Post by Andrei Tchentchik on Jun 17, 2019 11:18:39 GMT 2
(.#200).- And if the nearest exoplanet of the Earth was covered with an ocean.
And if the nearest exoplanet of the Earth was covered with an ocean.
By Tristan Vey - Published 06/10/2016 at 18: 28
In an extreme case, Proxima b could be covered by a gigantic ocean 200 km deep. Belinda.
Researchers have imagined what our closest neighbor, Proxima b, could look like this summer, using the very patchy data we have on her at the moment.
What does Proxima b, the closest neighbor of the Earth outside the Solar System, look like? We know very little about this planet discovered this summer. It is 4.2 light years from us, orbiting the nearest star of the Sun, Proxima Centauri. This little red dwarf is nearly 10 times smaller than our star and 600 times less luminous. Proxima b orbits nevertheless much closer to her than the Earth of the Sun: it thus makes only 11 days to make a complete turn of it. The equilibrium temperature at its surface, in the absence of an atmosphere, would be between -30 and -50 ° C. For comparison, if the Earth had no atmosphere, it would average -15 ° C on the surface. Finally, we know the approximate mass of this planet: about 1.3 times that of the Earth.
Based on these rather limited data, researchers from the Marseille Astrophysics Laboratory (LAM) and the Department of Astronomy at Cornell University, in an article in The Astrophyscial Journal Letters. "We made the assumption that it was a rocky world and not a gaseous world," says Bastien Brugger, a young PhD student at LAM and the first author of this study. "It would not be impossible, but in this case, the chances of finding a life in a form similar to the one we know seems almost nil."
Planet ocean or metallic planet ?
As we do not know the composition of this star, it is difficult to know what the planet can consist of. "So we took what we know best in reference: our solar system," says the young researcher. The two extremes that we find are Mercury, the planet closest to the Sun, and the frozen moons of Jupiter. In the first case, the planet is made up of two-thirds of a metal core (iron) covered with a small coat of rocks. In the second case, they are oceanic planets composed of half water (in liquid and ice) which conceals a rocky heart containing perhaps a little iron.
The two extreme cases
Applied to Proxima b, this gives as extreme cases a planet slightly smaller than the Earth (94% of the terrestrial radius) with a metal core of 4500 km radius and a thin layer of 1500 km of silicate rocks. In the other case, Proxima b would be almost half as big as the Earth (a radius 40% larger) with a liquid ocean 200 km deep covering its entire surface. Under pressure, the water would then turn to ice at this depth. There would be a thickness of 2900 km before reaching a rocky heart about the size of the Earth. In both cases, there might be an atmosphere sufficient for the temperature to be compatible with the existence of liquid water.
"We made the assumption that it was a rocky world and not a gaseous planet" : Bastien Brugger, astrophysicist at LAM
We can not decide between these different scenarios until we know the radius of the planet. "It would require that it transits in front of his star, which does not seem to be the case," regrets Magali Deleuil, an astrophysicist at LAM who contributed to this work. If Proxima b does not intercalate between us and its star, there is only one solution to know its radius: take a picture. For the moment, the current tools do not make it possible to make an image of a star so small planet located as close to its star, but it may be the case in the future. There is actually a third option: to go there. But the journey is long: it is necessary to cover 700,000 times the distance that separates us from Mars, a journey that would take nearly 80,000 years with the fastest ships existing today.
If Bastien Brugger says he has a weakness for the planet-ocean scenario, he concedes that it is not the most likely. "The planet must have formed farther from its star and migrated to its present position. There are also other conditions which do not make this hypothesis the most favorable. It is more likely that we are between these two extreme cases, with a metal core representing thirty percent of the global mass. In which case Proxima b would be 10% larger than the Earth.
F I N .
And if the nearest exoplanet of the Earth was covered with an ocean.
By Tristan Vey - Published 06/10/2016 at 18: 28
In an extreme case, Proxima b could be covered by a gigantic ocean 200 km deep. Belinda.
Researchers have imagined what our closest neighbor, Proxima b, could look like this summer, using the very patchy data we have on her at the moment.
What does Proxima b, the closest neighbor of the Earth outside the Solar System, look like? We know very little about this planet discovered this summer. It is 4.2 light years from us, orbiting the nearest star of the Sun, Proxima Centauri. This little red dwarf is nearly 10 times smaller than our star and 600 times less luminous. Proxima b orbits nevertheless much closer to her than the Earth of the Sun: it thus makes only 11 days to make a complete turn of it. The equilibrium temperature at its surface, in the absence of an atmosphere, would be between -30 and -50 ° C. For comparison, if the Earth had no atmosphere, it would average -15 ° C on the surface. Finally, we know the approximate mass of this planet: about 1.3 times that of the Earth.
Based on these rather limited data, researchers from the Marseille Astrophysics Laboratory (LAM) and the Department of Astronomy at Cornell University, in an article in The Astrophyscial Journal Letters. "We made the assumption that it was a rocky world and not a gaseous world," says Bastien Brugger, a young PhD student at LAM and the first author of this study. "It would not be impossible, but in this case, the chances of finding a life in a form similar to the one we know seems almost nil."
Planet ocean or metallic planet ?
As we do not know the composition of this star, it is difficult to know what the planet can consist of. "So we took what we know best in reference: our solar system," says the young researcher. The two extremes that we find are Mercury, the planet closest to the Sun, and the frozen moons of Jupiter. In the first case, the planet is made up of two-thirds of a metal core (iron) covered with a small coat of rocks. In the second case, they are oceanic planets composed of half water (in liquid and ice) which conceals a rocky heart containing perhaps a little iron.
The two extreme cases
Applied to Proxima b, this gives as extreme cases a planet slightly smaller than the Earth (94% of the terrestrial radius) with a metal core of 4500 km radius and a thin layer of 1500 km of silicate rocks. In the other case, Proxima b would be almost half as big as the Earth (a radius 40% larger) with a liquid ocean 200 km deep covering its entire surface. Under pressure, the water would then turn to ice at this depth. There would be a thickness of 2900 km before reaching a rocky heart about the size of the Earth. In both cases, there might be an atmosphere sufficient for the temperature to be compatible with the existence of liquid water.
"We made the assumption that it was a rocky world and not a gaseous planet" : Bastien Brugger, astrophysicist at LAM
We can not decide between these different scenarios until we know the radius of the planet. "It would require that it transits in front of his star, which does not seem to be the case," regrets Magali Deleuil, an astrophysicist at LAM who contributed to this work. If Proxima b does not intercalate between us and its star, there is only one solution to know its radius: take a picture. For the moment, the current tools do not make it possible to make an image of a star so small planet located as close to its star, but it may be the case in the future. There is actually a third option: to go there. But the journey is long: it is necessary to cover 700,000 times the distance that separates us from Mars, a journey that would take nearly 80,000 years with the fastest ships existing today.
If Bastien Brugger says he has a weakness for the planet-ocean scenario, he concedes that it is not the most likely. "The planet must have formed farther from its star and migrated to its present position. There are also other conditions which do not make this hypothesis the most favorable. It is more likely that we are between these two extreme cases, with a metal core representing thirty percent of the global mass. In which case Proxima b would be 10% larger than the Earth.
F I N .
