If your household is like most American families, then on Thursday (Nov. 23) you likely will be sitting down with family and friends for a traditional Thanksgiving turkey dinner during the mid-to-late afternoon hours.
Then, as darkness falls, some of you will probably migrate into the living room to catch some football or other holiday fare on television. But if you have a large gathering of family and friends at your home — and if your skies are mainly clear — why not invite everyone outside to gaze at the evening sky?
If you have binoculars, or better yet, a telescope, you just might end up turning this into a memorable family tradition of its own.
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This year, on Thanksgiving evening, about 90 minutes after sundown, the moon will be at a waxing gibbous phase, four days before reaching full phase, 85% illuminated and shining brightly well up in the southeast sky.
You might assume that the best time to look at the moon through a telescope is when it’s at full phase, but that’s probably the worst time to look at it. When the moon is full, it tends to be dazzlingly bright, as well as flat and one-dimensional in appearance.
In contrast, a gibbous moon is when we get a better view of the lunar landscape right along the sunrise-sunset line, or terminator.
The terminator is that variable line between the illuminated portion and the part of the moon in shadow. Along with the fact that a gibbous moon offers more viewing comfort to the eye than a full moon does, using a telescope with just small optical power (magnifications of 20x to 40x), or even good binoculars, we can see a wealth of detail on its surface. Around those times when the moon is half-lit or in its gibbous phase, those features lying close to the terminator stand out in sharp, clear relief.
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And two bright planets
Along with the moon, we also have two prominent planets in the Thanksgiving night sky.
Due south, we can see Saturn, shining with a sedate, yellow-white glow about one-third up in the south-southwest sky. With a telescope magnifying 30x, the famous rings begin to come into view. If you have a 4-inch (10 centimeters) telescope, a 100x eyepiece will readily bring Saturn’s most famous appendage into view.
Meanwhile, far brighter and standing about one-third up in the eastern sky will be Jupiter, appearing like a dazzling, silvery-white, non-twinkling star. You’ll see it glowing 20 degrees to the lower left of the moon. Since your clenched fist held at arm’s length measures roughly 10 degrees, Jupiter on this night will be about “two fists” to the moon’s left.
Steadily held binoculars will provide a glimpse of the four big Galilean satellites, first glimpsed by Galileo Galilei in 1610. A telescope will easily show the disk of the biggest planet in our solar system — 11 times wider than our Earth — with all four moons in view on one side of the big planet on this holiday night.
Going outbound from Jupiter, we can see Io, Europa, Callisto and Ganymede.
Stars of late autumn
If we concentrate on the stars and constellations, it’s interesting to note that many of the star groups and rich Milky Way fields of summer evenings are still very much evident in the western part of the sky, while the brilliant yellow star Capella ascending in the northeast is a promise of even more dazzling luminaries to come. For, in just another few weeks, Orion and his retinue will be dominating our winter skies.
Still very well placed high in the west is the Summer Triangle, a roughly isosceles figure composed of the stars Vega, Altair and Deneb. As we move deeper into the autumn season and the evenings grow chillier, this configuration sinks lower and lower in the west. If you have binoculars, invite family and friends to use them to sweep among the splendid star fields of the Summer Triangle. They may very well share Galileo’s awe of more than four centuries ago, when he first turned his telescope on the myriad faint stars that compose our Milky Way.
Looking high in the south-southeast — almost overhead — are the four bright stars that compose the Great Square of Pegasus, a landmark of the autumn sky. And if you have a clear view of the northern horizon, it is there you will find the familiar Big Dipper, looking abnormally large due to the “moon illusion,” which makes, the sun, the moon and even star patterns like the Dipper appear larger than normal when they are situated near the horizon.
Meanwhile, the striking zig-zag row of five bright stars forming the “M” of Cassiopeia, the Queen, soars high above the Dipper in the north.
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Looking back in time
The very first Thanksgiving is said to have taken place in the year 1621. We see many stars whose light started its immense journey before our country was born. Are there any stars that are around 400 light-years away?
Because of the difficulty in measuring parallaxes (distant objects’ changing positions when viewed from Earth), astronomers cannot determine such distances with an accuracy of one light-year. However, in its table of the 288 brightest stars, the 2023 “Observer’s Handbook” of the Royal Astronomical Society of Canada lists two that are about 400 light-years away and are above the horizon on November evenings: third-magnitude Algenib, the star in the lower left corner of the Great Square of Pegasus, and second-magnitude Almach, at the end of the chain of stars marking the constellation of Andromeda, the princess.
If you see either of these stars on your next clear night, keep in mind that you are looking at light that started on its journey to Earth at about the same time that the first pilgrims were arriving in what we now call the state of Massachusetts.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers’ Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook.