TRAPPIST-1

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BDanielMayfield
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Re: Astronomers Explain Formation of Seven Exoplanets around TRAPPIST-1

Postby BDanielMayfield » Sat Jun 10, 2017 3:37 am

bystander wrote:Astronomers Explain Formation of Seven Exoplanets around TRAPPIST-1
Netherlands Research School for Astronomy (NOVA) | 2017 Jun 08

Astronomers from the University of Amsterdam (the Netherlands) explain with a model how seven earth-sized planets could have been formed in the planetary system Trappist-1. The crux is on the line where ice changes in water.
...
Now, the Amsterdam researchers come up with a model where pebbles migrate instead of complete planets. The model begins with pebbles that are floating from outside regions to the star. Such pebbles consist largely of ice. When the pebbles arrive near the so-called ice line, the point where it is warm enough for liquid water, they get an additional portion of water vapor to process. As a result, they clot together into a protoplanet. Then the protoplanet moves a little closer to the star. On its way it sweeps up more pebbles like a vacuum cleaner, until it reaches the size of the Earth. The planet then moves in a little further and makes room for the formation of the next planet.

The crux, according to the researchers, is in the clotting of pebbles near the ice line. By crossing the ice line, pebbles lose their water ice. But that water is re-used by the following load of pebbles that is drifting from the outer regions of the dust disk. At Trappist-1, this process repeated until seven planets were formed. ...

[i]Formation of TRAPPIST-1 and Other Compact Systems
- Chris Ormel, Beibei Liu, Djoeke Schoonenberg


This is a very interesting model. It reminds me somewhat of how hail stones grow in thunderstorms here on Earth. In the case of hail, gravity is pulling ice pellets down while strong up-drafts blow the pellets repeatedly up into freezing temp regions of the cloud. In the case of young red dwarf stars, there might be considerable back and forth migration of the ice line due to all the flaring of the star.

Presumably, such a process could be at work around any young star, no matter its mass, as all young stars are very active at first. I also wonder if other chemicals or elements besides H2O might play similar roles at their respective ice lines.

I've always wondered how pebbles with negligible gravitational attraction manage to stick together and grow into a protoplanet massive enough to start gravitational growth. This model provides a very logical explanation. Nice :!:

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Re: NASA news conference about exoplanet (TRAPPIST-1)

Postby Ann » Sat Jun 10, 2017 5:13 am

Meteorologist Jeff Haby wrote:
What Causes Giant Snowflakes?

Whether snow is more dry or more wet depends on the snow to liquid equivalent. When the temperature throughout the troposphere is well below freezing the snow is term a "dry snow". A dry snow has little to no liquid within the snowflakes. During a dry snow, snowflakes tend to be smaller. Also, when trying to make a snowball, it falls apart for the most part.

In a situation in which part of the troposphere is very near or just above freezing, the snowflake will partially melt. This produces a liquid film on the snowflake. This makes it much easier for snowflakes to stick together. Thus, it is liquid water that is the "glue" to producing large snowflakes and snow that is easy to make snowballs with. While a dry heavy snow tends to have a huge amount of small snowflakes, a heavy wet snow tends to have a smaller number of snowflakes but the individual snowflakes are large.


Of course, this begs the question how planets formed on the cold side of the snow line. Did their building blocks smash together with such force that they partially melted, thereby helping them to stick together?

But how did those big building blocks, big enough to smash together with sufficient force to partly melt each other, form in the first place?

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Re: NASA news conference about exoplanet (TRAPPIST-1)

Postby warmingwarmingwarming » Tue Jun 13, 2017 3:38 pm

I think I think, though I'm not sure if I all the thoughts I think I think, or if they come to me from .. goodness knows where. :)

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CfA: More to Life Than the Habitable Zone

Postby bystander » Thu Jul 13, 2017 7:10 pm

More to Life Than the Habitable Zone
Harvard Smithsonian Center for Astrophysics | 2017 Jul 13

Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet systems, TRAPPIST-1.

The teams, both led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., say the behavior of the star in the TRAPPIST-1 system makes it much less likely than generally thought, that planets there could support life.

The TRAPPIST-1 star, a red dwarf, is much fainter and less massive than the Sun. It is rapidly spinning and generates energetic flares of ultraviolet (UV) radiation.

The first team, a pair of CfA theorists, considered many factors that could affect conditions on the surfaces of planets orbiting red dwarfs. For the TRAPPIST-1 system they looked at how temperature could have an impact on ecology and evolution, plus whether ultraviolet radiation from the central star might erode atmospheres around the seven planets surrounding it. These planets are all much closer to the star than the Earth is to the Sun, and three of them are located well within the habitable zone. ...

Lingam and his co-author, Harvard professor Avi Loeb, found that planets in the TRAPPIST-1 system would be barraged by UV radiation with an intensity far greater than experienced by Earth. ... Lingam and Loeb estimate that the chance of complex life existing on any of the three TRAPPIST-1 planets in the habitable zone is less than 1% of that for life existing on Earth.

In a separate study, another research team from the CfA and the University of Massachusetts in Lowell found that the star in TRAPPIST-1 poses another threat to life on planets surrounding it. Like the Sun, the red dwarf in TRAPPIST-1 is sending a stream of particles outwards into space. However, the pressure applied by the wind from TRAPPIST-1's star on its planets is 1,000 to 100,000 times greater than what the solar wind exerts on the Earth.

The authors argue that the star’s magnetic field will connect to the magnetic fields of any planets in orbit around it, allowing particles from the star’s wind to directly flow onto the planet’s atmosphere. If this flow of particles is strong enough, it could strip the planet's atmosphere and perhaps evaporate it entirely. ...

Physical Constraints on the Likelihood of Life on Exoplanets - Manasvi Lingam, Abraham Loeb
The Threatening Magnetic and Plasma Environment of the TRAPPIST-1 Planets - Cecilia Garraffo et al
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BDanielMayfield
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Re: TRAPPIST-1

Postby BDanielMayfield » Fri Jul 14, 2017 8:40 am

And, as TRAPPIST-1 goes, so went/goes/will go billions of other Red Dwarf systems.

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Re: CfA: More to Life Than the Habitable Zone

Postby neufer » Fri Jul 14, 2017 11:14 am

bystander wrote:More to Life Than the Habitable Zone
Harvard Smithsonian Center for Astrophysics | 2017 Jul 13
Click to play embedded YouTube video.
In a separate study, another research team from the CfA and the University of Massachusetts in Lowell found that the star in TRAPPIST-1 poses another threat to life on planets surrounding it. Like the Sun, the red dwarf in TRAPPIST-1 is sending a stream of particles outwards into space. However, the pressure applied by the wind from TRAPPIST-1's star on its planets is 1,000 to 100,000 times greater than what the solar wind exerts on the Earth. The authors argue that the star’s magnetic field will connect to the magnetic fields of any planets in orbit around it, allowing particles from the star’s wind to directly flow onto the planet’s atmosphere. If this flow of particles is strong enough, it could strip the planet's atmosphere and perhaps evaporate it entirely. ...
Art Neuendorffer


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