July 26
The Dragon's Eye Proves Earth Moves
Sun Position
The Sun is in Leo at about +19.1° declination. Northern Hemisphere summer; Southern Hemisphere winter. Draco is circumpolar from most Northern Hemisphere latitudes and well above the horizon on July evenings.
Sky Highlight
No major annual event peaks on July 26. Draco winds between Ursa Major and Ursa Minor, making it a permanent fixture in Northern Hemisphere skies year-round. July evenings are a good time to trace the full constellation from its tail near the Big Dipper's bowl to its head near Hercules.
Deep Sky Object
NGC 6543, the Cat's Eye Nebula in Draco, roughly 3,000 light-years away. Its concentric shell structure is one of the most complex known for a planetary nebula; Hubble imaging shows at least eleven nested rings, possibly formed by a central binary star shedding material at irregular intervals. Circumpolar from most Northern Hemisphere latitudes and well-placed in July.
Featured Star
Etamin (γ Dra) is an orange giant 148 light-years away in Draco, classified K5III. In 1728, astronomer James Bradley was attempting to measure its parallax as part of an ongoing project by Robert Hooke, but instead found an annual stellar wobble that was too large and in the wrong direction for parallax, leading him to discover stellar aberration, the first direct evidence that Earth orbits the Sun.
Around This Date
- July 26, 1971Apollo 15 launched, carrying astronauts David Scott, James Irwin, and Alfred Worden on the most scientifically ambitious Moon landing to that point, including deployment of the first lunar roving vehicle.
- July 28, 1955President Eisenhower and the National Security Council received a full briefing on the Atlas ICBM program from General Bernard Schriever and John von Neumann; the Atlas would later serve as the rocket that launched John Glenn into orbit in 1962.
Etamin was not trying to prove anything, it just moved at the wrong speed, and James Bradley paid close enough attention to notice.