From the Director




by Rex Parker, Phd

November 13 Meeting – “glass universe meets high tech”. Hope to see you at Peyton Hall auditorium on the Princeton Campus on Tues, Nov 13 at 7:30pm. We’ll pick up where Dava Sobel left off in her amazing talk on the Glass Universe (her book title) back in April 2017. Please see Ira’s article in this edition for information about the guest speaker and topic.

November 17 – Home Observatory Tour. Some members have expressed a curiosity about astrophotography, how it is done, and how the hardware is set up. In addition to using the club’s facility at Washington Crossing, building a home astronomical observatory is an option. 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. Interested members are invited to visit and see firsthand some of the approaches to the issues of telescope, mount, and camera hardware, software and observatory design. On Saturday morning, November 17, we are offering a two-site tour of home observatories – at my house in Titusville and member Bill Murray’s house in Bordentown. This will give interested members the chance to see two main designs, a roll-off roof type and a dome. If you are interested but have not yet replied, please send an e-mail to to join the small group tour. Further details will be sent by e-mail reply.

The Irony of Iron. Halloween mythology has it that a bullet made of argentium (silver, Ag) can kill a werewolf. And it’s sometimes said that iron (Fe) can kill a star, at least in a colloquial sense of astrophysics. Is this mythical or true? Iron is essential to the evolution of biological life and to human civilization as much or more than any material on our planet. Can it actually be like a silver bullet to a star? As we learned from Dr. Jack Hughes last month, fusion of elements lighter than iron releases energy, and fission of elements heavier than iron also releases energy. Among all the elements, iron Fe (atomic number 26, atomic weight 56) has the highest binding energy or in other words the most stable nucleus (nickel is slightly more stable but its major isotope quickly decays to iron in stars). This means that iron ironically has the lowest mass per nuclear particle (nucleon), even though we think of iron as a very heavy element (density ~8 times water). Iron is at the end of the road for the standard atomic fusion process in stars of high mass, and when Fe accumulates fusion declines and the core temperature drops, setting the stage for a supernova explosion – the death of the star. Not so much a silver bullet as an iron curtain falling on the previous acts!

Thank you, Observatory Keyholders. Another season of public outreach has concluded at the Washington Crossing Observatory. Once again we have educated, entertained, and provided fascinating views and images of the celestial sphere to many hundreds of people. On behalf of AAAP I would like to thank all 35 of our Keyholders who have run the show and generously gave their time and expertise upon many nights under the stars.


AAAP Annual Membership Renewal. Our fiscal year runs Oct-Sept, so it’s time to renew now if you have not already done so. Members are urged to renew on-line rather than by mail or at meetings – it’s better for our record keeping. The fee is $40/year. Renewal on the website:

This entry was posted in November 2018, Sidereal Times and tagged , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s