July 23
The Sting Returns
Sun Position
The Sun is in Leo at about +20.1° declination. Northern Hemisphere summer; Southern Hemisphere winter. Scorpius is still well-placed in the southern evening sky for much of the world.
Sky Highlight
The Southern Delta Aquariids meteor shower is building toward its peak around July 29–30. On July 23, rates are increasing and the shower is already productive from dark southern sites. The radiant in Aquarius rises after midnight; the shower is strongly favored for Southern Hemisphere and equatorial observers, with northern observers seeing significantly fewer meteors.
Deep Sky Object
M7 (NGC 6475), a large open cluster in Scorpius roughly 800 light-years away. It is one of the closest and most prominent open clusters in the sky, bright enough to have been noted by Ptolemy in the second century CE. In a dark sky it is visible to the naked eye as a fuzzy patch; binoculars resolve dozens of stars. Southern Hemisphere observers see it high overhead; northern observers below about 50°N can find it low in the south.
Featured Star
Shaula (λ Sco) is 700 light-years away in Scorpius, a triple star with a hot blue subgiant primary classified B1.5IV. It marks the tip of the scorpion's curved tail and is one of the twenty brightest stars in the sky; its triple-star nature was confirmed by spectroscopy rather than visual separation since the components are too close to split in a telescope.
Around This Date
- July 23, 1999NASA's Chandra X-Ray Observatory launched (one of the agency's four Great Observatories alongside Hubble, Compton, and SIRTF) carrying the most sensitive X-ray telescope ever built to study the composition of galaxies, stellar remnants, and interstellar phenomena.
- July 23, 1999Eileen Collins commanded the STS-93 mission that carried Chandra to orbit, becoming the first woman to command a Space Shuttle mission.
Shaula is 700 light-years of hot blue starlight waiting at the tip of a scorpion's tail, the sky's most patient sting.