by Rex Parker, PhD director@princetonastronomers.org

Denizens of Planet Earth Declare a New Year!
There are good reasons to have a little more hope this new year than the last few. The best development for AAAP in 2022 came late in the year as we returned to in-person meetings at our long-time base, the auditorium in Princeton’s Peyton Hall — home of the Astrophysical Sciences Dept.  In 2023 we will conduct monthly “hybrid” in-person live plus remote Zooming meetings to give members and public the choice of how to attend.   Of course, we want you to come in person when you can.  However, note that the January 10 meeting will be remote by Zoom only.  This is actually good news, as Peyton auditorium will be closed for the month for significant audiovisual hardware upgrade work by the university.  This should make the technical part even better for our return on February 14 (monthly meetings are always the 2^nd Tuesday at 7:30pm).  

With the new year comes opportunity to improve. Though the club made progress last year in running virtual meetings and increasing membership, there are two areas that could be improved upon to enhance member experience and our effectiveness as a science-outreach organization.

• Increase participation and contribution by members in regular monthly club meetings
• Provide opportunities for learning and doing astro-photography in its many forms

One way to approach these goals is to take part in AAAP’s observing activities, for example the “AstroVideo Live!” sessions being held again this winter as they were on several occasions last year.  You can participate even if you don’t have your own equipment, indeed the point is to show and demonstrate how it’s being done with the technology and equipment within reach of amateurs today.  Announcements for these members-only sessions (plus family and friends) are sent by e-mail to the full membership.  We look forward to seeing you in person either on campus or on Zoom over the next several months.

The “Un-journal Club” Wants You
AAAP’s monthly meetings feature a guest speaker, usually a professional, followed by highlights of club activities and member conversations.  We’re developing a tradition called the Un-journal Club, brief informal presentations given in the second half of the meeting by members.  “Un-journal” means this is not grad school, and these short episodes don’t need scholarly journal-like topics, they only seek to engage members with what you care about in astronomy.  You can use PowerPoint slides, JPEG’s, astro-images, travel pictures, book reviews, whatever you want (if desired, bring a USB memory stick or your own laptop).  To get on the schedule for an upcoming meeting, please contact me or program chair Victor Davis.

“Robin’s Egg” Planetary Nebula NGC 1360 in the southern constellation Fornax.  The distinct blue colors (image below) indicate high levels of ionized oxygen illuminated by the central white dwarf star, now known to be a binary star.  The reddish arc indicates a jet of matter ejected from the suspected binary star during nebula formation.  Distance ~1800 light years, angular size ~11×7.5 arc-min.  Did this nebula come from a binary star system as discussed in the section below?  Astro-photo by Rex Parker taken with the 16” Planewave PROMPT-2 telescope at Cerro Tololo in the Chile Andes.

Will Our Sun Become a Planetary Nebula?
Among the most beautiful celestial objects we can see and image in our telescopes are the colorful planetary nebulae, for example the Robin’s Egg Nebula above.  These are not planets of course, the name is a hold-over from the hazier views of astronomers centuries ago.  The prevailing theory for their formation is that stars of a certain size range will eventually become planetary nebulae as their nuclear fusion fuel runs low.  It has been thought that in the fullness of time our sun, sol – a G-type main sequence star – is destined to become a red giant engulfing the inner planets including earth. The subsequent physics are pretty well understood.  As nuclear energy release diminishes, the core of the red giant collapses into a super-dense white dwarf, followed by expulsion of the outer layers of gases away from the surface, ergo a planetary nebula forms. 

Writing these lines led me to do a little review, and I was startled to read that the thinking is changing.  This may not be our future glorious doom after all.  Sol is now being reclassified as a yellow dwarf star (G-type stars with mass range 80-100% of sol), which may be too small to drive the physics needed to enter the red giant/nebula sequence. At least our sun is big within its peer group, though I prefer to associate “dwarf’ with JRR Tolkien rather than our sun.  The thinking now, though still debated of course, is that G-type stars need to be at least one-fifth heavier than our sun in order to drive the planetary nebula process.  The proposal is that most planetary nebula we see in our galaxy actually formed from binary star systems.  Think about this next time you observe a planetary nebula in your telescope.  Oh well… where would humanity be without classifying and theorizing?  Ask Linnaeus, the 18^th century scientist who developed the classification mania whose influence still grips the way natural sciences operate.