Astro Bob: What's up in September? Check out these highlights
A look at the best and brightest night-sky sights as we transition from summer to fall.
It’s hard to believe summer is slipping by. We see it in earlier sunsets and seasonal changes in the weather and woods. The sky is no different. Warm-weather constellations like Sagittarius and Aquila still hold sway during the early evening hours, but the fall groups are itching to take over. By 10 p.m. local time, the eastern half of the sky is fully decked out in autumnal garb, with the likes of Cassiopeia, Pegasus, Andromeda and Aquarius.
Even the Big Dipper, the most recognizable part of Ursa Major the Great Bear, is skedaddling, sinking toward the northwestern horizon. From the southern U.S. the bear will soon “hibernate” out of view at the bottom of the northern sky. For those living in the northern part of the country, the bruin never sets. After a light nap under the Pole Star, he climbs back into view standing on his tail.
The Great Square of Pegasus is a great place to begin learning the early fall constellations. Face east around 9 p.m. and look for four equally bright stars enclosing a big, empty space about two fists directly above the brilliant planet Jupiter. Although the stars outline a square, Pegasus is tipped on its end early in the evening and looks more like a diamond.
Jupiter is by far the most captivating planet this month, dominating the eastern sky after 9:30 p.m. You can hardly take your eye off the brilliant gas giant. Saturn remains low in the southeastern sky, but it's the brightest "star" in that direction and well placed for viewing by 9 p.m.
If you're up late, the red eye of Mars makes its first appearance low in the northeastern sky around 11:30 p.m. Venus is still visible very low in the east at dawn early in the month but will disappear in the solar glare around the first day of fall. This year that falls (pardon the pun) on Thursday, September 22.
*Note: When “a.m.” follows the date, it refers to an event visible in the morning sky after midnight. All times are Central Daylight Time (CDT) unless otherwise noted.
Sept. 3 — First quarter moon.
Sept. 7 — Waxing gibbous moon shines to the right and below Saturn.
Sept. 9 and 10 — Full Harvest Moon. For several nights in a row, the delay between successive moonrises will be just 20 minutes.
Sept. 10-11 — Full moon will shine near Jupiter on both nights.
Sept. 16 a.m. — Waning moon will beam just to the left (east) of bright Mars.
Sept. 17 — Last quarter moon.
Sept. 20 a.m. — Thin crescent moon lines up directly below Gemini’s two brightest stars, Pollux and Castor.
Sept. 22 — Fall begins at 8:03 p.m. when the sun crosses the celestial equator moving south. Day and night are both 12 hours long no matter where you are on the planet.
Sept. 23 to Oct. 6 — Look for the zodiacal light towering in the eastern sky starting about an hour before dawn for the next two weeks. Only visible from dark skies, it looks like a big, cone-shaped glow tapering upward from the horizon. You’re seeing comet dust — and possibly also dust from Martian dust storms — back-lit by the sun.
Sept. 24 a.m. — Very thin lunar crescent stands about 9° above Venus this morning a half-hour before sunrise.
Sept. 25 — New Moon.
Sept. 26 — Jupiter will be at opposition, when it’s brightest and closest to the Earth for the year. Although oppositions occur each year, some are closer than others. This one is exceptional — the two planets won’t get closer until Oct. 21-29. Face east around 8:30-9 p.m. You can't miss Jupiter!
Sept. 30 — Thin crescent moon passes 1.6° above red Antares, the brightest star in Scorpius, low in the southwestern sky at dusk.