Exoplanets survive their star's fiery death. Or were they born from it…?

By Phil Plait | October 22, 2010 10:42 am

nnserpentisIt’s kind of amazing that with nearly 500 planets discovered orbiting other stars, we’re still finding ones that are really weird. Massive planets orbiting so close to their stars they are practically plowing through the stellar atmosphere; hot spots on the planet not aligned with their stars; planets orbiting so far out it’s a struggle to understand how they got there.

And now we can add the planets NN Serpentis c and d to that list.

Lying about 1500 light years from Earth, NN Ser is a binary star — most stars in the sky are part of multiple systems, so that in itself isn’t all that odd. But NN Ser is weird: it’s a very dinky red dwarf orbiting very close to a white dwarf. And by very close, I mean really close: they’re separated by only 600,000 km (360,000 miles), which isn’t much farther apart than the Earth and the Moon!

The planets

I’ll get back to the stars in a sec. The planets found (named c and d because the two stars are a and b, according to the naming conventions) are Jupiter-scale beasts, with masses of about 6 and 2 times Jupiter’s, orbiting the binary stars at a distance of roughly 825 and 450 million km (500 million and 270 million miles).

Those numbers don’t seem too odd; lots of planets have been found with similar characteristics. But when you take a closer look at the system…


The stars

Let’s go back to the stars. They orbit each other very rapidly: a complete orbit only takes about 3 hours! So those stars are really hauling. As it happens, the orbit is seen almost edge-on from here on Earth, so we literally see the stars pass in front of each other twice per orbit. That’s pretty cool, because it means that over a short time we can watch lots of eclipses and get really good statistics on how long the eclipses last, what the time period is between them, and so on. What the astronomers found is that the period of the eclipses is very slowly changing, and the best explanation is that of the two planets tugging on the stars as they orbit.

This turns out to be an incredibly difficult thing to measure; in fact a possible planet was reported just last year for this system, but the parameters for the planet didn’t fit more recent data. These new results for two planets are based on more data and analysis, and look pretty solid to me.

The bizarre history of NN Ser

Where things get really weird is when you look at the stars, or more specifically, the white dwarf. These are dense balls of compressed material left over when a star like the Sun dies. As it ages, a star like this will turn into a red giant, swelling up to hundreds of times its current size, and blow off vast amounts of material. Over tens of thousands of years or more, it loses mass, shedding its outer layers. Eventually, all that’s left is the core of the star, a hot compact object we call a white dwarf.

So that one star in NN Ser must have once been a star like the Sun which swelled up, blew off its material, then became a white dwarf. But wait a second… when it was a red giant, it was probably a hundred million kilometers across! But the other star in the system, the red dwarf, is only a few hundred thousand kilometers away. How does that work?

Almost certainly, the red dwarf used to be millions of kilometers or more away from the primary star. When the more massive star turned into a red giant, it would have literally engulfed the dwarf. Through friction, the red dwarf would’ve spiraled in, getting closer and closer to the core of the star. Eventually, when the bigger star blew off its outer bits, what was left was that white dwarf, and the red dwarf in its current, extremely tight orbit. It sounds incredible, but we’ve seen this happen before, and may be a relatively common occurrence in the Universe.

But hang on again! What about those two planets? How did this affect them?

Well, that’s a bit of a poser. There are two scenarios. One is that they formed along with the stars long ago, and somehow survived this cataclysm. However, this strikes me as pretty unlikely. When the primary star went red giant and started blowing off matter, it was losing mass, and therefore its gravity got weaker. That means its hold on those planets would’ve gotten more tenuous, and they would have migrated outwards. This in turn means they would’ve been much closer to the star in the past. But we know the red dwarf is there, and while it’s a dinky star, it’s far more massive than a planet. It’s very hard to see how planets could be in stable orbits so close to such a massive object. Models show they’d be ejected from the system relatively quickly.

That makes it unlikely they formed with the two stars. That leaves the second scenario: they formed after the primary star turned into a red giant!

That’s pretty weird, too. But some models suggest that as the red dwarf spiraled into the core of the red giant, a massive disk of material would form around it. This disk could then be the raw material from which the two planets were formed. That seems fantastic to me as well, but look: we have two planets orbiting a very tight binary star where one is a white dwarf and the other is red dwarf. Something weird must’ve happened here! The real choice is to pick which is the least bizarre.

The view

Whatever happened, we’ve got what we’ve got: two planets orbiting this weird binary. Now imagine you’re standing on one of those planets (well, since they’re almost certainly gas giants, imagine you’re standing on the surface of one of their moons). Look up. What would you see?

From the inner of the two planets, the two stars would be a bit less than a tenth of a degree apart; about 1/5th the width of the full Moon. You’d be able to see them as separate stars. The red dwarf would barely resolve itself as a disk; it wouldn’t look like just a dot in the sky. The star is far less luminous than the Sun, but would still shine about 20 times brighter than the full Moon on Earth. In other words, if it were the only object in the sky you could read by it, and looking at it would make you squint a bit.

The white dwarf, on the other hand, is tiny: only about 30,000 km (roughly 20,000 miles) across. It would be a dot in the sky from that distance. However, it’s so hot that it shines more brightly than the Sun does, and from that inner planet would be about half as bright as the Sun appears to us from the Earth. It would be an intense pinprick in the sky, a brilliant dot that would be very painful to look at. In fact, it would drown out the red dwarf completely, shining thousands of times more brightly.

What an incredible sight that would be! If alien life developed on a moon of one of those worlds, the only way they’d know of the existence of the red star would be due to the eclipses. Every 3 hours and 7 minutes, the primary star would suddenly disappear for a few minutes as the bigger but far less massive and bright star blocked it out. At that time, and pretty much only then, would the faint red star be visible at all.

Cultures all over the Earth worshiped the Sun for obvious reasons: bringer of light and heat, we depended and still depend on it. What sort of myths would have arisen had the Sun’s light been completely cut off a half dozen times a day?

And I have to wonder what other strange things await us as we discover more planets orbiting other stars. We have a pretty good idea of how stars age and die, but there will always be systems on the edge, ones we’ll have a hard time understanding. What new things will we uncover then? And what would the sky look like from those alien worlds?


Related posts:

Gallery of exoplanet images: real pictures of alien worlds
Sunburned star turns hot face away from star
Star: Om nom nom! Planet: Aiieee!
Dying beautifully in a crowd


CATEGORIZED UNDER: Astronomy, Cool stuff, Top Post

Comments (60)

  1. Man that is just a brain teaser and a great story. I would love to hear more on this as we figure it out.

  2. Chief

    Going with the second option, the material from the red giant would be captured into orbits (defined by the red dwarf) and form the two planets. At this stage, what would the likely elements be. I guess the gas giants would be absent of any rocky material and composed entirely of gas. Do you think enough solid material could be present at this time to form moons?

  3. Keith Bowden

    Such a bizarrely cool concept!

  4. I wonder whether that red dwarf was originally just another planet (a Hot Jupiter, that is) that sucked up a lot of gas form the expanded enveloppe of the red giant precursor of the white dwarf…

  5. Reading the story, a thought struck me (this may actually be rather stupid, but I’m going to share it anyway). Mentioning the friction that slowed the red dwarf and brought it’s orbit closer and closer to the larger star, it struck me that before this process took place, the now red dwarf may have been a brown dwarf or large gas giant planet and by passing through the atmosphere (heliosphere, astrosphere?) of the dying star may have picked up enough mass graviationally to become a red dwarf star.

    Does anyone know if this remotely approaches a realistic scenario?

  6. Chris A.

    Just to be clear: Is the distance you quote between the star and white dwarf (600,000 km) center to center, or surface to surface? When they’re that close, it matters!

  7. @4 and 5 – Hey that’s a good question. I didn’t even think about that. Seeing as this is a bizarro system in the first place. Perhaps that isn’t out of the question?

    That’s truly fascinating. Fact is stranger than fiction time and time again.

    I did some really rough math and I got that the dwarf is clocking in at something like 200+ miles a second. I could be off but well, my math seemed decent enough. :) Wow, just wow.

  8. FabianWilcox

    Reminds one of “Nightfall” by I. Asimov.

  9. amstrad

    Effing NN Serpentis, how does that work?

  10. Chris

    Amazing that the accuracy is good enough that a few second difference can revel the presence of two planets.

  11. gopher65

    4 and 5, that’s an awesome idea. I wonder if a small star like a red dwarf would put out enough energy to blast away any in-falling material from the red giant as it spiralled inward? If so, then it might not have gained a significant amount of gas during its near death spiral.

  12. Rick W.

    With all of the unusual planetary systems being discovered, what’s the possibility of a binary star system with a life supporting planet in a figure 8 orbit around both stars. Oh, and, could that be a stable system?

  13. Jason

    That is a very strange system. I had thought conventional wisdom is that Binary systems like that could not support planets. Obviously if we detect the planets then we are wrong, but still fascinating.

  14. andy

    There are a handful of circumbinary planetary systems known: another one similar to NN Serpentis is HW Virginis, which consists of a red dwarf and an sdB star (short for subdwarf-B) with two orbiting giant planets. sdB stars are basically the cores of red giants which have had their outer layers removed, in the cases of NN Ser and HW Vir probably by gravitational interaction with the companion stars, and they evolve to become low-mass white dwarfs. HW Vir therefore looks something like a younger version of NN Ser. It is expected in both cases that the systems will become cataclysmic variables, where the white dwarf accretes matter from the companion red dwarf. Another planet-host system, DP Leonis is already in the cataclysmic variable stage of its evolution, so it seems that planetary systems can survive the various insults that binary star evolution can throw at them.

    As for whether the planets formed with the star system or formed as second-generation planets from material ejected from the white dwarf progenitor, one thing to note is that they are likely in resonant orbits (this probably also is the case for the HW Vir system). This suggests they migrated in a disc of material, as it is unlikely that orbital evolution without a disc would bring them into resonance. Such a disc would tend to stabilise the orbits of the planets, so first-generation planet formation cannot be ruled out. If primordial, the planets may have originally been significantly less massive and then accreted further material from the white dwarf progenitor.

    As for other possible cases of second-generation planets, there is Gliese 86 Ab, which orbits in a binary system consisting of a K-dwarf and a white dwarf, with a semimajor axis of only 20 AU. The white dwarf progenitor was initially more massive, and also in a closer orbit (mass loss expands the orbits). This is an extremely unfavourable environment for forming giant planets around the secondary star, so perhaps second-generation planet formation can explain its existence.

  15. AJ in CA

    Wow, so many fascinating questions brought up! I’ve also been fascinated by the idea of an ancient brown dwarf accreting enough matter from a Wolf-Rayet star or or red giant to finally make the leap to star status.

  16. JoeSmithCA

    That’d be fun to model the terrain of a rocky world orbiting the stars close enough for life. Imagine the lighting and how things would look like at various times of day and night. Imagine what a moon orbiting the planet would look like as the light from the stars changed. Cool…

  17. Pat

    Apparently, in that system, Apophis is a lot more energetic.

  18. Grimbold

    “Cultures all over the Earth worshiped the Sun for obvious reasons: bringer of light and heat, we depended and still depend on it. What sort of myths would have arisen had the Sun’s light been completely cut off a half dozen times a day?”

    What else do we know that is absolutely vital to life and pulsates regularly? I think the obvious myth that would spring up around a star like that is that it’s the heart of God beating.

  19. Awesome post!

    But isn’t the planet around Pollux at a similar distance to these ones?

  20. Trucker Doug

    I love having my mind blown and my universe expanded. This accomplished both in spades. Incredible stuff. The universe truly is stranger than we can imagine.

  21. Brian Too

    @13. Jason,

    The stellar mechanics descriptions say that, while most combinations of planets and multiple star systems are unstable, there are 2 that work.

    First, you have this type of deal. Two stars in a tight orbit. The planets orbit both stars much farther out. As a result the planets experience one combined gravity well, with no variations big enough to eject them from their orbits.

    The second is positionally reversed. One star has planets orbiting it reasonably close in. There’s a second star orbiting the star/planet combo, but it’s way far out. The net result is that the peripheral star experiences a combined gravity well from the inner star/planet combo, with no perturbations.

    Any other orbital arrangement is unstable and results in catastrophe for the planet(s). They usually leave the star system but collision with one of the stars is possible too.

  22. SysKoll

    Imagine this scenario: The two planets were initially at a reasonably large distance from the stars and survived the formation of the red giant.

    When the larger star ejected its material, it could have formed a relatively dense hydrogen cloud around the star. In particular, the cloud could have englobed the orbits of the two planets, causing them to lose kinetic energy through friction (drag). The planets thus started spiraling down, scrubbing off hydrogen from the cloud on their way. Eventually, stellar wind and initial speed moved the cloud far away from the stars so that friction disappeared.

    Is this a plausible scenario?

  23. Crudely Wrott

    What an incredible sight that would be! If alien life developed on a moon of one of those worlds, the only way they’d know of the existence of the red star would be due to the eclipses. Every 3 hours and 7 minutes, the primary star would suddenly disappear for a few minutes as the bigger but far less massive and bright star blocked it out. At that time, and pretty much only then, would the faint red star be visible at all.

    Wow! Light tides.

    The tides of earth’s oceans brought on by the moon (mostly) may well have played important roles in the development of life on this remarkably comfortable speck. I am wondering about the affects of a cyclic light cycle on same.

    Has the thought occurred to anyone else?

  24. Gunnar

    Wow! What an intriguing system! Is there any reasonable probability that the current state of that kind of binary system could have been stable long enough to have permitted the evolution of life on one or more of the moons of the large planets now associated with it (assuming, of course that at least one of those planets were in the “goldilocks range” or that other factors such as tidal or other interactions between the planet and its moons provided just enough additional heating to permit the existence of liquid water on one or more of its moons). What a wonderfully interesting scenario that could be! I would be surprised if this possibility did not inspire at least one of the more imaginative science fiction authors to create a story or novel set in that kind of scenario. If I had the requisite writing skills, I would probably try write one myself!

  25. Messier Tidy Upper

    Astonishing, superluminous news about one of the strangest and most remarkable ewxoplanetary systems I’ve yet heard of & very well written up as always – Thanks Bad Astronomer. :-)

    Some great comments and ideas here from others too; incl. esp. (#23) SysKoll, (#18) Grimbold, (#14) andy (great mention of Gliese 86 Ab hand’nt heard of that ‘un – cheers! :-) ), (#7) Lewis, (#5) Meng Bomin & (#4) Bynaus. Some excellent thoughts there. 8) :-)

  26. Gunnar

    @Rick W., #12

    I don’t have any idea whether a life bearing planet in a figure 8 orbit around two binary stars could be stable, but I remember reading a quite humorous science fiction story years ago with that scenario. I don’t remember the title or the author, though, and the story seemed to be very much “tongue in cheek.”

  27. Messier Tidy Upper

    @ 19. Lab Lemming Says:

    Awesome post! But isn’t the planet around Pollux at a similar distance to these ones?

    See via Kaler’s Stars website :

    http://stars.astro.illinois.edu/sow/pollux.html

    Pollux b or ‘Polydeuces’ (from an alternative name for the star & mythological hero) is in a circular 590 day (a bit over a year and a half) orbit 1.69 AU from Pollux and weighs in at triple Jupiter’s mass. Polydeuces is located in the equivalent position of between just beyond Mars in our solar system but with its giant orange sun bathing it in 16 times the solar radiation and looming six times larger in its skies, this superjovian world and any of its moons are – beyond much reasonable doubt – currently uninhabitable. If still amazing and fascinating places! :-)

    BTW. Pollux is the brightest star in our sky hosting a confirmed exoplanet. Pollux (Beta Geminorum) is the 17th brightest star in our sky (apparent magnitude~wise) just pipping Fomalhaut which is the 18th brightest star and also hosts an exoplanet – although a recent comment here in another thread apparently casts some doubt on whether Fomalhaut b exists despite it being imaged!

  28. Gunnar

    @#21, Brian Too or Phil Plait

    Are the stars in the Alpha Centauri system too close to each other to permit any planets with stable enough orbits to support life as we know it?

  29. Messier Tidy Upper

    @ ^ Gunnar : No. They’re far apart enough that either or both stars of the Alpha Centauri duo* could safely host planets – although at distances that extend only up to the equivalent of a bit beyond Mars in our solar system. :-)

    Ken Croswell had a very good article discussing the prospects of planets and life there “Does life exist at Alpha Centauri” in the April 1991 issue of ‘Astronomy’ magazine if you can find a copy.

    In it Croswell notes :

    “Celestial mechanics shows that stable orbits definitely exist around either [Alpha Centauri] star – provided the planets lie no further from their star than one-fifth the closest distance the two stars ever get to each other. Since A and B get as close as 11 AU, this means that each star could have planets with stable orbits out to a distance of at least 2 AU. … Therefore Alpha Centauri A and B could each have four planets with orbits just like those of the inner solar system.”

    – Page 36, Ken Croswell, Astronomy magazine, Kalmbach Publishing, April 1991.

    Note here that Mars orbits at 1.5 AU and Ceres at 2.8 in our solar system.

    —————-

    *Proxima Centauri which may be part of the Alpha Centauri system as well could also have exoplanets orbiting it.

  30. Gunnar

    @Messier Tidy Upper

    Thanks for answering my question. I have long been intrigued by the possibility that one or both of the main stars in that system could have at least one planet with intelligent life on it. If we lived in a system like that, what a tremendous incentive that might be to develop space travel, especially if we had convincing evidence that the companion star also had a life-bearing planet! :)

    And thanks for the reference to Ken Croswell’s article. I will definitely have to look that one up!

  31. Messier Tidy Upper

    @ ^ Gunnar : No worries, my pleasure. Me too! :-)

    I’d love for Babylon 5 to be right about there being a Centauri alien species although I think we could do without the Shadows! ;-)

    (Yeah, I know, the fictional B5 Centauri are too humanoid by far to be at all likely, but still .. )

    Incidentally, sources and reading matter~wise, there was a great study conducted by Rand corp’s Stephen Dole – twice – both with and without Isaac Asimov too which is well worth reading if you can find it somewhere :

    Dole, Stephen, ‘Habitable planets for Man’ Santa Monica: Rand Corporation report, 1964.
    Dole, Stephen, & Asimov, Isaac, ‘Planets for Man’ New York, Random House, 1964.

    Whilst Isaac Asimov also wrote a book on Alpha Centauri as well which I’d thoroughly recommend despite being a tad out of date :

    Asimov, Isaac, Alpha Centauri, The nearest star, Lothrop, Lee & Shepard Company, 1976.

    BTW. The BA also posted this article :

    http://blogs.discovermagazine.com/badastronomy/2008/03/07/theoretically-alpha-centauri-should-have-planets/

    back in March 2008 discussing the likelihood of planets around Alpha Centauri based on a study by a team of astronomers including Javiera Guedes and Greg Laughlin. They used computer simulations to see how planets could form in the Alpha Cen system specifically.

    They did what’s called a Monte Carlo test, running the simulation over and over again with slightly different input parameters every time (like, disk density, composition, and so on). Remarkably, what they found is that they got a terrestrial (rocky) planet about the size of Earth orbiting Alpha Cen B every single time, and in many cases was at the right distance from the star to have liquid water.

    Source the BA blog post linked above.

    Plus, natch, Jim Kaler has also got a good webpage on Alpha Centauri here :

    http://stars.astro.illinois.edu/sow/rigil-kent.html

    Albeit under its alternative lesser known name of Rigil Kentaurus. Other obscure proper names for Alpha incl. Toliman and Bungula – and if exoplanets are one day found for Alpha Cen then I’d like to suggest those old star names be applied to those planets. :-)

  32. BoringJoe

    Just imagine if the Star Wars or Star Trek franchises understood the scope and depth of stories that could emerge from this. Imagine if they included factors like atmospheric conditions (instead of Star Trek’s lame Class M excuse), dust / gas storms, regular eclipses, varying gravity, and so on in their plots. That would make for some really brilliant special effects. Even MMORPGs designed based on variations in these, rather than on cosmetic variations in background scenery, would make the games much more interesting.
    His Liarship, President Obama could make a new “Revive Science” project an become a hit with the younger generation. Heck, even the Chinese/Japanese can do all this.

    Instead, we geeks sit around making 1000s of versions of the same stupid web software, keep watching the same stories in Star Wars, and so on.

    Astronomy can give more science-based thrills to even Joe Sixpack than soaps give cheap thrills to girls.

    You’re doing a great job putting the ideas out in text format. But imagine, what if someone could rent an Amazon Cloud slice and create visuals based on the text we write here.
    I remember feeling a great humbling wonderment while watching the first shot of dinosaurs in the first Jurassic Park movie. I felt the same watching Naboo, Coruscant, and Tatooine. The grand spaceships in ID4 were fantastic. The last shot (zooming out) of Men in Black – where some big aliens play around with galaxies as marbles. The floating mountains and connected planet-mind of Pandora are fantastic.

    That’s the kind of effects you can get with properly simulated exoplanets and moons, with the variety of atmospheres, gravity, lighting effects, and so on.
    That kind of stuff gets kids hooked to science for life.
    Not F=ma and E=mc2. That is as drab as studying Egyptian cave paintings would be for Joe Sixpack.
    I hope Discovery, Lucas, Pixar, or Cameron are thinking on these things. Second Life would also be a great place to start this right away, but the plots must be scientific. The DoD / Army burns a lot of big money on simulations and projects that are thrown away eventually. If that money came to such projects, imagine the transformative power.

    People would actually love science. Even if someone from MIT picks this up, it would be successful, but the MIT guys would not figure out how to make it attractive. You need Pixar or Cameron or Roland Emmerich for the real polish.

    Man, how I wish these guys would work together with each other, like we do in open source (or don’t, if you work on Linux distros or hang around Wikipedia ;-) )

    It’s an opportunity sitting there to be exploited and looted.

  33. Wesley Parish

    The thought struck me, while reading the comments – is there much chance the non-explosive star in such a binary system – the red dwarf in this case – could’ve had enough of a gravitational focusing effect on the outflow of the red giant’s atmosphere, so as to force a gas/dust disk’s formation?

    Most of the knowledge we have of the outflow of dust and gas from an exploding star, comes from the planetary nebulae, and they have distinct hourglass shapes – they also tend not to have binary partners. But the gravity well of a smaller star in a close binary orbit should, if my memory serves me correctly, serve several functions – one, it’d slow some of the gas/dust outflow down while accelerating the rest; two, it would channel that slowed-down outflow into an equatorial orbit; and three, it’d give it quite a bit of turbulence, sufficient to cause clumping, and thus the nuclei of jovians …

    Does my memory serve me right?

  34. DF2

    Truth is far more stranger than fiction…..there you go.

  35. greylion

    As long as most people consider gravity to be the only force at work in this system (and the universe), all guesses to what’s going on here, are going to be way off.

    Hint: Electric Universe
    http://www.holoscience.com/synopsis.php?page=1

  36. greylion

    Sorry, duplicate comment.

  37. greylion (37): Ah the Electric Universe, which doesn’t work at all. Seriously. Time to move on, guys.

  38. RockDoctor

    Several comments on a great article on an even greater (and weirder!) star system :

    @6 : distances would be centre-to-center (pick a side of the Atlantic ). More strictly, they’d be barycentre-to-barycentre, because in such a system the fluid red dwarf may well be significantly non-spherical. The Moon is nearly spherical, but it’s distribution of mass is noticeably non-spherical, and this star is certainly going to be more fluid than that.

    @8 (and others) – very “Nightfall” indeed.

    @13, 21,30 (stability of planets around binary stars) I recall that in the late 1990s Paul Weigart (of “Cruithne” “fame”, at a Canadian university) did a study on the general stability of planets around binary stars. If I can find a link … It’s on ADSABS http://adsabs.harvard.edu/full/1997AJ….113.1445

    Really intrigued about the Monte Carlo simulations that say that the Alpha Centauri system should/must have planets. Got some reading to do!

  39. Denver7M

    Phil,
    Is there any chance that the white dwarf was actually a rogue loner and was captured in this system after the planets were already formed? I don’t know any of the science behind this really but as you were describing this system, I kept thinking that maybe they didn’t form in the same space, from the same stellar nusery, you know. Maybe the white dwarf was thrown out of the system it was native to and wandered around till it was captured by mututal gravitation with the star it is now a binary to? Is that possible?

  40. andy

    @Denver7M: that is highly unlikely: close stellar encounters of that kind are very rare outside globular clusters. Cataclysmic variables and their progenitor systems (like NN Serpentis) are far too common for capture to be a plausible formation mechanism and in addition we can see examples of progenitor systems. There are currently 3 known planetary systems around cataclysmic variables or their progenitors (the others are DP Leonis and HW Virginis), all located within a few hundred parsecs which is far more frequent than you’d expect from the capture mechanism. Furthermore capture would tend to be disruptive to the planetary system, you wouldn’t expect to find two planets in a resonant configuration after the event.

    The other circumbinary planetary system, PSR B1620-26 (a binary composed of a millisecond pulsar and a low-mass white dwarf) may be an example of capture but it is located in a globular cluster where close encounters between star systems are much more frequent.

  41. Gunnar

    @#33, MTU

    Thanks again for the additional references. I found the first one by BA to be particularly interesting. I somehow missed seeing that one before.

    I have probably already read Asimov’s book about Alpha Centauri before (there are few books by him that I haven’t read or at least glanced at). I’ll have to look it up again. Most all of his books are well worth more than one read, especially his non-fiction works (though he is also one of my all-time favorite science fiction writers). As you probably know, Arthur C. Clarke (another one of my favorite science fiction writers) also wrote a lot of good, hard science fact books. Are you familiar with the Asimov-Clarke pact in which Asimov acknowledged that Clarke was the worlds best science fiction author and the world’s second best science fact author, and Clarke acknowledged that Asimov was the world’s best science fact author and the world’s second best science fiction author?

  42. Both Asimov and Clarke are great sci-fi writers. My personal favorite is Larry Niven. Indeed, let’s start building a starship – so we can at least send probes out closer to some of these fascinating solar systems.
    My guess is, if there’s intelligent life near the binary system described herein, it would be highly mutable in its thinking. In other words, frequent changes in their suns would flip flop their way of thinking – as opposed to having one sun which would have a steady influence.

  43. katwagner

    Mmmmm! The first time I stared at the sun I was just a little kid on a New Jersey beach. So while Phil’s story unfolded, I saw myself on that beach staring at the red dwarf and the white teeny tiny dwarf and they’d go around each other and the waves were crashing and I was looking at sea stars- anyway I read this post last night and what a great bedtime story!

  44. Messier Tidy Upper

    @^ Katwagner : Staring at the Sun? That’s not so advisable eyesight~wise. :-o

    Also I think for this particular close binary only one of the stars can be seen as the other is drowned out by the other’s light.

    But it’s a nice thought & Niven is another of my fave authors too. :-)

    @43. Gunnar Says:

    I have probably already read Asimov’s book about Alpha Centauri before (there are few books by him that I haven’t read or at least glanced at). I’ll have to look it up again. Most all of his books are well worth more than one read, especially his non-fiction works (though he is also one of my all-time favorite science fiction writers).

    Agreed. Isaac Asimov is one of my favourite authors ever & a literary hero of mine along with Arthur C. Clarke & Robert Heinlein plus add for astronomical non-fiction Patrick Moore & Jim Kaler! :-)

    Yes, I’m aware of the Clarke-Asimov treaty although frankly, IMHON its a tie! ;-)

  45. Jim Starluck

    Man… that conjurs one hell of a mental image. Imagine what that must have looked like as the main sequence star expanded: the red dwarf would start plowing through its outer layers, slowly moving deeper and deeper, ejecting plumes of stellar material–so vast they’d make a solar flare look like a hiccup in comparison–spiraling off into space…

    I would be fascinated to see a computer simulation done to figure out exactly what that would’ve looked like.

  46. Messier Tidy Upper

    @ ^ Jim Starluck : Yes – a computer simulation of the view would be awesome. I second that request! :-)

    @45 Katwagner :

    <blockquoteAlso I think for this particular close binary only one of the stars can be seen as the other is drowned out by the other’s light.

    Yes, the BA writes in the original post above :

    The white dwarf, … … would be an intense pinprick in the sky, a brilliant dot that would be very painful to look at. In fact, it would drown out the red dwarf completely, shining thousands of times more brightly. If alien life developed on a moon of one of those worlds, the only way they’d know of the existence of the red star would be due to the eclipses. Every 3 hours and 7 minutes, the primary star would suddenly disappear for a few minutes as the bigger but far less massive and bright star blocked it out. At that time, and pretty much only then, would the faint red star be visible at all.

    Mind you, that doesn’t mean there anre’t many other star systems that are similar but where both a red dwraf and a white dwarf partner aren’t visible together in the sky. (Eg. More widely separated stars, less brilliant white dwarf*, etc ..) So I’m sure there’d be some worlds with such marvellous views out there! 8)

    Sorry if I sounded mean earlier – had to rush off & type quickly.

    —-

    * The White Dwarf sun here will gradually get less luminous as it ages and cools down too so given enough millions or billion of years, it should reach a state where it no longer overpowers the red dwarf. Furthermore, the red dwarf sun may (I’m not sure but its highly probable) flare up and get much, much, brighter at times. ;-)

  47. Todd

    There was no need for an elipsis in the title….

  48. Patrick

    With some 22 years of data (including a 7 year gap without observations) it is impossible to prove that there is a periodic signal with a period of 15 years. One needs at least 2 complete and preferably 3 cycles. I don’t have another explanation for the period changes, but two planets orbiting where they shouldn’t, is not really a good explantion either. Next year’s data may well be incompatible with this hypothesis, as were the recent data with last year’s prediction of a third body.

  49. réalta fuar

    The odds of these planets being “second-generation” are just about zero (all kinds of things wrong with that scenario, we’re not talking about a pulsar here). They almost certainly evolved normally in the disc around the close binary, then migrated in during the red giant phase of the primary. Gas drag can easily win out over mass loss so planets can migrate OUT or in during a star’s evolution off the main sequence. So, they didn’t have to have been in resonance orbits before the primary became a red giant (and planetary nebula) as they could have evolved into resonance afterwards.

  50. Messier Tidy Upper

    “Imagine M-dwarf [red dwarf] bathing on a beach and having your star suddenly – with no warning at all – become ten times brighter.”

    Source : Pages 30-31 “The Faintest Stars” article by James B. Kaler in ‘Astronomy’ magazine, August 1991.

    Wonder what the presence of the white dwarf so near this red dwarf does to its magnetic fields and consequent starspots and flare activity?

  51. Glaisne

    What exactly is the material that makes up the white dwarf. What elements are it composed of. How does the white dwarf shine if not through nuclear fusion?

  52. AJ in CA

    @Glaisne: In my understanding, a white dwarf is the final state of a star with roughly sun-like mass that has exhausted its fuel and gone through the red giant phase.
    Ultimately it contracts until it can’t contract any further (at this point it has lost some of its original mass, and is not massive enough to overcome electron pressure and shrink down to a neutron star). This compression heats its surface again, and its surface area is so small that it takes billions and billions of years for it to cool off. Theoretically, white dwarfs will eventually cool down enough to become “black dwarfs” – essentially huge balls of gas, depleted of hydrogen (and helium, depending on the mass of the star) – it’s thought that the universe is not yet old enough for any white dwarfs to have reached this stage, yet. A white dwarf contains all the elements that were created through fusion, such as oxygen, neon, and carbon, as well as whatever metals existed in the cloud that it first coalesced from.
    It’s a bit of confusing terminology, because “red dwarfs” and “white dwarfs” differ in more ways than just coloration. A white dwarf is the hot and slowly cooling “corpse” of a star, while a red dwarf is a very low-mass star that’s still “live” (fusing hydrogen). Red dwarfs burn their fuel so slowly that first-generation red dwarfs (some of the first stars to form in the universe) would still exist, and continue to do so for a very long time.

  53. andy

    @Glaisne: same reason every star shines: because they are hot. Heat something up enough and it will begin to glow red, heat it further and it glows yellow, then white, then blue. It doesn’t matter why the object is hot, it only matters that it is hot.

    The reason the Sun is hot and the reason a white dwarf is hot are different though: the Sun’s temperature is a result of energy being produced by nuclear fusion reactions in its core. The white dwarf is hot because it was once the core of a giant star and hasn’t managed to cool down yet.

  54. AJ in CA

    @Messier: IIRC, Larry Niven wrote a story about a tidally locked planet orbiting a red dwarf, and the life that lived in the “twilight zone” near the terminator between the light and dark sides of the planet. I think the story was called “Flare Time”. It addressed how different life forms had evolved the means to hide from the sun during flares.

    IIRC, the book was a collection of short stories called N-Space. It also had a really fun one called “Night on Mispec Moor” about a planet with a local life form that essentially caused the recently dead to rise as zombies and attack the living :)

    Eh, sorry to bring science fiction up in a blog about science fact, but IMHO, sci-fi is great fodder for thought experiments that may one day turn into real experiments.
    Except the zombie one. Hopefully :)

  55. TripCyclone

    I know it doesn’t seem like much to some of you, but this little tidbit is exciting to me. In the main article BA linked to near the beginning of this post, it mentions “Many of these Texas observations were in large part facilitated by George Miller…” I thought I’d add a note of pride here as about seven years ago, George was a middle school student who was participating in Science Olympiad. As a member of the local astronomy club, a request came in asking for some help in teaching George and another student some basic astronomy for the “Reach for the Stars” event that year. While he got some assistance attending a star party, I went to the school to help them, using a Starlab portable planetarium. When a notice went out about this recent news from his father, I contacted the father and confirmed that it was the same kid. Seems the extra help both from myself when visiting the school and his visit to a star party helped spur his interest in astronomy as a career path.

    I also told his father that this was the first time I had worked with Science Olympiad, and it was one of the reasons I became an assistant coach for Science Olympiad at the middle school I teach at now. As a teacher, it’s always great when you get to hear about how your efforts positively influenced a student. Especially when they get to be involved in exciting research such as this.

  56. Dennis

    What program is used to build these models to test star formation over time? More to the point, is there a commercial version I can “play” with?

  57. amphiox

    re #4,5 and other replies to them;

    The minimum mass for a red dwarf star is about 80J (it’s the minimum mass for hydrogen fusion in the core), while a hot Jupiter planet would have a mass between about 0.5 to 13J, and a brown dwarf would be anywhere from about 13J to 70-80J.

    So for a planet to gain enough mass to become a red dwarf star would require quite a lot of mass gain. Not sure if there would even be enough material in the outer atmosphere of a red giant along the pertinent orbital paths to be sucked up for that to happen. It would be more likely with a big brown dwarf.

    (Must say that the actual transition, when the formerly dark object finally ignites fusion and starts to produce it’s own visible light, would be hell of an interesting thing to observe in real time, assuming a method existed to do so against the glare of the red giant star!)

  58. amphiox

    What exactly is the material that makes up the white dwarf. What elements are it composed of. How does the white dwarf shine if not through nuclear fusion?

    A white dwarf’s composition will depend how big a star it was before (which determines how many rounds of fusion it will get done before fusion ceases). Small ones will be mostly helium, while larger ones will have a lot of carbon or oxygen.

    White dwarf’s shine entirely from the heat of their final core collapse, I think, so they will gradually cool down and get dimmer as time passes.

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