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Wednesday, November 25, 2015

Earthsky Tonight – February 20, 2010: Orion shows you the ecliptic and summer solstice point

Courtesy of EarthSky

A Clear Voice for Science

Diana asks, “Why is the waxing moon always so high in the evening sky in late winter and early spring?” In a nutshell, Diana, it is because the ecliptic arcs high across the evening sky right now. The ecliptic is the Earth’s orbital plane projected onto stellar sphere, or the dome of sky. The ecliptic is often shown on sky charts because the moon and planets are found on or near the ecliptic.

If you are familiar with the constellation Orion, you will always know when the ecliptic soars highest in the northern hemisphere sky. The ecliptic arcs from east to west, and swings way over Orion. Whenever Orion appears in the southern sky, the ecliptic stands highest in the sky.

More specifically, the ecliptic is most inclined to the horizon when the summer solstice point resides on the meridian (or due south). Orion’s brilliant ruddy star Betelgeuse and the summer solstice point cross the meridian at nearly the same time this evening, at about 8 p.m. local time. Betelgeuse (and the summer solstice point) return to the meridian about 4 minutes earlier daily, or 2 hours earlier with every passing month.

Watch the waxing moon at early evening for the next week or so, and note that the moon sweeps close to the summer solstice point on February 23.

Ecliptic highest in sky:

Sunset on the spring equinox

Noon on the summer solstice

Sunrise on the autumn equinox

Midnight on the winter solstice,


Transit (meridian crossing) time for Betelgeuse in your sky

Written by Bruce McClure

Other Links:

Sky and Telescope

National Geographic

Space Com

Amazing Space

The York County Astronomical Society

Scope City

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