August 5
The Sting at the Tail
Sun Position
The Sun is in mid-Leo at roughly +16° declination. Days shorten perceptibly now in the Northern Hemisphere; Southern Hemisphere nights grow noticeably shorter as the planet tilts toward spring.
Sky Highlight
The Perseid shower is very close to peak; zenithal hourly rates are rising sharply, and on moonless years the nights of August 11-13 can deliver 100 or more meteors per hour. In the nights immediately before the peak, rates of 30-50 per hour are typical for Northern Hemisphere observers after midnight.
Deep Sky Object
M7, also known as Ptolemy's Cluster, is a large, bright open cluster in Scorpius containing roughly 80 stars and lying about 980 light-years away. It is one of the most ancient catalogued deep-sky objects (Ptolemy noted it in the 2nd century CE) and is easiest from the Southern Hemisphere or low northern latitudes where Scorpius rises high.
Featured Star
Shaula, the lambda Scorpii blue subgiant marking the scorpion's sting, is actually a triple-star system roughly 700 light-years away, with a spectral type of B1.5IV for the primary component. Three stars, one tip of a tail, the geometry is more complicated than the mythology.
Around This Date
- August 5, 2011NASA's Juno spacecraft launched from Cape Canaveral, carrying instruments designed to peer beneath Jupiter's cloud tops and map the planet's powerful magnetic field.
- August 6, 2012Curiosity, NASA's car-sized Mars Science Laboratory rover, successfully landed in Gale Crater, Mars, in one of the most technically complex spacecraft landings ever attempted.
A scorpion's sting is already a warning; finding three stars hiding in one point of light is astronomy's version of that surprise.