back to article Science non-fiction: Newly spotted alien world bathes in glow of three stars

A newly discovered planet is wedged in-between three stars and experiences triple sunrises and sunsets every day, according to new research published in Science. The planet, HD 131399Ab, is 340 light years away from Earth and can be found in Centaurus constellation – one of the largest constellations in the sky. "HD 131399Ab …

  1. Youngone Silver badge

    Am I missing something?

    TFA says the planet and two smaller stars all orbit the large star, and the image caption says the same thing, but the image seems to show the two smaller stars orbiting a common centre with the large star while the planet orbits the large star alone.

    I'm sure I've missed something here.

    1. Ragequit

      Re: Am I missing something?

      Well the graphic is a 2-d representation of something that is 3-d. I'm guessing that the twin-stars aren't necessarily on the same elliptical orbit as the planet? Though that's gotta make for some extra weirdness when they are nearest the primary star. It seems to me it would be nothing approaching stable. But what do I know?

      Stranger is the notion of how life would evolve on such a planet if it was given the time to. Life that didn't depend on a day-night cycle would be most likely. Though I suppose a 140 year dormant/hibernation cycle might be possible. Though the opposite is a possibility. Life that flourishes only during the almost constant day. It might only get warm enough during these periods of constant day?

      Intelligent life with an evolutionary means of hibernating during interstellar flight? Space vampires.

      1. Vic

        Re: Am I missing something?

        Space vampires.

        On a planet with a 140-year constant daytime?

        They're not going to like that...


    2. Bryn Jones

      Re: Am I missing something?

      Yes you are. The star on the right of the image is 2 stars very close together. I guess the object with the red orbit is infact the huge gas giant exoplanet.

      1. Charlie van Becelaere

        Re: Am I missing something?

        Thank you - I wasn't noticing the double star on the right either.

        Brings up both Heinlein (Double Star) and Peter Pan / James T. Kirk ("first star on the right ....")

        1. Sir Runcible Spoon

          Re: Am I missing something?

          Please tell me they've named it Helliconia.

          I wouldn't like to be an astrologer in that system.

    3. DJO Silver badge

      Re: Am I missing something?

      You've not missed anything, just they've simplified things a bit.

      Look up "barycentre"

  2. Vladimir Plouzhnikov

    Three body problem

    The question is - whether anyone by any chance has sent a message in the direction of that system. Cause if they had - we're in for a lot of trouble...

  3. JeffyPoooh

    Define: Stable

    " simulations showed that the system they modelled was stable, but little changes meant it 'could become unstable very quickly.' "


    1. Myvekk

      Re: Define: Stable

      They probably had a much better description, but after it was dumbed down by/for general press release/reporters, we end up with that sort of thing.

      "The suspect was alive until he was killed." sort of thing.


      "Homicide victims rarely talk to police." Really?

      "Statistics show teen pregnancy drops off significantly after age 25." Ya think?

      And hard to go past: "Death is nation's top killer"

      1. Swarthy Silver badge

        Re: Define: Stable

        The probably used the word "Metastable" and when asked "What does that mean" they answered: "It's stable for now, but a small change would make it unstable quickly" And that's what got reported.

        A house of cards is metastable, if nothing mucks with it, it will stand indefinitly, but a very small change (bump the table, wind blows, anything more energetic than a harsh look...) and it becomes unstable (falls) and then very stable (heap o' cards).

    2. Anonymous Coward
      Anonymous Coward

      Re: Define: Stable

      The orbital configuration of this system will be stable if the orbit of the planet is in resonance with the orbit of the two close binary stars. However, if the orbits were not in resonance then this configuration would very quickly come apart.

      For this particular arrangement of stars and planet[s] there will be relatively few possible configurations where the orbits are in resonance but many possible configurations where they are not so, whilst resonant configurations, once established, are to a degree, self-aligning, it would still only need a relatively small change in the configuration to break the resonance (this is from the modelling point of view; the authors aren't suggesting that the system may actually become unstable).

  4. Anonymous Coward
    Anonymous Coward

    Liu Cixin was right!!

    Clearly this sci-fi author was very prescient about the future - much like Arthur C. Clarke and Star Wank Trek.

    Batten down the hatches!! The aliens are coming to eat us.

    1. 's water music

      Re: Liu Cixin was right!!

      well at least the Chinese have already built the world's largest radio telescope so now we have the trisolaran's coordinates we can get on with the transmission

    2. Anonymous Coward
      Anonymous Coward

      Re: Liu Cixin was right!!

      Clearly this sci-fi author was very prescient about the future


  5. POSitality

    One to read...

    Isaac Azimov's "Nightfall" :)

    Icon? Read the novel!

    1. James 51

      Re: One to read...

      I am trying desperately to remember the line about the sky being filled with stars but keep running into B5 episode guides.

      1. VinceH

        Re: One to read...


        (That's the short, not the Asimov/Silverburg novel)

        1. Pedigree-Pete
          Thumb Up

          Re: One to read...

          Thanks VinceH. I'm now going to have nightmares of a world where it's always light and probably bloody hot. There are no stars and no sleep and no dreams. PP

          Bloody good read tho' Shame I can't use more than 1 icon.

        2. Pedigree-Pete

          Re: One to read...

          Oh wait VinceH, Have one of these too. PP

  6. PleebSmasher


    So we have a planet more massive than Jupiter, super young (super hot?). If it has satellites, they could be tidally heated by the planet. The system is also exposed to light from 3 stars, albeit far-away stars.

    Now this configuration doesn't seem like enough to make the conditions for life better than say, Europa. But perhaps there are other binary/triple star systems with an enlarged habitable zone due to the additional solar energy hitting planets.

    1. Torben Mogensen

      Re: habitable?

      From the orbit of Pluto (which is a similar distance to our sun as this planet is from its main star), our sun just looks like a very bright star. The two other stars are even further away, so there is very little light indeed.

      It is plausible that the planet is still somewhat hot, since it is only 16 million years old, and it is possible that tidal heating might warm some moons. But there is little chance that life has had time to evolve: Initially, the planet would be too hot for life, so if it has the right temperature for life now, it has only had that for a couple of million years, which is probably not enough. The moons are not much better off.

      There are much better candidates for life among the known exoplanets.

    2. Richard Wharram

      Re: habitable?

      Only the most hardened Geordies in T-shirts out on the 'toon' could possibly consider this place habitable.

  7. Winkypop Silver badge

    Triple sunrises!

    To coin a new phrase:

    Busier than a rooster on HD 131399Ab!

  8. John Mangan

    Where did the 16 million year planetary age come from?

    Is it concluded from the composition on the stars?

    1. Vladimir Plouzhnikov

      Re: Where did the 16 million year planetary age come from?

      And is it legal to take revealing pictures of a planet under the age of 18, anyway?

      1. Francis Boyle

        Re: Where did the 16 million year planetary age come from?

        Legal? It's fine if you put in on page three of The Three Suns.

    2. cray74

      Re: Where did the 16 million year planetary age come from?

      Is it concluded from the composition on the stars?

      Identifying the age of stars and planets works by several techniques. A summary is presented at wikipedia, which includes the two techniques I wrote up in this reply before finding wiki's summary page. :)

      One method is that you can look at a star's neighbor's for a rough idea. If the star's in a cluster, are there fresh, bright blue stars? Those don't live long, so if they're present the cluster and specific star is probably pretty young. The same goes for stars of other ages and colors - blue-white, white, and yellow stars may have lifespans less than that of the universe, so you can set bounds on the age of a cluster by their presence or absence. A cluster of only red dwarfs is probably old. Presence of absence of stellar remnants like white dwarfs or neutron stars is also somewhat indicative of age. Many clusters also scatter with time, so looking at the scatter of a cluster can give some ideas about age of cluster members.

      There's a pretty strict relationship between stellar lifespan and stellar mass so if you get a good estimate of stellar mass - maybe the star has a companion or you have a good idea of its absolute luminosity - the door is opened to a lot of techniques for age estimation. For example, stars gradually brighten during their time on the main sequence (hydrogen burning stage of life), so knowing mass and brightness tells you the stars age. Similarly, "gyrochronology" just demonstrated the ability to estimate a star's age by its spin and mass: stars' spins slow down with age.

      There are a few other features that help: protoplanetary disks don't last long, for example. If you see one, then it's a young system.

      Planet ages would normally be estimated by the age of the star if you couldn't land a probe on the planet and do some radioactive dating like Apollo did for Luna. However, in this case the planet IS visible and several useful facts are known about it:

      1) Its mass is 4 Jovian masses. That means it is not a brown dwarf and thus never had deuterium fusion in its core.

      2) It's quite far from its bright primary, far enough that its would be Pluto cold

      3) It's quite far from the pair of dwarf stars, far enough they add no supplemental heating

      4) It's hot as hell

      While the Kelvin-Helmholtz mechanism (energy release by gravitational contraction) flopped in attempting to explain the sun, it does give some idea about the age of a planet since the heat released drops with time. It helps to know the amount of sunlight falling on it (so you can subtract that and figure out just the K-H heat release) and the mass of the planet (so you can crunch the K-H equation). Knowing this planet's mass, distant orbit, and high temperature allows you to guess this planet is young and freshly formed, still radiating huge amounts of heat from its gravitational collapse.

  9. Anonymous Coward
    Anonymous Coward

    Its the planet from Pitch Black

    I wonder what nasties might come out when it finally gets dark after 140 years of constant sunlight?

  10. David Pollard

    Dr Kildare!

    Can't get the theme song out of my head now.

    Link for those who missed this enthralling series:

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