Jared May: What's Up September 24 - October 1, 2021

What’s Up This Last Week of September

Wednesday was the autumnal equinox which marks the start of fall. The season made its presence known with a dramatic shift to cooler temperatures. Sunset this week occurs just before 7:30 PM, so most faint stars and deep-sky objects are visible around 8:30 PM. The early sunsets mean you do not have to stay up super late to do some stargazing or to break out your telescope for the night. The fall season is also a great time to catch the last of the summer constellations and deep-sky objects and the rising winter constellations and objects. This week may actually give multiple clear nights but with nighttime temperatures dropping into the low 50s. During the clear nights this week, be on the lookout for the bright moon creeping in from the East, rising Pleiades, Uranus, Cygnus the Swan at the zenith, and the faint Little Dipper.

If you find yourself up late in the evening or early in the morning, odds are you have seen the waning gibbous moon. Since the moon is in its waning phase, it will rise later and later every night after the sun has set. It is best to get an early start with stargazing because just a few hours after sunset the sky will slowly brighten as the moon’s glow fills the night sky. Tuesday, September 28, will mark the moon’s official Third Quarter phase.

The waning gibbous moon rises on Friday evening near midnight.

If you are still outside at 10:30 PM anytime this week, look low on the east/northeast horizon to spot the faint and twinkling Pleiades. The reason this brilliant open cluster will appear so faint and will be twinkling so much is caused by the atmosphere. When something is close to the horizon, its light must pass through a lot more of the Earth’s atmosphere than when the object is directly overhead. Light passing through the air will be scattered, reddened, and will pass through more turbulence (hence more twinkling).

Look northeast before midnight to see the distinct star cluster in the sky, the Pleiades, rising.

For the next few days, the moon will be hanging close to one of the outer planets, Uranus. If you want to see this gas giant, use a telescope or a pair of binoculars and wait a few days until the moon has passed. Despite being a gas giant and 63x the volume of the Earth, Uranus only shines at magnitude 5.7 which is nearing the limit to what the naked eye can see under ideal skies.

Uranus is very faint, but can be made out with the naked eye under ideal conditions. Mere mortals can easily spot it in binoculars.

One of the more popular summer constellations and one I tend to mention from time to time is Cygnus the Swan. This constellation is home to a busy part of the sky, and it includes Deneb, the North America Nebula, the Pelican Nebula, the Veil Nebulae, the Crescent Nebula, and more. This region of the sky also contains a section of one of the arms of the Milky Way. If you spot the core of the Milky Way low in the southwest just after sunset, you can follow this trail of dense stars through Cygnus. This time of year, the Swan is near the zenith, or the most overhead point in the sky.

Everybody knows the Big Dipper by name and could probably recognize it if they saw a picture of the constellation. And many people also know about its little brother, the Little Dipper (a.k.a Ursa Minor). But have you actually ever found this famous constellation? Well, the Big Dipper points right to it. If you follow the two stars at the “front” of the cup of the Big Dipper it will lead you to Polaris, the North Star, which is the last star in the handle of the Little Dipper. That’s right, the Little Dipper is hanging out at the North Star. The caveat is that the Little Dipper is composed of fainter stars, so it is tricky to spot under light-polluted skies. This time of year, this constellation hangs upside down, almost like it is pouring something into the Big Dipper!

Get outside to stargaze under the night sky as it transitions from summer to fall. These may be the last few weeks of “comfortable” temperatures for nighttime stargazing and astrophotography. Despite the pesky bright moon rising just a few hours after sunset, there are still plenty of bright and interesting objects to observe. Be on the lookout this week for the third quarter moon, the twinkling Pleiades, Uranus, a swan in the sky, and the Big Dipper’s little brother.

Clear Skies!