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Summer’s Waning Lights

Less daytime and a waning moon leave plenty to see

With summer on the wane, the sun sets around 7:30 at week’s end, shedding more than a minute of evening sunlight each night. In the morning it’s more of the same, as the sun rises at 6:37 Saturday and almost a minute later each morning.

The setting sun reveals three bright objects in its wake: Venus and Mars, and the first-magnitude star Spica, all within five degrees of one another, the field of view of most binoculars. Look to the west immediately after sunset. While closest to the horizon, Venus is by far the brightest and the first to appear through the haze of twilight. Even without its telltale twinkle, Spica stands out compared to Mars’ dull, ruddy glow. Through the week, Venus and Mars pivot around Sipca, but don’t dally — all three set before 9pm.

As Venus sets in the west, the next-brightest planet rises in the east. There should be no mistaking Jupiter between the dim water constellations Pisces and Aquarius. Watch as Jupiter grows leading up to its opposition later this month. Just as the moon appears full when at its own opposition, Jupiter’s entire disc will be illuminated, coinciding with an unusually close approach to Earth.

While hurricane Earl may cloud our skies, the waning moon, which reaches new phase Wednesday, doesn’t rise until the wee hours before dawn. If the weather breaks and you have a dark spot, look for our home galaxy, the Milky Way. Our solar system sits toward the end of one of its spiral arms, and the entire galaxy stretches across more than 100,000 light years of space. When we look toward its center, we see what appears as a milky haze, but what is actually the diffused light of hundreds of billions of stars. From the constellations Auriga and Cassiopeia in the northeast, it flows southwest to teapot-shaped Sagittarius and the tail of Scorpius.