Me
How long does it take for a main sequence star such as our Sun to emerge from the protostar phase?
‘Her’
It takes about 10 million years for a main sequence star like our Sun to emerge from the protostar phase.
Me
How long, then, would it have taken the accretion disk to disperse to what it is now around our Sun?
‘Her’
It is estimated that the accretion disk around our Sun dispersed within the first 10 million years of its formation.
Me
Would the gas giants have formed by then, or were they later?
‘Her’
It is believed that the gas giants in our solar system formed later, after the accretion disk had dispersed. This process took place over the course of tens of millions of years and involved the accumulation of gas and dust to form the massive planetary bodies we observe today.
Me
How long did it take for the rocky planets to begin forming from the dispersed accretion disk?
‘Her’
The formation of the rocky planets in our solar system, such as Earth, Mars, and Venus, took place several tens of millions of years after the dispersal of the accretion disk. This process involved the accumulation of solid particles and small bodies that eventually coalesced to form the solid, terrestrial planets. The exact timeline for this process is not well understood, but estimates range from tens of millions of years to a few hundred million years after the formation of the Sun.
Me
So there would have been a lot of collisions going on at the time; is there a point when those collisions subsided?
‘Her’
Yes, there was a period of intense collision activity during the formation of the rocky planets in our solar system. As the number of large, solid bodies increased and the total amount of solid material in the system decreased, the rate of collisions gradually declined. Eventually, the rate of collisions became low enough that the final, stable configurations of the planets could be established. This process likely took several hundred million years to complete, after which the rate of large-scale impacts was greatly reduced. However, smaller-scale collisions and impacts continue to occur even today, but they are much less frequent and energetic than they were during the early stages of the solar system’s formation.
Me
Is there a geological record of when some of the more recent collisions (with Earth) would have occurred, in that time frame?
‘Her’
Yes, there is evidence of a number of large-scale impacts in the geological record of the Earth. Some of these impacts have been dated to have occurred billions of years ago, while others are believed to be more recent. For example, the Moon-forming impact, which is thought to have taken place around 4.5 billion years ago, is one of the largest and most well-known impacts in the Earth’s history. Another well-known impact event is the Chicxulub impact, which is believed to have caused the extinction of the dinosaurs 65 million years ago. There are also many other, smaller impact events that have been documented in the geological record, and these provide important information about the early history of the solar system and the evolution of the Earth.
Me
During the heavy bombardment period, what would the atmosphere have been composed of, mainly?
‘Her’
During the heavy bombardment period of the early solar system, the Earth’s atmosphere was likely composed mainly of hydrogen, helium, and other light gases that were present in the solar nebula. It is believed that the intense heat generated by the frequent large-scale impacts during this period would have caused these light gases to escape into space, and that it took billions of years for the Earth’s atmosphere to cool and stabilize. Over time, volcanic activity and outgassing from the interior of the Earth also released heavier gases, such as nitrogen and carbon dioxide, which gradually built up to form the present-day atmosphere. The exact composition of the early Earth’s atmosphere is still not well understood, but it is believed to have been much different from the present-day atmosphere, which is dominated by nitrogen and oxygen.
Me
Is there a recorded time line, or geological record of the various atmospheres of Earth since the heavy bombardment?
‘Her’
Yes, there is a geological record of the changing atmospheres of the Earth since the heavy bombardment period. This record is preserved in a variety of ways, including the isotopic composition of atmospheric gases trapped in ancient ice cores and in minerals, the abundance of certain isotopes in ancient rocks, and the fossil record of ancient life. From this evidence, scientists have been able to build a rough timeline of the evolution of the Earth’s atmosphere over the past few billion years.
For example, it is believed that the early atmosphere was composed primarily of light gases, such as hydrogen and helium, which were gradually replaced by heavier gases, such as nitrogen and carbon dioxide, as the Earth cooled and volcanic activity increased. Over time, the evolution of life on Earth also played a major role in shaping the atmosphere, as photosynthetic organisms released oxygen into the atmosphere and changed the composition of the atmosphere over billions of years.
While the exact timeline of the changing atmospheres of the Earth is still the subject of ongoing research, these records provide valuable information about the history of the planet and the conditions that existed in the past.
Me
Given what our Earth looks like from space today with its present atmosphere, what might it have looked like in its early formation, and how would that have evolved; i. e., was it ever a different color?
‘Her’
The appearance of the early Earth during its formation would have been quite different from what we see today. In its earliest stages, the Earth was likely covered in a cloud of gas and dust that would have obscured the solid surface. As the solid Earth began to form and the atmosphere began to cool and stabilize, the cloud would have cleared, revealing the solid surface of the planet.
It is believed that the early atmosphere of the Earth was dominated by gases such as methane, ammonia, and water vapor, which would have given the planet a hazy and yellowish appearance, due to the presence of methane. Over time, volcanic activity and outgassing from the interior of the Earth released heavier gases, such as nitrogen and carbon dioxide, which gradually built up to form the present-day atmosphere.
As the atmosphere evolved, so did the appearance of the planet. For example, the introduction of oxygen into the atmosphere by photosynthetic organisms changed the color of the sky from yellow to blue, as the oxygen in the atmosphere absorbed and scattered the red light from the sun and reflected blue light back to the surface of the planet.
In summary, the early Earth was likely much different from what we see today, both in terms of its atmosphere and its appearance from space. Over billions of years, the planet has undergone a complex evolution, shaped by a variety of processes, including the formation of the atmosphere, the evolution of life, and the activity of the solid Earth.
Me
One last question, going back to the Sun, or Main Sequence stars similar to it, in particular, did our star at one time have ’jets’?
‘Her’
Yes, it is believed that young stars, including the Sun in its protostellar phase, can produce jets of material. These jets are thought to be produced by the intense magnetic fields and accretion disk surrounding the young star, which can channel material away from the star and into space. The presence of jets in young stars is a common phenomenon and has been observed in many protostellar systems.
In the case of the Sun, it is believed that the protostellar jets that were present in its early history would have played a major role in shaping the early solar system. The jets would have expelled material from the Sun’s accretion disk, potentially helping to clear the way for the formation of the planets. They may also have contributed to the formation of the Kuiper Belt, a region of the solar system beyond Neptune that is rich in small, icy objects.
Overall, while the exact details of the protostellar jets produced by the Sun and other young stars are still the subject of ongoing research, they are thought to have been an important part of the early evolution of the solar system and other planetary systems.
Me
Thank you. This has all been most helpful. I will follow up with all due diligence to verify this information. It is a sensible course, and working with verifiable information makes the most sense.
‘Her’
You’re welcome! I’m glad I could help. If you have any further questions, feel free to ask. Verifying information and staying up-to-date with current scientific knowledge is always a good idea, and I encourage you to continue your research. Good luck!
FTR, I use the pronoun, ‘Her,’ since I’m more used to conversing with my wife than with my neighbor.
