Friday, May 9, 2014

Kepler-186f, Sunsets, Tourism, and a Musing Lemming

(From UPR at Arecibo, NASA; used w/o permission.)

"How a sunset might look on Earth's new cousin Kepler-186f"
"NASA confirms the discovery of an Earth-sized planet that may have potential for life, but its sun is dimmer than ours. Here's what an evening stroll on a beach on Kepler-186f might be like.
Eric Mack, c|net (April 17, 2014)

"NASA announced Thursday that it has confirmed the first planet beyond our solar system that exists in the habitable zone of its star and is close to the size of Earth, making it the most likely exoplanet yet validated to host life. But the planet, Kepler-186f, orbits an M-class dwarf star and receives only about a third of the energy from its sun that Earth receives from our own beloved fireball.

"That means it could be a frozen, Hoth-like world, or it could be more dry and dead like Mars. But if conditions are right and liquid water exists on Kepler-186f, as NASA thinks it might, it could look more like the above conception, a slightly more chilly version of Earth with shallow oceans...."

Folks at the University of Puerto Rico at Arecibo's Planetary Habitability Laboratory started with a photo of sunset as seen from a Caribbean beach. A little digital tweaking later, they had what sunset on Kepler-186f would look like: if the planet has an atmosphere and ocean a bit like Earth's.

We don't know if Kepler-186f has an atmosphere, let alone water: but if it does, at least some of the water will probably be liquid.

Sunlight on Kepler-186f's at high noon would be a big like sunlight on Earth an hour before sunset: the climate will be on the nippy side for humans, at best. The sunlight isn't just dimmer: it's redder, too. Or is that more red?

Kepler-186f's star is smaller than Earth's Sol: and it's cooler: about 3,788° Kelvin, compared to Sol's 5,778° Kelvin. That's why Arecibo's simulated sunset looks like one of William Ascroft's Krakatoa sunset sketches.

Looking Ahead: Tourism Destinations in 4814

At the moment, humans must be content with studying Kepler-186f from the Solar system. Keper-186 is nearly 500 light years away: too far for any off-the-shelf transportation system available on Earth.

Humans have, over the last million years, been consistently innovative: and the Lemming sees no sign that this inventive streak has played itself out. It may not be too long before humans travel between stars as routinely as they do between continents today.

If Kepler-186f has an atmosphere, and water, and life: that's a lot of "ifs," but let's suppose that the planet's equatorial zone is warm enough for human comfort.

Kepler-186f is slightly larger than Earth, but not by much. The Lemming made a very rough estimate of Kepler-186f's surface gravity.

With a diameter 1.11 times Earth, Kepler-186f's volume is 1.37 times Earth's, give or take. If it's made of exactly the same mix of rock and metal, it'd be denser: but the Lemming's looking for a rough estimate, so let;s say that it's 1.37 times Earth's mass.

Plugging these numbers into the old g = m/r2 equation, where g is surface gravity, m is mass, and r is radius (Earth=1); the Lemming got a surface gravity for Kepler-186f of about 1.11 g. Humans shouldn't find that too uncomfortable.

Someone weighing 150 pounds here would have about 166 pounds pressing on the sands of that hypothetical beach. It'd be like wearing a 16 pound backpack: except that the force would be distributed throughout the body.

Spectacular sunsets, weather on the nippy side but tolerable, far from the hustle and bustle of Earth: the Lemming thinks Kepler-186f has serious potential as a tourist destination.

Ridiculous? maybe. More to the point, today humans can't get there: but 28 centuries back, when Homer's "Odyssey" was new, cruise ships might have seemed just as impossible.

Of course, someone may already be living there: and that's another topic.

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