Skywatch Line for Wednesday and Thursday, October 22 and 23, 2025, written by Alan French
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, October 22 and 23, 2025, written by Alan French.
The Sun rises at 7:17 A.M. on Wednesday and sets at 6:01 P.M. On Thursday it rises at 7:19 A.M. and sets at 6:02 A.M. Thursday lost just over 19 minutes 17 seconds of daylight compared to last Thursday. As we move toward the Winter Solstice on December 21, the rate we lose daylight will decrease.
The Moon was new Tuesday morning and is moving toward first quarter. On Wednesday the Moon, well south of the Sun, sets just 12 minutes after sunset and is not visible. The situation is little improved on Thursday with the Moon, five percent in sunlight, just one degree above the southwestern horizon 30 minutes after sunset, setting at 6:41. With moonset soon after sunset, these nights will continue the dark skies we enjoyed early in the week.
Saturn is 38 degrees above the southeastern sky at 9 P.M. shining at magnitude +0.8. The planet’s lovely rings are tilted less than a degree as seen from Earth. (The tilt is now -0.82 degrees, the “-“ meaning the south pole of Saturn is tilted toward us.) Saturn’s axial tilt is ~26 ¾ degrees, which is why we can sometimes have a spectacular view of Saturn’s rings through a telescope. Why do we see them almost edge on and poorly now? (For seasoned Saturn fans, it is fun to see the rings so narrow, which allows less obstructed views of the planet’s atmosphere and easier views of the fainter moons.)
As you know, our Earth is tilted about 23 ½ degrees. At the winter solstice Earth’s north pole is tilted away from the Sun and we officially start winter. The Sun is well south in our sky, takes less time to cross the sky, our days are shorter, and the weather is colder. In the Southern Hemisphere, tipped toward the Sun, it is summer.
At our summer solstice, the north pole is tilted toward the Sun, the Sun is well north in our sky, takes more time to cross our sky, the days are longer, and the weather is hotter. The Sun is low from the Southern Hemisphere, and it is winter.
Saturn also experiences seasons. As the Earth and Saturn orbit the Sun, Earth taking 365 days and change to complete one orbit and Saturn taking about 29 ½ years to complete one trip around the Sun, our view of the rings changes and, from our perspective, the tilt change. On March 23 this year, Earth passed through Saturn’s ring plane, so the rings were edge on from Earth’s perspective. Saturn, however, was only 10 ½ degrees from the Sun, too close to observe. Afterwards, Earth was moving out of the Saturn’s ring plane.
By early July the rings appeared tipped a little over 3 ½ degrees from Earth. As Earth moved farther around the Sun, with Saturn moving far more slowly, their tilt decreased or “closed.” The rings will continue to close through late November, reaching a minimum of ~0.37 degrees. Afterwards, the tilt will increase again, reaching a maximum of a little over -9 degrees in late July 26 before decreasing again. This cycle of increases and decreases will continue, with both values increasing, improving our views at maximum, until we get our best views of the rings again in 2032. The rings will be tilted more than 26 degrees as seen from Earth.
Astronomers believe that, in the early solar system, four billion years ago, Saturn was only tilted a few degrees. How did its tilt increase to provide such fine views? More about that next week.