Hydrogen is the predominant element of the Sun, accounting for some 74% of its mass, and 92% of its volume.
Helium accounts for 24% of its mass but only 7% of its volume.
Traces of oxygen, iron, silicon, sulphur, carbon, neon, nickel, magnesium, calcium and chromium make up the missing percentage.
The most abundant metals are oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%).
Any elements heavier than iron have come from the interstellar medium from nucleosynthesis in previous generations of stars heavier than our Sun.
The Sun is made of plasma, almost entirely hydrogen and helium. Plasma is superheated matter that is so hot that the elements have lost some or all of their electrons, it is beyond a gaseous state.
Our Sun is massive, more massive than some 80% of the known stars, but is still relatively small by comparison with some of the giants. Most of the stars in our galaxy are less than half the mass of our Sun.
The sun's energy output, about 400 * 1018 Watts, is produced by nuclear fusion of hydrogen and helium which create the heavier elements and release energy at the same time - some mass is converted into energy according to the well known E=mc2 equation that Einstein formulated.
The process of fusion constantly creates some heavier elements in the core of the Sun, although some are also rapidly destroyed.
No, it has changed over time. The original atmosphere of the Earth was mostly carbon dioxide with some water vapour, ammonia and methane, and was probably formed by volcanic outgassing. Living things introduced oxygen, and were one of the causes of reduced carbon dioxide. The ammonia then reacted with the oxygen.
NASA considers people to be astronauts once they've traveled higher than 80 km (50 miles). The earth's atmosphere officially ends at approximately 800 km (500 miles) but shuttles and the northern lights have been seen at altitudes of around 690 km (431 miles).
Various agencies have designated lower altitudes for the beginning of space. The Federation Aeronautique Internationale has established the Karman line at an altitude of 100 km (62 miles).
The reality is that there is no clear boundary between the Earth and outer space.
I am not no NASA but I would say around 20Miles up from Ground we would be in Space, it kind of hard to believe but if you think a plane climbs around 1mile, -50 degrees, and you travel up another 19 miles you would be in no gravity Zone with no air, so to me that's the point of Space.
If I am wrong then I can live with that, but it would be good to get exact zone and degrees.
As for shuttles and northern lights, well they are both seen at low altitudes, however you can see satellites very clearly from you own back garden on clear night. So space and orbit can not be that far as its only approx 250klm above ground level which you can see the Space station very clear.
The solar system did not form from a nebula at all. Our solar system formed from a rotating cloud of gas and dust, our sun formed at the center and planets formed from the surrounding matter. when our sun became large enough to support nuclear fusion, the solar wind created blew away most of the gases present. A planetary nebula is formed after a star runs out of fuel (Helium) and collapses inward on itself due to the massive amount of gravity and the now unstable balance of the star. the pressure then becomes so great that the gases that had been pulled inward explode outward at an incredible speed. The Cats Eye Nebula is a good example
The rocks present in earth like Basalts when cools to a certain temperature(Curie point),the earth's magnetic field is frozen into it known as fossil magnetism.It records both direction of N-S pole & the latitude of the rock.Evidence from this it has been reveled that on geologic past earth has reversed it's magnetic field many atimes.