Kapteyn b, Habitable Zones, and Using Our Brains

Some scientists say that a star's habitable zone may be wider than we thought. Others found a planet that's only a few times more massive than Earth, nearby: and about 11,500,000,000 years old.

1. Rubber Bands, Planets, and Elastic Friction
2. Kapteyn b: Super-Earth in a Habitable Zone
   • Planetary Systems: There's Much More to Learn
   • Years, Days, and Spin-Orbit Resonance
   • Searching the Sky, Looking Ahead

I like living in a vast and ancient universe.

Not all Christians feel that way: but since I'm a Catholic, I don't have to reject what we've learned since the days of Copernicus.

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Copernicus and Newfangled Ideas

Nicolaus Copernicus lived during the Renaissance. He was a physician, classics scholar, translator, governor, diplomat, economist: and held a degree in Canon Law.

These days, he's probably best-known as a mathematician and astronomer: and someone whose book got banned.

Considering what was going on in his day, it's mildly remarkable that his "De Revolutionibus" didn't get blacklisted until six decades after publication.

The 16th century was a lively era. The Protestant Reformation was getting hijacked by northern princes, and starting to worry some entrenched officials in Rome. Barbary pirates were raiding the French coast. The Ottoman empire had taken Belgrade and Rhodes, before its defeat at the Siege of Vienna. Pope Gregory XIII issued the Gregorian calendar: which was controversial for centuries.

The point of that history lesson is that newfangled ideas, and threats of a lethally physical nature, were sprouting like mushrooms. It's a wonder that a book saying the sun goes around Earth, despite what we read in Joshua 10:13 didn't stir up more trouble, sooner.

Poetry isn't Science

Galileo's abrasive personality, stress from the tumultuous events of the 16th through 19th centuries, and mistaking poetry for science, put Copernicus' "De revolutionibus orbium coelestium" on the "Index Librorum Prohibitorum." ("List of Prohibited Books") My opinion.

"De revolutionibus" went on the "Index Librorum Prohibitorum" in 1616. It had company, like Kepler's "Epitome astronomiae Copernicanae:" put on the Index in 1621. Both were removed in 1835. Interestingly, Charles Darwin's books never got 'blacklisted.' The "Index Librorum Prohibitorum" was finally put on the shelf, metaphorically speaking, in 1966.

I'm very serious about my faith, with a convert's enthusiasm. I look for the "nihil obstat" in a book's front matter: sometimes. It's a statement that the book doesn't contain objectionable material about "questions of religion or morals." (Code of Canon Law, Book III, Title IV, 824, 832)

Looking for the "nihil obstat" in a book of prayers makes sense: expecting to see it in a physics textbook doesn't.

Instead of kvetching about newfangled ideas, or insisting that knowledge of this creation threatens faith in a creating God — I'll speculate about what we might find. Or, more accurately, who we might meet.

Life in the Universe?

As I said two weeks ago, I don't think that we're alone in the universe: or that we are not alone. Right now, we don't know. (June 27, 2014)

If scientists find definite signs of life on another planet in the next few years, I'll be delighted. Even if it's no more than an unmistakable biosignature, or a fossil that's more nearly similar to familiar organisms than whatever's in the Allan Hills 84001 meteorite, we'd finally know that life is not unique to Earth. (April 11, 2014; October 18, 2013)

We've seen plenty of space aliens in movies: memory-sucking invaders; improbably-groovy saviors; and the usual assortment of rampaging monsters. Some of those screen dramas were moderately good entertainment, some weren't: the point is that they're entertainment.

I like a good story, but I think that if we do find people whose ancestors come from another planet: they won't be human. I've speculated about why we aren't hip-deep in the Galactic Federation equivalent of 50-gallon oil drums and six-pack rings, and what sort of folks we may find:

• "Life in the Universe: Where is Everybody?"
  Apathetic Lemming of the North (March 15, 2013)
• "Gods, Demons, and Used Spaceship Dealers"
  Drifting at the Edge of Time and Space (February 13, 2010)

Before getting to what tidal heating may have to do with habitability, and a planetary system with a 7,000,000,000-year head start on ours, I'll look for intimations of what forms intelligence might take in Earth's fossil archives.

Playing 'What If' With Fossils

(From D.W. Miller, via Smithsonian Institution/Smithsonian Magazine, used w/o permission.)
(Cambrian animals, including Anomalocaris, Hallucigenia, Wiwaxia, and Ottoia.)

Some of the animals buried in a mudslide 505,000,000 years ago, like the Burgessochaeta worm, are modestly familiar. Others, like that five-eyed — thing — with a probably-prehensile tentacle, are only vaguely similar to some of today's critters.

There may be a reason why nearly all largish animals on Earth have two eyes, two pairs of limbs, and a tentacle inside the mouth. Or maybe we're just one possible variation on a theme.

I've taken a look over the last half-billion years or so, to see what might have happened: but didn't.


(© Marianne Collins, via burgess-shale.rom.on.ca, used w/o permission.)
(Reconstruction of Yohoia tenuis, a Cambrian critter, by Marianne Collins.)

Yohoia looked a little like today's shrimp. This arthropod was small: no more than 23 millimeters long: just under an inch. But it had two 'arms' ending in four spikes that look a lot like stiff fingers.

Leanchoilia was a little bigger: about five centimeters, two inches, long. The odds are pretty good that it used those whip-like feelers at the ends of its arms to find food.

I've no idea how likely it is that animals like these would, over the course of a half-billion years, get bigger and smarter to the point that they'd be our analogues. But I don't see that it's impossible.

Tiny as they are, those almost-hands let me see them as looking a bit more like potential 'people' prototypes than the lobe-finned fish that came along later.

Earth's crinoids, like today's feather stars, are animals: but don't have much in the way of a nervous system. Maybe that's typical of all sessile animals: but maybe not.

Before the Permian-Triassic extinction event, about a quarter-billion years back, about two thirds of animals in Earth's ocean were sessile, like that fossil crinoid. After the Great Dying, we had a lot more animals that moved around.

Again, maybe that's a universal pattern of development: or maybe not. For all I know, this galaxy may be teeming with folks who spend their lives quietly anchored to a nice, safe seafloor.

All this is speculation, of course. We may be alone in the universe: or we may find that people throughout the universe bear an uncanny resemblance to Michael Rennie and Chris Hemsworth.

Using Our Brains

Whatever, and perhaps whoever, we find: I'm not concerned that we will learn 'things which man was not supposed to know.'

God gave us brains and a thirst for knowledge.

Studying this creation isn't a problem. (Catechism of the Catholic Church, 282-289)

Science and technology, studying this astounding universe and developing new tools, is part of being human. (Catechism, 2293-2295)

We can misuse either of these tools: but the problem is in ourselves, not in our tools. (Catechism, 397-401, 1849-1851)

I think refusing to take an interest in the handiwork of God is an odd way of showing respect.

Besides, as Pope Leo XIII pointed out: God, the source of all truth, created both the universe and inspired Sacred Scripture. We will understand what may seem like discrepancies — eventually, after we use our brains. "Truth cannot contradict truth." (Catechism, 159,2465, ; "Providentissimus Deus")

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1. Rubber Bands, Planets, and Elastic Friction

(From NASA's Goddard Space Flight Center, via Astrobiology Magazine, used w/o permission.)
("Planets in eccentric orbits can experience powerful tidal forces. A planet covered by a very thick ice shell (left) is springy enough to flex a great deal, generating a lot of internal friction and heat. Some terrestrial planets (right) also will flex, especially with partially molten inner layers."
(Astrobiology Magazine))

"Habitability: Friction in Orbit"
Aaron L. Gronstal, Astrobiology Magazine (July 15, 2014)

"NASA researchers have shown that friction could be the key to habitability on Earth-sized planets in treacherous, elliptical orbits. The study might have implications in defining the habitable zone around distant stars.

"Eccentric Heat

"A highly elliptical, non-circular orbit can be a dangerous route of travel for a small planet. It increases the odds that a celestial body will cross paths with another large object, or be pulled into and consumed by its host star. Planets in highly elliptical orbits also stand a chance of being ejected from the system entirely.

"However, the new study shows that, despite the added dangers, elliptical orbits could also provide a source of heat for small worlds and aid in their ability to support life. It all comes down to tidal heating.

"Tidal heating refers to the way in which an object is deformed as it passes close to a larger body and then moves farther away. It’s the same process that allows for a subsurface ocean on moons of giant planets – like Jupiter’s moon Europa. This 'flexing' of the world produces heat...."

Io, orbiting Jupiter in a track inside Europa's, experiences tidal heating, too. Its surface flexes by about 100 meters: which may not seem like much, but makes Io a remarkably volcanic moon.

I don't necessarily recommend trying this, but a Wikipedia page on rubber elasticity says that when you stretch a rubber band, and press it against you lips: you can tell that the stretching heated it. I'd think it's also a good way to get sore lips, if the rubber band snaps.

Getting back to planets and life in the universe: Looks like we'll have to refine definitions for stellar habitable zones again. These scientists say that tidal heating could warm up a planet with an orbit that's outside — or partly outside — the zone where water melts, but doesn't boil.

More about eccentric orbits and habitability:

• Circumstellar habitable zone
  Wikipedia
  Particularly
  • Other considerations
• "NASA Finds Friction from Tides Could Help Distant Earths Survive, and Thrive"
  NASA press release (July 8, 2014)
• "Earth-like worlds on eccentric orbits: excursions beyond the habitable zone"
  Darren M. Williams, David Pollard; International Journal of Astrobiology, 1 (1) (2002)
  (From http://courses.ncssm.edu/kolena/life/eccentricorbitplanets.pdf) July 16, 2014)

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2. Kapteyn b: Super-Earth in a Habitable Zone

(From Planetary Habitability Laboratory, University of Puerto Rico at Arecibo; used w/o permission.)
("Artistic representation of the potentially habitable exoplanet Kapteyn b as compared with Earth. Kapteyn b is represented here as an old and cold ocean planet with a network of channels of flowing water under a thin cloud cover. The relative size of the planet in the figure assumes a rocky composition but could be larger for a ice/gas composition."
(Planetary Habitability Laboratory))

"Oldest Known Potentially Habitable Exoplanet Found"
Abel Mendez Torres, Planetary Habitability Laboratory, University of Puerto Rico at Arecibo (June 3, 2014)

"The planets around the nearby red-dwarf Kapteyn's star are over twice as old as Earth

"An international team of astronomers, led by Guillem Anglada-Escude from Queen Mary University, reports two new planets orbiting a very old and nearby star to the Sun named Kapteyn's star. One of the newly-discovered planets, Kapteyn b, is potentially habitable as it has the right-size and orbit to support liquid water on its surface. What makes this discovery highly interesting is the peculiar story and age of the star. Kapteyn b is likely over twice the age of Earth and the oldest known potentially habitable planet listed in the Habitable Exoplanets Catalog.

"The Super-Earth Kapteyn b orbits the star every 48 days and has a mass at least five times that of Earth's. The second planet, Kapteyn c, is a more massive Super-Earth with an orbit of 121 days and too cold to support liquid water. At the moment, only a few properties of the planets are known: minimum masses, orbital periods, and distances to the star. By measuring their atmospheres with future instruments, scientists will try to find out whether some of these planets are truly habitable worlds.

"Kapteyn b is probably colder than Earth given a similar atmosphere. However a denser atmosphere could easily provide for equal or even higher temperatures. Based on its stellar flux (45% that of Earth's) and mass (≥ 4.8 Earth masses) the Earth Similarity Index (ESI) of Kapteyn b is comparable to Kepler-62f and Kepler-186f. Given its old age (~11.5 years), Kapteyn b has had plenty of time to develop life, as we know it...."

"Potentially habitable" is an important phrase here. All we've got, so far, about Kapteyn b and c are the planets' orbital data, and a pretty good estimate of how massive each is. Kapteyen b, for example, could be an airless world: or a mini-Neptune.

We've got a very good idea of how long each planet's year is, and how far each is from its star on average. But the scientists aren't sure about how eccentric their orbits are: whether they're nearly circular, like Earth's; or more obviously elliptical, like Pluto's or Mercury's.

Illustrations in the Planetary Habitability Laboratory article show somewhat elliptical orbits: which may turn out to be spot-on accurate, or not.

If Kapteyn b is a rocky world, like Earth; with a similar atmosphere; and plenty of water. If it's rocky, like Earth, it'll be as big as shown in that image: about 168% times Earth's diameter — but we don't know what Kapteyn b is made of. Not yet.

One thing that caught my attention about Kapteyn's planetary system is its age: about 11,500,000,000 years. Kapteyn's star and its planets had been around for roughly 7,000,000,000 years when the Solar system — and Earth — formed.

Our planet won't be that old for another 2,500,000,000 years, give or take.

Planetary Systems: There's Much More to Learn

(From Planetary Habitability Laboratory, University of Puerto Rico at Arecibo; used w/o permission.)
("Comparison of the relative size of the orbits and the planets of Kapteyn's Star and the inner planets of our Solar System. The two planets of the Kapteyn's star fit within the orbit of Mercury. Planets are magnify x100 and stars x10 with respect to the orbit scale for clarity. The size of the corresponding optimistic (light green) and conservative (dark green) habitable zones are shown."
(Planetary Habitability Laboratory))

Something we don't know yet is whether systems like ours and Epsilon Eridani's are the oddballs, with planets in widely-spaced near-circular orbits; or the tightly-packed planetary systems are the unusual ones.

My guess is that so many of the known planetary systems have planets in tight orbits because those are the most easily-detected systems.

As astronomers develop more sensitive equipment, and have more data to process, we may find planetary systems more nearly like ours: or not.

Years, Days, and Spin-Orbit Resonance

(From Planetary Habitability Laboratory, University of Puerto Rico at Arecibo; used w/o permission.)
("Details of the orbits of the two planets around the Kapteyn's star. Only one planet is shown in each diagram using a different orbital scale for clarity. The eccentricity of the planets correspond to the upper 99% confidence level, but they are more likely close to circular orbits."
(Planetary Habitability Laboratory))

Assuming that Kapteyn b has an atmosphere and oceans like Earth's, seasons there would be extreme: even at the equator. But it looks like the planet could be suitable for 'life as we know it.'

With a mass in the neighborhood of five times Earth's, or more, we wouldn't be comfortable there. If it's a rocky world, like ours, we'd weigh something like two thirds again as much on Kapteyn b.

In other words, someone weighing 150 pounds would be pressed against the floor with a force of more than 250 pounds. That's almost as much extra weight as we'd have, carrying someone. I'm pretty sure that most folks could learn to walk on Kapteyn b: but it might not be healthy for us.

It looks like Kapteyn's rotation is tidally locked to its star: either spinning once during every orbit, with one side always toward the sun; or in a spin-orbit resonance, like Mercury.

A spin-orbit resonance is a situation where the planet spins at a precise fraction of its orbit. Mercury's resonance is 3:2, three revolutions for every two orbits. Gliese 581 d may have a spin-orbit resonance of 2:1, spinning twice each local year.

Some scientists have assumed that, since Earth spins 365.256363 times during each orbit — roughly — all habitable planets must spin like whirligigs. Others are developing mathematical models, trying to predict what weather on a tidally-locked world would be like. (May 10, 2013)

I wouldn't be surprised if we learn that natural philosophers living on Kapteyn b decided that Earth couldn't support life: because our days are too short. That might explain why we don't get any visitors, and that's another topic. Topics. (May 9, 2014; April 11, 2014; January 17, 2014)

Searching the Sky, Looking Ahead

(From Planetary Habitability Laboratory, University of Puerto Rico at Arecibo; used w/o permission.)
("The Habitable Exoplanets Catalog now has 22 objects of interest including Kapteyn b, the oldest and second closest to Earth potentially habitable exoplanet."
(Planetary Habitability Laboratory))


(From Planetary Habitability Laboratory, University of Puerto Rico at Arecibo; used w/o permission.)
("Stellar map with the position of all the stars with potentially habitable exoplanets including now Kapteyn's star."
(Planetary Habitability Laboratory))

This star chart shows a heavy concentration of potentially-habitable exoplanets in the general direction of Cygnus, Draco, and Lyra.

That's because the Kepler observatory was looking in that direction. Kepler mission planners picked that direction because it's close to the Milky Way galaxy's plane, looking 'ahead,' in the direction of our sun's orbit.

Scientists sifting through the Kepler data have spotted well over a thousand planets, some of which are very roughly Earth's temperature and size. As more of the sky is surveyed, I'm pretty sure that we'll find a great many more worlds.

Images of Jupiter, Neptune, Earth, and Mars on the "Current Potentially Habitable Exoplanets" chart are accurate representations of those planets. The expolanets listed may look like that: or not. As it says on that red bar, they're "Artistic Representations."

I think the "Current Potentially Habitable Planets" chart is a pretty good way of displaying the number and approximate size of these worlds. As we learn more, it may turn out that none of them can support life: or that some could, but don't.

Or we may discover a billion-year-old civilization on Kapteyn b.



Background:

• Super Earth
  Wikipedia
  Particularly
  • Density and bulk composition
  • Geologic activity
  • Evolution
• Exoplanet Orbit Database
  University of Massachusetts and IPAC/Caltech
• The Extrasolar Planets Encyclopaedia
  Exoplanet Team
• The Habitable Exoplanets Catalog
  Planetary Habitability Laboratory, University of Puerto Rico at Arecibo
• Kepler
  NASA

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  Particularly
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  • Eldritch Horrors and SETI
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