by Rex Parker, Phd director@princetonastronomy.org

October 9 Meeting – “It’s Elemental, My Dear Watson”! Hope to see you at Peyton Hall auditorium on the Princeton Campus for our next meeting (Tuesday, Oct 9 at 7:30pm). Please see Ira’s article in this edition for information about the guest speaker, Dr Jack Hughes, Rutgers Dept of Physics and Astronomy. Over the years I’ve always been fascinated by a Big Question: How did the elements form? How did we go from just Hydrogen and Helium from the Big Bang to the 92 natural elements – those we all learned in the periodic table, those that form the basis for all of planetary geology and the origins of life? How does stellar nucleosynthesis work? The answers to these may not come easy, but astrophysics does have answers. On Tuesday night, thanks to Dr Hughes, for the first time in AAAP we’ll take a deep dive into nucleosynthesis; no exam afterwards :> .

Astronomy, Tides, and Hurricanes. Earth is a blue marble rolling through the heavens, shaped by astronomical forces that profoundly affect the course of human life. When hurricane Florence struck North Carolina last month, the flooding and damage along the coast was astronomical in multiple meanings of the term. NOAA defines storm tide as the coastal water level rise during a storm due to the combination of storm surge and astronomical tide. The surge is highest where the strongest winds of a hurricane occur, in this case the northeast quadrant as the eye made landfall. But the magnitude of the inland surge also depends on the astronomical tide.

Tides result from the combined gravitational force of the moon and the sun on the fluid outer layer of the blue marble. Lunar gravity pulls the oceans about twice as strongly as the sun – the sun’s gravity is moderated by distance. If earth had no large continents then all areas would see two high and two low tides every lunar day (approx. 24 hr, 50 min). But as the earth rotates the westerly passage of the bulge of seawater is blocked by the continents, making the pattern of tides complex within each ocean basin. Diurnal tide cycles exhibit one high and one low tide every lunar day, e.g., in the Gulf of Mexico. Most of the U.S. east coast has a semidiurnal tide cycle with two high and two low tides of similar size every lunar day (Figure below; also see https://oceanservice.noaa.gov/education/tutorial_tides/tides07_cycles.html). The U.S. west coast has a mixed semidiurnal cycle with two high and two low tides of different size every lunar day.

Since hurricane Florence was so slow-moving as it made landfall in North Carolina, the storm surge was integrated across multiple tide cycles over more than a day. The multiple astronomical high tides during that period added several feet of depth to the surging seawater and contributed to the flood scenario as the storm surge approached 10 ft and higher along the Carolina coast.

Opportunity for Members to Visit Home Observatories. Some members have expressed a curiosity about astrophotography, how it is done, and especially how the hardware is set up. In addition to using the club’s facility at Washington Crossing, many of us have thought about building a home astronomical observatory. There are many potential designs ranging from basic pedestal/mount installations with weather covers, to aluminum or fiberglass/plastic domes, to roll-off roof designs. I’ve been fortunate to have the opportunity to create a home observatory in my back yard, which is now operating hands-on and can be run remotely through automation software. I would like to invite interested members to visit and see firsthand one approach to the issues of telescope, mount, and camera hardware, software and observatory design. Please send me a note (send e-mail to ) if you would like to join a small group tour of this observatory in the near future. Once I hear from you, we can arrange a date(s).