September 14
The Flank of the Horse
Sun Position
The Sun is in Virgo at roughly 0° declination, effectively on the celestial equator. Day length is very close to 12 hours everywhere; the equinox is about one week away.
Sky Highlight
The Great Square of Pegasus transits the meridian around midnight this week, making the coming nights ideal for surveying Pegasus, Andromeda, and the surrounding autumn constellations from northern latitudes. No major annual meteor shower peaks today.
Deep Sky Object
NGC 7331, spiral Galaxy, Pegasus. A large tilted spiral about 40 million light-years away, NGC 7331 is often compared to the Milky Way in size and structure. It is well-placed for Northern Hemisphere observers; low but accessible from mid-southern latitudes.
Featured Star
Algenib (γ Peg) is a hot blue subgiant of spectral type B2IV, about 391 light-years away, one of the most physically energetic of the four Great Square stars. It is also a Beta Cephei variable, pulsating with a period of just 3.64 hours and a luminosity variation so small it was detected only by precise photometry.
Around This Date
- September 14, 2015LIGO detected gravitational waves for the first time, from the merger of two black holes roughly 1.3 billion light-years away, confirming a prediction of general relativity that Einstein himself doubted could ever be measured.
- September 14, 1959Luna 2's impact on the Moon was confirmed by tracking stations in the UK, establishing the first ground-truth timing of a human-made object reaching another world.
Algenib is the quietest corner of the Square to the eye, but photometrically it is pulsing in three-hour cycles, the sky keeps secrets that numbers reveal.