April 28

April 28

Pulcherrima

Sun Position

The Sun is in Taurus near +23° declination. Northern hemisphere days are near their longest; southern hemisphere observers have entered the best dark-sky season of the year.

Sky Highlight

The eta Aquariids continue building. Pre-dawn observers in the southern hemisphere may already be seeing 10 or more per hour, the radiant in Aquarius rises higher before dawn from the southern hemisphere than from northern latitudes, giving southern observers a substantially better view of this shower than their northern counterparts.

Deep Sky Object

M3 (NGC 5272), globular cluster in Canes Venatici, about 34,000 light-years. On a transparent April night, M3 is bright enough to see in binoculars as a fuzzy star; a 4-inch telescope at moderate power will begin to resolve its outer stars. It contains an unusual number of blue straggler stars, which appear younger than the cluster's 11-billion-year age and are thought to result from stellar mergers. Visible from both hemispheres.

Featured Star

Izar (ε Boo) returns: 203 light-years, a K0II orange giant and A2V white companion orbiting each other at a separation that requires modest telescope aperture to split. William Herschel's 'Pulcherrima' designation reflects the striking visual contrast between warm and cool: the orange primary glows at K = 2,700 K above the white secondary's 8,500 K, separated by a color gap of nearly 6,000 degrees.

Around This Date

  • April 28, 2001Dennis Tito launched to the International Space Station aboard Soyuz TM-32, becoming the first self-funded private space traveler, after NASA initially opposed his flight on safety grounds.
  • April 28, 1900Jan Oort was born in Franeker, Netherlands; he would go on to establish that the Milky Way rotates differentially, determine our galaxy's center lies in Sagittarius, and propose the existence of the distant comet reservoir now bearing his name.

Izar's color contrast has been noticed since William Herschel named it 'the most beautiful', a judgment that holds up when you actually put it in a telescope.