April 11
The Pulsing Shield
Sun Position
The Sun is in Aries near +14° declination. Northern days are now substantially longer than nights; southern mid-latitude evenings are shortening noticeably as the hemisphere tilts away from the Sun.
Sky Highlight
The Hydra-Centaurus Supercluster, the enormous large-scale structure toward which the Milky Way and Virgo Cluster are both drifting (sometimes called the Great Attractor region) lies in the direction of Centaurus and Norma. While not directly visible, late April evenings are when this region transits in the south; Centaurus is well placed for southern observers.
Deep Sky Object
NGC 3242, the Ghost of Jupiter, planetary nebula in Hydra, about 1,400 light-years. NGC 3242 is a bright, compact planetary nebula with a bluish-green double shell structure, visible even in small telescopes; its blue-green color comes from ionized oxygen in the outer shell. Best from northern and southern mid-latitudes; circumpolar or low depending on latitude.
Featured Star
Tureis (ρ Pup) lies 63.5 light-years away, classified as an F6IIp, a yellow-white bright giant with a 'p' denoting peculiar properties. It is a Delta Scuti variable, pulsing in brightness every 3.4 hours as its outer layers oscillate, making it a useful reference star for the study of stellar seismology. Tureis is the brightest star in Puppis easily visible from northern mid-latitudes.
Around This Date
- April 11, 1970Apollo 13 launched from Kennedy Space Center; fifty-six hours later an oxygen tank explosion crippled the service module, forcing a dramatic emergency return using the lunar module as a lifeboat.
- April 13, 1970The oxygen tank in Apollo 13's service module exploded, transforming a planned lunar landing into a survival mission that the crew completed safely on April 17.
Tureis pulses every three hours like a slow breath, a rhythm too subtle for the naked eye but plain enough in a photometer.