April 30
Month's End in Virgo
Sun Position
The Sun is in Taurus near +23° declination, the last day of April with daylight at its northern maximum approaching. Northern skies do not fully darken until late; southern hemisphere observers have excellent long nights and Virgo is well placed.
Sky Highlight
April closes with the eta Aquariids still building and the Virgo Cluster at nearly optimal elevation from both hemispheres. The month has been defined by spring galaxy season in the north and autumn's long dark skies in the south; both converge tonight for a final look at the great congregation of galaxies 55 million light-years away.
Deep Sky Object
M87 (NGC 4486), giant elliptical galaxy, Virgo Cluster, about 53 million light-years. A fitting close to April's galaxy season: M87 is visible in any telescope and holds the record for the first photographed black hole shadow. Its relativistic jet, powered by the 6.5-billion-solar-mass central black hole, extends several thousand light-years and is detectable in large amateur instruments under excellent conditions.
Featured Star
Heze (ζ Vir) closes the month: 74.1 light-years, an A3V main-sequence star in the body of Virgo. Quiet, stable, slightly hotter and more luminous than the Sun, unremarkable in nearly every catalog entry. Its name is genuinely lost (no confident etymology has survived) which makes it an honest representative of the many named stars whose names have outlasted their meanings.
Around This Date
- April 30, 1897Joseph Larmor published results connecting the precession of electron orbits to magnetic fields, work that later contributed to the theoretical understanding of spectral line splitting in stellar magnetic environments (the Zeeman effect in stellar physics).
- April 30, 1777Carl Friedrich Gauss was born in Brunswick; his method of orbit determination, developed in 1801 to recover the asteroid Ceres after it was lost, established the mathematical toolkit that astronomers still use to compute orbits from sparse observations.
April hands the sky to May with the galaxy season still open and the eta Aquariids still falling, the calendar changes but the stream does not.