May 12
The Split Sky
Sun Position
The Sun is in Taurus at roughly +18.4° declination. Northern Hemisphere twilight stretches late; observers below 50°N still have good evening darkness by 10 PM. Southern evenings are cool and lengthening.
Sky Highlight
The Scorpius-Centaurus OB association (a sprawling region of young, massive stars) is now rising in the southeast for southern observers and low in the south for equatorial viewers. It is the nearest OB association to the Sun, roughly 400 light-years away, and its stars include several of the brightest in the sky.
Deep Sky Object
M5 (NGC 5904), globular cluster in Serpens, about 24,500 light-years away. One of the oldest known globular clusters at roughly 13 billion years, M5 is considered among the finest in the northern sky, with a brilliantly concentrated core and outer regions that resolve beautifully at moderate power. Visible from both hemispheres.
Featured Star
Unukalhai (α Serpentis) returns on tonight's chart, an orange giant 73 light-years away, spectral class K2IIIb. Serpens is the only constellation formally divided into two disconnected parts by an intervening constellation (Ophiuchus), and Unukalhai in Serpens Caput is the brightest star of the whole divided figure, marking the creature's neck.
Around This Date
- May 12, 1910Halley's Comet reached perihelion during its 1910 apparition, and Earth passed through the comet's tail on May 19 of that year, an event widely anticipated and discussed but found to be harmless.
- May 13, 1964The first radio detection of the quasar 3C 273 at optical wavelengths was confirmed, helping establish that quasars were at cosmological distances and among the most luminous objects in the universe.
The snake's two halves are real; the constellation merely names what the sky shows.