April 26
The Lion's Rib
Sun Position
The Sun is in Taurus near +22° declination. Northern mid-latitudes now have more than 14 hours of daylight; southern hemisphere is past the equinox, settling into proper autumn nights.
Sky Highlight
Leo is prominent in the south from northern mid-latitudes on April evenings, reaching its highest point after dark in the early hours of the night. The Leo Triplet (M65, M66, NGC 3628) is well placed for evening observation this week, fitting within the same low-power telescope field and offering all three members of the interacting group simultaneously.
Deep Sky Object
M65 (NGC 3623), spiral galaxy in Leo, Leo Triplet, about 35 million light-years. M65 is the most symmetric of the Leo Triplet, with tightly wound arms and a bright, well-defined nucleus; it shows the least distortion of the three, consistent with its somewhat greater separation from its neighbors. Best from northern and southern mid-latitudes.
Featured Star
Chertan (θ Leo) lies 165 light-years away, a white A2V main-sequence star in Leo's hindquarters. Its Arabic name, from a phrase meaning 'two small ribs,' was originally applied to a pair of stars now separated by naming conventions, the other star once sharing the name being Zosma. Chertan is a fast rotator, spinning at about 180 km/s at its equator.
Around This Date
- April 26, 1920The Great Debate between Harlow Shapley and Heber Curtis was held at the Smithsonian in Washington, in which they argued respectively that the Milky Way encompassed all observed nebulae, or that the spiral nebulae were external galaxies comparable in size to our own.
- April 28, 2001Denis Tito became the first paying passenger to reach the International Space Station, traveling aboard a Soyuz rocket after NASA initially opposed his flight.
The Great Debate of 1920 had no clear winner that night; five years later Hubble's Cepheid measurements settled it, and the universe turned out to be larger than either debater had argued.