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Astronomers: Companion planets increase chance of finding life in older star solar systems

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Companion planets increase life chances?/Rory Barnes, U Washington

Not that we have ever been confirmed as finding a single live cell anywhere but planet Earth but, as ScienceDaily explains:

Planets cool as they age. Over time their molten cores solidify and inner heat-generating activity dwindles, becoming less able to keep the world habitable by regulating carbon dioxide to prevent runaway heating or cooling.
But astronomers at the University of Washington and the University of Arizona have found that for certain planets about the size of our own, the gravitational pull of an outer companion planet could generate enough heat — through a process called tidal heating — to effectively prevent that internal cooling, and extend the inner world’s chance at hosting life.

The outer planet is necessary, Barnes added, to keep the potentially habitable planet’s orbit noncircular. When a planet’s orbit is circular, the gravitational pull from its host star is constant, so its shape never changes, and there is no tidal heating.

And so, the researchers conclude, any discoveries of Earth-sized planets in the habitable zone of old, small stars should be followed by searches for outer companion planets that might improve the inner world’s chance at hosting life. More.

File:Moon nearside LRO.jpg

Based on our present experience, wouldn’t a large moon do just as well?  Maybe we should discuss that more.

We actually don’t even know how life got started on Earth. See The Science Fictions series at your fingertips (origin of life) for a quick. handy guide to why.

Meanwhile, …

Abstract Earth-scale planets in the classical habitable zone (HZ) are more likely to be habitable if they possess active geophysics. Without a constant internal energy source, planets cool as they age, eventually terminating tectonic activity. Planets orbiting low-mass stars can be very old, due to the longevity of such stars, so they may be rendered sterile to life in this way. However, the presence of an outer companion could generate enough tidal heat in the HZ planet to prevent such cooling. The range of mass and orbital parameters for the companion that give adequate long-term heating of the inner HZ planet, while avoiding very early total desiccation, is probably substantial. We locate the ideal location for the outer of a pair of planets, under the assumption that the inner planet has the same incident flux as Earth, orbiting example stars: a generic late M dwarf (Teff = 2670?K) and the M9V/L0 dwarf DEN1048. Thus discoveries of Earth-scale planets in the HZ zone of old small stars should be followed by searches for outer companion planets that might be essential for current habitability. – C. Van Laerhoven, R. Barnes, R. Greenberg. Tides, planetary companions, and habitability: habitability in the habitable zone of low-mass stars. Monthly Notices of the Royal Astronomical Society, 2014; 441 (3): 1888 DOI: 10.1093/mnras/stu685

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4 Replies to “Astronomers: Companion planets increase chance of finding life in older star solar systems

  1. 1
    johnspenn says:

    Conversation with an atheist on ET life-

    Me: I’m curious as to if you have any sense of what motivates this “overly optimistic” attitude that seems to be so pervasive in today’s culture, including the scientific culture. Any thoughts? Why do those in question seem to be so eager to find extra-terrestrial life, to the point of making such “overly optimistic” and scientifically unfounded claims?

    Atheist: Likely because optimism drives discovery. The more a person hopes to find something, the more motivated they become to create new tools and technologies for that search. These tools, themselves, lead to an expansion of knowledge and fuel further optimism.

    Me: If you’re right, I’m curious as to which “expansion of knowledge” in particular has added fuel to further optimism that there must be extra-terrestrial life. Any ideas?

    Me: To elaborate, SETI has thus far received NO evidence of ETI whatsoever. The more scientists study abiogenesis, the more they realize how improbable and rare (unique?) the event seems to be. The more we learn about our universe and earth’s place in it (ie in the Goldilocks zone), and all of the factors that make earth habitable, the more improbable finding another “just right” planet seems to be. Where has any of our knowledge expanded in a way that would cause us to be more optimistic of ET instead of more skeptical of the same, given the evidence before us?

    Atheist: crickets….

  2. 2
    mahuna says:

    Um, in order to tug the interior of the planet enough to cause any measurable heating of the surface, I’m guessing this would have to be something like Mars as a companion to Jupiter.

    And if both planets are in highly elliptical orbits, the companion will get close enough to move the “home world” perhaps once a YEAR??

    And I can’t imagine that this is a stable situation for anything like 500 million years. Either the companion will simply suck the “home world” in and swallow it. Or the companion will nudge it just a bit too much and send it on a death spiral into the star.

    And the effects on the SURFACE of this planet would be terrible. Tides 1,000 feet high in whatever oceans and lakes might form. And assuming the planet has continental plates (one of those MANY necessary attributes of “habitable”), a gravity bulge would create continuous earthquakes (um, Zeta Reticuli quakes?), again making any advanced form of Life impossible.

    But I get the idea that the Saganites are so desperate that they consider “pond scum” to be “advanced life”.

  3. 3
    velikovskys says:

    johnspenn:
    Me: If you’re right, I’m curious as to which “expansion of knowledge” in particular has added fuel to further optimism that there must be extra-terrestrial life. Any ideas?

    The abundance of planetary systems detected by Kepler on just a small slice of the sky comes to mind. That is one of the parameters in Drake’s equation I believe

    The more scientists study abiogenesis, the more they realize how improbable and rare (unique?) the event seems to be.

    Since they don’t know how it happened, the probabilities are unknown

    The more we learn about our universe and earth’s place in it (ie in the Goldilocks zone), and all of the factors that make earth habitable, the more improbable finding another “just right” planet seems to be.

    That seems to fly in the face of the fine tuning argument, a fine tuned universe with only one speck of life? The previous argument for the rarity of life used to be that planetary systems were rare, this argument has been refuted. As for habitable zone planets,12 have been confirmed so far.

    where has any of our knowledge expanded in a way that would cause us to be more optimistic of ET instead of more skeptical of the same, given the evidence before us?

    See above an atheist might say.

  4. 4
    VunderGuy says:

    @velikovskys

    “That seems to fly in the face of the fine tuning argument, a fine tuned universe with only one speck of life?”

    Ummm… yeah. A finely tuned universe and a universe with only one speck of life are logically compatible. Hell, a finely tuned universe with only one speck of life makes the strongest case for a finely tuned universe, so I don’t know what you’re getting at here.

    “The previous argument for the rarity of life used to be that planetary systems were rare, this argument has been refuted. As for habitable zone planets,12 have been confirmed so far.”

    Don’t they still have to pass like a few dozen more tests though?

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