maiden flight, becoming the world's first jet-powered commercial airliner, opening the era of rapid intercontinental travel that would soon connect observatories, telescope sites, and astronomical conferences across the globe.
- July 22, 1951Soviet dogs Dezik and Tsygan completed the first suborbital spaceflight by living animals to return safely, launched from Kapustin Yar, a precursor to the animal and human spaceflight programs that followed within the decade.
If the Sun were replaced by Deneb, every planet out to about Uranus's orbit would be inside the star, a reminder that 'supergiant' is not a metaphor.