THE SOUTHWORTH PLANETARIUM 70 Falmouth Street Portland, Maine 04103 (207) 780-4249 usm.maine.edu/planet 43.6667° N 70.2667° W Founded January 1970 2022-2023: LXXVI Sunrise: 6:32 a.m. Sunset: 7:02 p.m. Civil twilight begins: 6:03 a.m. Civil twilight ends: 7:30 p.m. Sun's host constellation: Pisces Moon phase: Waxing crescent (36% illuminated) Moonrise: 9:40 a.m. Moonset: 2:09 a.m. (3/28/2023) Julian date: 2460031.29 "People usually consider walking on water or thin air a miracle. But I think the real miracle is not to walk either on water or thin air, but to walk on Earth. Every day we are engaged in a miracle which we don't even recognize: a blue sky, white clouds, green leaves, the black, curious eyes of a child - our own two eyes. All is a miracle." -Thich Nhat Hahn THE DAILY ASTRONOMER Monday, March 27, 2023 Perigee, Apogee and Lunar Phases *If the moon accelerates and slows down at its apogee and perigee phases, does this affect the durations of the moon phases? -S.L* Yes, it certainly does. When the moon is at apogee, its point of greatest distance from Earth, it is moving more slowly than at any other position along its orbit. Conversely, when at perigee, its closest point to Earth, it is moving more quickly than at any other position along its orbit.* Let’s examine the moon orbit graphic below: [Image credit: MoonConnection.com] In order for the moon to move from, let’s say, the full phase (opposition) to third quarter (quadrature), it must travel along the arc separating the two phase positions. When the moon is at apogee, the duration of this transition will be greater than it will be when the moon is at perigee.* As an example, let’s regard the ‘micromoon’ that occurred on February 5, 2023 and the supermoon that will occur on August 1, 2023. [Image credit: timeanddate.com] A micromoon refers to a full moon that occurs at or around apogee. A supermoon refers to a full moon that occurs at or around perigee. The moon was at apogee on 4 February and was full on 5 February. This micromoon occurred precisely at 5 February at 1:28 p.m. The moon reached the third quarter phase at 11:00 a.m. on 13 February. The time span separating these two phases, known as the waning gibbous moon period, was 7 days, 21 hours and 32 minutes. The first full moon in August will occur at 2:31 p.m. 1 August. As the moon will reach perigee on the following day, this full moon will be a supermoon. The moon will reach the third quarter phase on 8 August at 6:28 a.m. The waning gibbous phase during this lunar cycle will be 6 days, 15 hours and 57 minutes. A difference of 1 day, 5 hours and 35 minutes. If the moon traveled along a perfectly circular orbit, the time period separating successive phases would remain constant. We can clearly see that it does not. I hope this answer proves helpful. *Kepler’s second law of planetary motion states that an orbiting body’s speed around its parent body will be greatest when the object is closest to the parent and slowest when the planet is at its greatest distance. To subscribe or unsubscribe from the "Daily Astronomer" http://lists.maine.edu/cgi/wa?A0=DAILY-ASTRONOMER