July 13
The Circumpolar Guard
Sun Position
The Sun is in Cancer at about +20.5° declination. Northern Hemisphere midsummer continues; Southern Hemisphere observers have the longest nights of the year for circumpolar targets, though Ursa Minor is only marginally visible from deep southern latitudes.
Sky Highlight
No major annual event peaks on July 13. Ursa Minor circles the north celestial pole continuously, making it one of the few constellations Northern Hemisphere observers can find every clear night of the year. Pherkad and Kochab (the two outer stars of the Little Dipper's bowl) are called the 'Guardians of the Pole' in Arabic tradition.
Deep Sky Object
NGC 6826, the Blinking Planetary, a planetary nebula in Cygnus roughly 4,000 light-years away. Its common name comes from the way direct vision shows the central star while averted vision reveals the surrounding nebula, causing it to appear to 'blink.' A distinctive target for small telescopes. Best from the Northern Hemisphere.
Featured Star
Pherkad (γ UMi) is a white giant about 487 light-years away in Ursa Minor, classified A3II-III. Together with Kochab, it forms the pair known historically as 'the two calves' in Arabic tradition, rotating slowly around the celestial north pole. At spectral class A3, it is among the hotter and more luminous stars in the Little Dipper.
Around This Date
- July 13, 1995Comet Hale-Bopp was discovered by Alan Hale and Thomas Bopp independently on this night, a full 18 months before its closest approach to the Sun, one of the earliest prediscovery detections of a bright comet.
- July 14, 1965Mariner 4 completed the first successful flyby of Mars, transmitting 21 grainy photographs showing impact craters and no signs of surface water, fundamentally revising 20th-century views of the planet.
Pherkad has circled the pole without pause since long before anyone named it, and will continue after every name it carries is forgotten.