May 25
The Ancient Pole
Sun Position
The Sun is in Gemini at roughly +21.1° declination. Northern days are near their annual maximum length; astronomical twilight may not fully end at latitudes above 55°N. Southern days are approaching their winter solstice minimum.
Sky Highlight
The late May sky is rich with globular clusters in the evening sky. M3, M5, M13, and M92 are all well up at nightfall from northern mid-latitudes. M13, the Great Hercules Cluster, is rising toward its best position of the year, and on the clearest nights it is just detectable without optical aid as a dim fuzzy spot.
Deep Sky Object
M13 (NGC 6205), the Great Hercules Cluster, about 22,000 light-years away. The showpiece globular cluster of the Northern Hemisphere summer sky, M13 contains several hundred thousand stars packed into a sphere roughly 145 light-years across. It is bright enough to be seen with the naked eye from a dark site and resolves into a brilliant salt-spill of stars in any telescope. Best from northern and equatorial latitudes.
Featured Star
Kochab (β Ursae Minoris) is an orange giant 130.9 light-years away, spectral class K4III. Due to the slow wobble of Earth's rotation axis called axial precession, Kochab served as the North Pole Star from roughly 1500 BCE to 500 CE (the era of ancient Greece and Rome) before the pole drifted to its current position near Polaris. It sits at the lip of the Little Dipper's bowl.
Around This Date
- May 25, 1961President Kennedy challenged Congress and the nation to reach the Moon before 1970, a commitment that directly led to the six successful Apollo lunar landings between 1969 and 1972.
- May 28, 1959Able and Miss Baker, a rhesus monkey and a squirrel monkey, became the first animals to survive spaceflight and recovery after a suborbital mission aboard a Jupiter AM-18 rocket.
The pole wanders slowly; every civilization gets a different north star.