Astronomers from KU Leuven, Belgium, have shown that the interaction between the surface and the atmosphere of an exoplanet has major consequences for the temperature on the planet. This temperature, in turn, is a crucial element in the quest for habitable planets outside our Solar System.
CREDIT KU Leuven – Ludmila Carone and Leen Decin
In the quest for habitable planets outside our Solar System – also known as exoplanets – astronomers are currently focusing on rocky planets that don’t look like Earth. These planets orbit so-called M dwarfs – stars that are smaller than our Sun. In our universe, there are many more M dwarfs than there are sun-like stars, making it more likely that astronomers will discover the first habitable exoplanet around an M dwarf. Most planets orbiting these M dwarfs always face their star with the same side. As a result, they have permanent day and night sides. The day side is too hot to make life possible, while the night side is too cold.
Last year, KU Leuven researchers Ludmila Carone, Professor Rony Keppens, and Professor Leen Decin already showed that planets with permanent day sides may still be habitable depending on their ‘air conditioning’ system. Two out of three possible ‘air conditioning’ systems on these exoplanets use the cold air of the night side to cool down the day side. And with the right atmosphere and temperature, planets with permanent day and night sides are potentially habitable.
Whether the ‘air conditioning’ system is actually effective depends on the interaction between the surface of the planet and its atmosphere, Ludmila Carone’s new study shows.
Carone: “We built hundreds of computer models to examine this interaction. In an ideal situation, the cool air is transported from the night to the day side. On the latter side, the air is gradually heated by the star. This hot air rises to the upper layers of the atmosphere, where it is transported to the night side of the planet again.”
But this is not always the case: on the equator of many of these rocky planets, a strong air current in the upper layers of the atmosphere interferes with the circulation of hot air to the night side. The ‘air conditioning’ system stops working, and the planet becomes uninhabitable because the temperatures are too extreme.
Ludmila Carone: “Our models show that friction between the surface of the planet and the lower layers of the atmosphere can suppress these strong air currents. When there is a lot of surface friction, the ‘air conditioning’ system still works.”
The KU Leuven researchers created models in which the surface-atmosphere interaction on the exoplanet is the same as on Earth, and models in which there is ten times as much interaction as on Earth. In the latter case, the exoplanets had a more habitable climate. If planets with a well-functioning ‘air conditioning’ system also have the right atmosphere composition, there’s a good chance that these exoplanets are habitable.
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An essential component to make Exoplanets habitable is water and GHG.
Without GHG you could end up with eternal inversion, where the upper parts of the atmosphere gets warmer and warmer, because it can not cool down by radiation, which is the only way a planet can cool.
In fact you could end up with a glowing hot upper atmosphere more or less independent of the surface of the planet.
For all the looking, I think we can make a planet that would suit our needs. But I think that as far far future hollow out the inside of a large asteroid and live in that. There would be no limit to how many. There’d be a lot of advantages. Large scale extinction would be less likely. And be able to move out of the way of hazards.
Hollowed-out asteriods are the future. Once we get sophisticated enough, we can build artificial hollow habitat structures in space. But we will start out with hollowed-out asteriods.
There are numerous advantage to using an asteroid instead of building structures. First, the thickness is a valuable asset in warding off energies since it doesn’t have an atmosphere. Second, micro meteors, again the thickness and density are a shield. A medium size rock would do a lot of damage to a man made structure.
While I generally oppose nuclear energy on the surface of this planet, that is not the case in an asteroid.
Asteriod material could be used as radiation shielding for artificial structures. Some asteriods are not very dense, described as “rubble piles” which could be broken up and used as fill for the artificial structures. Like blown-in insulation.
Humans definitely have to be protected from radiation in space, and they definitely have to have artificial “gravity” equivalent to the gravity on the Earth’s surface to be healthy, and large structures are required for both.
Asteriods that would be suitable for human habitation should be sized from two to five miles in diameter. The smaller, the better, to begin with, because they would be easier to handle.
Let’s say we find ourselves a good, solid asteriod about two miles in diameter and eight miles long. We go into the center of this asteriod and hollow out a cylinder one mile in diameter and the length of the asteriod. We now have a huge chamber inside a solid mile of asteriod. The mile of asteriod material in the walls will serve to block out harmful radiation from space.
The one mile diameter spec is the minimum size to use when spinning up the asteriod to create artificial gravity (centrifugal force) in the interior of the asteriod that is equivalent to the gravity on Earth, without giving humans motion sickness.
The one-mile-diameter asteriod habitat would be spun at one revolution per minute (imagine you are sitting on the end of the second hand on a clock that is one mile in diameter. That’s how fast you would be moving. You say, you don’t know what a second hand on a clock is? Oh, well.:)
This leads to my formula: 1+1=1 One mile in diameter, plus one revolution per minute, equals one Earth-equivalent “gravity”. 🙂
It is claimed that humans don’t experience any motion sickness at one rpm and would not be able to tell you were spinning while inside the habitat.
If that proved to be a problem, the solution would be to go bigger. A two mile diameter habitat could be spun at half the rate of the one mile habitat to get the same Earth-equivalent “gravity”.
I don’t know that any large-scale asteriod habitat searches have been done to date, but I’ll bet there are people looking at the question right now.
We just need cheap access to space, and the human race will be off to the races. The Breakout is getting closer.
Such large temperature differences would tend to produce hurricane-force winds.
Pangaea was NOT on the tropics–it was the entire sphere, about 2/3 of the diameter of today’s Earth, as proved by sea-floor spreading. Google expanding Earth and you should soon find one of the videos that demonstrates this.
These astronomers should stop playing with their computer and start observing daily weather. Change in a day’s minimum to maximum temperatures is not abrupt but gradual following the Earth’s rotation. If an exoplanet has one side at constant day and one side at constant night, there are certain longitudes at constant dawn. The temperature here is between the maximum and minimum. The temperature change would be gradual as one moves away from this Goldilocks zone.
“”” Most planets orbiting these M dwarfs always face their star with the same side. As a result, they have permanent day and night sides. The day side is too hot to make life possible, while the night side is too cold.”””
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What kind of magnetic field/magnetosphere could these non-rotating planets have to protect them from the M dwarf? Are their daytime atmospheres always being stripped off by the M dwarf’s stellar wind flow?
This image is a great perspective view on the magnetosphere of Jupiter (see image).
And because there might be others somewhere else in the galaxy, like us here, that also are looking for exoplanets.
Jupiter might likely be findable and viewable to them that are trying to find us….
Enjoy
http://lasp.colorado.edu/home/mop/files/2012/04/FluxTubes.jpg
Fluxtubes connecting the Galilean satellites to Jupiter, plus the aurora at the foot of their fluxtubes.
Credit: John Clarke & John Spencer
This webpage is a cornucopia of our solar systems planetary magnetospheres… and growing. One of the images depicts the spacecraft Juno trajectory thru this somewhat tricky magnetosphere.
http://lasp.colorado.edu/home/mop/graphics/graphics/
Brown dwarf compared to Jupiter for size.
BrownDwarfCompare-WISE-thumb-500×299-321750.jpg
Scientists Discover Smallest Known Star
http://www.iflscience.com/space/scientists-discover-smallest-known-star/
http://cdn.iflscience.com/images/d598ab3a-ce80-5e73-bb8c-e4d85996196d/extra_large-1464355874-1190-scientists-discover-smallest-known-star.jpg
Astronomers recently stumbled upon a teeny star called 2MASS J0523-1403 located just 40 light years away. It’s not only the smallest star discovered so far – it may also represent the smallest possible star. By studying stars such as this, scientists are starting to be able to answer the question: where do stars end and brown dwarfs begin?
Stars are burning balls of gas held together by gravity that are fuelled by the fusion of hydrogen atoms to helium in their cores. Stars come in a variety of sizes; the smallest stars, known as red dwarfs, can possess as little as 10% of the mass of our Sun, whereas the biggest stars (hypergiants) can be over 100 times as massive as the Sun. But just how small can an object be and still be defined as a star? This has mystified astronomers for years. All that was previously known is that objects below this limit don’t have enough mass to ignite the fusion of hydrogen in their cores. These objects are known as brown dwarfs.
Brown dwarfs are elusive objects that are thought to be the missing link between gas giants and low-mass stars such as red dwarfs. They’re generally around the size of Jupiter, but they don’t have enough mass to become a star. Unlike stars, brown dwarfs have no internal energy source.
http://www.stsci.edu/~inr/thisweek1/thisweek/browndwarf.jpg
Completing the Census of Ultracool Brown Dwarfs in the Solar Neighborhood using HST/WFC3
Brown dwarfs are objects that form in the same manner as stars, by gravitational collapse within molecular clouds, but which do not accrete sufficient mass to raise the central temperature above ~2 million Kelvin and ignite hydrogen fusion. As a result, these objects, which have masses less than 0.075 MSun or ~75 MJup, lack a sustained source of energy, and they fade and cool on relatively short astronomical (albeit, long anthropological) timescales. Following their discovery over a decade ago, considerable observational and theoretical attention has focused on the evolution of their intrinsic properties, particularly the details of the atmospheric changes. At their formation, most brown dwarfs have temperatures of ~3,000 to 3,500K, comparable with early-type M dwarfs, but they rapidly cool, with the rate of cooling increasing with decreasing mass. As temperatures drop below ~2,000K, dust condenses within the atmosphere, molecular bands of titanium oxide and vanadium oxide disappear from the spectrum to be replaced by metal hydrides, and the objects are characterised as spectral type L. Below 1,300K, strong methane bands appear in the near-infrared, characteristics of spectral type T. At present, the coolest T dwarfs known have temperatures of ~650 to 700K. At lower temperatures, other species, notably ammonia, are expected to become prominent, and a number of efforts have been undertaken recently to find examples of these “Y” dwarfs. ….
http://www.stsci.edu/~inr/thisweek1/thisweek/M-dwarf-planet.jpg
Investigating the nature of GJ 3470b, the missing link between super-Earths and Neptunes
M dwarfs are the most common stars in the galaxy and, with the continued accumulation of observations showing that the presence of planetary companions, they are also likely to the best candidates for finding nearby habitable planets. GJ 3470 is an early type M dwarf (spectral type M1.5) a mass approximately half that of the Sun lying at a distance of 25 parsecs lying in the constellation of Cancer. Early last year (February-April, 2012), the HARPS planet search team announced the discovery of a ~14 MEarth planetary companion with a 3.3371 day period orbit, corresponding to a semi-major axis of 0.035 Astronomical units, or 10% the size of Mercury’s orbit. The radial velocity semi-amplitude is less than 10 m/sec. Crucially, the planet transits the parent star, allowing its diameter to be measured as 4.2 Earth radii. With these parameters, the companion is more comparable with Uranus than with the “hot Neptune” systems like Gl 436b (a ~22 Earth-mass planet in a 2.64 day, 0.0278 AU orbit around the M2 dwarf, ~10 parsecs distant). Those parameters indicate a relatively low density, suggestive of a thick hydrogen/helium atmosphere and/or substantial water-ice content. The present program aims to obtain transit spectroscopy using the G141 grating on the WFC3-IR camera. The observations cover significant water features, whose detection might indicate that the former model is correct, and whose non-detection might argue for a water-rich interior content or high altitude hazes within the atmosphere.
http://www.stsci.edu/~inr/thisweek1/2013/thisweek035.html
Love all those size comparisons. Thanks, Carla.
And where did the Oort Cloud, Kuiper Belt and Asteroid Belt come from? Don’t forget about the debris in Earth’s orbit, with more and more being discovered every year!!! Should we be referring to the Asteroid belt as belonging to Jupiter, that somehow it’s location is not coincidental???
Rack em Up
Johnny Lang, “there aint no shame in beaten by a master,””
I get the first shot….see (my bold in text)
Warm Jupiters not as lonely as expected
http://phys.org/news/2016-07-jupiters-lonely.html
July 14, 2016
….Because of their proximity to their parent stars, they are warmer than our system’s cold gas giants—though not as hot as Hot Jupiters, which are typically closer to their parent stars than Mercury.
It has generally been thought that Warm Jupiters didn’t form where we find them today; they are too close to their parent stars to have accumulated large, gas-giant-like atmospheres. So, it appeared likely that they formed in the outer reaches of their planetary systems and migrated inward to their current positions, and might in fact continue their inward journey to become Hot Jupiters. On such a migration, the gravity of any Warm Jupiter would have disturbed neighbouring or companion planets, ejecting them from the system.
But, instead of finding “lonely”, companion-less Warm Jupiters, the team found that 11 of the 27 targets they studied have companions ranging in size from Earth-like to Neptune-like.
“And when we take into account that there is more analysis to come,” says Huang, “the number of Warm Jupiters with smaller neighbours may be even higher. We may find that more than half have companions.”..
On such exoplanets, wouldn’t the day side be bone dry.
Moist air moves from the day side to the night side where it cools to the point that water condenses out of it and falls as first water, then snow.
Depending on the topography, the water might run back to the day side, where it will evaporate and return to the night side where it will falls as both water and snow.
Repeat ad infinitum, each cycle there is less liquid water because some fraction of the water that migrates to the night side will always fall as snow.
Since the night side will always be in the shadow, there is nothing to melt the snow that has fallen.
Eventually, all the water will be trapped in glaciers on the night side.