October 17
The Ram Overhead
Sun Position
The Sun is in Libra near -11.5° declination. At 40°N latitude, the Sun now sets before 6:15 PM local standard time; at 40°S, it sets around 7:15 PM.
Sky Highlight
Aries reaches its best evening positioning in mid-to-late October, rising in the east by sunset and crossing the meridian near midnight, putting all three principal stars (Hamal, Sheratan, Mesarthim) in easy reach for telescopic observers. The compact triangle they form is a natural target for systematic double-star work.
Deep Sky Object
NGC 772, a spiral galaxy about 130 million light-years away. NGC 772 in Aries presents an unbarred spiral seen at a moderate angle, with a prominent asymmetric arm that extends further than its counterpart on the other side, a structural peculiarity directly attributed to tidal tugging from its smaller companion. Accessible from both hemispheres; best from Northern Hemisphere mid-latitudes in October.
Featured Star
Hamal (α Ari) is an orange giant (K2IIICa-1) about 66 light-years away with a confirmed exoplanet (Hamal b) orbiting it, discovered in 2011. The planet orbits well beyond where any habitable zone would be expected for its evolved host star, but its presence underlines how common planetary companions are around giants. Hamal, the ram's head, once the star that marked the start of spring.
Around This Date
- October 17, 1604Galileo Galilei lectured on the new star (Kepler's Supernova) visible in Ophiuchus, using it to argue publicly against the Aristotelian doctrine that the celestial realm was unchanging.
- October 18, 1963The French space agency CNES conducted a suborbital crewed animal flight, sending the cat Félicette to an altitude of roughly 157 km before a successful recovery.
Hamal's exoplanet is a quiet footnote to its long history, a modern layer written on top of an ancient calendar star.