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Glimpsing Our Solar System’s Future

The star L2 Puppis (HD 56096), a red giant in the direction of the southern constellation Puppis (the Poop Deck), is the subject of interesting new investigations using data from the ALMA array in Chile. The star appears to belong on the asymptotic giant branch of the Hertzsprung-Russell diagram, a category dominated by highly evolved cool stars. The new study sees L2 Puppis as an analog for what our own Sun will become in billions of years. Thus Ward Homan (KU Leuven Institute of Astronomy, Belgium):

“We discovered that L2 Puppis is about 10 billion years old. Five billion years ago, the star was an almost perfect twin of our Sun as it is today, with the same mass. One third of this mass was lost during the evolution of the star. The same will happen with our Sun in the very distant future.”

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Image: Composite view of L2 Puppis in visible light | © P. Kervella et al. (CNRS/U. de Chile/Observatoire de Paris/LESIA/ESO/ALMA).

But L2 Puppis is more than just an interesting glimpse at what our Sun could become. It also offers a view of the fate of our own planet in the form of what may be an exoplanet discovered orbiting the star about 300 million kilometers out. Because as the Sun eventually moves into the red giant phase and grows more than a hundred times larger than it is today, Mercury and Venus will be destroyed, but the Earth may just hang on as a rocky core eventually orbiting a white dwarf. How the red giant phase affects planets in a system is what the L2 Puppis study is all about. Will a future Earth survive, and will it, as seems likely, be lifeless?

Asymptotic giant branch stars are undergoing a transition from red giants into the white dwarf remnants they will leave behind, meaning there is extreme loss of mass through a strong stellar wind. The resulting white dwarf at L2 Puppis should be about the size of the Earth, though compressed to the point where a single teaspoon weighs 5 tons. Stars like this also go through extreme changes in brightness and temperature, but studying the effects of these changes on their planetary systems is tricky because the planets are becoming embedded in a late-phase circumstellar envelope that can obscure observation.

At a distance of just over 200 light years, the circumstellar dust disk surrounding L2 Puppis is seen almost edge-on. The new work has allowed astronomers to arrive at a mass estimate for the star that, when adjusted through evolutionary models, shows it to have had a mass very similar to the Sun when it was on the main sequence. At 10 billion years old, the star also shows signs of a companion that, based upon its estimated mass is either a planet or a low-mass brown dwarf now accreting material from the star’s stellar wind.

It’s too early to call this a planet because the researchers have no firm lower limit on its mass, but this is an interesting object with an orbital period of about 5 years. From the paper:

From its observed properties, L2 Pup and its companion emerge as a plausible analog of the solar system at an age of approximately 10 Gyr. It provides a view on the complex interactions occurring between a solar-type star entering the planetary nebula phase and its planetary system. The companion could also play an important role in the shaping of the bipolar envelope of L2 Pup and subsequently of the planetary nebula…

So we’re learning more about the complex interactions involved when a star at this phase of its life undergoes the changes that will eventually lead to its becoming a white dwarf. Future observations both at ALMA and with the European Extremely Large Telescope (now under construction in Chile’s Atacama Desert) should offer a further window into these processes.

The paper is Kervella et al., “ALMA Observations of the nearby AGB star L2 Puppis,” published online by Astronomy & Astrophysics 8 December 2016 (abstract / preprint).

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Comments on this entry are closed.

  • Bruce December 12, 2016, 14:28

    A planet or BD in a 5 year orbit of a solar (future) analog? Sounds Jupiter-like, does it not?

  • FrankH December 12, 2016, 15:54

    @Bruce – Except the planet/BD would have had a shorter period/been closer in when L2 Puppis was on the main sequence – the star has lost a fair amount of mass since then.

    • Bruce December 13, 2016, 0:33

      Yes, that’s right. Also I had gotten jovian period crossed with its distance. (About 12 earth years & 5
      au from sun.)

  • Michael December 12, 2016, 16:34

    If you look closely it lools like there is a connection between the star and object via a red gas stream, BD’s have powerful magnetic fields due to high rotation rates and could funnel material towards itself.

  • Geoffrey Hillend December 12, 2016, 17:45

    Yes

  • DCM December 12, 2016, 17:55

    We gotta get outa here.

  • GatorALLin December 12, 2016, 19:32

    Just a friendly reminder that we have about 1.7 Billion years or so before our sun heats up enough to boil off all our oceans and water… then will expand out and deep fry every living organism to death at the 9 billion year mark or maybe sooner. Lots of time of course to venture out to Mars or change our DNA to survive in deep space, or just invent the next AI or robot hybrid that can keep going. I am glad we still have some time to figure things out…. maybe this is just one of many great filters ahead for us to bypass…

  • Gerry December 12, 2016, 22:00

    Does the similarity to our Sun extend to the metallicity of the star? If so, would that be statistically exceptional, given the extreme age of the star? As I understand it, Sun-like metallicity would be an intriguing result with respect to questions about what kinds of planets and–who knows–life, might have been able to arise in the L2 Puppis system eons ago.

  • Phil Tynan December 13, 2016, 4:17

    At 2.43 AU orbiting a red giant around two thousand times as luminous as the sun, any exomoons of the giant planet would get around 390 times Earth’s current insolation, so obviously they’d not be candidates for any analogue of terrestrial-life. But what of planets further out?

    As an evolved Solar analogue star, I’d expect (hope) there to be some Neptunian Ice Giants and a host of KBO analogues. It’d be interesting to speculate on the nature of the thawed KBO’s. Depending on the star’s original mass – and Jim Kaler’s article on L2-Puppis implies it could be anywhere between 1 and 3 solar masses – L2 Puppis might have undergone a Helium Flash a little over a billion years after it left the Main Sequence, which would probably have substantially modified the composition of the primordial atmospheres/cryospheres of any KBO’s (assuming they are like the small bodies in our system, possessing little in the way of a planetary magnetic field). Interestingly, Stern in 2003 suggested worlds like Pluto and the nearer KBO’s will be in the liquid water habitable zone for many millions of years after the Helium Flash. The increased insolation would probably create saturated water vapour atmospheres. Water vapour is a potent greenhouse gas, so I would speculate that the duration of the habitable period might(?) be substantially prolonged, with all the interesting effects on prebiotic organic chemistry that would imply.

    As a red giant slowly cools down from its thermal maximum, the habitable zone will migrate inwards and stabilize for some hundreds of millions of years as it occupies the long-lived Horizontal Branch stage. Potentially with better telescopes we might be able to see the remains of worlds around L2-Puppis like a warmed-up Titan where prebiotic chemistry developed further than it has in the Solar System (and maybe, if Lorenz and McKay were right…we might see the remnants of a 200K water-ammonia ocean under a methane greenhouse…maybe even nonequilibrium chemistry, either from early developing endogenous life or the result of an in-system panspermia from an Earth-like world now long since gone). Jim Kaler states L2-Puppis has a low-velocity solar wind (which, I gather, may be typical of early-stage Mira variables) which may bode well for preserving traces of these sites.

    I’d like to add L2-Puppis to the JWT watch list (lol).

    Phil Tynan

  • Andrew Palfreyman December 13, 2016, 5:01

    We have probably 800 million years or so before things start getting uncomfortable. If we’re still in the neighbourhood and nostalgic enough, and still growing our tech abilities, we could use sunshades to extend that grace period. We could also start pushing Earth slowly outwards too. Of course, there’s no telling what sort of tech we’d have almost a billion years hence. But if we can imagine it now, in this our relatively primitive state, it’s surely possible in the future to save Earth for a very long time – billions of years.

    • H. Floyd December 13, 2016, 14:05

      800 MY, or 800 PPM.

    • Bruce December 13, 2016, 14:33

      Slowly expanding Earth’s orbit to keep this jewel of a planet in the sweet spot of our sun’s HV seems very logical IMO.

      I’ve read that this could be done by redirecting an object of the right mass into an orbit that aproaches both Earth and Jupiter, thereby gravitationaly towing Earth further from the sun as it warms. (I’m new to this site. Has this ‘move the Earth’ concept been discussed here?)

      • Paul Gilster December 13, 2016, 16:18

        Yes. Check “Moving (and Saving) the Planet”:

        https://centauri-dreams.org/?p=1765

        and you might also find the article “Moving Stars: The Shkadov Thrust” interesting:

        https://centauri-dreams.org/?p=29579

        • Bruce December 14, 2016, 1:09

          Thanks Paul, and great website btw. Your “Moving (and Saving) the Planet” piece was great as were some of the comments it generated. Something like this does definately seem doable. Otoh the Shkadov star mover seems like mission REALLY imposible. How could such a system handle getting hit by strong CME events at close range?

          • Paul Gilster December 14, 2016, 9:29

            I don’t know about the CME issue in relation to Shkadov thrusters — good question! Let me see what I can dig up about this.

  • Michael December 14, 2016, 2:42

    To move the planet we could dismantle Mercury with its abundant energy and materials or Mars or even the Moon.

  • Michael December 14, 2016, 16:23

    I don’t think we will mourn the end of our star as it will give off vast amounts of element and compounds. We can collect these with powerful magnetic fields, enough for 30 000 earth masses!

  • ljk December 15, 2016, 10:09

    Has everyone here forgotten about Dyson Swarms/Shells/Spheres:

    http://www.orionsarm.com/eg-article/4845fbe091a18