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Day 13 of OC-tober

I already drew a full drawing today that I can't post here. So heres a sketch of my old oc Gliese

#my art #oc #anime #manga #ococtober #ococtober2018 #my oc #sketch #gliese

Notes from Gliese, Part 9

1. Slow cooker pork roast: The meat was cut down, floured and seasoned, seared off, and then put to bed on aromatics. Deglaze the pan with bourbon, chicken stock, and a little firey salsa. Pour. Now set it aside until 6pm.

2. Serve mashed potatoes. Life is short, and most meals are held in hand -- make this one count. How you live your hours is how you live your days, and how you live your days is how you live your life. Use real cream and butter. Savour it. Pay attention.

3. My mind has been taken with the world I left behind. All rises and falls around you still, you know? The burr and hubbub of work, and tending to the home, and minding friendships. And there is this bit like a sore tooth I kept poking at absentmindedly with my tongue. I think I have it. I think the kernel of pain is right there, right there. I am so very sad.

4. Do you know what consoles? This is the kindness we give to ourselves: a bath. Sweeping and tidying the little home. Kisses between furry ears. Some music, raw and rough, and dancing. A good meal.

5. All is the same as it was before. There is nothing new under the sun. We roil around in the undersea darkness, but the light is always there above, waiting. Remember it. Be well.

#gliese

The end of the habitable zone

The planet Earth sits in something of a “goldilocks” location in the solar system. It sits within a spot known as the “radiative habitable zone” relative to our star, sol, seen here coming up over the horizon from the International Space Station. The radiative habitable zone is an area of any solar system where liquid water is possible. If a planet exists inside this zone, it will receive enough light where a planet-sized object with an atmosphere will host liquid water on its surface. Outside this zone, it is either too hot or too cold for liquid water solely from the star’s radiation.

Obviously there are a lot of variables in that paragraph. A planet needs an atmosphere, needs to be of a certain size, etc. But, based on this concept, scientists using the Kepler Space Telescope have discovered dozens of planets outside our solar system that seem to be within the habitable zone around their stars.

But, stars are not stagnant things. Over their lifetimes, they change. Several billion years ago, our sun wasn’t as hot as it is now; its output when the Earth formed was about 70% of what it is today. These changes take a long time to happen and would never be noticed on a human timescale, but given the presence of these newly discovered extra-solar planets, it makes sense to ask how long planets stay in the habitable zone of their stars.

Some planets might move into the habitable zone and be there only a short time. This could occur around red giant stars, for example; stars expand late in their lifetimes and could make planets in the outer part of the solar system suddenly enter the habitable zone, but they might only stay there for a few million years.

New research from scientists at the University of East Anglia have attempted to put together all the constraints we have, both from the Kepler telescope and from our knowledge of this solar system, to ask how long planets stay in the habitable zone.

One of their main conclusions is that the smaller a star is, the slower it changes. Stars smaller than our sun don’t heat up as fast and burn longer, so their habitable zones are more stable, while stars larger than our sun have shorter lifetimes and the habitable zones migrate across their solar systems more quickly.

One planet found by the Kepler telescope, Gliese 581d, has a habitable zone lifetime of nearly 50 billion years. Alternatively, other planets move more quickly out of the habitable zone; Venus, for example, may at one point have resided within the habitable zone of the sun, but it only remained there for 1.5 billion years.

Based solely on how the sun heats up, it is sensible to ask when the Earth will leave the habitable zone. Using their model, they find that this state happens about 1.75 billion years from now. That’s well before the sun would become a red giant, so in that sense it does say a lot about the future of the planet Earth we know so well.

Of course, that’s not the entire story. There are other atmospheric changes that could make Earth uninhabitable before that, such as a CO2-driven runaway greenhouse as may have happened to Venus or other changes in the atmospheric structure of the planet, and it might well be possible to come up with ways to shield the Earth as well, if intelligent life still exists at those points in the future.

I’m sure the most interesting takeaway from this study will be the date of the end of habitability on planet Earth, but from the perspective of astrobiology this is a really interesting study. It took life less than a billion years to take hold of Earth, but it took life intelligent enough to develop this model 4.56 billion years to evolve. If a planet only stays in the habitable zone for 1-2 billion years, it might not have enough time to develop intelligent life. Understanding how planets move in and out of the habitable zone is therefore another key variable to understanding the chances of intelligent life forming on a body like the Earth throughout the universe.

-JBB

Image credit: NASA/Chris Hadfield https://twitter.com/Cmdr_Hadfield/status/334011022815944705

Original study: http://online.liebertpub.com/doi/full/10.1089/ast.2012.0938

Press release: http://www.sciencedaily.com/releases/2013/09/130918211434.htm