Tuesday, July 16, 2024

Double Stars in Lyra's Parallelogram (all night)

Each corner of Lyra's parallelogram is marked by a double star. Zeta Lyrae,
the corner closest to bright Vega, can be split with binoculars. Both components are white - one star slightly brighter than the other. Each of
these stars also has a partner that is too close together to split visually. Moving clockwise, the southwest corner star is Sheliak, the brightest of a tight little grouping of stars visible in a telescope. Sheliak itself has a close-in, dim companion in an eclipsing binary system with a 13-day period.
The hot, blue giant star Sulafat sits at the farthest corner from Vega. 620 light-years-distant Sulafat is much larger than Vega - an old star on its way to becoming an orange giant many years from now. Add the slightly dimmer stars Lambda Lyrae and HD 176051 to its south and west, respectively to form a naked-eye triple. Delta Lyrae marks the northeast corner of the parallelogram. Sharp eyes and binoculars will easily split the double into one blue and one red star. The blue star is one hundred light-years farther away than the red one; they just happen to appear close together along the same line of sight.


Shadows and the GRS on Jupiter

From time to time, observers with good quality telescopes can watch the small, round, black shadows of the Galilean moons traverse Jupiter's disk. On Wednesday morning, July 17, sky-watchers located in eastern Europe, the Middle East, and eastern Africa can watch two shadows crossing the southern
hemisphere of Jupiter at the same time for about 22 minutes. At 4:08 a.m. Eastern European Summer Time (or 01:08 UT), the shadow of Io and the Great Red Spot will join the shadow of Europa, which began its own crossing of the
planet two hours earlier. Europa's shadow will move clear of Jupiter at 4:31 a.m. EEST (or 01:31 UT), leaving Io's shadow and the spot to continue on alone until 6:15 a.m. EEST (or 03:15 UT). By then the sky will be brightening.

(Data courtesy of Starry Night)
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