New exoplanet too big for its stars

May 4, 2015

Credit ANU

By Phys.org

The Australian discovery of a strange exoplanet orbiting a small cool star 500 light years away is challenging ideas about how planets form.

“We have found a small star, with a giant planet the size of Jupiter, orbiting very closely,” said researcher George Zhou from the Research School of Astrophysics and Astronomy.

“It must have formed further out and migrated in, but our theories can’t explain how this happened.”

In the past two decades more than 1,800 (or exoplanets) have been discovered outside our solar system orbiting around other stars.

The of the latest exoplanet, HATS-6, is classed as an M-dwarf, which is one of the most numerous types of stars in galaxy. Although they are common, M-dwarf are not well understood. Because they are cool they are also dim, making them difficult to study.


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29 comments on “New exoplanet too big for its stars

  • While stars and accretion disks form solar systems, that does not have to be the only type of formation or origin of orbits.
    In gravitational interactions with other planets of stars, planets can be flung out of solar systems and could end up near other small stars.

    We can see from Pluto and its moons, (and asteroids and comets) that if bodies are far from forces of strong gravitational bodies, they can drift together and go into close orbits, or even merge without heavy impacts.



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  • Guys, help me, please. I have to understand this, otherwise I’ll not sleep anymore. Just one question: what about the migration of planets? I mean, let’s suppose than tomorrow a giant star collapses into a black hole. The planets orbiting around it would be attracted towards the black hole, isn’t it? In theory they will be sucked in the black hole (this reminds me of ‘Interstellar’: it is since that movie that I wonder about planets orbiting black holes) but I suppose this is not always true. A distant planet could migrate inward, toward the black hole? In this case, its orbit should be like a spiral, right? How is it possible for a planet to stabilize on a new orbit around a black hole or, as in the case of the article above, on a star, without falling into it?



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  • If the Sun became a black hole right now, it would have no implications for the planets’ orbits at all. A gravitating mass M has a “Schwarzschild radius” proportional to M such that, if it were a black hole, its mass would be contained within that radius, anything that got that close would be unable to escape. However, at greater distances the usual inverse-square law for gravity is business as usual. The Sun’s Schwarzschild radius is 3 km; the Sun’s actual radius in practice is 700,000 km (hence it not being a black hole yet); Mercurcy is about 55,000,000 km from the Sun.



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  • In the past two decades more than 1,800 extrasolar planets (or exoplanets) have been discovered outside our solar system orbiting around other stars.

    It appears that during the formation of a star, small knots of left over material coalesce into planets. This is predicted by prevailing models. So if we have a 100 billion stars in the Milky Way, and most stars have a few planets, that’s a lot of planets. Time still to establish Asimov’s Foundation, as long as we don’t commit self induced extinction.



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  • Jos Gibbons is absolutely correct however I’d add this as well. One of the ways we know about black holes is the existence of stars orbiting nothing we can see. Stars are wobbled about the galaxy by nearby stars and can end up falling towards and orbiting around a black hole, when they swell at the end of their lives their outer gases can end up being sucked into the black hole, or if they have been flung near enough a black hole they can end up in it. Our sun however is not big enough to produce a black hole at the end of it’s life. But if it was we likely wouldn’t have to worry that far as the supernova preceding it would blast us to pieces anyway. As it is our planet will likely end up engulfed by our swelling sun as it reaches the end of it’s life. When it sheds its outer shells into space it will probably make a quite pretty planetary nebular like this one here



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  • Its about time we upgraded the Drake equation and rewrote it in terms of life we do understand and put in parameters for the probiotic physics and chemistry we do know about rather than the more hand-wavy probabilities it used.

    So we know a lot more about planet occurence rates and increasingly about planet types. Can we form ideas about the frequency of axis stabilising moons and the protective force field of a rotating metal core? Presence of watery commets? Feedstock elements seem not a problem but a thorium heated core driving plate tectonics to create acid hot black smokers are their alkaline cool white opposites? Can we define circumstances like sufficiently sustained high nutrient fluxes and constant enough temperatures that support the first endosymbiotic events with their hugely improbable thermodynamic hump?

    This is all being very narrow but the “like us” version of the equation as opposed to the single cell one is the most interesting. Simple life is a cert. But the careful conditions to create eukaryotes and support their capacity for teamwork is where the final time dependent bottleneck is.

    Maybe we just need to put a new equation out there on its own website perhaps and invite the learned to place their idea of the value of the parameters? Maybe here? An updated headline of intelligent civilisations, in the galaxy/universe could sit well on RD.net.



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  • -whew, I was | this | close to ignoring everything else you had to say

    😉

    —-//—-

    Good idea Phil. I’ve never been able to convince myself that we are the only builders in the universe.



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  • donnie86dc
    May 5, 2015 at 5:28 am

    Guys, help me, please. I have to understand this, otherwise I’ll not sleep anymore. Just one question: what about the migration of planets?

    Migration of planets within a solar-system is about planets interacting and swapping orbits etc.

    There is a link on the formation of our Solar-System and a hypothesis about interactions of Jupiter, Saturn, changing the orbits of the outer planets.

    https://astroclock2010.wordpress.com/cosmic-timeline-17/

    The orbits of planets and of moons change by interactions between their spin and their orbit due to tidal drag, or by resonances causing orbits to become elliptical, where they cross the paths of other planets and either collide or get deflected into a new position.



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  • donnie86dc
    May 5, 2015 at 5:28 am

    Just one question: what about the migration of planets? I mean, let’s suppose than tomorrow a giant star collapses into a black hole. The planets orbiting around it would be attracted towards the black hole, isn’t it? In theory they will be sucked in the black hole.

    As others have pointed out, if a star collapses and becomes a black hole, its mass does not change, so its gravity remains about the same. (The distribution of mass will be a little different).

    Where black holes come into planetary and stellar migration, is when binary star systems are spiralling into a black hole, and one of the stars (+ planets) is sling shot fired across, or out of the galaxy, as hyper-velocity a star, while the other falls into the black hole.

    https://www.cfa.harvard.edu/oir/sp/hypervel.html



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  • donnie86dc
    May 5, 2015 at 5:28 am

    Just one question: what about the migration of planets?

    Another way planetary orbits can be disturbed, is (particularly when galaxies collide) other stars can pass close to, or even through, solar systems, with their large gravity, deflecting the planets into new orbits or even ejecting them from the parent star’s system altogether.



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  • Nothing stimulates the science mind better than a curious discovery that doesn’t comply with our knowledge. Go forth and discover!



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  • Phil.

    Did you catch Prof Brian Cox’s Human Universe 3 part series. They explored the Drake equation with the increased knowledge they had at the time of the production. It’s very near the end of the third episode, (Caution – Aging Memory in action). The Drake equation suggests that the universe should be teeming with life.

    But they also overlaid the conclusions of the SETI work over a long period of time now, and found that Drake and SETI were at odds. If life is teeming, SETI should have heard something. The chilling conclusion to this piece that it’s possible we may be the only intelligent life in the universe. There may be plenty of slime, but we may be freaks. (My opinion) He then added the more chilling rider that if we are alone, and we are “probably” going to commit self extinction, we need a serious rethink on our place in time.



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  • I don’t know a lot about the cosmos but curious beyond believe. Maybe I’m thinking wrong but wouldn’t a star that’s in the stage of being a red giant, would have grown in diameter, to a size that would engulf the smaller planets and would appear that the outer planets (like those the size of Jupiter) is closer than expected? And the star would be cooler. Just thinking. Maybe we’re looking at a star system that’s at a much later stage than ours.



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  • wouldn’t a star that’s in the stage of being a red giant, would have grown in diameter, to a size that would engulf the smaller planets and would appear that the outer planets (like those the size of Jupiter) is closer than expected?

    A reasonable proposition. Maybe one of our regular science posters will help with this idea.



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  • Hi Josh,

    you have this mostly right. Our Sun when it goes to a Red Giant will engulf all the inner planets possibly even Mars. In terms of temperature the while there is fusion going on in the core the temperatures will similar at the core but because much of the mass over the life of the star has been turned into energy the star itself will have less mass and therefore less gravity to hold onto the gases that make up the star so it will swell in size (correct me if I’m wrong Alan). The surface temperature is a factor of how much energy being generated over the distance that energy is spread out. So in the case of the red giant the fusion still occurring at the centre (now fusing helium to carbon) will produce plenty of energy but due to the inverse square law the temperature (and therefore colour- hence red giant) will be cooler at the surface. Of course our planet will be inside it or ripped apart (not sure which) certainly the atmosphere would have been ripped off long before the earth was engulfed. Either way if there is still intelligent life about it would want to have moved off long before.

    As for how this would appear to another civilisation. Would Jupiter look like a hot Jupiter from another vantage point at then red giant phase of our Sun? That’s great thinking but I suspect not. The reason being that there are a number of methods of telling a red giant apart from a red dwarf. The spectral signature is different from memory as I don’t think red dwarves ever get to the stage of fusing helium to carbon. Also the mass is significantly different, while the temp is the same the brightness is different between red dwarves and red giants.



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  • To date SETI searches have been ludicrously 20th Century in concept, imagining advance civilisations producing interstellar communications to be like tune-in-able radio stations KDKA or 2LO.

    Hedy Lamarr produced a system far more likely to be used and only now despite its daily use on all our interconnected doodads, spread spectrum is only just impinging on the SETI community. We need to start guessing universal numbers, physical constants, prime numbers that might be the key to even detecting a signal is there.

    Nor do we have the faintest idea that radio spectrum electromagnetic radiation is the medium. It could be neutrino flux (hard to detect, but also hard to attenuate) from some as yet unimagined searchlight. It could be the phased modulation of two planets magnetic field by flux shorting in specific directions, netting very very long wave magnetic transitioning to electromagnetic signals but as steerable beams.

    A null result from SETI seems inevitable at the moment to me, so I completely disagree with Cox. Besides big powerful radio transmitters for home use are a very transitory phenomenon.



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  • “Where black holes come into planetary and stellar migration, is when binary star systems are spiralling into a black hole, and one of the stars (+ planets) is sling shot fired across, or out of the galaxy, as hyper-velocity a star, while the other falls into the black hole.”

    Hi, Alan4. I know very little about this subject. I get the concept of of how a “star+ planets might be sling shot fired across..the galaxy…” I’m confused about how it/they could be sling shot fired out of the galaxy.
    If the propelled star + planets left the milky way galaxy, where would they go? The distance to our nearest galaxy moving away from ours at increasing light-year speed would be too great for it to travel there. I also read that there is a massive stellar black hole at the center of each galaxy formed at the time the galaxy was formed. The milky way has a black hole at the center with a million times the mass of our sun but the size of only several million earths. The NASA article also said that black holes are too far from earth to gobble it up and do not “wander” in any event. When the sun explodes in a supernova, the article said, our sun would not have enough mass to form a black hole. (“The sun will never turn into a black hole. The sun is not a big enough star to make a black hole.”)



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  • Alan4, I think I read something that answered my question. Though galaxies are moving away from each other at accelerating rates -at the local level, regular gravitational forces are still strong enough to bring proximate galaxies together in interactive or colliding ways to form “clusters.” Tamara Davis explains: “Nevertheless, the cosmic dance continues. Galaxies that had been pulled together before the universe began accelerating still have the chance to collide. Collectively they form overdense patches of the universe in which gravity still reigns. In our neighborhood the Andromeda galaxy, our largest companion, is actually falling toward us, and we will have our first close encounter with it in just a few billion years’ time.” The formation of these clusters will be limited in membership like the passengers on a cruise ship (Tamara) as the gravitational force between galaxies or galaxy clusters weakens with the rapid expansion of distance between them. The local clusters will sail along separately with no affect on other clusters as they mutually move further and further apart until they exert no interactive gravitational force on each other at all. Lawrence Krauss says that in several billion years no observer on earth will be able to see another galaxy, outside our own Milky Way (and Andromeda etc.??), or observe the background radiation -any evidence- for the big bang. We’re simply lucky, he says, to be born at the right time with the advanced science and tuned equipment to catch this phenomena while they are still close enough to us. (I’m certain there is considerable qualification and controversy regrading the science, I’ve roughly tried to summarize.)



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  • Melvin
    May 6, 2015 at 11:28 am

    Hi, Alan4. I know very little about this subject. I get the concept of of how a “star+ planets might be sling shot fired across..the galaxy…” I’m confused about how it/they could be sling shot fired out of the galaxy.

    Any that reach galactic escape velocity will eventually leave the galaxy if nothing gets in their way.

    If the propelled star + planets left the milky way galaxy, where would they go?

    They would not need to go “anywhere in particular”, – just into inter galactic space. and the hyper-velocity star and its hyper-velocity planets would not necessarily stay together while doing so.



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  • Melvin
    May 6, 2015 at 11:28 am

    The NASA article also said that black holes are too far from earth to gobble it up and do not “wander” in any event.

    The black hole at the centre of the Milky-Way does not “wander” in relation to its orbiting stars, but the whole galaxy is wandering in response to the gravity of other nearby galaxies such as Andromeda.

    In addition to this the are small satellite galaxies with their own black holes, orbiting the the Milky Way, and probably some black holes orbiting within it! There are also other smaller galaxies “nearby” (on galactic scales)!

    http://en.wikipedia.org/wiki/List_of_satellite_galaxies_of_the_Milky_Way



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  • David R Allen
    May 5, 2015 at 9:10 pm

    Phil.

    Did you catch Prof Brian Cox’s Human Universe 3 part series. They explored the Drake equation with the increased knowledge they had at the time of the production. It’s very near the end of the third episode, (Caution – Aging Memory in action). The Drake equation suggests that the universe should be teeming with life.

    http://rationalwiki.org/wiki/Drake_Equation

    The problem with the Drake Equation, is that several of its variables are unknown.

    It is also worth looking at the original, and the Sagan up-grades, because some people jump to the conclusions they see through rosy or murky spectacles, and misquote the Drake equation!



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  • I think there is some merit in acting as if we are the only self aware intelligent life form in the universe and hoping we’re not. If I can find Prof Cox video clip of just this section where he deals with the Drake equation and SETI results, you will see the argument he makes, which I can’t replicate in here.



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  • Darn, lost a biggish post.

    David, I think its just Drake in this one.

    But not only do I think Cox wrong on SETI (the absence of evidence proves nothing here) but I also think his ideas of the implausibility of advanced life are increasingly out of date. We can see, given planetary make ups like thus and so, how life can readily form, (Andreas Wagner and Nick Lane) and how, given high nutrient fluxes and stable enough conditions (Lunar rotational axis locking, photosyntheic bacterial thermostats,) endosymbiosis can happen, against the thermodynamic hump, enough times and the eukarya then formed gang up like Spanish castells; Cambrian explosions of complex life may be the simple result of more planetary attributes (Infra Cambrian ice age ending) or chemistry such that oceans become clear, unleashing a photo-sensitive/vision-based evolutionary arms race.

    We shan’t experience contact, though, except deliberately from the most advanced of civilisation and we haven’t the faintest idea that these are even possible.



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  • Melvin
    May 6, 2015 at 12:23 pm

    Alan4, I think I read something that answered my question. Though galaxies are moving away from each other at accelerating rates -at the local level, regular gravitational forces are still strong enough to bring proximate galaxies together in interactive or colliding

    Various projections and animations have been done on the collision of the Milky-Way and the Andromeda Galaxy.

    http://www.quora.com/What-will-happen-when-the-Milky-Way-Galaxy-and-Andromeda-Galaxy-collide



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  • There is no such thing as an orbiting body which is “too big”.

    Sizes vary from galaxies orbiting each other , binary stars orbiting each other, planets with planet size moons, right down to dust particles and ice crystals forming rings around planets, or dust clouds orbiting asteroids and comets.



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