August 9
The Preceding One
Sun Position
The Sun is in late Leo approaching Virgo, at about +15° declination. Northern Hemisphere nights are now noticeably longer than at the summer solstice; Southern Hemisphere observers are gaining daylight.
Sky Highlight
The Perseid meteor shower is peaking or very near peak. Under dark skies without interference from moonlight, zenithal hourly rates can reach 100 or more around August 11-13. The show is best from the Northern Hemisphere but visible worldwide; the radiant in Perseus never sets for observers above about 50° N.
Deep Sky Object
M12, a globular cluster in Ophiuchus, lies roughly 16,000 light-years away and is a companion object to M10, similarly well placed on August evenings near the celestial equator. It is somewhat less concentrated than M10 and resolves more easily, making both clusters a rewarding pair to compare on a single evening.
Featured Star
Sabik, the eta Ophiuchi system, is a matched white pair, an A2V and A3V binary roughly 88 light-years away whose two stars orbit each other over a period of about 88 years. The name means 'the preceding one' in Arabic, a navigational reference from when these stars helped chart the sky.
Around This Date
- August 12, 1877Asaph Hall discovered Deimos while searching for Martian moons; the find ended a long drought of new Solar System satellite discoveries and proved Mars was not moonless.
- August 18, 1877Six nights after Deimos, Asaph Hall found Phobos orbiting even closer to Mars, completing one of the most productive single observing campaigns in 19th-century planetary astronomy.
Two stars that take nearly a century to orbit each other, and they have been doing it since before we named them, the patience of binary systems makes human timelines feel brief.