This deserves a “whoa”: astronomers have discovered where a sextuple (six-) star system, if you look at it for a few days, all existing stars will go under eclipse at some point.
Whoa.
Multiples are just as interestingly cool: Unlike our Sun, which floats alone through space, it is multiples where two or more stars orbit each other in a fixed system, attached to pressure. Half of the stars in the galaxy are in several such systems. Most of them are binaries (two stars orbiting each other) and some in trinaries (three stars). There are even fewer in high-end systems.
That’s the first thing that makes TYC 7037-89-1 special: It’s a sextuplet, a six-star system. It’s a little over 1,900 light-years away, so medium distance, but clear enough to be discovered by TESS, the Satellite Survey Transiting Exoplanet. TESS scans the skies measuring the brightness of stars to look over exoplanets, which make micro-eclipses of their host stars, revealing their presence.
But it can also find a lot of other interesting things. TYC 7037-89-1 looks like one star in TESS data, but one that changes its brightness – a variable star. The astronomers he finds look in TESS data for stars that change brightness in a certain way, revealing that they are multi-star systems.
What they were looking for was binaries eclipsing: Stars that not only orbit each other, but also ones where we see the orbit near a corner, so that the stars appear to pass in front of one another. When that happens the total light from the pair drops slightly in a normal way. The astronauts set up automated software to look for such stars, and out of nearly half a million they found 100 that looked like three-star or larger systems.
And that’s what brings up the second cool thing about TYC 7037-89-1: Ripping is not just six stars all the way, but they’re arranged in binaries: Yes one pair of orbit stars. other a pair of stars, and a third pair of orbits both!
The binary pairs are named A, B, and C in order of brightness, and each star in them gets the number 1 or 2 (again in order of brightness). The two inner binaries are then A (made up of stars A1 and A2) and C (C1 and C2), torn apart by the binary B (B1 and B2). A and C are separated by about 600 million kilometers (very close to Jupiter’s distance from the Sun), taking about 4 years to orbit – this has been confirmed using archival data. from other telescopes, including WASP and ASAS-SN. B moves around the two of them at a distance of about 38 billion km, taking 2,000 years to complete one time.
And that now brings up the coldest thing about this system: All three pairs of stars are building binaries! We see the three binary orbits near the edge. A1 and A2 orbit each other (A1 eclipses A2, then half orbit after A2 eclipses A1) every 1.57 days, so they are very close to each other. C1 and C2 cycle each other every 1.31 days, and B1 and B2 take 8.2 days.
Since each star in any pair echoes the other, by measuring how long the eclipse will take in addition to other parameters (including taking spectra) we can learn important things like how big the stars are, how hot they are, and more. And this pays off other surprise: The three binaries are very similar. They are triplets!
In each, the largest star is about 1.5 times the diameter of the sun, slightly warmer, and about 1.25 times the mass of the sun. Also in each one, the smallest stars are about the same as each other, too: about 0.6 times the mass of the sun and 0.6 times its diameter. They change a bit, but the point is that they are very close, which is special.
This type of system is just incredibly unique. Models of how stars appear show that far more often sextuples are made up of two test systems orbiting each other, not three binaries. So that’s rare enough, but it’s impossible to see all three binaries.
… “it seems.” In fact they seem to have formed from a swirling disk of material, each star falling off. Because of this it is very likely that the three orbital planes of the binaries are the same. So if we see one edge, we see them all on the edge, or almost that. That makes it so unlike what you would think all three are eclipsing.
I also note the orbits of the binaries around each other they are not margins. We can see orbits A and C around each other from an angle of about 40 °, even as we see the individual stars in the binaries on the edge. But the orientation of orbit B around them both is not well limited by the observations.
We hope that a long-term study of this system will reveal more about how they came to be. We don’t know much about many systems like this one, so it would be interesting to understand under what conditions they create.
I know, this is a headache. So many orbits, angles, stars … Sometimes nature is complex, and difficult to maintain. If it helps, I describe a similar fictional system that played a key role in the first season of Star Trek: Picard. And there are known to be a few more systems like TYC 7037-89-1; for example CzeV1640 is a rectangular system with two pairs of eclipsing binaries. The complex, but sometimes frugal, nature repeats the same idea over and over again.
But oh my gosh, would I like a boat like that Campaign Right now! Until you see such a thing close to me, keep an eye on these six stars – six! – dance around each other…
Strange new worlds indeed.