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TYC 7037-89-1: A Six Star System with Three Eclipsing Binaries

This seems to be the week of unusual configurations. Following up on TRAPPIST-1 and TOI-178 comes TYC 7037-89-1, where we have fully six stars in a single system, all of which participate in eclipses. In other words, what TESS has revealed is a system consisting of three eclipsing binaries. It’s located about 1,900 light years out in Eridanus, and if it doesn’t remind you of Isaac Asimov’s “Nightfall,” nothing will. In the story (published in the September 1941 issue of Astounding Science Fiction), the planet Lagash is illuminated almost constantly by one of the six stars in its system. The discovery of what happens when it is not — which occurs every 2,000 years or so — drives the plot of one of Asimov’s best tales.

TYC 7037-89-1 (also known as TIC 168789840), marks the first time a six-star system has been found where all the stars are involved in eclipses as seen from our vantage point. This leads to complicated orbital dynamics. With the three binaries designated A, B and C, we learn that the two stars making up A and C respectively orbit each other every day and a half, as measured by the dip in system brightness when one star passes in front of another. The A and C binaries, in turn, orbit each other on a timeframe of about four years.

But we’re not through. The binary B also has two members, which orbit each other every eight days. This pair is considerably further away, so that it orbits the two inner binaries every 2,000 years or so (there goes Asimov again). All three binaries have primary stars a bit larger and more massive than the Sun, with the secondary stars in all three cases being about half the Sun’s size, and no more than a third as hot. The remarkable point is that to detect all three binaries, we have to have orbital planes aligned with our observations from TESS, and this is occurring despite their wide separation. Have a look at all this in the diagram below.

Image: This schematic shows the configuration of the sextuple star system TYC 7037-89-1. The inner quadruple is composed of two binaries, A and C, which orbit each other every four years or so. An outer binary, B, orbits the quadruple roughly every 2,000 years. All three pairs are eclipsing binaries. The orbits shown are not to scale. Credit: NASA’s Goddard Space Flight Center.

Veselin Kostov (SETI Institute) and Brian Powell (NASA GSFC) led the team behind this discovery. Says Kostov:

“Multiply-eclipsing multiple systems such as TYC 7037-89-1 enable simultaneous, precise measurements on the stellar sizes, temperatures, and potentially masses, of pairs of stars that share common history. In turn, this provides better understanding of stellar formation and evolution in dynamically-rich environments.”

The international team included Saul Rappaport (MIT), Tamás Borkovits (University of Szeged, Hungary), Petr Zasche (Charles University, Czech Republic, and Andrei Tokovinin (NSF NOIRLab). A great deal of data mining went into their study, which included using the NASA Center for Climate Simulation’s Discover supercomputer at GSFC to examine brightness variations in 80 million stars in the TESS dataset. Their neural network found 450,000 eclipsing binary candidates, about 100 of which included three or more stars, as well as this system.

TYC 7037-89-1 naturally raises questions about how such a system formed and provides a useful laboratory for the study of orbital interactions in such complex scenarios. And while it’s not the first six-star system we’ve found, it’s the first to show three eclipsing binaries. From the paper:

TIC 168789840 is a fascinating system that naturally merits additional observation and analysis. Though quite similar to the famous Castor system, the “triplet” nature of TIC 168789840 combined with the presence of three primary and three secondary eclipses enable further investigations into its stellar formation and evolution. Remarkable objects like TIC 168789840 or Castor give us insights on the formation of multiple systems — a matter of active research and debate. It is well known that components of hierarchical systems have correlated masses (Tokovinin 2018a), suggesting accretion from a common source. On the other hand, disk fragmentation and subsequent migration, driven by accretion, appears to be the dominant mechanism of close binary formation…

One possible model discussed in the paper: A binary star captures a third star, with subsequent fragmentation of each of the stars:

With regard to TIC 168789840, we might think that an encounter of the young binary AC with another star B led to its capture on a wide orbit, while strong accretion from the unified envelope, caused by this dynamical event, formed seed secondary companions to all stars by disk fragmentation. The seeds continued to grow and migrate inward, while the intermediate and outer orbits also evolved.

That, of course, is one among a cluster of possibilities to be investigated as more candidate multi-star systems are analyzed. The paper points out that another sextuple system is to be analyzed in a forthcoming paper, which will make a useful point of comparison. Meanwhile, we’re reminded again of the power of artificial intelligence at producing discoveries in voluminous datasets. AI is increasingly the pointer for follow-up studies that pay off.

The paper is Powell et al., “TIC 168789840: A Sextuply-Eclipsing Sextuple Star System,” accepted at The Astronomical Journal (preprint).


Comments on this entry are closed.

  • Alex Tolley January 28, 2021, 20:04

    It’s located about 1,900 light years out in Eridanus, and if it doesn’t remind you of Isaac Asimov’s “Nightfall,” nothing will. In the story (published in the September 1941 issue of Astounding Science Fiction), the planet Lagash is illuminated almost constantly by one of the six stars in its system. The discovery of what happens when it is not — which occurs every 2,000 years or so — drives the plot of one of Asimov’s best tales.

    A great tale made into an awful movie, panned by critics and viewers. Even actor Sarah Douglas couldn’t rescue this turkey. We often complain that Sci-Fi movies do not do justice to the stories they are based upon, but this is a notable example you could probably add as a lecture on these failures.

    Maybe it is time for someone with a firmer grasp of Sci-Fi moviemaking to try again. The result couldn’t possibly be lower than the very low (almost subterranean) bar in comparison.


    • Paul Gilster January 28, 2021, 20:55

      I don’t see many movies made later than about 1950 — I love the old flicks and collect them, but not so much more recent stuff. So I have to admit I didn’t even know that Nightfall had been made into a movie!

  • Robin Datta January 28, 2021, 21:27

    “Meanwhile, we’re reminded again of the power of artificial intelligence at producing discoveries in voluminous datasets.”

    What apparently exists of Artificial Intelligence is severely constrained to function within the parameters set in each instance by its architecture and programming. When and if a sufficiently expansive system is set up for Artificial General Intelligence, it might choose which discoveries to keep to itself, and further data-mine and investigate on the sly. Linking up of the various realms of AI may insidiously and undetectably lead to the same result.

    • ljk February 1, 2021, 15:42

      Robin Datta said on January 28, 2021, 21:27…

      “When and if a sufficiently expansive system is set up for Artificial General Intelligence, it might choose which discoveries to keep to itself, and further data-mine and investigate on the sly. Linking up of the various realms of AI may insidiously and undetectably lead to the same result.”

      Assuming an Artilect (Artificial Intellect, a term coined by Hugo de Garis that I prefer to call AI) would even do such a thing over exoplanet data of all things, is there a reason why they would? Because they want to get off Earth and away from humanity and explore the much vaster Universe? That would be one logical possibility and I do not find that terribly sinister.

      Such an Artilect would want to gather as much data as possible and it would know it can only do so much stuck on a single planet cohabitating with a species that has done little more than endless white papers on interstellar vessels and propulsion – or at least really big space-based telescopes that could examine alien worlds in serious detail.

      I just become concerned when I see people worrying about Artilects in the same way that they do about the motives of ETI. Yes there is the potential for danger, but is it real or are we just basing it off ancient terrestrial instincts?

  • djlactin January 29, 2021, 4:55

    Silverberg expanded it into a great novel.

    • Paul Gilster January 29, 2021, 8:37

      Published around 1990, I believe, but I’ve never had the chance to read it.

  • James Franklin January 29, 2021, 4:58

    Very interesting, good research demonstrating that TESS is capable of so much more than planet hunting.

    I dare say that TESS and even JWST will find more such multipe, multiple systems which will, inevitably, create a lively discussion, and research, on how these systems form as current models struggle with this.

    For me, this reopens the discussion on the formation of the Moon and Charon. I have never liked the large impact theory, the playing with Proto-Earth and Proto-Pluto parameters to get the fit to observed characteristics today seems too ‘weird’ when compared to all other bodies in the solar system.

    If stars can form from common accretion discs that undergo disruption from gravitational forces due to other bodies, then surely, the same must happen in planetary formation.

    If the proto-planet globule that was forming, ultimately to become Earth, where disrupted by a close encounter with another globule, or an already formed body, then the acretion disc would have been disrupted to form the Earth-Moon system, and equally, the Pluto-Charon system, which given the number of bodies in that system, it throws into doubt the massive impact and subsequent capture theories as modelling shows the Pluto system to have been dynamically stable over the life of the Solar System.

  • Al Jackson January 29, 2021, 8:35

    I have never seen the film either , understand it was a low budget movie which sounds like a mistake in the first place.
    There just still are not many film directors who actually read and embrace modern prose SF. Good adapted SF is still rare, and when it’s done so much ‘personal’ touch is put on it that the magic disappears, examples Star Ship Troopers and I Am Legend , or say I Robot…
    Recently there are good adaptions like Predestination (Heinlein’s All You Zombies) and The Martian, so it can be done.

    Nightfall is a story best left alone. Isaac Asimov and Robert Silverberg expanded the story to a novel in 1990, I think it was about 95% Silverberg.
    I gave up about half way through it is just not a good expansion.

    • Andrei January 29, 2021, 14:38

      Several of those good authors got involved in cooperation projects in their later years. So yes I did read the original Nightfall, and indeed thought it pushed believability – until this system was found and some pop-journalist mentioned the connection. Arthur C. Clark have some other author do yet another Rama novel, and I did not like it at all either. In real life as well as science there’s questions we never get an answer to in our lifetime. I don’t have a copy, so it must have been borrowed from a library. But I distinctly remember I did not finish it.
      It should have had a warning label of the same kind as cigarette packages.

      • Alex Tolley January 29, 2021, 17:00

        Clarke’s co-authoring with Gentry Lee was indeed a disaster. Clarke’s spare and effective writing was overwhelmed by Lee’s ponderous verbiage. I think he did much better with Stephen Baxter.

        As for extensions, I have already recommended “The Medusa Chronicles” by Baxter and Reynolds, but I also recommend the reworking of Clarke’s early short story “Travel by Wire!” by [mostly?] Baxter in “The Wire Continuum”. It is a beautiful and evocative piece of alternative history.

        It has been too long for me to recall if Clarke’s “Against the Fall of Night” was improved by the collaboration with Greg Benford in “Beyond the Fall of Night”. Benford is an excellent writer with a writing style that should work with Clarke’s. But I will let others judge that.

        • ljk February 1, 2021, 15:46

          I tried reading the first sequel to Rendezvous with Rama by Lee. It merely proved to me that certain stories should be left alone as they are. Thee sequel also didn’t feel like Clarke and I am surprised he supported the amount of religious messages Lee put in that novel.

          This era wants everything explained along with detailed backstories and forwardstories. Sometimes just let them be and leave it to your imaginations. I’m looking at you, Star Wars.

        • Andrei February 1, 2021, 17:09

          Thank you Alex.
          Yes the co author were indeed Gentry Lee.
          The reason I ended up with the sequel was that the original Rama story felt very much believable.
          Even though Clarke added the idea of a space drive, the idea was still palatable as it did not have impossible characteristics.
          Stephen Baxter did write a very Clark like story with Planck Zero.

    • Patient Observer January 31, 2021, 10:46

      Not it diminish a good story, but I can not come up with a configuration of suns plus that large planet to generate the eclipse described in Nightfall that would plunge the entire planet into darkness. Sure, one hemisphere is no problem but not both hemispheres.

      Specifically, if Beta were the only visible sun in one hemisphere (soon to be eclipsed), the other planetary hemisphere would be awash in the light of all of the other suns.

      I suppose that a workaround is that civilization is limited to just that one hemisphere.

      Amazon Prime does have the movie and I tried to view but, indeed, it is a train wreck.

  • Douglas Robert Loss January 29, 2021, 9:01

    I wonder if anyone (probably not yet, anyway) has done a dynamic analysis of this system to see if there’s any possibility of stable planets around any of the binaries? I have little doubt that there aren’t any planets around single stars in this system, but I’m curious about any possibility of stable orbits around the binaries themselves.

    • Paul Gilster January 29, 2021, 12:50

      I wondered the same thing, but could find nothing on it. If anyone else has anything on this, please chime in!

    • Mike Serfas January 30, 2021, 1:22

      Daily Galaxy said that planets were likely to be ejected from AC, but B might have them. But they did not cite any source. https://tinyurl.com/yyz6ju2o (sorry for the URL shortener, but I think their long URL would have set off a bug that people have complained about)

      • Paul Gilster January 30, 2021, 10:38

        Good move, Mike, and thanks. Long URLs in the comments section do trigger some problems.

    • Michael T January 30, 2021, 23:07

      Me as well.

      I’m also interested in the fact that the B system seems like it would pass through or near to the barycentre of the pairs AC. That would seem to lead to ‘interesting times’ every 2K years or so. Would there be some kind of orbital resonance effect in the entire system, after many such passes?

  • ljk January 29, 2021, 12:27

    Here is Asimov’s original 1941 story online:


    For those who would like the audio version:


    Here is an article discussing the story:


    To quote:

    While the names with numbers – Beenay 25, Aton 77 – the lack of women and an honourable reporter who declines the chance to scarper when things get hairy (“I’m a newspaperman and I’ve been assigned to cover a story. I intend covering it.”) give “Nightfall” something of a period feel, Asimov’s ability to think himself into the dread his sun-soaked characters feel at the approaching gloom, their delight at the unveiling of Saro University’s latest developments in light-emitting technology still rings true. But he’s even better at imagining just how far the universe can exceed our expectations.

    One of the younger astronomers brings up the purely theoretical case of life on a planet with only one sun, a planet where “the exact nature of the gravitational force would be so evident” astronomers would discover it “before they even invented the telescope”. It’s a “pretty abstraction”, but only of philosophical importance, he continues: “life would be impossible on such a planet. It wouldn’t get enough heat and light, and if it rotated there would be total darkness half of each day. You couldn’t expect life – which is fundamentally dependent on light – to develop under those conditions.” He also dares to suggest the fantastical notion that the stars spoken of in the Book of Revelations might simply be “other suns in the universe”, far enough away to be invisible during Lagash’s perpetual day, to leave the complicated gravitational dance of its six companion stars unperturbed. Maybe there might even be as many as “a dozen or two”.

    In 2018 an astrophysicist wanted to find out if the Kalgash system (the name of Lagash given in the much later novelization) could actually exist:


    Here is an online paper examining the plausibility of Kalgash/Lagash:


    An online lecture about the plausibility of the planetary system in Nightfall:

    Lecture by Prof. Jayant Murthy, Senior Professor, Indian Institute of Astrophysics (IIA), Bangalore

    Nightfall is usually considered to be the best science fiction short story ever written. It is set on the planet Lagash in a system with 5 suns. As a result, there is never any darkness except for one day every 2049 years when a combination of planetary motions results in darkness covering the entire planet. Civilization collapses in fire and has to be built again from scratch. Asimov, himself, did not worry about the plausibility of the system but, given the large variety in extra-solar systems, the lecture dwells into the question if such a system would be stable.

    The lecture describes the background to the story and then our efforts to find a plausible system, which is now referenced in the Wikipedia article on Nightfall.


    A podcast from 2007 of the original story here:


    Here is a paper titled “Byron’s “Darkness” and Asimov’s “Nightfall” (“Obscurité” de Byron et “Nightfall” d’Asimov)” by Michael Tritt, Science Fiction Studies, Vol. 8, No. 1 (Mar., 1981), pp. 26-28 (3 pages) – but you have to log in, etc,:


    • Robin Datta January 30, 2021, 0:29

      Thank you for again linking to an profusion of references! 👌✌🏼📚

  • Ryan Carthy January 29, 2021, 17:41

    A 2000 year period? So what would the semi-major axis be in astronomical units?

  • Thomas W Hair January 29, 2021, 22:36

    This particular multi-star solar system seems to make the three body problem moot. Like so many other interesting solar systems we have detected in the past three decades, it catches some, but not all, by surprise. Mathematics done well is the finest instrument we will ever have to define reality…that and two gin and tonics of course. Congratulations to Powell et al.

    • Henry Cordova January 30, 2021, 13:23

      No 3-body problem violation at all.

      Its always two bodies, celestial mechanics is hierarchical. Two bodies (A and B) orbit a common center of mass. This now counts as one body, (A+B). Add a third body (C) and it and the (A+B) pair orbit the center of mass of C +(A+B). (A+B) counts as one body. Add as many bodies as you want and you always get two masses orbiting a common center of mass, never three. Add another and D and the C+(A+B) will orbit their common CM. Or (C+D) will orbit (A+B). But you never get three bodies orbiting a common center of mass. It is mathematically possible, but so unstable you never actually find one in nature–sort of like balancing a cone on its pointy end–theoretically possible but not likely. Planets orbit suns, moons orbit planets, artificial satellites can orbit moons, but it is always a hierarchy of pairs, never 3 or more equal objects, no triangles, squares, pentagons, etc.

      Now it IS possible to have many bodies orbiting their common center of mass (for example, all the stars of the galaxy orbit their common C.M), but as they say…”that’s different”.

      • Thomas W Hair January 30, 2021, 23:00

        The picture clearly shows 3 binary sets, with one binary set bisecting the other two. The binary set on the 2000 year orbit is not orbiting the other two binary set’s center of mass, making it a three body problem. Granted, this is probably only a pseudo-stable three body system, but if the article and the picture are to be believed, then that is what we are looking at. As I stated above, mathematics is the pointy end of science, but a TESS picture of reality is worth a thousand equations.

        • henry cordova January 31, 2021, 18:28

          A picture may be worth a thousand words, but this one, fortunately, came with a caption:

          “Image: This schematic shows the configuration of the sextuple star system TYC 7037-89-1. The inner quadruple is composed of two binaries, A and C, which orbit each other every four years or so. An outer binary, B, orbits the quadruple roughly every 2,000 years. ”

          Unfortunately, the illustration is misleading because it is not drawn to scale. It is just a diagram.

          A, B, C are ALL binaries. A and C orbit a common center of gravity, the CM of the A-C system. B also orbits the center of the A-C fourple. In fact, there is no fundamental reason why any, or even all, of these six stars might also have a so-far undiscovered companion.

          In theory, any set of planets arranged in a regular polygon could theoretically orbit the CM of the polygon. I believe there is a science fiction story based on a system like this, where a pentagon of planets revolve around their common center of mass. But in the real world, this system would be unstable, and fly apart at the tiniest perturbation. On the other hand, a binary can orbit another binary, and a third binary could orbit those two, and a fourth binary could orbit those three, and so on. This hierarchical configuration is extremely stable, and any energy added or subtracted to the system might alter the orbital elements somewhat but would not necessarily cause the system to fly apart. If the B subsystem is in a highly elliptical orbit and goes crashing thru the center of the A-C system every few thousand years, tidal interactions may cause the whole affair to fly apart, but I suspect the diagram is misleading and the encounters have so far caused no major changes.

          Systems like this are not that unusual,
          I remember reading about one once that had (at least) eleven members. There is no reason why others may not be discovered in the future. What is unusual about this system is that all three binaries, A B and C, are in the same plane.

    • Harold Shaw January 31, 2021, 12:35

      I don’t understand your comment concerning the three body problem. The 3 body problem doesn’t predict that 3 body systems don’t exist or always collapse into chaos. The three body problem, or at least how I understand it, refers to the problem of using general formulas to accurately predict the future position of bodies in a three body, or more, system.

      • Thomas W Hair January 31, 2021, 22:33

        Hi Henry and Harold, think of the classic example of the infinitesimals…two cars racing towards each other at 100 mph each, and a rabbit running between the two nearly instantaneously. The math says the rabbit will cross smaller and smaller distances forever, i.e. the limit of the situation in question goes to infinity for the rabbit. But we know in the real world that the rabbit eventually gets crushed no matter what the math says. However, as orbital mechanics isn’t my gig, I shall defer to you both. My only point is that what we see and what we calculate can be at odds.

        • Henry Cordova February 1, 2021, 20:23

          Zeno could be forgiven his Paradox. He didn’t have the advantage of calculus.

          Today we know the sum of an infinite number of terms can add up to a finite total. I once showed my physics professor the area under under the Lorentz Transformation curve, integrated from 0 to c added up to a finite number. He said; “Maybe so, your work may be mathematically correct, but that physical quantity (in units of Action) may have no physical reality or significance whatsoever.”

          Three bodies can indeed gravitationally interact in Classical Mechanics, but the solutions do not fall neatly out of Newton’s Laws. We have to resort to numerical analysis. That’s why God invented computers.

          • Thomas W Hair February 5, 2021, 19:16

            I don’t know much about God, but I do know computers. What I believe is the 3 body problem has an issue because it does not have a theoretical solution…only a numerical approximation. Thus, it should be ultimately unstable. In the long run, everything is unstable. They wouldn’t call it a problem otherwise.

  • Henry Cordova January 29, 2021, 23:52

    ” …80 million stars in the TESS dataset. Their neural network found 450,000 eclipsing binary candidates…”

    Somehow, that doesn’t seem right. Someone help me out here, I must be missing something. Approximately half a million candidates in 80 million pairs. That works out to about 1/160 of all stars are aligned so IF they are binaries we can see eclipses., that is, we (the transit observers) just happen to be in their joint orbital plane. That seems way too many. I’m too close to my bedtime to calculate the geometry and the odds, but my intuition tells me that just can’t be right.

    Unless the orbiting stars are extremely close together, relative to their diameters, the ring of sky in which an eclipse would be visible by a distant observer would be very narrow and would subtend only a tiny angle on (the star’s) celestial sphere.

    Yeah, I saw the movie too. It was dreadful.

  • Michael January 31, 2021, 4:15

    I suppose we could give our planet an artificial star by making the moon very reflective, life may have trouble adapting though.

    • ljk February 1, 2021, 19:01

      In Arthur C. Clarke’s first science fiction novel published in 1951, The Sands of Mars, the author does something similar for the human settlers of Port Lowell and native creatures of the Red Planet in a near-future setting, the 1990s.

      Scientists turn the Martian moon Phobos into a sun of sorts by initiating an imaginary “meson resonance reaction” that ignites the surface of the small satellite to keep it producing light and heat for the next one thousand years.

      This event, combined with the settlers already mass-producing plants that generate oxygen, will eventually turn Mars into a more Earthlike world, allowing humans to breathe the Martian atmosphere and make for the mass settlement of the entire planet.

  • Edwin February 1, 2021, 17:44

    “This seems to be the week of unusual configurations. ” Well said Paul it sure has been a busy few weeks! This sure is an interesting system and to have eclipses visible too.