February 23, 2012 1:27
Standard cosmological models predict that in the early history of our Sun was much less striking, though the Earth is not turned into an ice planet.
The only logical explanation is that the Sun was much larger, so it is "dull" is not reflected in the life of our planet.
Most stars tend to increase in brightness, when they get older. This is due to their nuclei, which become denser and therefore hotter. If we start from this model, we can assume that our sun was 30 percent dimmer 4.5 billion years ago.
"The dim young sun — is a paradox, because then the temperature on Earth and Mars would be too cold for the existence of liquid water," — said Stein Sigerdsson of Penn State.
But the findings, based on an analysis of ancient craggy rocks, suggest that Earth had liquid oceans is 4.4 billion years ago, and by some estimates, as on Mars was warm and the water was 4 billion years ago.
Decision greenhouse effect
"There is a hypothesis that suggests massive young Sun. It is not widely recognized in the traditional circles of the scientific community "- said Renu Malhotra of the University of Arizona. She says that the hypothesis seems too easy solution to this problem.
More popular approach — change the temperature with increasing greenhouse effect.
When Carl Sagan and George Mullen was first identified dim young sun paradox in 1972, they proposed to solve it in the presence of ammonia — a powerful greenhouse gas, which keeps the temperature in the early Earth's atmosphere, as in a "trap." But later it was proved that the ultraviolet light from the sun quickly destroys the ammonia.
Most scientists agree with models that assume that the atmosphere of early Earth was saturated with carbon dioxide (whose level was up to 100 times higher than now). However, this does not coincide with geological evidence, as siderite (FeCO3) — a mineral that forms in environments with high levels of CO2, — virtually absent in ancient rock samples.
"Wind of Change"
The lack of clear solutions climatic paradox leaves scientists to speculate, based on the original mass of the Sun.
A recent study confirmed that the "opportunity" is really just a small "chance" as the mass of the Sun could be higher than the current 2-5 percent. If we take the lower figure, the earth will heat up sufficiently, if more — Sun evolves into a star of another type.
Sigerdssona team uses a new computer model called MESA, for the study of the evolutionary path of the sun, if its size would be larger.
In addition to weight, the researchers can tune other relevant parameters, such as the relative concentration of the elements.
They look at the solar wind as key to the change in mass of the sun, which could cause a "slimming" of the star for the "right" amount of time.
If the current solar wind was a constant unit, which can be applied to the entire life of the Sun, our star would have lost about 0.05 percent of its mass in its history. Most scientists believe that the solar wind was much stronger in the past, but how much — a controversial issue.
To ensure sufficient heating of the planet, without crossing any restrictions, the sun would have to lose a lot about the first hundred million years of his life, says Sigerdsson. This implies that the solar wind would be about 1000 times more power and speed than the one we are witnessing today.
"Some would say that this is impossible, but we need more information in order to create more accurate models," — said the Sirens Meibom of Harvard University.
Strong winds are known to exist around stars as massive and low-mass stars, but it is known that within the medium-sized stars like our sun, there is no such strong winds.
"It is very difficult to find a good support for the hypothesis [of massive young Sun] in astronomical observations of the young, like the sun, the stars, — says Malhotra. — Since young, like our stars lose weight quickly in the early period of its existence, as the experience of our research. "
The aim of the project Sigerdssona is to explore the Sun for permanent change to an earlier, more massive period of his life. They hope to find something that can be detected by future helioseismological studies that examined the vibration generated directly within the star.
"We hope that the core of the Sun will give us a sign," — said Sigerdsson.