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. ...
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
Bruce
Re: NASA news conference about exoplanet (TRAPPIST-1)
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?
Ann
Re: NASA news conference about exoplanet (TRAPPIST-1)
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
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. ...
Re: TRAPPIST-1
Posted: Sat Aug 12, 2017 4:49 pm
by Doum
BDanielMayfield wrote:And, as TRAPPIST-1 goes, so went/goes/will go billions of other Red Dwarf systems.
"There's no place like home."
Bruce
TRAPPIST-1 twice as old as our solar system
EXO WORLDS
TRAPPIST-1 twice as old as our solar system
by Brooks Hays
Washington (UPI) Aug 11, 2017
Astronomers have narrowed in on a more precise estimate of the TRAPPIST-1 system.
Scientists believe the star and its exoplanets are between 5.4 and 9.8 billion years old
It will be great if life did survive all the Young age of the star. And with the older age of trappist one, may be now life is abondant.
Deaming dreaming dreaming.
Interesting article Doum. Don't know about your wishful thinking though. On the one hand, older stars put out less flares than when they were young. But otoh, they still flare often enough to be a problem for the retention of atmospheres and oceans. That's a lot of blasting to take from close range over the billions of years.
Here's something new I learn from that article:
Astronomers reevaluated the TRAPPIST-1's age after measuring the speed at which the system is traveling through the Milky Way. Older stars are faster. They also studied the star's atmosphere as well as the frequency of its flares. All three factors suggest the system is significantly older than our solar system.
"Older stars are faster." Imagine that. I wish I was faster ... oh well. Must be a conservation of momentum thing.
Bruce
Re: TRAPPIST-1
Posted: Sun Aug 13, 2017 12:38 pm
by neufer
BDanielMayfield wrote:
Here's something new I learn from that article:
Astronomers reevaluated the TRAPPIST-1's age after measuring the speed at which the system is traveling through the Milky Way. Older stars are faster. They also studied the star's atmosphere as well as the frequency of its flares. All three factors suggest the system is significantly older than our solar system.
"Older stars are faster." Imagine that. I wish I was faster ... oh well.
Must be a conservation of momentum thing.
A 'random walk' of the velocity vector after multiple collisions
Re: TRAPPIST-1
Posted: Sat Aug 19, 2017 6:00 pm
by Doum
BDanielMayfield wrote:Interesting article Doum. Don't know about your wishful thinking though. On the one hand, older stars put out less flares than when they were young. But otoh, they still flare often enough to be a problem for the retention of atmospheres and oceans. That's a lot of blasting to take from close range over the billions of years.
Here's something new I learn from that article:
Astronomers reevaluated the TRAPPIST-1's age after measuring the speed at which the system is traveling through the Milky Way. Older stars are faster. They also studied the star's atmosphere as well as the frequency of its flares. All three factors suggest the system is significantly older than our solar system.
"Older stars are faster." Imagine that. I wish I was faster ... oh well. Must be a conservation of momentum thing.
Bruce
The wishfull thinking have many IF.
If one of the planet have a strong magnetic field, if life was able to appear, if it was able to survive the first few billion years. Then now that the star is stable maybe life start florishing overthere. That is why i said dreaming dreaming dreaming. I could say the samething with tau ceti earth size 4 planets. 2 are in the watery zone (habitable zone.) its just dreaming
P.S. i still havent retry to make the collision of a 5 mass blackhole with the sun with the universe sandbox. i will try someday. But they are using term that i dont know. So i cant put a number in there if i dunno what it mean.
Cya!
Doum
Re: TRAPPIST-1
Posted: Sun Aug 20, 2017 11:45 am
by Ann
BDanielMayfield wrote:
Interesting article Doum. Don't know about your wishful thinking though. On the one hand, older stars put out less flares than when they were young. But otoh, they still flare often enough to be a problem for the retention of atmospheres and oceans. That's a lot of blasting to take from close range over the billions of years.
Here's something new I learn from that article:
Astronomers reevaluated the TRAPPIST-1's age after measuring the speed at which the system is traveling through the Milky Way. Older stars are faster. They also studied the star's atmosphere as well as the frequency of its flares. All three factors suggest the system is significantly older than our solar system.
"Older stars are faster." Imagine that. I wish I was faster ... oh well. Must be a conservation of momentum thing.
Bruce
How weird. Why would older stars be faster?
The only logical answer that I can think of - insert Spock ears here - is that the the shape of the orbits of older stars have changed over the years, due to, well, due to whatever. But if their orbits have changed, they may be comparatively different from the orbit of the Sun. If so, their relative speed (the speed of the Sun along its orbit minus the speed of the other star along its orbit) might be higher than the relative speed of young stars, whose orbits have not had time to change much and may be relatively similar to the Sun's.
Orbit of Arcturus vs. orbit of the Sun. Credit: ESO.
Relatively close at 36.7 light-years from the Sun, Arcturus is a red giant of spectral type K0III—an ageing star around 7.1 billion years old that has used up its core hydrogen and moved off the main sequence. It is 1.08 ± 0.06 times as massive as the Sun, but has expanded to 25.4 ± 0.2 times its diameter and is around 170 times as luminous.
...
Arcturus has a high proper motion, two arcseconds a year, greater than any first magnitude star other than α Centauri. It is moving rapidly (122 km/s) relative to the Solar System, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. Arcturus is thought to be an old disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.
Ann
Re: TRAPPIST-1
Posted: Sun Aug 20, 2017 12:26 pm
by neufer
https://en.wikipedia.org/wiki/Arcturus_moving_group wrote:
<<In astronomy, the Arcturus moving group or Arcturus stream is a moving group or stellar stream which includes the nearby bright star Arcturus. It comprises many stars which share similar proper motion and so appear to be physically associated.
This group of stars is not in the plane of the Milky Way galaxy and has been proposed as a remnant of an ancient dwarf satellite galaxy, long since disrupted and assimilated into the Milky Way. It consists of old stars deficient in heavy elements. However, Bensby and colleagues in analysing chemical composition of F and G dwarf stars in the solar neighbourhood found there was no difference in chemical makeup of stars from the stream, suggesting an intragalactic rather than extragalactic origin.
Research from the Radial Velocity Experiment at the Australian Astronomical Observatory headed by Quentin Parker was first to quantify the nature of the group, though astronomers had known of its existence for some time. It was first discovered in 1971.
Other members include the red giant κ Gruis and the M-class stars 27 Cancri, Alpha Vulpeculae and RT Hydrae.>>
Hubble Delivers First Hints of Possible Water Content of TRAPPIST-1 Planets
An international team of astronomers used the NASA/ESA Hubble Space Telescope to estimate whether there might be water on the seven earth-sized planets orbiting the nearby dwarf star TRAPPIST-1. The results suggest that the outer planets of the system might still harbour substantial amounts of water. This includes the three planets within the habitable zone of the star, lending further weight to the possibility that they may indeed be habitable.
On 22 February 2017 astronomers announced the discovery of seven Earth-sized planets orbiting the ultracool dwarf star TRAPPIST-1, 40 light-years away [1]. This makes TRAPPIST-1 the planetary system with the largest number of Earth-sized planets discovered so far.
Following up on the discovery, an international team of scientists led by the Swiss astronomer Vincent Bourrier from the Observatoire de l’Université de Genève, used the Space Telescope Imaging Spectrograph (STIS) on the NASA/ESA Hubble Space Telescope to study the amount of ultraviolet radiation received by the individual planets of the system. ...
While lower-energy ultraviolet radiation breaks up water molecules — a process called photodissociation — ultraviolet rays with more energy (XUV radiation) and X-rays heat the upper atmosphere of a planet, which allows the products of photodissociation, hydrogen and oxygen, to escape.
As it is very light, hydrogen gas can escape the exoplanets’ atmospheres and be detected around the exoplanets with Hubble, acting as a possible indicator of atmospheric water vapour [2]. The observed amount of ultraviolet radiation emitted by TRAPPIST-1 indeed suggests that the planets could have lost gigantic amounts of water over the course of their history. ...
New work from a team of Carnegie scientists (and one Carnegie alumnus) asked whether any gas giant planets could potentially orbit TRAPPIST-1 at distances greater than that of the star’s seven known planets. If gas giant planets are found in this system’s outer edges, it could help scientists understand how our own Solar System’s gas giants like Jupiter and Saturn formed.
Earlier this year, NASA’s Spitzer Space Telescope thrilled the world as it revealed that TRAPPIST-1, an ultra-cool dwarf star in the Aquarius constellation, was the first-known system of seven Earth-sized planets orbiting a single star. Three of these planets are in the so-called habitable zone—the distance from the central star at which liquid water is most likely to be found.
But it’s possible that like our own Solar System, TRAPPIST-1 is also orbited by gas giant planets at a much-greater distance than the Earth-sized planets that we already know are part of the system. ...
Astrometric Constraints on the Masses of Long-period
Gas Giant Planets in the TRAPPIST-1 Planetary System - Alan P. Boss et al
Two exoplanets in the TRAPPIST-1 system have been identified as most likely to be habitable, a paper by PSI Senior Scientist Amy Barr says.
The TRAPPIST-1 system has been of great interest to observers and planetary scientists because it seems to contain seven planets that are all roughly Earth-sized ...
The planets studied are referred to by letter, planets b through h, in order of their distance from the star. Analyses performed by co-author Vera Dobos show that planets d and e are the most likely to be habitable due to their moderate surface temperatures, modest amounts of tidal heating, and because their heat fluxes are low enough to avoid entering a runaway greenhouse state. A global water ocean likely covers planet d. ...
Interior Structures and Tidal Heating in the TRAPPIST-1 Planets - Amy C. Barr, Vera Dobos, László L. Kiss
New Clues to Compositions of TRAPPIST-1 Planets NASA | JPL-Caltech | Spitzer | 2018 Feb 05
Click to play embedded YouTube video.
In the year since NASA announced the seven Earth-sized planets of the TRAPPIST-1 system, scientists have been working hard to better understand these enticing worlds just 40 light-years away. Thanks to data from a combination of space- and ground-based telescopes, we know more about TRAPPIST-1 than any other planetary system besides our solar system.
A new study, using data from NASA's Spitzer and Kepler space telescopes, offers the best-yet picture of what these planets are made of. They used the telescope observations to calculate the densities more precisely than ever, then used those numbers in complex simulations. Researchers determined that all of the planets are mostly made of rock. Additionally, some have up to 5 percent of their mass in water, which is 250 times more than the oceans on Earth.
The form that water takes on TRAPPIST-1 planets would depend on how much heat they receive from their ultra-cool dwarf star, which is only about 9 percent as massive as our Sun. Planets closest to the star are more likely to host water in the form of atmospheric vapor, while those farther away may have water frozen on their surfaces as ice. TRAPPIST-1e is the rockiest planet of them all, but is still believed to have the potential to host some liquid water. ...
The Nature of the TRAPPIST-1 Exoplanets - Simon L. Grimm et al
Astronomy & Astrophysics (accepted 31 Jan 2018) (pdf)
Re: TRAPPIST-1
Posted: Tue Feb 13, 2018 3:02 am
by Doum
So, water world might be plausible untill proven otherwise. Interesting possibility. Can a philosopher have an happy life just thinking? (no access to fire and metal and ....) what would be the thought overthere?
ASU: TRAPPIST-1 Planets Provide Clues to the Nature of Habitable Worlds
TRAPPIST-1 is an ultra-cool red dwarf star that is slightly larger, but much more massive, than the planet Jupiter, located about 40 light-years from the Sun in the constellation Aquarius.
Among planetary systems, TRAPPIST-1 is of particular interest because seven planets have been detected orbiting this star, a larger number of planets than have been than detected in any other exoplanetary system. In addition, all of the TRAPPIST-1 planets are Earth-sized and terrestrial, making them an ideal focus of study for planet formation and potential habitability. ...
The TRAPPIST-1 planets are curiously light. From their measured mass and volume, all of this system’s planets are less dense than rock. On many other, similarly low-density worlds, it is thought that this less-dense component consists of atmospheric gases.
“But the TRAPPIST-1 planets are too small in mass to hold onto enough gas to make up the density deficit,” explains geoscientist Unterborn. “Even if they were able to hold onto the gas, the amount needed to make up the density deficit would make the planet much puffier than we see.”
So scientists studying this planetary system have determined that the low-density component must be something else that is abundant: water. This has been predicted before, and possibly even seen on larger planets like GJ 1214b, so the interdisciplinary ASU-Vanderbilt team, comprised of geoscientists and astrophysicists, set out to determine just how much water could be present on these Earth-sized planets and how and where the planets may have formed. ...
Inward Migration of the TRAPPIST-1 Planets as Inferred from Their Water-Rich Compositions - Cayman T. Unterborn et al
Not all stars are like the sun, so not all planetary systems can be studied with the same expectations. New research from a University of Washington-led team of astronomers gives updated climate models for the seven planets around the star TRAPPIST-1. ...
The team found, briefly put, that due to an extremely hot, bright early stellar phase, all seven of the star’s worlds may have evolved like Venus, with any early oceans they may have had evaporating and leaving dense, uninhabitable atmospheres. However, one planet, TRAPPIST-1 e, could be an Earthlike ocean world worth further study, as previous research also has indicated.
TRAPPIST-1, 39 light-years or about 235 trillion miles away, is about as small as a star can be and still be a star. A relatively cool “M dwarf” star — the most common type in the universe — it has about 9 percent the mass of the sun and about 12 percent its radius. TRAPPIST-1 has a radius only a little bigger than the planet Jupiter, though it is much greater in mass.
All seven of TRAPPIST-1’s planets are about the size of Earth and three of them — planets labeled e, f and g — are believed to be in its habitable zone, that swath of space around a star where a rocky planet could have liquid water on its surface, thus giving life a chance. TRAPPIST-1 d rides the inner edge of the habitable zone, while farther out, TRAPPIST-1 h, orbits just past that zone’s outer edge. ...
Evolved Climates and Observational Discriminants for the TRAPPIST-1 Planetary System ~ Andrew P. Lincowski et al
- is that the the shape of the orbits of older stars have changed over the years, due to, well, due to whatever. But if their orbits have changed, they may be comparatively different from the orbit of the Sun. If so, their 
