0
$\begingroup$

Several years ago, I asked the question on here, "How do the orbits of Nu Scorpii and AR Cassiopeiae work?" At the time, these two stellar systems were the most populated (I don't know the technical term), meaning these were the only two septuple star systems known at the time, and there were no star systems containing more stars. On that question, I received a fantastic answer that perfectly described the orbits of all 7 of the stars in a way that was really easy to understand.

Then, today, I looked to see if any other multiple star systems have been found that are bigger. According to Wikipedia, there are three new star systems of note: a new septuple named V871 Centauri, an octuple named Gamma Cassiopeiae, and a nonuple named QZ Carinae. None of these seem concrete, however, and none of the sources provided explain the orbits completely.

For V0871 C., the source from wikipedia (Multiply eclipsing candidates from the TESS satellite) says "V0871 Cen is probably a septuple-star system of architecture (Aa-Ab)-B-C-D." In that paper, it describes the probable orbits thusly:

The most inner two pairs are the 2.8 and 2.09 days binaries (we name it Aa-Ab), accompanied with a more distant component B with its only poorly-constrained orbit by Zasche et al. (2009). And much more distant C and D components are probably bound (due to their similar proper motion), but only very weakly.

I take this to mean that there are two separate binary star systems in the center. The first binary pair (Aa) are orbiting each other very closely every 2.8 days, while the second binary pair (Ab) orbit each other even faster at 2.09 days. Apparently, they don't know the rate at which the two binaries orbit each other? Then, a fifth star (B) orbits these four a little further out, but its exact orbit is unknown? Finally, sixth (C) and seventh (D) stars orbit each other distantly while also orbiting Aa-Ab much more distantly, but again, how is unclear? Hopefully, someone can fill in the gaps

Then for Gamma Cassiopeiae, the source given on Wikipedia (Surveying the Bright Stars by Optical Interferometry III: A Magnitude-Limited Multiplicity Survey of Classical Be-Stars), so far as I can tell, does not give any orbital periods but does confirm that it is likely an octuple star system. On page 6 there is a graph whose last column is multiplicity, Gamma Cassiopeiae is listed 8. Further, on page 40, a description of the star system is given. It is incredibly technically dense, but so far as I can tell it is largely talking about stellar magnitudes and angular distances. Maybe the orbital periods can be determined from this information I don't know.

One note on that last source (Surveying the Bright Stars...). Gamma Cassiopeiae is referred to as "Γ Cas". In order to type the Greek letter gamma, press the alt button, and while holding that down, press and release 2, then 2, then 6, then release the alt key. The document doesn't mention it much, but this will help you skim the document for related material.

Lastly, the source given on Wikipedia for QZ Carinae (Towards a consistent model of the hot quadruple system HD 93206 = QZ Carinæ), a description of some of the 4 major, inner orbits of this system. From my understanding, there is a binary pair, Ac1 and Ac2, collectively known as Ac, that have an orbital period of 5.9987 days. Then, there is another binary, Aa1 and Aa2, collectively known as Aa, that have an orbital period of 20.734 days. Then, I believe it is saying that these two binary systems, Ac and Aa, orbit each other at approximately 14,500 days (just shy of 40 years). As for the rest of the stars in the system, it says that "all other known components [were] too faint to affect the photometric measurements, even if observed with an electronic detector with larger pixel size. The rest of this study will therefore deal with the close quadruple system only." So, no data on the orbital periods of the other 5 stars, which is especially frustrating, because what the heck is going on with Ab Ad? Wouldn't their names suggest they are involved in the orbit with Ac and Aa? Also, on their graph in that paper, on page 2, is component A a different star, or is that the combination of Aa, Ab, Ac, and Ad? Because, if it is its own star, then 8 stars are listed, but Aa and Ac are binaries, so that would make 10 stars. So, I am pretty sure that the A component is made up of the other A's.

So, the question is, how do the orbits of these systems: V0871 Centauri, Gamma Cassiopeiae, and QZ Carinae work? As an example for how to answer this question, I will again suggest this answer to how the orbits of two other septuple star systems works. If the answer is in that type of format, I will easily understand. Now, given that all of these papers were published rather recently (the oldest being 15 September 2021) and they do not seem to have these orbits fully worked out, I imagine it's just the case that humanity does not have the answers to these questions, yet. But, I am confident that we will someday. Still, I had to wait over three years for an answer to my last question, and those systems had been known for a long time, so I will be patient with this answer. Hopefully, this will be popular enough to pop back up in 2030 when we have answers to all these questions.

As always, I appreciate any help. Thanks.

$\endgroup$

0

You must log in to answer this question.