by Theodore R. Frimet
Are Mizar and Alcor sexting?
Mizar was presented to us as an optical double star, by NJ State Planetarium staffer and professional astronomer Bill Murray, at our Bright Spring Deep Sky Objects (DSO) presentation at the planetarium, on a rainy Saturday morning of May 13th.
As Mizar is the first double star on the list (part of the Big Dipper), I made this my priority to learn as much as this amateur could muster. The stellar light, I learned, that appears to broadcast to us from Mizar, is also imparted by its double dater, Alcor.
Mizar and Alcor, after the passing of 120 years of astronomical observation, and research, were revealed to be more than an optical binary. Below, I offer you, below, a revealing look at what is now known to be a our sextuplet!
Zeta Ursae Majoris (aka Mizar A & B), is my newest best friend and first on the bright star DSO list for AAAP Public Nights. Mizar is truly a quadruple system. Alcor, is a binary, and the pair, which I’ll dub, “AlcorUm” is therefore a sextuple (six part) system, about 83 light-years away from Sol..
Referencing author Dava Sobel’s “The Glass Universe”, pages 34-35, we give credit to Edward Pickering who noticed the “unprecedented doubling of the spectrum’s K line” on a Draper Memorial image taken March 29, 1887. Unfortunately, as soon as it was found, it was lost. Later, due to the diligence of Vassar College graduate, Miss Antonia Maury, (with honors in physics, astronomy and philosophy), saw it once again on January 7, 1889.
Sobel writes that Pickerings note read that sometimes it appears as a single, and at other times, a double! His theory eventually was proved that the small k-line separation effect is due to the two stars rotation about each other and that it completes “an orbital period every six months” (Wikipedia – Mizar and Alcor – May 13th 2017 19:42)
To be rock solid truthful, however, although the Draper Memorial group were the first to spectroscopically observe this double dating duo, credit is also due to Riccioli in 1650, G. Kirch and spouse in 1700, and “measured repeatedly since the time of Bradley in 1755”, as read from Robert Burnham’s Celestial Handbook, Volume 3, pages 1953-1954.
From Burnham we find that our optical double star has an observed separation of 8 degrees within the span of 200 years, then the period of our visually observed binary is many thousands of years. A quoted reference from Miss Agnes Clerke in 1905 speaks of a “possible accomplishment of a circuit in 10,000 years…”. Full rotation however, is reported occurring every 20.5386 days. I conclude that Miss Clerke was referring to the separation of the optical binaries, as they fall towards each other gravitationally, and push apart with their remaining momentum. As an aside, if we were able to live a few “circuits”, due diligence would divulge chaos directing the non-ordinary push and shove of such a system. This theory of mine is the result of my most current fling with author, James Gleick’s “Chaos, Making a New Science”.
Ms. Clerke made her observations two years after her honorary election into the Royal Astronomical Society, along with Lady Huggins, in 1903. She was the third woman to have held this rank. Ms. Clerke is referenced in the Sobel bibliography. I must admit to being a slow savory reader, and not having finished The Glass Universe, I cannot vouch for this lady of the Royal Astronomical Society being a Harvard Computer per se. However, at the speed of wiki, we find that overseas she was known for her collating, interpretation and summarization of astronomical research. (Wikipedia – Agnes Mary Clerke – May 14th 2017, 17:36 ).
In summary, so far…“Mizar A was the first spectroscopic binary to be discovered, by Pickering in 1889. Some spectroscopic binaries cannot be visually resolved and are discovered by studying the spectral lines of the suspect system over a long period of time. The two components of Mizar A are both about 35 times as bright as the Sun, and revolve around each other in about 20 days 12 hours and 55 minutes. Mizar B was later found to be a spectroscopic binary as well, its components completing an orbital period every six months.” (ibid)
Mizar’s fainter component, however, has different observed velocity shifts, and periods. Additional measurements showed us a third star within its grasp. Our wiki reference, and subsequent Google search leads us to an article at Sky and Telescope ( http://www.skyandtelescope.com/observing/mizar-a-fresh-look-at-an-old-friend03252015/ ) where further spectroscopy reinforces the observation that Mizar B to be a close orbiting pair of stars.
According to author and amateur astronomer Bob King, in his March 25, 2015 web article cited above, our optical binary double daters have not been found to be outside the family of our sextuplets, since 2009. It was at that time that space.com reported that the 200 inch Hale telescope at California’s Palomar Observatory discovered the companion to Alcor, an M-dwarf star, more commonly referred to as a “red dwarf”. Despite it’s small sounding name, the 2009 observation reports it to be “250 times the mass of Jupiter”, which is according to my star sense, bigger than a bread box, and one-fourth the size of Sol.
With our ventures into exoplanets, perhaps a vying eye, with an acquaintance with high resolutions, (gigahertz, hint hint radio astronomers…) we may be pleasantly surprised with a septuple (seven parts) or a perhaps even a new planetary discovery in AlcorUm.
If only red shift detection could be done at will, and fully funded to keep research active for years to come at the Green Bank Telescope, West Virginia, we’d only need to ask once or maybe twice for a peek under the bed-sheets of our sextuplet daters.