Move over Tatooine – a planet with triple suns has been discovered

This artist's impression shows a view of the triple star system HD 131399 from close to the giant planet orbiting in the system. The planet is known as HD 131399Ab and appears at the lower-left of the picture. CREDIT: ESO/L. Calçada

This artist’s impression shows a view of the triple star system HD 131399 from close to the giant planet orbiting in the system. The planet is known as HD 131399Ab and appears at the lower-left of the picture. CREDIT: ESO/L. Calçada

 

A team of astronomers have used the SPHERE instrument on ESO’s Very Large Telescope to image the first planet ever found in a wide orbit inside a triple-star system. The orbit of such a planet had been expected to be unstable, probably resulting in the planet being quickly ejected from the system. But somehow this one survives. This unexpected observation suggests that such systems may actually be more common than previously thought. The results will be published online in the journal Science on 7 July 2016.

Luke Skywalker’s home planet, Tatooine, in the Star Wars saga, was a strange world with two suns in the sky, but astronomers have now found a planet in an even more exotic system, where an observer would either experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the seasons, which last longer than human lifetimes.

luke-skywalker-on-tatooine

Luke Skywalker staring out from his home planet of Tatooine in Star Wars: Episode IV – A New Hope Credit: LucasFilms

This world has been discovered by a team of astronomers led by the University of Arizona, USA, using direct imaging at ESO’s Very Large Telescope (VLT) in Chile. The planet, HD 131399Ab [1], is unlike any other known world — its orbit around the brightest of the three stars is by far the widest known within a multi-star system. Such orbits are often unstable, because of the complex and changing gravitational attraction from the other two stars in the system, and planets in stable orbits were thought to be very unlikely.

Located about 320 light-years from Earth in the constellation of Centaurus (The Centaur), HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets. With a temperature of around 580 degrees Celsius and an estimated mass of four Jupiter masses, it is also one of the coldest and least massive directly-imaged exoplanets.

“HD 131399Ab is one of the few exoplanets that have been directly imaged, and it’s the first one in such an interesting dynamical configuration,” said Daniel Apai, from the University of Arizona, USA, and one of the co-authors of the new paper.

“For about half of the planet’s orbit, which lasts 550 Earth-years, three stars are visible in the sky; the fainter two are always much closer together, and change in apparent separation from the brightest star throughout the year,” adds Kevin Wagner, the paper’s first author and discoverer of HD 131399Ab [2].

Kevin Wagner, who is a PhD student at the University of Arizona, identified the planet among hundreds of candidate planets and led the follow-up observations to verify its nature.

The planet also marks the first discovery of an exoplanet made with the SPHERE instrument on the VLT. SPHERE is sensitive to infrared light, allowing it to detect the heat signatures of young planets, along with sophisticated features correcting for atmospheric disturbances and blocking out the otherwise blinding light of their host stars.

Although repeated and long-term observations will be needed to precisely determine the planet’s trajectory among its host stars, observations and simulations seem to suggest the following scenario: the brightest star is estimated to be eighty percent more massive than the Sun and dubbed HD 131399A, which itself is orbited by the less massive stars, B and C, at about 300 au (one au, or astronomical unit, equals the average distance between the Earth and the Sun). All the while, B and C twirl around each other like a spinning dumbbell, separated by a distance roughly equal to that between the Sun and Saturn (10 au).

In this scenario, planet HD 131399Ab travels around the star A in an orbit with a radius of about 80 au, about twice as large as Pluto’s in the Solar System, and brings the planet to about one third of the separation between star A and the B/C star pair. The authors point out that a range of orbital scenarios is possible, and the verdict on the long-term stability of the system will have to wait for planned follow-up observations that will better constrain the planet’s orbit.

“If the planet was further away from the most massive star in the system, it would be kicked out of the system,” Apai explained. “Our computer simulations have shown that this type of orbit can be stable, but if you change things around just a little bit, it can become unstable very quickly.”

Planets in multi-star systems are of special interest to astronomers and planetary scientists because they provide an example of how the mechanism of planetary formation functions in these more extreme scenarios. While multi-star systems seem exotic to us in our orbit around our solitary star, multi-star systems are in fact just as common as single stars.

“It is not clear how this planet ended up on its wide orbit in this extreme system, and we can’t say yet what this means for our broader understanding of the types of planetary systems, but it shows that there is more variety out there than many would have deemed possible,” concludes Kevin Wagner. “What we do know is that planets in multi-star systems have been studied far less often, but are potentially just as numerous as planets in single-star systems.”

Notes

[1] The three components of the triple star are named HD 131399A, HD 131399B and HD 131399C respectively, in decreasing order of brightness. The planet orbits the brightest star and hence is named HD 131399Ab.

[2] For much of the planet’s year the stars would appear close together in the sky, giving it a familiar night-side and day-side with a unique triple sunset and sunrise each day. As the planet moves along its orbit the stars grow further apart each day, until they reach a point where the setting of one coincides with the rising of the other — at which point the planet is in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years.

More information

This research was presented in a paper entitled “Direct Imaging Discovery of a Jovian Exoplanet Within a Triple Star System”, by K. Wagner et al., to appear online in the journalScience on 7 July 2016.

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77 thoughts on “Move over Tatooine – a planet with triple suns has been discovered

    • Science fiction is as destructive as fictional science. We have whole generations wasting time with science fiction and finger toys.
      G
      Get to work and do something useful for a change. (not person specific).

      • Science fiction writers get to call a spade a spade, while pretending that they’re talking about different worlds. It’s one way to get the truth out there without getting shot for it.
        Reading fiction (science fiction included) is good for you.

      • I don’t recall saying I was against anything; well anything legal as well as ethical.
        Just expressing an opinion. Do what you like. If that is walking off a cliff or under a train while being entertained; it is your choice.
        G

      • I say; Hey, they ought to be allowed to spend their money on entertainment for a few geeks who get off on this sort of useless information, it’s a free country . . ; )

      • “Located about 320 light-years from Earth in the constellation of Centaurus (The Centaur), HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets.”
        It is somewhat disturbing to me that otherwise intelligent people actually believe anyone knows that thing is 16 million years old . . but it goes a long way toward explaining how the CAGW hypothesis could be considered settled science by so many . . and I accuse (gently) those who read these words and say nothing about how that is not possible to know in a scientific sense. I accuse you of helping to generate a virtual God, in the minds of less educated people, Which could easily determine something so relatively observable and testable as the effects our CO2 emissions are having right here on this planet . .
        Be consistent, I advise, and don’t just sit there while obvious conjecture is pawned off as a scientific known.

  1. I can imagine the orbital complexities of a planet in such a system but I cannot fathom the loci specifically. I would also like to see the interactions of a three star system regardless of the planet’s involvement,

    • http://phys.org/news/2016-07-newly-planet-suns.html
      http://cdn.phys.org/newman/csz/news/800/2016/17-newlydiscove.jpg
      This graphic shows the orbit of the planet in the HD 131399 system (red line) and the orbits of the stars (blue lines). Credit: ESO
      http://cdn.phys.org/newman/csz/news/800/2016/16-newlydiscove.jpg
      This artist’s impression shows a view of the triple star system HD 131399 from close to the giant planet orbiting in the system. The planet is known as HD 131399Ab and appears at the lower-left of the picture.Located about 340 light years from Earth in the constellation of Centaurus (The Centaur), HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets. With a temperature of around 580 degrees Celsius and having an estimated mass of four Jupiter masses, it is also one of the coldest and least massive directly imaged exoplanets. Credit: ESO/L. Calçada

    • One simple stable non-exotic version would just be to imagine our sun and planets on a larger scale. Jupiter, if a few time larger, would be a sun as the gasses ignite, then those moons would be planets instead… At even larger scale, Saturn would light up…
      So were our sun a giant, instead of small, it could easily support a couple of dwarf stars instead of planets, and without the more exotic loopy orbits that sometimes can happen.

      • The minimum size for a brown dwarf is 13 joven masses, for a M class star it is ~72 joven masses.
        We can get into the physics of this if you want.

      • I had envisioned it like this: a large central star, with a planet large planet orbiting it, 40% of the size needed to be a brown dwarf. Much farther out is another largish orbiting star with a small moon-star that stays near it. Nothing says a planet can’t glow. Just scale up our system and you get that one. There might be a Star out there with 9 orbiting little stars.
        That is much less complicated conceptually than the free-three-body illustration (which I greatly enjoyed).

      • 3D space…
        the 3 stars always form a plane so the orbits, though rendered on a 2D projection, obey 3d mechanics, so the plane precesses accordingly.
        Is this 2d projection confined by 2d mechanics? Or a 2d view of 3d mechanics?

      • Three points not on a line always form a plane.
        They don’t necessarily stay in the same plane, but there always is a plane the three of them lie in, unless they are on a line.
        G

    • Vukevic,
      That video looks like some of my computational physics final project runs from when I solved for Tatooine in the undergraduate computational physics course. My presentation to the class was talked about for years. I presented a series of videos showing all the crash and burn cases first which drew big laughs – planet crashing into stars or getting flung into deep space were very entertaining. Finally I showed two general cases for configurations which produced stable orbits. One was with a close binary with the planet out wide, and the other was with a wide binary with the planet in close to one of them. The article actually shows the orbits for this system as essentially a wide spaced binary with a tertiary orbiting “close” to one of the binary pair and the planet orbiting the tertiary. In my simulations, this was almost always a stable configuration, though there was a critical point for the mass and distance ratios that led to more chaotic patterns. Initial conditions were very critical to stable orbits.

      • Hi Owen
        googling “Restricted 3-Body Problem With Osculating Orbits” will lead you to link for the source with more details.

    • Thanks for that Vuk.
      If only I’d had video in my undergraduate days, instead of pages of calculus, things might have been a lot clearer!

    • I don’t think this simulation is right at all. Look at the later stages where the wandering sun (green) interacts with the outer sun. The outer one is in a perfectly circular orbit, which is a bit suspect anyway since the center of gravity keeps shifting, but as the wandering sun approaches, its orbit is wildly perturbed as it approaches the outer sun, which isn’t affected at all, it just sails on in its perfectly circular orbit.

    • Another example:

      Vuk’s example has two larger masses and one light one, the red anb blue bodies following near-circular paths. Depending on proximity, mass and the number of bodies involved, it can get pretty spectacular. The link show some examples of other n-body problems from a simple two-body system to a Plummer Sphere. Poincaré showed that there were no general solutions to n-body problems. With a system like our solar system, the concentration of mass in the sun simplifies things, though I have read that over geological spans of time no reliable retrodiction of planetary positions can be made. The estimates begin to “hunt” seriously.

  2. According to the bit I read in Sky & Telescope magazine, the planet if still very young and probably in an unstable orbit. More observations and study needed.

    • I don’t think Tatooine needs to worry about being displaced from the top of the wow factor list by this new planet having more suns in its sky. Tatooine’s suns have visible discs, these new stars would not. I think the view from the moon of Endor had a bigger wow factor than Tatooine’s, though.
      SR

    • Wasn’t one of the Casher O’Neil [Cordwainer Smith] stories set on a planet with five suns?
      Bit like the EU with their five Presidents,
      The suns weren’t elected . . . . .
      Auto

    • Asimov was my thought as well when I read: “An observer would either experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the seasons, which last longer than human lifetimes.”
      “Nightfall” is still one of the best short stories of all time IMHO.

      • @Tom Yoke – that is most likely a pirate copy. All of Asimov’s works are still under copyright, and use of them without his estate’s permission is illegal. There is no notice here that they have permission (in fact, there is no acknowledgement that it is even copyrighted!)
        No, it doesn’t matter that it is a university website – they are among the worst offenders of copyright law.

      • Reality Observer, you may be right. I was a bit surprised to see the story come up as the 2nd item in the Google search, but I consequently assumed that the copyright must have expired.

      • Tom
        Certainly agree. “Nightfall” was the first thing that came to my mind when I read this post’s headline.

  3. The stability of the orbit of 131399Ab is dependent upon the disparity of mass between 131399A and the other bodies.
    If 131399B and 131399C are much smaller than A and orbit at a much greater distance (as Jupiter or Saturn do around our sun), there is no reason why Ab’s orbit would not be as stable as that of Earth.
    The important thing to the stability of the orbit of Ab is that the gravity of it’s primary (A) where b orbits consistently overwhelms that of the other satellites (B and C) of the primary.

  4. “It’s worse than we thought” stated Lilly Green (author of ‘men pump out the C02, but it is women how will primarily suffer the brunt of man made climate change’) who works at the Institute for Global Man Made Climate change Anthropogenic Carbon Warming Centre. She added: “These extra suns could exacerbate an already dire situation. However more research and grants are needed to ascertain the depths of our future horrors due to this”.

  5. Kind of reminds me of the Issac Asimov novel “Nightfall” wherein the people on a planet with 6 suns never experience darkness, except once in 1000 years when civilization takes a bad turn.

  6. This article here nice to see . Of interest might also be …
    NASA’s recent findings about the mysterious planet Niribu – confirmed that something is out there on a huge elliptical orbit taking tens of thousands of years to orbit our sun.

    • For the sake of accuracy, the findings of a planet far outside the orbits of the known solar planets was not by NASA and it’s not called Niribu (or Nibiru), simply Planet X for now.

  7. Obviously the planet and the suns are in orbital resonance.
    Personally, I am looking forward to the discovery of Planet Pitooi which is within spitting distance of Planet Tatooine.

  8. Anthony if you are a relativist then Gravity does not in fact attract at all :p
    I wish you relativists would make up your minds

      • Either way, gravity sucks.
        Good thing too, otherwise goodbye us.
        The Coulomb force is pretty much good for nothing, if there is no gravity.
        G

      • True, but in the cases in which Newton’s equations hold, Einstein’s must necessarily reduce to them. There is no reason to apply the much more complicated math to a problem which is described accurately by a simpler formula.
        The bending of space-time by massive bodies is interesting only so far as the math envisaged by that framework predicts observations. It is great for correcting GPS satellites timings for their position in the Earth’s gravity well, and necessary for accurately predicting the position of Mercury, but using it to predict the position of Jupiter is more complicated than it needs to be unless you are trying to make million year predictions and need accuracy greater than the diameter of Jupiter.

    • I wish you “anti-relativists” would find a cogent argument.
      Honestly, if you don’t understand the common usage of the English word “attraction” — like the use of the word “suck” in relationship to vacuums — then not only is it unlikely you will ever understand why so many people insist on clinging to a “failed paradigm,” it’s even LESS likely you’ll have any success convincing others of their mistake using a language you yourself clearly don’t understand.

  9. The two smaller stars are orbiting each other close enough and are far enough away from the primary that the difference between them and a point mass is not significant.
    Beyond that given how far out they are, I wonder if Jupiter would have more gravitational affect on the earth, as these two stars do on the planet that has been found.

  10. “potentially just as numerous…”
    I suppose that there is an infinite number of both, so their respective quantities would be equal.

    • Georg Cantor proved that infinities have different sizes. The set of all whole numbers is infinite. So is set of all real numbers. But there are more real numbers than whole numbers.

      • Even the rational numbers are infinite in number.
        G
        And infinity / infinity is not necessarily indeterminate. Depends how you get there from a rational number.

      • ristvan, thanks. And if A0 is the “infinity” of the integers, then the “infinity” of he real line on (0,1) was given as A1 = 2^A0. It is fun to show that A1>A0 by mapping the reciprocal of the integers onto the line between 0 and 1, i.e. 1/1=1, 1/2=0.5, 1/3= 0.333…, 1/4=0.25……1/A0 = 0. There are “blank” intervals between 1 and 0.5, 0.5 and 0.333…, etc..

  11. Forget about the irrelevancy of distant exo-planets, it is our planet which we need to worry about, it is loosing its atmosphere !
    The curious case of Earth’s leaking atmosphere
    Every day, around 90 tonnes of material escapes from our planet’s upper atmosphere and streams out into space.
    That sounds to me a bit worse than expected.
    More recent studies have unambiguously confirmed another source – Earth’s atmosphere is constantly leaking! Alongside the aforementioned plumes, a steady, continuous flow of material (comprising oxygen, hydrogen, and helium ions) leaves our planet’s plasmasphere from the polar regions, replenishing the plasma within the magnetosphere. Cluster found proof of this wind, and has quantified its strength for both overall (reported in a paper published in 2013) and for hydrogen ions in particular (reported in 2009).
    http://cdn.phys.org/newman/csz/news/800/2016/2-thecuriousca.jpg
    Artist’s impression of the plasmasphere in Earth’s magnetosphere. Credit: European Space Agency /ATG medialab
    Question: Can the UK when outside of the EU, participate in the European Space Agency’s decision making ?
    Apparently yes.
    ESA has 22 Member States: Austria, Belgium, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Luxembourg, the Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland and the United Kingdom, of whom 20 are Member States of the EU.
    ESA has established formal cooperation with seven other Member States of the EU. Canada takes part in some ESA programmes under a Cooperation Agreement.
    Rem: Norway and Switzerland are not members of EU but pay hefty contribution to the EU for free trade agreement (same as UK does now /head of population) and have to agree to free people movement major reason for the UK’s Brexit.
    http://phys.org/news/2016-07-curious-case-earth-leaking-atmosphere.html

    • That’s right. The planet will dry out from Hydrogen loss, before the Sun expires, or so they say. What, me worry?

    • So if the atmosphere contains 5,500,000,000,000,000 tonnes of material we should be good for a
      looooooooooooong time.

    • https://cdn.eso.org/images/thumb700x/eso1624g.jpg
      This composite image shows the newly discovered exoplanet HD 131399Ab in the triple-star system HD 131399. The image of the planet was obtained with the SPHERE imager on the ESO Very Large Telescope in Chile. This is the first exoplanet to be discovered by SPHERE and one of very few directly-imaged planets. With a temperature of around 580 degrees Celsius and an estimated mass of four Jupiter masses, it is also one of the coldest and least massive directly-imaged exoplanets.
      This picture was created from two separate SPHERE observations: one to image the three stars and one to detect the faint planet. The planet appears vastly brighter in this image than in would in reality in comparison to the stars.
      Credit:ESO/K. Wagner et al.

  12. Mass from orbital projections and spectroscopic analysis of the stars. Estimates I am sure.

  13. At those distances, sizes, and magnitudes, calling it sunrise and sunset is a bit of a stretch. But this is still really cool.

  14. Very coolth, but a couple of thoughts. My Physics is more than 4 decades back so I could be wrong on the first…
    My understanding is, as soon as there are more than 2 bodies involved, orbital calculations become fuzzy – at best we can approximate. The level of certainty implies in the article concerns me.
    Second – for some time I have criticised the Standard Model of Cosmology. (SMC) Not only is it becoming ever more complicated, they keep being ‘surprised’ by Reality. That to me suggests something fundamental is wrong with the SMC. In Science, if you keep being surprised, it’s time to find a new hypothesis, not just keep adding ever more fanciful ‘magic’ to try to make it all work. e.g. at lest 3 times I recall Cosmology has found stars not only bigger than anything seen, but bigger than the SMC says they CAN be.
    Once more, reality surpasses the understanding of people determined to hold on to their theory at all costs.
    Kinda reminds me of the Church of AGW… 😀

    • Well when they find something new, they are seeing it as it is now or was when the light from it left to come here.
      If some theory says something can’t exist; they often mean such a system is not stable so it can’t persist.
      But all that means is we are watching it destroy itself.
      So estimates of the age are not necessarily WAGs. From what they know of the system parameters, they can probably simulate it on their play station, and see how long it takes to crash and burn from where it is in its death throes.
      So I’m guessing (real WAG) that’s how they deduced how old it is. seems as good an idea as any.
      G

      • We are talking about a near instantaneous two dimensional glimpse of something that may not be within our capacity to actually “model” confidently if we saw it close up for a century, as I understand the matter. It’s funding justification BS to me.

    • @Mark

      “Six by nine. Forty two.”
      “That’s it. That’s all there is.”
      “I always thought something was fundamentally wrong with the universe.”
      Narrator: There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
      There is another theory mentioned, which states that this has already happened.
      Douglas Adams

      Any questions?

  15. Why don’t they try solar power on HD 131399Ab? Looks a lot more promising than on Earth.

  16. Some people believe in Planet X still orbits the Sun and yet it has never been discovered.

  17. I read an Asimov (so) short story nearly 50 years ago. Think it was called Night Sky. About a planet with 3 suns and daylight all the time, never saw stars or darkness. Don’t think it’s physically possible but it was a neat story!

  18. “This unexpected observation suggests that such systems may actually be more common than previously thought.”
    The discovery of a single system of a given type suggests absolutely NOTHING about how common or otherwise it may be,

  19. astronomers have now found a planet in an even more exotic system, where an observer would either experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the seasons, which last longer than human lifetimes.
    The dwellers on this planet are continually obsessed and anxious about climate change.

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